Global Geological And Climatic Events

Global Geological And Climatic Events

Mumbai billboard collapse: Why cities need to gear up for ‘multi-hazard weather events’

Note4Students

From UPSC perspective, the following things are important :

Prelims level: NA

Mains level: How do thunderstorms develop and are they becoming more intense?

Why in the news?

Earlier this week, a massive billboard collapsed in Mumbai due to a localized dust storm and rain, resulting in the deaths of 16 people and injuring over 75 others.

What happened in Mumbai?

  • Pre-monsoon thunderstorm: On May 13, 2024, Mumbai experienced a pre-monsoon thunderstorm between 3 pm and 4 pm. This event started with a dust storm followed by rain across the city and suburban areas. Wind speeds during the storm varied between 40 kmph and 90 kmph, with the Santacruz and Colaba weather stations recording top wind speeds of 87 kmph and 51 kmph, respectively.
  • Extensive damage: The high winds caused extensive damage to railway infrastructure, banners, hoardings, and trees. A massive 120×120 feet billboard in Ghatkopar (east) collapsed, resulting in the deaths of 16 people and injuries to more than 75 others.

How do thunderstorms develop and are they becoming more intense?

  • Natural phenomena common during peak summer: Thunderstorms and dust storms are natural phenomena common during peak summer and pre-monsoon periods. They develop due to persistent surface heating combined with favourable wind conditions.
  • Thunderstorms typically form in the late afternoon and evening, develop quickly, and dissipate rapidly. Rising global temperatures are contributing to more intense and frequent thunderstorms because a warmer atmosphere can hold more water vapor.
  • According to M Rajeevan Nair, former secretary of the Ministry of Earth Sciences, this increased moisture capacity can lead to stronger storms.

What are climate and weather-related hazards?

  • Climate and weather-related hazards are meteorological events that cause extensive damage to human life, properties, and animals.
  • The India Meteorological Department (IMD) has categorized 13 such hazards, including dust storms, thunderstorms, hailstorms, cyclones, drought, extreme rainfall events, floods, fog, lightning, snowfall, heatwaves, coldwaves, and strong winds.
  • These events can cause fatalities, displacement, property damage, livestock deaths, crop damage, and widespread infrastructure damage.

What is the impact of such events on human life?

  • According to the National Crime Records Bureau (NCRB) 2022 report, there were 8,060 accidental deaths in India in 2021 due to natural events.
  • Lightning was the leading cause, accounting for 35.8% of these deaths, with 2,887 fatalities. Other significant causes included floods (547 deaths), landslides (269 deaths), exposure to cold (720 deaths), and heat stroke (730 deaths).

Way Forward

  • The Mumbai billboard collapse underscores the need for climate-proofing infrastructure in densely populated cities. Urban planning must consider the risks of multi-hazard events, especially in coastal cities like Mumbai that face diverse weather-related threats.
  • There should be regular reviews and updates of building codes and standards to ensure they address the risks posed by local weather phenomena.
  • Improving early warning systems and disaster preparedness plans can help mitigate the impact of such events on human life and property.

Mains PYQ:

Q Troposphere is a very significant atmosphere layer that determines weather processes. How? (UPSC IAS/2022)

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Global Geological And Climatic Events

Aurora Borealis: What are Northern and Southern lights? Why do they occur?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Auroras and its types, Coronal Mass Ejections/ Solar Storm

Mains level: NA

Why in the news?

  • In a rare event, the night sky over Hanle village in Ladakh was illuminated by the northern lights or aurora borealis.
    • Concurrently, the southern lights, or aurora australis, were observed in New Zealand and Australia.

What are Auroras?

  • Auroras are natural light displays that appear as bright, swirling curtains in the night sky.
  • They are typically seen near the Poles but can occasionally be observed at lower latitudes.
  • These lights can display a range of colors, including blue, red, yellow, green, and orange, due to the interaction of solar particles with different gases in the Earth’s atmosphere.
  • The phenomenon is known as:
  1. Aurora borealis in Northern Hemisphere and
  2. Aurora australis in Southern Hemisphere

What causes Auroras?

  • Interaction with Earth’s Magnetic Field: As the solar wind approaches Earth, it interacts with the planet’s magnetic field, causing some charged particles to enter the atmosphere near the poles.
  • Interaction with Gases: These particles interact with gases in the upper atmosphere, producing colourful flashes of light. Collision with oxygen produces green light, while interaction with nitrogen results in shades of blue and purple.

Reasons for Aurora in Ladakh:

  • Intense Solar Activity: Auroras can extend to lower latitudes during periods of intense solar activity, such as solar flares and coronal mass ejections (CMEs).
    • The CMEs are from the AR13664 region of the sun that has produced several high-energy solar flares
  • Localized magnetic anomalies: Variations in Earth’s magnetic field could potentially influence the occurrence of auroras in specific areas, including regions at lower latitudes.

Impact on Tech Infrastructure 

  • Auroras can pose challenges to space-dependent technologies and operations.
  • Disruptions in Global Positioning Systems (GPS), radio communications, flight operations, power grids, and space exploration endeavors may occur during such events.

PYQ:

[2022] If a major solar storm (solar flare) reaches the Earth, which of the following are the possible effects on the Earth?

  1. GPS and navigation systems could fail.
  2. Tsunamis could occur at equatorial regions.
  3. Power grids could be damaged.
  4. Intense auroras could occur over much of the Earth.
  5. Forest fires could take place over much of the planet.
  6. Orbits of the satellites could be disturbed.
  7. Shortwave radio communication of the aircraft flying over Polar Regions could be interrupted.

Select the correct answer using the code given below:

(a) 1, 2, 4 and 5 only
(b) 2, 3, 5, 6 and 7 only
(c) 1, 3, 4, 6 and 7 only
(d) 1, 2, 3, 4, 5, 6 and 7

 

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Global Geological And Climatic Events

Positive Indian Ocean Dipole (IOD) to aid Monsoon this year

Note4Students

From UPSC perspective, the following things are important :

Prelims level: IOD and its phases, ENSO;

Why in the News?

Australian weather agencies predict the possible return of a positive Indian Ocean Dipole (IOD) in the latter half of 2024.

What is the Indian Ocean Dipole (IOD)?

  • The IOD is also known as the Indian Nino. It is characterized by the differential heating of ocean waters in the eastern and western parts of the basin.
  • Similar to the El Nino Southern Oscillation (ENSO) in the Pacific, the IOD involves phases of ocean temperatures and atmospheric conditions that affect weather patterns across the region and beyond.
  • There are two main phases of the IOD:
    • Positive Phase: In this phase, the western Indian Ocean becomes warmer than average, and the eastern part cooler than average. This results in greater convection and rainfall over the western Indian Ocean and adjacent land areas like East Africa, while reducing rainfall over the eastern Indian Ocean and places like Indonesia and Australia.
    • Negative Phase: The opposite conditions prevail during this phase, with cooler waters in the western Indian Ocean and warmer waters in the east. This leads to increased rainfall in the eastern Indian Ocean regions and drier conditions in the western part and East Africa.

Back2Basics: El Nino-Southern Oscillation (ENSO)

  • El Nino and La Nina are two opposite phases of the El Nino-Southern Oscillation (ENSO) cycle.
  • ENSO is a naturally occurring phenomenon that involves the interaction between the ocean and atmosphere in the equatorial Pacific.

Here is a detailed comparison of El Nino and La Nina

El Nino La Nina
Definition Warmer-than-normal sea surface temperatures Cooler-than-normal sea surface temperatures
Frequency Every two to seven years Every two to seven years
Duration Several months to a year or more Several months to a year or more
Impact on winds Weakens trade winds, leading to changes in patterns Strengthens trade winds, leading to changes in patterns
Impact on rains Reduces rainfall and can cause droughts Increases rainfall and can cause flooding
Impact on temp. Warmer-than-average temperatures Colder-than-average temperatures
Global effects Droughts in Asia and Africa, floods in Americas Floods in Asia and Africa, droughts in South America

 

Impact on the Indian Monsoon:

The Indian Ocean Dipole has significant impacts on the Indian monsoon system:

  1. Positive IOD often coincides with a stronger Southwest Monsoon, bringing more rainfall to India. This is due to the shift in warm water and accompanying convection towards India, which enhances the monsoon rainfall.
  2. Negative IOD can weaken the Southwest Monsoon, resulting in less rainfall and potential drought conditions in India. The shift of warm water away from India reduces the necessary heat and moisture that drive the monsoon rains.

PYQ:

[2017] With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?

1. IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.

2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.

Select the correct answer using the code given below:

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

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Global Geological And Climatic Events

Catatumbo Lightning: A Torrent of Current

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Catatumbo Lightning

Mains level: NA

Why in the news?

Catatumbo lightning is a natural event seen over the Catatumbo River in Venezuela, where lightning strikes almost nonstop.

What is Catatumbo Lightning?

  • Catatumbo Lightning is an atmospheric phenomenon that occurs over the Catatumbo River in Venezuela.
  • It specifically occurs at the Catatumbo Delta, where the river meets Lake Maracaibo.
  • It is known as one of the world’s largest lightning displays.
  • This natural spectacle involves frequent and nearly continuous lightning strikes that illuminate the night sky, creating a mesmerizing light show.
  • Catatumbo Lightning is most prevalent during the wet season, typically from April to November.
  • The consistent and abundant lightning activity has earned the region the moniker the lightning capital of the world.”

Factors behind Catatumbo Lightning

  • Weather Dynamics
  • Warm, moisture-laden air from the Caribbean Sea clashes with cooler air descending from the Andes mountains, creating a dynamic interplay of atmospheric forces.
  • This collision, accentuated by the local landscape, triggers rapid upward movement of warm air, leading to the formation of towering cumulonimbus clouds.
  • Electrical Charge Generation
  • Strong winds and temperature differentials within these clouds generate electrical charges.
  • Cumulonimbus clouds, towering over 5 km high, accumulate vast amounts of static electricity.
  • Lightning Discharge: When the electrical potential within the clouds reaches a critical level, it discharges in the form of lightning strikes.

Characteristics of Catatumbo Lightning

  • Catatumbo lightning occurs on approximately 160 nights annually, exhibiting a remarkable longevity.
  • At its peak, the phenomenon generates an astonishing average of 28 lightning strikes per minute.

PYQ:

[2013] During a thunderstorm, the thunder in the skies is produced by the

1. Meeting of cumulonimbus clouds in the sky

2. Lightning that separates the nimbus clouds

3. Violent upward movement of air and water particles

Select the correct answer using the codes given below:

(a) 1 only

(b) 2 and 3

(c) 1 and 3

(d) None of the above produces the thunder

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Global Geological And Climatic Events

Eta Aquariid Meteor Shower and how it can be spotted

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Eta Aquariid Meteor Shower, Halley’s Comet

Mains level: NA

Why in the news?

  • The Eta Aquariid meteor shower, an annual event, will reach its peak on May 5 and 6.
  • This meteor shower is a result of Earth intersecting with the debris trail left by Halley’s Comet during its orbit.

Halley’s Comet

  • Halley’s Comet is a short-period comet visible from Earth every 75–79 years.
  • It was last seen in Earth’s skies in 1986 and was met in space by an international fleet of spacecraft. It will return in 2061 on its regular journey around the Sun.

What are Meteoric Showers?

  • Meteors, fragments of dust, rock and ice, are expelled from comets during their celestial orbits around the sun.
  • The Earth’s atmosphere heats these space rocks as they descend, leaving luminous streaks of gas in their way.
  • NASA’s records confirms existence of over 30 meteor showers annually.

Origin of Meteor Showers:

  • Meteor showers originate from comets, remnants of the solar system’s formation composed of dust, rock, and ice.
  • Comets orbit the Sun in highly elliptical paths, and as they approach, they heat up, releasing gases and dust to form a glowing head and a tail stretching millions of miles.
  • When Earth traverses through the debris left behind by comets along their orbital plane, we witness meteor showers.

About Eta Aquariids

  • Known for their rapid speed, Eta Aquariid meteors produce long, glowing tails lasting several minutes.
  • Observers in the Southern Hemisphere can witness approximately 30 to 40 meteors per hour during the peak, while those in the Northern Hemisphere may see around 10 meteors per hour.
  • They seem to originate from the Aquarius constellation, hence the name ‘Eta Aquariid.’

PYQ:

[2014] What is a coma, in the content of astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

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Global Geological And Climatic Events

[PREMIUM] To the South Pole – Antarctica

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Antarctica Region

Mains level: NA

Why in the news?

The Antarctic Treaty has sparked debates among policymakers, scientists, and the public, as they weigh the balance between environmental conservation, economic interests, and geopolitical concerns in Antarctica.

About Antarctica

    • Antarctica is the fifth-largest continent, covering an area of approximately 14 million square km.
    • It is situated entirely within the Antarctic Circle, with its geographic center near the South Pole.
    • It is the coldest, driest, and windiest continent on Earth.
    • The interior of Antarctica is a polar desert, receiving very little precipitation, mostly in the form of snow.
  • The Antarctic Ice Sheet is the largest single mass of ice on Earth, containing approximately 70% of the world’s freshwater.

Geographical Features:

Description
Mountains
  • The continent is home to several mountain ranges, including the Transantarctic Mountains.
  • Vinson Massif is the highest peak at 4,892 meters (16,050 feet) above sea level.
Ice Shelves Large floating ice shelves extend along the coast, formed by glaciers flowing from the interior, crucial for stabilizing the Antarctic ice sheet.
Glaciers Numerous glaciers flow from the high interior to the coast, including Pine Island Glacier and Thwaites Glacier, among the largest and fastest-moving in the world.
Icebergs
  • Glaciers calve off large chunks of ice, forming icebergs of various sizes.
  • Antarctic Iceberg A-68, which broke off from the Larsen C Ice Shelf in 2017, was one of the largest recorded.
Plateaus Much of Antarctica’s interior consists of high, flat plateaus covered by ice, reaching elevations over 4,000 meters (13,000 feet) above sea level.
Ice-Free Areas Despite being predominantly ice-covered, some ice-free areas exist along the coastlines and in the Antarctic Peninsula region, supporting limited vegetation and wildlife.

Territorial Claims on Antarctica:

The countries with territorial claims in Antarctica are:

  1. Argentina: Claims a sector of Antarctica known as Argentine Antarctica.
  2. Australia: Claims the Australian Antarctic Territory.
  3. Chile: Claims a sector of Antarctica known as Chilean Antarctic Territory.
  4. France: Claims a sector of Antarctica known as Adélie Land.
  5. New Zealand: Claims the Ross Dependency.
  6. Norway: Claims a sector of Antarctica known as Queen Maud Land.
  7. United Kingdom: Claims a sector of Antarctica known as the British Antarctic Territory.
  8. United States: Claims a sector of Antarctica known as the Marie Byrd Land.

India’s Antarctic Outreach

  • Initiated in 1981, India’s Antarctic Program, managed by National Centre for Polar and Ocean Research, encompasses multi-disciplinary research expeditions.
  • With the establishment of research bases like Dakshin Gangotri (1983) (now decommissioned), Maitri (1989), and Bharati (2012), India contributes significantly to Antarctic exploration.
  • Notably, India’s presence in Antarctica includes a Post Office established in 1984, facilitating communication and research logistics.

 

PYQ:

[2011] The formation of ozone hole in the Antarctic region has been a cause of concern. What could be the reason for the formation of this hole?

(a) Presence of prominent tropospheric turbulence; and inflow of chlorofluorocarbons

(b) Presence of prominent polar front and stratospheric’: Clouds; and inflow of chlorofluorocarbons

(c) Absence of polar front and stratospheric clouds; and inflow of methane and chlorofluorocarbons

(d) Increased temperature at polar region due to global warming.

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Global Geological And Climatic Events

Taam Ja’: World’s Deepest Blue Hole

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Taam Ja’ Blue Hole (TJBH) and its location

Mains level: NA

Why in the news?

Researchers have made a discovery in Mexico, uncovering the world’s deepest blue hole, known as Taam Ja’ Blue Hole (TJBH).

What are Blue Holes?

  • Blue holes, such as TJBH, are formed in coastal regions with soluble bedrock, such as limestone, marble, or gypsum.
  • Water percolates through the rock, dissolving minerals and widening cracks, ultimately leading to the formation of sinkholes.
  • Famous examples: 410-foot Great Blue Hole in Belize, the 663-foot Dean’s Blue Hole in the Bahamas and the 328-foot Blue Hole in the Red Sea near Dahab, Egypt.

About Taam Ja’ Blue Hole (TJBH)

  • TJBH extends at least 1,380 feet (420 meters) below sea level, making it the deepest known underwater sinkhole in the world.
  • It is located in Chetumal Bay off the southeast coast of the Yucatan Peninsula.
  • It was first discovered in 2021, was originally thought to be 900 feet deep.
  • This discovery surpasses the previous record-holder, the Sansha Yongle Blue Hole in the South China Sea, by an impressive 480 feet.

Research Expedition and Findings

  • Scientists utilized a conductivity, temperature, and depth (CTD) profiler to collect data about the environmental conditions within the blue hole.
  • Despite reaching depths of 1,640 feet (500 meters), the CTD profiler was unable to reach the bottom of TJBH, indicating its remarkable depth.
  • Data from the profiler suggested the presence of different water layers within the blue hole, with conditions resembling those of the Caribbean Sea at depths below 1,312 feet (400 meters).

PYQ:

[2017] In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be the potential sites for carbon sequestration?

1. Abandoned and uneconomic coal seams.

2. Depleted oil and gas reservoirs.

3. Subterranean deep saline formations.

Select the correct answer using the code given below:

(a) 1 and 2 only

(b) 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

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Global Geological And Climatic Events

Anticyclones, hanging even now over India, link warming to heat | Explained

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Anticyclone and El Nina

Mains level: Link between anticyclone and heat

Why in the news?

The record warming of 2023 has so far not been fully explained since it was much warmer than expected just from the superposition of El Nino on global warming.

About Anticyclone:

  • An anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

The link between ElNino and Anticyclone: 

  • El Nino events can lead to the formation of anticyclone events. During El Niño, the weakening or reversal of the Walker circulation and strengthening of the Hadley circulation caused warm ocean water to develop in the central and east-central equatorial Pacific.

The link between anticyclone and heat 

  • Stability and Weather Patterns: Anticyclones are areas of high pressure in the atmosphere characterized by descending air, which stop the cloud formation and precipitation. This stable air mass tends to promote clear skies and can lead to prolonged periods of hot and dry weather.
  • Amplification by Global Warming: Studies suggest that global warming can intensify anticyclones, making them stronger and more persistent. Warmer temperatures due to climate change can enhance the evaporation of moisture from land and water surfaces, further reinforcing the stability of anticyclonic conditions.
  • Feedback Loop: Anticyclones can create a feedback loop with global warming. As anticyclones persist, they can exacerbate heatwaves by trapping heat near the surface, preventing it from escaping into the upper atmosphere. This trapped heat can then further strengthen the anticyclone, leading to a self-reinforcing cycle of heat and stability.

What are the stages of early warnings?

The stages of early warnings on the ‘ready-set-go’ system for disaster management

  • Ready: This stage involves providing a seasonal outlook based on background states and external factors like global warming and El Niño. The aim is to maximize the accuracy of longer-lead forecasts, enabling organizations like the National Disaster Management Agency (NDMA) and local governments to prepare their disaster response systems accordingly.
  • Set: In this stage, subseasonal predictions for weeks two to four are utilized. Resource allocations are made, and potential hotspots are identified to ensure that disaster preparedness is in place. This step involves moving resources, including personnel, to areas that are identified as at risk based on the extended range forecasts.
  • Go: The final stage, based on short- and medium-range forecasts (days 1-10), involves the activation of disaster response efforts. This includes implementing rescue operations, setting up hydration centers, heat shelters, and other necessary measures to manage the disaster effectively.

Conclusion: All evidence suggests India’s prediction system and early warning systems continue to improve and the NDMA has worked these details well into its ‘ready-set-go’ system.The remaining challenges are to build resilience for the future by better predicting the trajectory of the weather at every location over India.

Mains PYQ 

Q Drought has been recognized as a disaster in view of its spatial expanse, temporal duration, slow onset and lasting effects on vulnerable sections. With a focus on the September 2010 guidelines from the National Disaster Management Authority (NDMA), discuss the mechanisms for preparedness to deal with likely El Nino and La Nina fallouts in India.

https://www.thehindu.com/sci-tech/science/anticyclones-hanging-even-now-over-india-link-warming-to-heat/article68117359.ece

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Global Geological And Climatic Events

Sympathetic Solar Flares

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Sympathetic Solar Flares, Coronal Mass Ejections (CME), Solar Cycle

Mains level: NA

Why in the news?

A rare celestial event unfolded as four solar flares called as Sympathetic Solar Flares simultaneously, signaling the onset of the Sun’s dynamic 11-year solar cycle.

What is a Solar Cycle?

  • Given the Sun’s dynamic nature, electrically charged gases on its surface generate powerful magnetic fields, known as magnetic fields.
  • These magnetic fields undergo stretching, twisting, and tangling due to the constant movement of gases on the Sun’s surface, resulting in solar activity.
  • Scientists monitor solar cycles using sunspots. Solar activity fluctuates throughout the solar cycle, which typically spans about 11 years
  • The onset of a solar cycle typically features minimal sunspot activity, termed as a solar minimum.
  • For instance, the last Solar Cycle 25 commenced in December 2019, characterized by a low number of sunspots.

What are Sympathetic Solar Flares?

  • Sympathetic solar flares are solar eruptions that occur in close temporal and spatial proximity to another solar flare or eruption.
  • These events are believed to be interconnected through magnetic fields or other physical processes occurring on the Sun.
  • When a solar flare or eruption happens on the Sun, it releases a burst of electromagnetic radiation and charged particles into space.
  • In some cases, the energy released during these events can cause disturbances in the Sun’s magnetic field.
  • These disturbances can trigger the occurrence of additional flares loop or eruptions in nearby regions of the Sun’s surface.
  • This event follows coronal mass ejections (CMEs) and intense plasma bursts.

Implications for Earth

  • Potential impacts include disruptions to power grids, interference with communication networks, and increased radiation exposure for astronauts and aircraft passengers.
  • Solar storms can lead to spectacular natural light shows known as auroras, which are typically visible near the Earth’s magnetic poles.

PYQ:

[2012] The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs:

(a) the water vapour of the air and retains its heat

(b) the ultraviolet part of the solar radiation

(c) all the solar radiations

(d) the infrared part of the solar radiation

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Global Geological And Climatic Events

PREMIUM – Travelling the Regions of South America

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Areas in South America;

Mains level: NA

Why in the News?

South America, known for its diverse landscapes and cultures, also harbors several disputed territories, each with its own historical, geopolitical, and economic significance. These disputes often arise from conflicting territorial claims, historical grievances, or resource-rich areas. 

Diverse Landscapes of South America:

  • The Pacific Coastal Strip:
    • Between the ocean and the Andes mountain Range.
    • The coastline of South America is smooth and regular. At the river mouths, some inlets are used as harbors. The southwestern coast of the continent has fiords or deep inlets of the sea.
  • Andes Mountain Range:
    • The Andes stretch through the entire continent, running in the north-south direction from the Isthmus of Panama to the Strait of Magellan. The second-highest mountain system in the world.
    • Mount Aconcagua (an extinct volcano lies in Argentina)
    • Mount Ojas del Salado is the highest active volcano in the world of Argentina.
    • Part of seven countries: Venezuela, Colombia, Ecuador, Bolivia, Peru, Chile, and Argentina.
    • They form a chain of ranges and knots with enclosed intermontane plateaus namely in Ecuador and Bolivia.
    • Being part of the Pacific Ring of Fire, there are many volcanoes and frequent earthquakes in this region. Mount Cotopaxi and Mount Chimborazo are active volcanic peaks, which is the highest peak in South America.
  • About the Amazon River:
    • It is the world’s largest and second-longest (6,400 km) river in the world after the Nile.
    • Its journey begins high in the Andes Mountains. The river then makes its way east through thousands of miles of rainforests and lowlands until it empties into the Atlantic Ocean on the northeastern coast of Brazil
    • Its watershed spans the countries of Brazil, Peru, Ecuador, Colombia, Venezuela, and Bolivia.
    • It has more than 1,100 tributaries, which include the rivers like the Rio Negro, the Madeira River, and the Xingu River, etc.
    • The Amazon Rainforest, which represents about half of the Earth’s remaining rainforest, also constitutes its single largest reserve of biological resources.
    • It is sometimes referred to as the “lungs of the Earth” due to its role in regulating the planet’s oxygen and carbon cycles.

Disputed Areas in South America

Countries Involved Key Points Geographical Features
Gulf of Venezuela Colombia, Venezuela
  • Inlet of the Caribbean Sea is Disputed over islands such as Los Monjes Archipelago due to Fishing rights and potential oil reserves.
  • Interpretation disputes regarding the 1941 Treaty of Delimitation            
  • Recent tensions over maritime confrontations and oil exploration activities.
Surrounded by coastal mountain ranges with waters fed by several rivers
Essequibo Region Guyana, Venezuela
  • Covers two-thirds of Guyana’s territory Historical grievances claimed by Venezuela.         
  • Recent oil discoveries raising tensions; ICJ case filed by Guyana.
  • Essequibo River flows through this region.
Diverse landscapes including rainforests, savannahs, and mountains with the Essequibo River
Atacama Desert Peru, Chile
  • Extremely Arid desert region            
  • War of the Pacific led to Chile’s control           
  • Valuable mineral resources contribute to disputes            
  • Bilateral talks and arbitration proposals for settlement
Bordered by the Andes Mountains and the Pacific Ocean with salt flats, sand dunes, and volcanic formations
Falkland Islands (Malvinas) Argentina, UK
  • Sovereignty disputes since 1833           
  • Economic interests include fisheries, tourism, and potential oil reserves           
  • Diplomatic efforts and UN resolutions for resolution
Consists of two main islands with rugged coastlines and low mountains
Darien Gap Colombia, Panama
  • Dense jungle terrain separating North and South America            
  • Challenges in illegal immigration discussions            
  • Characterized by dense rainforests, swamps, and mountains
Part of the Darien National Park with dense rainforests, mangroves, and steep mountain slopes
Arroyo de la Invernada or Rincon de Artigas… Brazil, Uruguay
  • Dispute over the Invernada River region near Masoller            
  • UN does not officially recognize the claim            
  • 237 km2 region with significant natural resources            
  • Efforts to resolve through bilateral talks and international mediation
Rolling hills, grasslands, and small rivers with the Invernada River
New River Triangle (Tigri Area) Suriname, Guyana
  • Disputed region within the Guiana Highlands            
  • Conflicting claims over territory interpretation of historical treaties and boundaries
Dense rainforests, mountain ranges, and numerous rivers
Isla Brasilera/Ilha Brasileira Brazil, Uruguay
  • Uruguay claims ownership of Isla Brasilera            
  • Strategically located near the tripoint with Argentina            
  • Efforts to resolve through diplomatic negotiations and legal arguments
Small island located in the Uruguay River with lush vegetation
Isla Suarez/Ilha de Guajara-mirim Bolivia, Brazil
  • Located in the Rio Mamore as a border between Bolivia and Brazil           
  • Economically dependent on Guajara-Mirim, Brazil            
  • Treaty signed in 1958 maintains the status quo            
  • Challenges of border management in riverine environments
Riverine island characterized by tropical vegetation and wetlands
Southern Patagonian Ice Field Argentina, Chile
  • Spanning parts of Argentina and Chile            
  • Border demarcation remains undefined in certain areas           
  • Bilateral efforts for resolution include scientific cooperation and mapping projects
Vast expanse of ice and snow covering rugged mountain ranges and deep valleys
Lithium Triangle  Argentina, Bolivia, and Chile
  • It is characterized by various salt pans or salars, concentrated along the Atacama Desert and adjacent arid regions.
  • The Salar de Atacama in Chile boasts the highest lithium concentration (0.15% by weight) among all brine sources worldwide. 
  • Argentina boasts more than half of the world’s total lithium resources and holds the distinction of having the 2nd-largest lithium resources, the 3rd-largest lithium reserves, and the 4th-largest lithium production in the world.
  • India’s KABIL (Khanij Bidesh India Ltd) has announced an investment of ₹211 crore ($25.712 million) over five years for exploration stage activities in five lithium blocks in the Fiambala area of Argentina.
Key reserves of Lithium include:

  1. Uyuni (Bolivia): This salt flat is not only the world’s largest salt flat but also contains significant lithium reserves.  
  2. Atacama (Chile): Located in the Atacama Desert, Salar de Atacama is home to one of the largest lithium reserves globally. 
  3. Hombre Muerto (Argentina): This salt flat in northwestern Argentina also hosts lithium extraction operations.

 

Note: Bolivia and Paraguay are land-locked countries in South America

PYQ:

[2013] “Climate is extreme, rainfall is scanty and the people used to be nomadic herders.”  

The above statement best describes which of the following regions?

(a) African Savannah

(b) Central Asian Steppe

(c) South American Tropical

(d) Siberian Tundra

 

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Global Geological And Climatic Events

Mount Ruang in Indonesia Erupts

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mount Ruang, Pacific Ring of Fire, Sangihe Islands arc, Tectonic Plates mentioned

Mains level: NA

Why in the news?

Indonesia witnessed a series of eruptions from Mount Ruang, a stratovolcano located in North Sulawesi Province.

About Mount Ruang 

  • Ruang is situated in the Sangihe Islands arc, North Sulawesi, Indonesia.
  • It comprises an island that is 4 by 5 kilometers wide, with a summit containing a partial lava dome reaching an altitude of 725 meters (2,379 ft).
  • From its summit, peaks such as Klabat, Siau, and Ternate can be observed in the south, north, and east, respectively.
  • The volcano’s first recorded eruption was in 1808.

Why so many volcanic eruptions in Indonesia this year?

  • Indonesia, an archipelago of 270 million people, has 120 active volcanoes.
  • It is prone to volcanic activity because it sits along the “Ring of Fire,” a horseshoe-shaped series of seismic fault lines around the Pacific Ocean.

What is the Pacific ‘Ring of Fire’?

  • The Pacific ‘Ring of Fire’ or Pacific Rim, or the Circum-Pacific Belt, is an area along the Pacific Ocean that is characterized by active volcanoes and frequent earthquakes.
  • Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire.
  • It is home to about 75 per cent of the world’s volcanoes – more than 450 volcanoes.
  • Also, about 90 per cent of the world’s earthquakes occur here.

Its spread

  • Its length is over 40,000 kilometres and traces from New Zealand clockwise in an almost circular arc covering Tonga, Kermadec Islands, Indonesia.
  • It is moving up to the Philippines, Japan, and stretching eastward to the Aleutian Islands, then southward along the western coast of North America and South America.

Seismic activity of the region

  • The area is along several tectonic plates including the:
  1. Pacific plate,
  2. Philippine Plate,
  3. Juan de Fuca plate,
  4. Cocos plate,
  5. Nazca plate, and
  6. North American plate.
  • The movement of these plates or tectonic activity makes the area witness abundant earthquakes and tsunamis every year.
  • Along much of the Ring, tectonic plates move towards each other creating subduction zones.

PYQ:

[2018] Consider the following statements:

  1. The Barren Island volcano is an active volcano located in the Indian Territory.
  2. Barren Island lies about 140 km east of Great Nicobar.
  3. The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3

(c) 3 only

(d) 1 and 3

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Global Geological And Climatic Events

India’s Arctic imperative

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Arctic Region

Mains level: Distribution of resources; Arctic Region;

Why in the news? 

The Indian government appears interested in capitalizing on seabed mining and resource exploitation in the Arctic

About Artice Region:

  • The Arctic region is rich in energy resources, including oil, natural gas, and renewable energy sources such as wind, solar, hydro, geothermal, and tidal power.
  • The Arctic covers an area of approximately 8 million square kilometers, with interests belonging to Denmark, Canada, Iceland, Finland, Russia, Norway, Sweden, and the United States

The reason behind the growing interest in the Arctic Region:

  • Climate Change Concerns: India’s increased interest in the Arctic stems from scientific data revealing accelerated warming in the region.
  • Trade Route Opportunities: India seeks to capitalize on the opening up of Arctic sea routes, particularly the Northern Sea Route, to enhance its trade efficiency.
  • Geopolitical Considerations: India’s focus on the Arctic is also driven by geopolitical factors, including concerns over China’s expanding presence and Russia’s decisions regarding access to Arctic routes.
  • Historical Engagement: India’s involvement in the Arctic dates back to 1920 with the signing of the Svalbard Treaty.

Indian Initiatives:

  • Arctic Council: As an Observer in the Arctic Council, India actively participates in various working groups and expert meetings. India’s involvement in these discussions helps in understanding Arctic governance issues and contributes to the development of sustainable policies for the region.
  • INS Himadri: In 2019, India launched its first scientific expedition to the Arctic with the INS Himadri, an ice-class research vessel. The expedition aimed to study climate change, oceanography, and marine biodiversity, furthering India’s expertise in polar research.
  • PAME: India’s commitment to sustainable development in the Arctic is reflected in its engagement with Arctic Council initiatives like the ‘Protection of the Arctic Marine Environment’ (PAME).

Way Forward – Potential for Collaboration:

  • Green Energy and Clean Industries: India’s current policy emphasizes cooperation with Arctic countries, particularly Norway, in green energy and clean industries. This aligns with India’s goal of positioning itself as a responsible stakeholder in global environmental initiatives.
  • Transformational Partnership: Collaboration with Norway could be transformative for India, offering opportunities for increased participation in Arctic Council working groups
  • Scientific Research and Environmental Protection: A partnership with Norway is expected to focus on scientific research, climate, and environmental protection. These areas align with India’s Arctic Policy pillars, emphasizing the importance of addressing environmental challenges through research and cooperation.

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Global Geological And Climatic Events

Mount Etna’s Volcanic Vortex Rings: A Rare Natural Phenomenon

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mt. Etna, Sisily, Stratovolcano, Volcanism, Vortex Rings

Mains level: NA

Mt. Etna

Why in the news?

Mount Etna, located on the east coast of Sicily in Italy recently gained attention for emitting circular rings of vapor from its summit, known as volcanic vortex rings.

About Mount Etna

  • Mount Etna is located on the east coast of Sicily, Italy.
  • It is an active stratovolcano, characterized by its conical shape formed by layers of hardened lava, ash, and volcanic rocks.
  • It is Europe’s tallest active volcano, standing at approximately 3,329 meters (10,922 feet) above sea level.
  • It is one of the most active volcanoes in the world and has been erupting for thousands of years, with the first recorded eruption dating back to around 1500 BCE.
  • Mount Etna and its surrounding area have been designated as a UNESCO World Heritage Site since 2013, recognizing its geological significance and natural beauty.
  • It boasts five craters responsible for eruptions, alongside numerous vents along its slopes.

What are Volcanic Vortex Rings?

  • Volcanic vortex rings are a rare phenomenon observed when gas, primarily water vapor, is rapidly released through a vent in the volcano’s crater, forming circular rings of smoke above the mountain.
  • This phenomenon, similar to smoke rings blown by cigarette smokers, occurs when gas is expelled through a nearly perfect circular vent in the crater.
  • These rings can rise in the air for up to 10 minutes but may disintegrate quickly under windy conditions.

Volcanism in Italy

  • The volcanism of Italy is due chiefly to the presence, a short distance to the south, of the boundary between the Eurasian Plate and the African Plate.
  • Italy is a volcanically active country, containing the only active volcanoes in mainland Europe (while volcanic islands are also present in Greece, in the volcanic arc of the southern Aegean).
  • The lava erupted by Italy’s volcanoes is thought to result from the subduction and melting of one plate below another.
  • Other active volcanoes include Mt. Stromboli and Vesuvius.

Historical and Recent Observations

  • Etna produces more vapor rings than any other volcano on Earth, making it a hotspot for studying this phenomenon.
  • The occurrence of volcanic vortex rings was first documented in 1724 at Mount Etna and Vesuvius in Italy, and has since been observed at various volcanoes worldwide.
  • Recent observations of this phenomenon have been reported at volcanoes in Alaska, Ecuador, Guatemala, Iceland, Italy, Japan, Vanuatu, New Zealand, and Nicaragua.

Recent Volcanic Eruptions in News:

Many of the world’s most active volcanoes are concentrated in the Pacific Ring of Fire, encompassing regions like New Zealand, Southeast Asia, Japan, and the western coast of the Americas. This volatile area also experiences about 90% of all earthquakes globally.

  • Kilauea, Hawaii: The Kilauea volcano in Hawaii captivated the world with a nearly nonstop eruption that began in 1983 and continued for an astonishing 35 years until 2018. Remarkably, it rekindled in 2021, with the eruption still ongoing.
  • Dukono, Indonesia: Erupting since August 1933, Dukono volcano in Indonesia stands as a testament to long-term volcanic activity, defying the passage of time.
  • Santa Maria, Guatemala: The eruption of Santa Maria in Guatemala commenced in June 1922 and persists to this day, underscoring the enduring nature of certain volcanic phenomena.
  • Yasur, Vanuatu: Yasur in Vanuatu first erupted around 1270 and has maintained its volcanic activity, continuing as of June 9, 2023.

Understanding Volcanoes

  • Volcanoes are geological features characterized by openings or vents through which lava, tephra (small rocks), and steam erupt onto the Earth’s surface.
  • They result from both their own eruptions and the broader processes of tectonic plate movement.
  • Volcanic eruptions are essentially the result of magma, or molten rock, beneath the Earth’s surface rising, bubbling, and ultimately overflowing, much like boiling milk spilling out of a pot on a stove.
  • The magma seeks pathways to vents within the volcano, where it erupts and is expelled across the land and into the atmosphere, a phenomenon referred to as lava.

Appearance Formation Eruption Style Notable Examples
Cinder Cones Small, steep, conical Formed from basaltic magma with high gas content Often explosive eruptions with cinders/scoria Paricutin (Mexico), Sunset Crater (USA)
Composite/Stratovolcanoes Tall and symmetrical Result from alternating layers of lava, ash, etc. Both explosive and effusive eruptions Mount St. Helens (USA), Mount Fuji (Japan)
Shield Volcanoes Broad and gently sloping Primarily formed from basaltic magma Primarily non-explosive with extensive lava flows Mauna Loa, Mauna Kea (Hawaii)
Lava Domes Rounded dome-like shape Formed from slow extrusion of viscous magma Typically non-explosive but can be dangerous Novarupta Dome (Alaska), Mount St. Helens’ Lava Dome (USA)

 

PYQ:

[2018] Consider the following statements:

1.    The Barren Island volcano is an active volcano located in the Indian Territory.

2.    Barren Island lies about 140 km east of Great Nicobar.

3.    The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3

(c) 3 only

(d) 1 and 3

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Global Geological And Climatic Events

In news: Total Solar Eclipse

Why in the news?

A rare Total Solar Eclipse will be visible across North America on April 8.

What are Eclipses?

  • Eclipses are astronomical events that occur when the sun, moon, and Earth align in specific ways.
  • There are two primary types of eclipses: solar and lunar.
  1. A solar eclipse happens when the moon comes between the sun and Earth during a new moon, blocking out the sun’s light.
  2. Conversely, a lunar eclipse occurs when the Earth is positioned between the sun and the moon during a full moon, casting a shadow on the moon.

What is a Total Solar Eclipse?

  • During a total solar eclipse, the moon passes between the sun and Earth, entirely covering the face of the sun along a small path of our planet’s surface.
  • This is called the “path of totality.”
  • The daytime sky turns dark, similar to dusk or dawn, and nocturnal animals have been known to wake up, confused into believing night has arrived.

Stages of a Total Solar Eclipse

A total solar eclipse unfolds in several distinct stages.

  1. It starts with a partial eclipse phase as the moon begins to pass between Earth and the sun, partially blocking it and leaving the sun looking like it has a crescent shape.
  2. In the subsequent Baily’s Beads phase, points of light from the sun shine around the moon’s edges because of the irregular lunar topography, producing small beads of light.
  3. In the diamond ring phase, a single bright spot appears along the lunar edge even as the sun’s atmosphere leaves a ring of light around the moon. This phenomenon precedes totality.
  4. After totality, the other phases repeat as the moon keeps moving along its path until the eclipse ends.

Other types of solar eclipses:

  1. Partial Solar Eclipse
  • This happens when the sun, moon and Earth are not exactly lined up.
  • The sun appears to have a dark shadow on only a small part of its surface.
  1. Annular Solar Eclipse
  • An annular eclipse happens when the moon is farthest from Earth. Because the moon is farther away from Earth, it seems smaller. It does not block the entire view of the sun. The moon in front of the sun looks like a dark disk on top of a larger sun-coloured disk. This creates what looks like a ring around the moon.
  • During a solar eclipse, the moon casts two shadows on Earth. The first shadow is called the Umbra. This shadow gets smaller as it reaches Earth. It is the dark centre of the moon’s shadow.
  • The second shadow is called the Penumbra. The penumbra gets larger as it reaches Earth. People standing in the penumbra will see a partial eclipse. People standing in the umbra will see a total eclipse.

Why don’t solar eclipses happen at every New Moon?

  • The reason is that the Moon’s orbit tilts 5° to Earth’s orbit around the Sun.
  • Astronomers call the two intersections of these paths nodes.
  • Eclipses only occur when the Sun lies at one node and the Moon is at its New (for solar eclipses) or Full (for lunar eclipses) phase.
  • During most (lunar) months, the Sun lies either above or below one of the nodes, and no eclipse happens.

PYQ:

2013:

Consider the following phenomena

1. Size of the sun at dusk

2. Colure of the sun at dawn

3. Moon being visible at dawn

4. Twinkle of stars in the sky

5. Polestar being visible in the sky

Which of the above are optical illusions?

(a) 1, 2 and 3

(b) 3, 4 and 5

(c) 1, 2 and 4

(d) 2, 3 and 5

 

Practice MCQ:

Which of the following statements best characterizes a Total Solar Eclipse?

(a) A total solar eclipse occurs when the Moon partially blocks the Sun, leaving a visible ring of sunlight around the Moon’s silhouette.

(b) During a total solar eclipse, the Moon completely covers the Sun, casting a shadow on a narrow path on the Earth’s surface called the umbra.

(c) Total solar eclipses occur more frequently than partial solar eclipses due to the precise alignment of the Sun, Earth, and Moon.

(d) Total solar eclipses can only be observed from specific locations on Earth, making them rare and highly sought-after astronomical events.

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Global Geological And Climatic Events

In news: Ramapo Fault

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Ramapo Fault, Appalachian Mountains

Mains level: NA

Why in the news?

  • An earthquake of magnitude 4.8 hit the New York City in a rare event.
  • The Ramapo Fault in Appalachian Mountains near New Jersey is a being considered as a reason behind this earthquake.

Appalachian Mountains

  • The Appalachian Mountains extend from the Canadian province of Newfoundland and Labrador in the north to central Alabama in the southern US.
  • The total length of the Appalachian Mountain range is approximately 2,200 miles (3,500 kilometers), making it one of the longest mountain chains in the world.
  • Geologically, it is one of the oldest mountain ranges on Earth, formed over 480 million years ago during the Ordovician Period. They are considered a Paleozoic mountain range.
  • They were formed through a series of tectonic collisions and uplift events, including the assembly of the supercontinent Pangaea.
  • The highest peak in the range is Mount Mitchell in North Carolina, standing at an elevation of 6,684 feet (2,037 meters) above sea level.
  • The Appalachian Mountains hold cultural significance for various indigenous tribes, including the Cherokee, as well as early European settlers who established communities in the region.

About Ramapo Fault

  • Fault lines are fractures in the Earth’s crust that facilitate movement of tectonic plates, triggering earthquakes.
  • The Ramapo Fault is resulted from tectonic activity associated with the breakup of the supercontinent Pangaea during the Mesozoic Era.
  • It is primarily a right-lateral strike-slip fault, formed by horizontal movement along the fault line due to the ongoing motion between the North American and Eurasian plates.
  • While the Ramapo Fault is not as seismically active as faults in other regions, it has experienced earthquakes in the past and remains a potential source of seismic hazards.

Geographical Distribution:

  • The fault extends across three states in the northeastern United States: Pennsylvania, New Jersey, and New York.
  • The fault crosses various topographic features, including rift valleys, hills, and ridges, reflecting the diverse geological history of the region.
  • It intersects with the Appalachian Mountains, influencing the overall topography of the surrounding areas.

PYQ:

[2012] When you travel in Himalayas, you will see the following:

1.    Deep gorges

2.    U-turn river courses

3.    Parallel mountain ranges

4.    Steep gradients causing land-sliding

Which of the above can be said to be the evidences for Himalayas being young fold mountains?

(a) 1 and 2 only

(b) 1, 2 and 4 only

(c) 3 and 4 only

(d) 1, 2, 3 and 4

 

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Global Geological And Climatic Events

Taiwan’s Earthquake and the Pacific Ring of Fire

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Pacific ‘Ring of Fire’

Mains level: NA

Why in the news?

  • Taiwan was struck by its most powerful earthquake in at least 25 years.
  • Its susceptibility to earthquakes is attributed to its location along the Pacific “Ring of Fire” where a majority of the world’s seismic activity occurs.
  • Taiwan is primarily influenced by the collision of the Philippine Sea Plate and the Eurasian Plate.

What is the Pacific ‘Ring of Fire’?

  • The Pacific ‘Ring of Fire’ or Pacific Rim, or the Circum-Pacific Belt, is an area along the Pacific Ocean that is characterized by active volcanoes and frequent earthquakes.
  • Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire.
  • It is home to about 75 per cent of the world’s volcanoes – more than 450 volcanoes.
  • Also, about 90 per cent of the world’s earthquakes occur here.

Its spread

  • Its length is over 40,000 kilometres and traces from New Zealand clockwise in an almost circular arc covering Tonga, Kermadec Islands, Indonesia.
  • It is moving up to the Philippines, Japan, and stretching eastward to the Aleutian Islands, then southward along the western coast of North America and South America.

Seismic activity of the region

  • The area is along several tectonic plates including the Pacific plate, Philippine Plate, Juan de Fuca plate, Cocos plate, Nazca plate, and North American plate.
  • The movement of these plates or tectonic activity makes the area witness abundant earthquakes and tsunamis every year.
  • Along much of the Ring, tectonic plates move towards each other creating subduction zones.
  • One plate gets pushed down or is subducted by the other plate.
  • This is a very slow process – a movement of just one or two inches per year.
  • As this subduction happens, rocks melt, become magma and move to Earth’s surface and cause volcanic activity.

PYQ:

2020: Discuss the geophysical characteristics of Circum-Pacific Zone.

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Global Geological And Climatic Events

Mother of Dragons Comet: A Rare Celestial Phenomenon

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mother of Dragons Comet, Its features

Mains level: NA

Why in the news?

  • The “Mother of Dragons” comet, officially named Comet 12P/Pons-Brooks, is making a rare appearance in the Northern Hemisphere skies.
  • This Halley-type comet, completing its orbit every 71 years, has emerged marking its first sighting since 1954.

What is a Comet?

 

  • A comet is a celestial object composed primarily of ice, dust, and rocky particles that orbit the Sun in elongated, elliptical paths.
  • These icy bodies originate from the outer regions of the solar system, specifically from two regions: the Kuiper Belt and the Oort Cloud.
  • Comets are often referred to as “dirty snowballs” or “icy dirtballs” due to their composition.
  • Halley’s Comet is a short-period comet visible from Earth every 75–79 years.
  • It was last seen in Earth’s skies in 1986 and was met in space by an international fleet of spacecraft. It will return in 2061 on its regular journey around the Sun.

 

About Mother of Dragons Comet

  • It is named by the European Space Agency (ESA).
  • The comet’s name is inspired by its link to the annual “kappa-Draconids” meteor shower, active from November 29 to December 13 each year.
  • It has a width of 17 km. the comet features an elliptical orbit adorned with a mysterious spiral of luminous light enveloping its icy nucleus.
  • It is comprised of ice, dust, rock, and diatomic carbon molecules.
  • It dissipates a radiant emerald hue when illuminated by the sun, captivating observers with its bright green appearance.

Display Features of the Comet

  • Renowned for its cryovolcanic eruptions, the comet periodically ejects material from its icy core into space, resulting in breath-taking luminosity.
  • Its most recent eruption in July 2023, after 69 years, earned it the moniker “devil comet” due to its dramatic outburst, resembling horns likely caused by internal features.

PYQ:

2014:

What is a coma, in the content of astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

 

Practice MCQ:

With reference to the “Mother of Dragons” Comet, consider the following statements:

1.    It is named by the NASA.

2.    It is comprised of ice, dust, rock, and diatomic carbon molecules.

3.    It makes appearances after every 10 years.

How many of the above statements is/are correct?

(a) One

(b) Two

(c) Three

(d) None

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Global Geological And Climatic Events

Negative Leap Second: Climate Change’s Impact on Timekeeping

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Leap Second, Leap Year, UTC, TAI

Mains level: NA

Why in the news?

  • A recent publication in the science journal Nature highlights how climate change-induced melting of glaciers and ice sheets is altering the Earth’s rotation, potentially disrupting our timekeeping systems.
  • Leap seconds were added almost every year between 1972 and 1999 to adjust for Earth’s slowing rotation. But there have only been four added in the last 23 years, and the last time a leap second was added was in 2016.

What is a Leap Second?

  • A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC) in order to synchronize atomic time with astronomical time, particularly with the Earth’s rotation.
  • The purpose of adding or subtracting a leap second is to keep International Atomic Time (IAT) (which is extremely precise) in close alignment with astronomical time, which is based on the Earth’s rotation and is subject to slight variations.

There are two types of leap seconds:

  1. Positive Leap Second:
    • A positive leap second is added to UTC when the Earth’s rotation slows down slightly, causing the length of a day to exceed 86,400 seconds.
    • This type of leap second is necessary to bring UTC back into alignment with the Earth’s rotational time.
    • Positive leap seconds are rare and occur less frequently than negative leap seconds.
  2. Negative Leap Second:
    • A negative leap second, also known as a deletion or removal of a second, occurs when the Earth’s rotation speeds up slightly, causing the length of a day to be less than 86,400 seconds.
    • Negative leap seconds are extremely rare and have only been proposed but never implemented. They are considered hypothetical and have not yet been needed to adjust UTC.
    • The concept of negative leap seconds is controversial and requires international agreement and coordination among timekeeping organizations.

International Atomic Time (TAI)

 

  • TAI is a high-precision time scale based on the weighted average of atomic clocks (usually involving caesium or rubidium atoms) from various laboratories around the world.
  • It is one of the primary time scales used for scientific and technical purposes, providing a continuous and uniform time reference that is independent of the Earth’s rotation.
  • TAI is maintained since 1958 by the International Bureau of Weights and Measures (BIPM) in Paris, France.
  • Unlike UTC, which is adjusted periodically to account for the Earth’s irregular rotation, TAI is a continuous time scale that does not include any corrections for Earth’s rotation.

 

How Climate Change causes Negative Leap Second?

  •  Glacial Melting: Accelerating melt rates in Greenland and Antarctica are redistributing weight across the planet, causing a slight deceleration in the Earth’s rotation.
  • Historical Context: Timekeepers have periodically added leap seconds to clocks worldwide to account for the Earth spinning faster than usual, with 27 instances recorded since the 1970s.
  • Planned Adjustment: The proposed “negative leap second” adjustment, scheduled for 2026, may be postponed until 2029 or later due to the recent deceleration in the Earth’s rotation.Top of Form

Practice MCQ:

What is a Leap Second?

(a) It is a periodic adjustment added to International Atomic Time (TAI) to compensate for irregularities in Earth’s rotation.

(b) It is an extra second added to Coordinated Universal Time (UTC) to synchronize atomic time with astronomical time.

(c) It is the time lag measured by the atomic clocks in Outer Space-Time conditions.

(d) It is a term used to describe the synchronization of atomic clocks with the oscillations of subatomic particles.

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Global Geological And Climatic Events

Subduction Zone discovered beneath Gibraltar Strait

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Gibraltar Strait, Tectonic Plate Boundaries, Subduction Zones

Mains level: Read the attached story

What is the news?

  • Scientists in Portugal have uncovered a concerning revelation about the fate of the Atlantic Ocean, highlighting a potential ‘Ring of Fire’ (a Subduction Zone).
  • Researchers caution that the Atlantic may be on the brink of closure due to subduction activity.

Why discuss this?

 

  • Closure of Gibraltar Strait: Computer simulations project the subduction zone’s expansion over the next 20 million years, forming the ‘Ring of Fire’ in the Atlantic leading to the closure of Gibraltar Strait.
  • Geological Parallel: This process mirrors the Pacific Ocean’s Ring of Fire, reshaping the ocean basin through gradual subduction of the ocean floor beneath continents.

 

About Gibraltar Strait

Details
Location
  • Connects the Atlantic Ocean to the Mediterranean Sea;
  • Separating the southern tip of the Iberian Peninsula of Europe from the northern coast of Africa.
Width Approximately 13 km (8.1 miles) at its narrowest point.
Depth Varies, with the deepest point reaching around 300 meters (984 feet).
Formation
  • Convergence point for the Eurasian Plate and the African Plate.
  • Formed around 5.33 million years ago during the Messinian salinity crisis when the Atlantic Ocean breached the barrier separating it from the Mediterranean Sea, resulting in a catastrophic flood known as the Zanclean flood.
  • The strait’s current shape and depth were further influenced by tectonic movements and erosional processes over geological time.
Historical Significance Serves as a key maritime passage for trade and military purposes.
Disputes
  • Subject of contention between Spain and the United Kingdom;
  • Gibraltar Overseas Territory under British control.

 

What are Subduction Zones?

  • Subduction zones occur at convergent plate boundaries, where two tectonic plates move toward each other.
  • This convergence is often between an oceanic plate and a continental plate or between two oceanic plates.
  • Subduction Process:
  1. Collision of Tectonic Plates: When two tectonic plates collide, the denser oceanic plate is forced beneath the less dense continental plate or another oceanic plate.
  2. Partial Melting: As the oceanic plate descends into the mantle, it generates intense heat and pressure, causing partial melting of the mantle material.
  3. Volcanic Activity: The molten material formed by the subduction process rises through the Earth’s crust, leading to volcanic eruptions at the surface.
  4. Formation of Volcanic Arcs: These eruptions often occur in chains known as volcanic arcs, which parallel the subduction zone. Ex. Andes in S. America; Cascade Range in North America.

Implications of this Activity

  • Earthquakes: Subduction zone earthquakes can be particularly destructive and may trigger tsunamis due to the displacement of large volumes of water.
  • Trench Formation: The surface expression of a subduction zone is often a deep oceanic trench, where the descending plate bends and plunges into the mantle.
  • Mountain Building: Over time, the continuous subduction of oceanic crust can lead to the uplift and deformation of the overriding plate, resulting in the formation of mountain ranges adjacent to the subduction zone. These mountains may exhibit complex geological structures, including folds and faults.
  • Recycling of Oceanic Crust: As oceanic plates are subducted, they are gradually consumed by the mantle, releasing minerals and elements that are eventually returned to the surface through volcanic activity.

PYQ:

2010: Which one of the following can one come across if one travels through the Strait of Malacca?

  1. Bali
  2. Brunei
  3. Java
  4. Singapore

 

2011: Between India and East Asia, the navigation time and distance can be greatly reduced by which of the following?

  1. Deepening the Malacca straits between Malaysia and Indonesia.
  2. Opening a new canal across the Kra Isthmus between the Gulf of Siam and Andaman sea.

Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2

 

Practice MCQ:

Which of the given statement about the Gibraltar Strait is NOT correct?

  1. It connects the Atlantic Ocean to the Mediterranean Sea.
  2. It is approximately 13 kilometers wide at its narrowest point.
  3. The deepest point of the Gibraltar Strait reaches around 300 meters.
  4. It was formed around 5.33 million years ago during the Holocene Epoch due to tectonic movements.

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Global Geological And Climatic Events

In news: Popocatepetl Volcano

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Popocatepetl Volcano

Mains level: NA

In the news

  • Popocatepetl, Mexico’s most dangerous active volcano has erupted 13 times in the past day, hurling columns of ash and smoke into the sky.

About Popocatepetl Volcano

  • Popocatepetl — which means “Smoking Mountain” in the Aztec Nahuatl language — is located in central Mexico roughly 72 km southeast of Mexico City.
  • Popocatepetl is situated in the eastern half of the Trans-Mexican Volcanic Belt, in Central Mexico.
  • It lies on the border between the states of Puebla and Morelos.
  • The summit of Popocatepetl stands at an elevation of about 5,426 meters above sea level, making it the second-highest peak in Mexico after Citlaltepetl (Pico de Orizaba).

Geological Details

  • Popocatepetl is a stratovolcano (composite volcano) characterized by its steep, conical shape built up by successive layers of volcanic ash, lava flows, and pyroclastic materials.
  • It is one of Mexico’s most active volcanoes, with documented eruptions dating back to the 14th century.
  • In the modern era, significant eruptions have occurred in 1947, 1994, 2000, 2005, and ongoing activity since 2013.
  • The volcano’s eruptions are primarily andesitic to dacitic in composition, characterized by the eruption of viscous lava flows and explosive eruptions producing ash clouds, pyroclastic flows, and lahars (mudflows).

Try this PYQ from CSE Mains 2021

Q. Mention the global occurrence of volcanic eruptions in 2021 and their impact on regional environment.

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Global Geological And Climatic Events

Scientists vote down Declaration of Anthropocene Epoch

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Geological Time Scale, Anthropocene Epoch

Mains level: Human Determinism and Geological Time Scale

In the news

  • The proposal to declare the start of the Anthropocene Epoch, signifying the impact of human activity on Earth’s geological history, has sparked debate among scientists.
  • Despite mounting evidence of human-induced changes to the planet, a recent vote by a scientific committee has rejected the notion.

Understanding Geological Time

  • Geologic Time Scale: Geoscientists use the Geologic Time Scale (GTS) to measure Earth’s history, categorizing it into aeons, eras, periods, epochs, and ages.
  • Chronostratigraphic Classification: The GTS is based on chronostratigraphic units, marked by significant geological events, shaping the planet’s conditions.

The Proposed ‘Human Epoch’

  • Holocene Epoch: The Holocene began approximately 11,700 years ago, following the Last Glacial Period, coinciding with the rise of human civilization.
  • Anthropocene Proposal: The Anthropocene concept suggests that human activities have altered Earth significantly, warranting recognition as a distinct geological epoch.

Understanding the Anthropocene Epoch

  • Coined Term: The Anthropocene epoch was first coined by Nobel Prize-winning chemist Paul Crutzen and biology professor Eugene Stoermer in 2000.
  • Human Impact: The Anthropocene represents the geological time interval characterized by radical changes in the Earth’s ecosystem due to human impact, particularly since the onset of the Industrial Revolution.
  • Environmental Changes: Numerous phenomena associated with the Anthropocene include global warming, sea-level rise, ocean acidification, mass-scale soil erosion, deadly heat waves, and environmental deterioration.
  • Geological Strata: The AWG’s website states that these changes are reflected in a distinctive body of geological strata, with the potential to be preserved into the far future.

Rejection of the Proposal

  • Scientific Deliberations: Despite the Anthropocene Working Group’s proposal, the Subcommission on Quaternary Stratigraphy voted against declaring the Anthropocene epoch.
  • Criticism and Concerns: Critics argue against defining the Anthropocene based on recent events, questioning the significance of the proposed start date and the boundary between epochs.

Geological Implications

  • Definition of Epochs: The rejection highlights the challenge of defining geological epochs based on human-induced changes, given the traditional criteria for epoch delineation.
  • Permanence and Recognition: While the vote does not negate human impact on the planet, it raises questions about the formal recognition of the Anthropocene as a distinct epoch.

Future of the Anthropocene Concept

  • Beyond Epochs: Some scientists propose viewing the Anthropocene as an “event” rather than a formal epoch, acknowledging its transformative nature without conforming to traditional geological classifications.
  • Relevance and Recognition: Regardless of formal classification, the concept of the Anthropocene underscores the profound impact of human activity on Earth’s systems, shaping discussions on environmental stewardship and sustainability.

Back2Basics: Geological Time Scale

  • The Geological Time Scale is a system used by geologists and palaeontologists to divide Earth’s history into distinct time intervals based on significant geological and biological events.
  • It provides a framework for organizing and understanding the vast expanse of time since the formation of the Earth, approximately 4.6 billion years ago, up to the present day.
  • The Scale is divided into several hierarchical units, including eons, eras, periods, epochs, and ages.

Here is a simplified overview of the major divisions:

(1) Eon: The largest division of time on the Geological Time Scale. The history of Earth is typically divided into four eons:

  • Hadean Eon: Represents the earliest stage of Earth’s history, from its formation to around 4 billion years ago.
  • Archean Eon: Covers the period from around 4 billion to 2.5 billion years ago. It includes the formation of the Earth’s crust, the emergence of life, and the development of the first continents.
  • Proterozoic Eon: Encompasses the time between 2.5 billion and 541 million years ago. It includes significant evolutionary developments, such as the emergence of complex multicellular life.
  • Phanerozoic Eon: The current eon, spanning from 541 million years ago to the present. It is further divided into eras.

(2) Era: The second-largest division of time, encompassing longer periods of geological history within an eon. The Phanerozoic Eon is divided into three eras:

  • Paleozoic Era: Covers the time from 541 million to 252 million years ago. It is known for the diversification of life, including the appearance of complex marine organisms, fish, insects, and the first terrestrial plants.
  • Mesozoic Era: Spans from 252 million to 66 million years ago. It is often referred to as the “Age of Reptiles” and includes the dominance of dinosaurs, as well as the rise of mammals and birds.
  • Cenozoic Era: Extends from 66 million years ago to the present. It is sometimes called the “Age of Mammals” and includes the diversification and proliferation of mammals, the appearance of humans, and the development of modern ecosystems.

(3) Period: A subdivision of an era, representing a distinct interval of time characterized by specific geological and biological events. For example:

  • The Paleozoic Era is divided into periods such as the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
  • The Mesozoic Era is divided into periods including the Triassic, Jurassic, and Cretaceous.
  • The Cenozoic Era is divided into periods such as the Paleogene, Neogene, and Quaternary.

(4) Epoch: A smaller subdivision of a period, representing a shorter interval of time. Epochs are defined by more localized geological and biological changes.

(5) Age: The smallest division of time on the Geological Time Scale. Ages represent relatively brief periods, often defined by specific fossil or rock layers.

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Global Geological And Climatic Events

Singhbhum Craton: Insights from the Archaean Age

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Singhbhum Craton, Archaen Eon

Mains level: NA

Why in the News?

  • Some recent study about the Singhbhum Craton in India, reveals that explosive volcanic eruptions were frequent around 3.5 billion years ago in regions that are also present in South Africa, and Australia.

What are Cratons?

  • Cratons are stable, ancient portions of the continental lithosphere, consisting of Earth’s two topmost layers—the crust and the uppermost mantle.
  • Cratons are typically found in the interiors of tectonic plates and are characterized by their ancient crystalline basement rock, often dating back to the Archean Eon.
  • Mantle plume events have played a significant role in the evolution of cratons.

About Singhbhum Craton:

  • The Singhbhum Craton is a geological region in India.
  • Location: It is located in eastern India, covering parts of the states of Jharkhand, Odisha, and West Bengal. The craton is separated from the Bastar Craton by the Mahanadi Graben and is in the vicinity of two Proterozoic mobile belts: the Satpura Mobile Belt and the Eastern Ghat Mobile Belt.
  • Geological features:
    • The rocks in the Singhbhum Craton are predominantly of Archean age, ranging from Paleoarchean to Paleoproterozoic.
    • It is a part of the larger Indian Shield, which is a stable continental crust that formed during the Archean Eon.
    • The Singhbhum Craton is known for its abundant occurrences of Banded Iron Formations (BIFs), which are closely associated with basic volcanic and ultrabasic intrusive. The craton is also known for its iron ore deposits, which are found in the Iron Ore Group (IOG) and are closely associated with lavas and tuffs.
    • The Singhbhum Craton has undergone regional metamorphism of the amphibolite facies and is believed to have evolved as a consequence of multiple phases of compressive deformation.
    • The craton is made up of multiple pulses of discrete mantle plume events, resulting in a complex geological history.

Archaean Eon

  • The Archaean Eon, one of the two formal divisions of Precambrian time, began about 4 billion years ago and extended to the start of the Proterozoic Eon.
  • During this period, life on Earth was limited to simple single-celled organisms lacking nuclei, known as Prokaryota.
  • The atmosphere lacked oxygen, and the Earth’s crust had cooled enough to allow the formation of continents.
  • Volcanic activity was considerably higher than today, with numerous lava eruptions.
  • The oldest rock formations exposed on Earth are from the Archaean Eon.
  • The Archaean rock system includes Archaean Gneisses and Schists, which are the oldest metamorphosed rocks found in abundance in regions like the Dharwar district of Karnataka.

What are the recent key findings?

  • Submarine Mafic Volcanism: The prevalence of submarine mafic volcanic eruptions between 3.5 and 3.3 billion years ago is documented, enriching our understanding of ancient volcanic and sedimentary processes.
  • Geodynamic Insights: Comparative analysis enhances our comprehension of early Earth tectonic activities and surface/atmospheric processes during the Archaean.

Research Methodology Used:

  • Field Studies and Radiometric Dating: Detailed field-based studies coupled with uranium-lead radiometric-age dating were employed to establish geological timelines and understand magma crystallization.
  • Comparative Analysis: The geological similarities between the Singhbhum Craton and counterparts in South Africa and Australia were studied, focusing on volcanic eruption patterns.

Implications and Significance of the study:

  • Earth’s Formative Years: Insights into Earth’s early tectonic activities contribute significantly to understanding the planet’s formative years.
  • Habitable Conditions: Unique geological features, such as greenstone belts, provide invaluable information about early habitable conditions and the emergence of life.
  • Global Geodynamic Processes: Comparative studies across cratons worldwide facilitate the construction of comprehensive models elucidating ancient geodynamic processes prevalent during the Archaean.

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Global Geological And Climatic Events

What is Humboldt’s Enigma and What does it mean for India?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Humboldt's Enigma

Mains level: NA

Humboldt’s Enigma

Introduction

  • The question of where biodiversity is concentrated has intrigued explorers and naturalists for centuries. Humboldt has tried to answer this question.

Humboldt’s Insights

  • Alexander von Humboldt: A polymath of the 18th century, Humboldt recorded diverse natural observations, proposing a relationship between temperature, altitude, humidity, and species distribution.
  • Mountain Exploration: During his exploration of South America, Humboldt studied plant distribution on mountains, noting variations with elevation.
  • Chimborazo Mountain: Humboldt used Chimborazo Mountain in Ecuador as an example, illustrating the concept of mountain diversity.

What is Humboldt’s Enigma?

  • Sun’s Energy: Tropical areas receive more solar energy, fostering greater primary productivity and biodiversity due to the availability of ecological niches.
  • Mountain Exception: Mountains, despite being outside the tropics, have been an exception to the rule, posing Humboldt’s enigma.

Biodiversity Drivers

  • Earth’s History, Geography, and Climate: These factors are the primary drivers of mountain diversity.
  • Geological Processes: Mountains serve as ‘cradles’ for new species due to geological processes like uplifts, creating new habitats.
  • Climatic Stability: Climatologically stable mountains act as ‘museums,’ preserving species over time.
  • Coastal Tropical Sky Islands: Examples like the Shola Sky Islands in the Western Ghats exhibit both cradle and museum characteristics.

Eastern Himalaya: An Anomaly

  • Diversity Beyond Tropics: Eastern Himalaya boasts exceptional diversity, challenging the conventional tropical biodiversity paradigm.
  • Multiple Factors: Climate dissimilarity and geological heterogeneity contribute to high biodiversity.
  • Climate Variability: Different temperature and rainfall levels on the same mountain support diverse biomes.

Unresolved Questions

  • Complexity of Biodiversity: Numerous factors drive diversification and Humboldt’s enigma in different regions, leading to over a hundred hypotheses.
  • Data Limitations: Fine-scale species occurrence data are lacking, hindering precise explanations.
  • Call for Research: India’s under-studied areas need more extensive research, including the use of genetics, to understand true biodiversity.
  • National Initiatives: Programs like the National Mission on Himalayan Studies and Biodiversity need strengthening to support basic research.

Conclusion

  • Humboldt’s enigma represents one facet of mountain biodiversity, offering opportunities for study and insights into global climate and landscape change issues.

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Global Geological And Climatic Events

Earthquake and Tsunami strikes Central Japan

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Earthquakes in Japan

Mains level: Read the attached story

japan

Central Idea

  • On January 1, 2024, a 7.5-magnitude earthquake hit Ishikawa prefecture in Japan, triggering tsunami waves over a meter high.

Japan’s Geographical Vulnerability

  • Japan’s geographical vulnerability, particularly concerning plate tectonics, is a critical aspect of its environmental and disaster management challenges.
  • The country’s location at the convergence of several major tectonic plates makes it highly susceptible to seismic activities.

Here’s a detailed look at how plate tectonics contribute to Japan’s geographical vulnerability:

[1] Convergent Plate Boundaries:

  • Pacific Ring of Fire: Japan is located on the Pacific Ring of Fire, an area with a high level of seismic activity due to the presence of numerous tectonic plate boundaries.
  • Plates Involved: The primary tectonic plates interacting near Japan are the Pacific Plate, the Philippine Sea Plate, the Eurasian Plate, and the North American Plate.
  • Subduction Zones: The Pacific and Philippine Sea plates are subducting beneath the Eurasian and North American plates. This subduction process is a significant source of seismic activity, including powerful earthquakes and volcanic eruptions.

[2] Earthquake Activity:

  • Frequent Earthquakes: The movement of these plates results in frequent earthquakes. Japan experiences thousands of tremors annually, ranging from minor to catastrophic.
  • Major Earthquakes: Historical events like the 2011 Great East Japan Earthquake and the 1995 Great Hanshin Earthquake demonstrate the potential for massive destruction and loss of life due to Japan’s tectonic setting.

[3] Tsunami Risk:

  • Generation of Tsunamis: Earthquakes occurring under the sea or along the coast can displace large volumes of water, leading to tsunamis. The 2011 tsunami, triggered by a massive undersea earthquake, caused widespread devastation and the Fukushima nuclear disaster.
  • Coastal Impact: Japan’s extensive coastline makes it particularly vulnerable to tsunamis, which can arrive within minutes of an undersea earthquake, leaving little time for evacuation.

[4] Volcanic Activity:

  • Volcanic Eruptions: The subduction of the Pacific and Philippine Sea plates not only causes earthquakes but also contributes to significant volcanic activity. Magma generated by the melting of the subducted plate rises to the surface, leading to volcanic eruptions.
  • Active Volcanoes: Japan has over 100 active volcanoes, a direct result of its tectonic setting. Eruptions pose risks to nearby populations and can disrupt air travel and local economies.

[5] Geological Complexity:

  • Intersecting Faults: The interaction of multiple tectonic plates creates a complex network of faults, increasing the unpredictability and variability of seismic events.
  • Diverse Seismic Phenomena: This complexity leads to a range of seismic phenomena, including deep-focus earthquakes, which occur at greater depths and can affect broader areas.

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Global Geological And Climatic Events

Private: Leap Years: Their Significance and Calculation

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Leap Year

Mains level: NA

Leap year

Central Idea

  • 2024 is a leap year, which occurs every four years, adding an extra day to the calendar.
  • This means that February 2024 will consist of 29 days instead of the usual 28 days.

What is a Leap Year?

  • Definition: A leap year has 366 days, one more than the usual 365 days, with the additional day added to February.
  • Purpose: The extra day compensates for the additional time the Earth takes to complete its orbit around the Sun.

Reason for Leap Year Introduction

  • Astronomical Basis: The Earth takes approximately 365 days, 5 hours, 48 minutes, and 46 seconds to orbit the Sun.
  • Time Adjustment: To align with this duration, an extra day is added every four years, rounding up the additional time to about six hours annually.

Historical Background

  • Julian Calendar: Introduced in 46 BC by scholars under Julius Caesar, the Julian calendar first implemented the leap year concept.
  • Gregorian Calendar Reform: In 1582, Pope Gregory XIII reformed the calendar by skipping 10 days to correct accumulated discrepancies.

Leap Year Calculation

  • Gregorian Calendar Rules: The leap year does not occur every four years precisely. Years ending in 00 are generally not leap years unless divisible by 400.
  • Examples: The year 1900 was not a leap year, but 2000 was, following this rule.

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Global Geological And Climatic Events

What are Polar Stratospheric Clouds (PSCs)?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Polar Stratospheric Clouds

Mains level: NA

Polar Stratospheric Clouds (PSCs)

Central Idea

  • Residents in the Arctic have witnessed an extraordinary atmospheric display of Polar Stratospheric Clouds (PSCs).

Polar Stratospheric Clouds (PSCs)

Details
Formation and Location Form in the polar stratosphere at altitudes of 15,000–25,000 meters; common over Antarctica and the Arctic.
Temperature Conditions Require extremely cold temperatures, typically below −78°C (−108°F).
Types Type I: Composed of water and nitric acid.

Type II: Made almost entirely of water ice.

Role in Ozone Depletion Facilitate chemical reactions that produce chlorine and bromine compounds, leading to ozone destruction.
Appearance Iridescent, shimmering pastel colors, leading to their nickname “nacreous” or “mother-of-pearl” clouds.
Observation Visible during twilight, illuminated from below by the Sun.
Research and Monitoring Studied for impact on ozone depletion and climate change; monitored via satellites and ground stations.
Environmental Concern Linked to human-made chemicals like CFCs; subject to international regulation like the Montreal Protocol.
Climate Change Connection Research ongoing into how climate change might affect PSCs’ frequency and distribution.
Discovery and Study History Observed since the 19th century; their role in ozone depletion understood in the 1980s.

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Global Geological And Climatic Events

Volcanic Eruption in Iceland

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Eyjafjallajokull Eruption

Mains level: Read the attached story

Iceland

Central Idea

  • A volcanic eruption occurred near Iceland’s capital between Sýlingarfell and Hagafell, near the town of Grindavik on the Reykjanes Peninsula.

Iceland: ‘Land of Fire and Ice’

  • Geographical Location: Iceland is situated just south of the Arctic Circle in the North Atlantic Ocean.
  • Tectonic Setting: The country lies on the Mid-Atlantic Ridge, marking the boundary between the North American and Eurasian tectonic plates.
  • Unique Landscape: Iceland’s landscape features geysers, glaciers, mountains, volcanoes, and lava fields, housing 33 active volcanoes – the highest number in Europe.
  • Historical Settlement: The first human settlement in Iceland dates back to 874 by Norsemen from Scandinavia, leading to the founding of Reykjavik.

Recent Volcanic Activity on the Reykjanes Peninsula

  • Historical Dormancy: The Reykjanes Peninsula had not experienced volcanic eruptions for 800 years until recently.
  • Recent Eruptions: The current eruption is the fourth in less than three years on the peninsula, indicating a potential new era of volcanic activity.
  • Eyjafjallajokull Eruption: The last major volcanic event in Iceland that gained global attention was the 2010 eruption of Eyjafjallajokull.
  • Eruption Timeline and Impact: The volcano erupted twice in March and April 2010, spreading an ash cloud across continents and disrupting air traffic on the North Atlantic route for six days – the longest disruption since World War II.

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Global Geological And Climatic Events

Places in news: Mount Merapi

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Merapi Volcano

Mains level: Pacific ring of fire

volcano

Central Idea

  • Mount Merapi in Indonesia has erupted yet again this year, spewing an ash tower 3,000 metres into the sky.

 

Merapi Volcano: A Brief Overview

  • Location: Situated in Central Java, Indonesia, Merapi is aptly named “Mountain of Fire” in Javanese.
  • Activity: It ranks among the world’s most active and perilous volcanoes, known for frequent and often violent eruptions.
  • 2010 Eruption: The last significant eruption in 2010 led to over 350 fatalities and extensive damage to surrounding areas.
  • Tourist Attraction: Despite its dangers, Merapi attracts hikers and tourists drawn to its beauty and geological significance.

Other active volcanoes in Indonesia

volcano

Indonesia is home to many active volcanoes, with over 120 active volcanoes located across the country. Some of the other major volcanoes in Indonesia include:

  • Mount Krakatoa: Located in the Sunda Strait, it’s notorious for the catastrophic 1883 eruption.
  • Mount Rinjani: On Lombok Island, it’s Indonesia’s second-highest volcano and a trekking hotspot.
  • Mount Tambora: Famous for the 1815 eruption, it caused the “year without summer” and is situated on Sumbawa Island.
  • Mount Batur: In Bali, known for scenic vistas and hot springs.
  • Mount Merbabu: The highest in Central Java, it’s a favored destination for climbers.

Why so many volcanoes in Indonesia?

  • Pacific Ring of Fire: Indonesia’s location on this seismic hotspot explains its high volcanic activity.
  • Volcanic Density: With over 120 active volcanoes, Indonesia faces frequent eruptions, posing risks to its population and infrastructure.

Back2Basics: Pacific Ring of Fire

  • Geographical Span: This 40,000 km horseshoe-shaped belt around the Pacific Ocean is a seismic hub.
  • Volcanic and Seismic Activity: Home to 75% of the world’s active volcanoes and 90% of earthquakes.
  • Tectonic Movements: The Pacific Plate’s collision with smaller plates leads to subduction, causing friction and pressure.
  • Resulting Phenomena: This tectonic activity results in frequent volcanic eruptions and earthquakes.
  • Countries Included: The Ring of Fire affects several regions, including Japan, Indonesia, the Philippines, Papua New Guinea, New Zealand, and the Americas’ west coasts.
  • Natural Resources: The region is rich in geothermal energy and minerals.

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Global Geological And Climatic Events

Cyclone Michaung makes landfall

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Cyclone Michaung

Mains level: Not Much

Central Idea

  • Cyclone Michaung (name suggested by Myanmar) makes landfall in Tamil Nadu and Andhra Pradesh.
  • Michaung is the fourth tropical cyclone over the Bay of Bengal this year.

About Cyclone Michaung

  • Uncommon Intensity: December cyclones in the North Indian Ocean typically do not reach high intensities. Michaung, with its severe storm classification, is an exception.
  • Upgraded Intensity: Initially predicted as a tropical cyclone, IMD upgraded Michaung to a ‘severe’ storm due to its unexpected intensification.
  • Heat Index Contribution: The intensification is attributed to the above-normal heat index values off the southern Andhra Pradesh coast.

Indian Tropical Storms: An Overview

  • Annual Cyclones: The North Indian Ocean basin averages about five cyclones per year, predominantly in the Bay of Bengal.
  • Arabian Sea Cyclones: Though less frequent, Arabian Sea cyclones often reach higher intensities and can cause extensive damage.
  • Peak Cyclone Seasons: Cyclones are most common during pre-monsoon (April-June) and post-monsoon (October-December) months, with May and November seeing more intense storms.

Factors Influencing Storm Intensification

  • Ocean Heat: Cyclones draw energy from warm ocean temperatures, typically around 26 degrees Celsius or higher.
  • Tropical Cyclone Heat Potential (TCHP): This oceanographic parameter is crucial in cyclone genesis and intensification.
  • Complex Atmospheric Conditions: Various atmospheric factors like wind shear, convection, and air-sea interactions also play a role in cyclone development.
  • Coriolis Effect: This effect influences cyclone formation in the northern hemisphere, causing air to move anticlockwise in low-pressure areas.

Back2Basics: Extratropical and Tropical Cyclones

  • General Definition: Cyclones are large-scale air systems rotating around a low-pressure center, often accompanied by violent storms.
  • Extratropical Cyclones: Found outside the tropics, these cyclones have a cold core and gain energy from interactions between cold and warm air masses. They can form over both land and sea.
  • Tropical Cyclones: These form in tropical regions and are powered by the condensation of water vapor. They lack associated warm or cold fronts and are known as hurricanes or typhoons in different regions.

Cyclone Naming Process

  • Rotational Basis for Naming: The naming of cyclones is done by countries on a rotational basis, following certain existing guidelines.
  • Responsibilities of RSMCs and TCWCs: Worldwide, there are six regional specialized meteorological centers (RSMCs) and five regional Tropical Cyclone Warning Centers (TCWCs) mandated for issuing advisories and naming of tropical cyclones.
  • IMD’s Role: IMD is one of the six RSMCs providing tropical cyclone and storm surge advisories to 13 member countries under the WMO/Economic and Social Commission for Asia-Pacific (ESCAP) Panel.
  • Naming Authority of IMD: RSMC, New Delhi, is also mandated to name the tropical cyclones developing over the north Indian Ocean, including the Bay of Bengal and the Arabian Sea.
  • Guidelines for Naming: Some rules are to be followed while naming cyclones, such as being neutral to politics, religious beliefs, cultures, and gender, avoiding offensive or cruel names, and keeping the name short and easy to pronounce.
  • Future Naming: After ‘Michaung’, the next cyclone as per India’s suggestion will be named ‘Tej’.

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Global Geological And Climatic Events

Southern Annular Mode (SAM) and Indian Ocean Weather Conditions

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Southern Annular Mode (SAM)

Mains level: NA

Southern Annular Mode

Central Idea

  • The Indian National Centre for Ocean Information Services (INCOIS), a division under the Ministry of Earth Sciences (MoES), has made a significant discovery regarding the Southern Annular Mode (SAM), a crucial climate pattern.
  • Their research has revealed that SAM plays a pivotal role in influencing sea conditions across the Indian Ocean.

What is Southern Annular Mode (SAM)?

Description

Idea behind
  • Mode of atmospheric variability representing north-south movement of the westerly wind belt around Antarctica.
  • Also known as Antarctic Oscillation (AAO).
Phases
  1. Positive Phase: Wind belt contracts towards Antarctica.
  2. Negative Phase: Wind belt expands towards the equator.
Impact on Weather Patterns
  • Influences temperature, rainfall, and storm intensity in the Southern Hemisphere.
  • Causes difference in the zonal mean sea level pressure at 40°S (mid-latitudes) and 65°S (Antarctica).
Influence on Indian Ocean Affects ocean currents and sea surface temperatures, impacting regional weather and marine life.
Climate Change Connection Trend towards more positive phases in recent decades, influenced by human-induced climate change.
Effect on Antarctic Ice Impacts Antarctic ice sheets and sea ice extent through changes in wind patterns.
Global Climate Interaction Interacts with other climate phenomena like ENSO.
Predictability and Variability Exhibits seasonal predictability and interannual variability, important for long-term forecasting.
Marine Ecosystems Affects marine ecosystems in the Southern Ocean, influencing productivity and species distribution.

Role of Ocean Surface Waves

  • Coastal Processes: Ocean surface waves are key players in shaping coastal processes, impacting shoreline erosion, sediment transport, coastal engineering, and recreational activities.
  • Scientific Approach: The scientific team leveraged 40 years of data (1979 to 2018) from the European Centre for Medium-Range Weather Forecast.

Positive and Negative SAM Phases

  • Positive SAM Phase: During a positive SAM phase, a cyclic pattern of warm sea surface temperature anomalies emerges, accompanied by strong winds that increase wave activity in the Indian Ocean. A new swell generation region along the east African coast contributes to heightened wave heights in the Arabian Sea.
  • Negative SAM Phase: Conversely, during a negative SAM phase, the eastern tropical southern Indian Ocean becomes the primary region for generating swells, resulting in reduced wave heights in the Arabian Sea.

Significance of SAM

  • Coastal Planning: Understanding SAM allows for better coastal planning, helping coastal communities prepare for the impact of changing sea conditions.
  • Resource Management: SAM insights can aid in more efficient resource management, optimizing the utilization of marine resources.
  • Disaster Preparedness: Knowledge of SAM patterns can enhance disaster preparedness efforts, enabling timely response to potential ocean-related disasters.
  • Wave Predictions: The research contributes to improving wave predictions, offering advanced forecasting capabilities.
  • Benefiting Stakeholders: Stakeholders in the blue economy, including shipping, maritime boards, and the oil industry, can optimize their multi-million-dollar operations at sea based on SAM insights.

Implications for Various Sectors

  • Monsoon Season Impact: Typically, inland vessel operations and oil exploration activities face restrictions during the monsoon season.
  • Fair Sea State Windows: Predicting SAM phases through the Ocean Forecasting System can identify “Fair Sea state windows” during monsoons.
  • Impact on Blue Economy: These fair windows can be leveraged by oil and shipping industries, making a significant contribution to blue economy activities along the Indian coast

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Global Geological And Climatic Events

Understanding Eclipses: Why they don’t happen every Month

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Eclipses

Mains level: Read the attached story

Eclipse

Central Idea

  • While Eclipses are intriguing, one might wonder why eclipses do not occur with every new and full moon.

What are Eclipses?

  • Eclipses are astronomical events that occur when the sun, moon, and Earth align in specific ways.
  • There are two primary types of eclipses: solar and lunar.
  • A solar eclipse happens when the moon comes between the sun and Earth during a new moon, blocking out the sun’s light.
  • Conversely, a lunar eclipse occurs when the Earth is positioned between the sun and the moon during a full moon, casting a shadow on the moon.

Visit this page to read more about Eclipses:

What are Eclipses?

Why is there no eclipse every full and new moon?

Ans. Moon’s Unique Orbit

  • Moon’s Path: The moon orbits around Earth, completing one orbit roughly every month.
  • Ecliptic Plane: In an ideal scenario, if the moon’s orbit matched Earth’s orbital plane, called the ecliptic, we would witness a solar eclipse during every new moon and a lunar eclipse during every full moon.
  • Moon’s Inclination: However, the moon’s orbit is inclined at an angle of about 5 degrees to Earth’s orbital plane, causing irregular eclipse patterns.

Role of Lunar Nodes

  • Lunar Nodes: The moon’s orbit intersects Earth’s orbital plane at specific points known as nodes, categorized as ascending or descending nodes depending on the moon’s orbital direction.
  • Eclipse Occurrence: Eclipses happen when a full or new moon closely aligns with one of these nodes, ensuring the sun, moon, and Earth are in alignment.

Eclipse Pairs and Seasons

  • Eclipse Pairs: Solar and lunar eclipses typically occur in pairs, with one following the other within a two-week period.
  • Eclipse Seasons: Eclipse seasons, lasting around 34 to 35 days, usually feature two eclipses – one solar and one lunar. Occasionally, three eclipses may occur in a single season.
  • Frequency: Contrary to common perception, there are more eclipses than expected, with the 21st century witnessing 224 solar eclipses and 230 lunar eclipses.

Understanding the Lunar Nodes and Eclipses

  • Eclipse Seasons: Eclipse seasons take place approximately every 173 days when the lunar nodes precisely align with the Earth and the sun.
  • Moon’s Progression: The moon’s phases shift about 30 degrees along the zodiac every month concerning the nodes.
  • Future Eclipses: After a pair of eclipses, the next pair usually occurs nearly 6 calendar months later.

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Global Geological And Climatic Events

Mount Etna in Italy erupts

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mount Etna

Mains level: NA

etna

Central Idea

  • Volcanic eruptions often make headlines only when iconic volcanoes like Etna, Kilauea, or Eyjafjallajokull erupt.
  • However, throughout any given year, our planet witnessed numerous volcanic eruptions, with as many as 50 to 80 occurring worldwide.

About Mount Etna

  • Mount Etna, located in Italy, holds the title of Europe’s most active volcano and ranks among the world’s largest.
  • Its recorded volcanic activity dates back to 1500 B.C., with over 200 eruptions documented since then.
  • Etna’s recent eruptions have disrupted air travel, leading to flight cancellations at the nearby Catania airport.
  • Additionally, the accumulation of volcanic ash on roads prompted authorities to temporarily ban the use of cars and motorbikes due to safety concerns.

Volcanic Eruptions this Year

Many of the world’s most active volcanoes are concentrated in the Pacific Ring of Fire, encompassing regions like New Zealand, Southeast Asia, Japan, and the western coast of the Americas. This volatile area also experiences about 90% of all earthquakes globally.

  • Kilauea, Hawaii: The Kilauea volcano in Hawaii captivated the world with a nearly nonstop eruption that began in 1983 and continued for an astonishing 35 years until 2018. Remarkably, it rekindled in 2021, with the eruption still ongoing.
  • Dukono, Indonesia: Erupting since August 1933, Dukono volcano in Indonesia stands as a testament to long-term volcanic activity, defying the passage of time.
  • Santa Maria, Guatemala: The eruption of Santa Maria in Guatemala commenced in June 1922 and persists to this day, underscoring the enduring nature of certain volcanic phenomena.
  • Yasur, Vanuatu: Yasur in Vanuatu first erupted around 1270 and has maintained its volcanic activity, continuing as of June 9, 2023.

Understanding Volcanoes

  • Volcanoes are geological features characterized by openings or vents through which lava, tephra (small rocks), and steam erupt onto the Earth’s surface.
  • They result from both their own eruptions and the broader processes of tectonic plate movement.
  • Volcanic eruptions are essentially the result of magma, or molten rock, beneath the Earth’s surface rising, bubbling, and ultimately overflowing, much like boiling milk spilling out of a pot on a stove.
  • The magma seeks pathways to vents within the volcano, where it erupts and is expelled across the land and into the atmosphere, a phenomenon referred to as lava.

Types of Volcanoes

Appearance Formation Eruption Style Notable Examples
Cinder Cones Small, steep, conical Formed from basaltic magma with high gas content Often explosive eruptions with cinders/scoria Paricutin (Mexico), Sunset Crater (USA)
Composite/Stratovolcanoes Tall and symmetrical Result from alternating layers of lava, ash, etc. Both explosive and effusive eruptions Mount St. Helens (USA), Mount Fuji (Japan)
Shield Volcanoes Broad and gently sloping Primarily formed from basaltic magma Primarily non-explosive with extensive lava flows Mauna Loa, Mauna Kea (Hawaii)
Lava Domes Rounded dome-like shape Formed from slow extrusion of viscous magma Typically non-explosive but can be dangerous Novarupta Dome (Alaska), Mount St. Helens’ Lava Dome (USA)

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Global Geological And Climatic Events

Unraveling the Mystery of Ball Lightning

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Ball Lightning

Mains level: NA

Ball Lightning

Central Idea

  • Ball lightning, an intriguing natural phenomenon characterized by luminous spherical objects appearing during thunderstorms, has intrigued observers for generations.
  • They are sometimes accompanied by hissing sounds and unusual odors, adding to the mystery surrounding their origin and behavior.

Understanding Lightning and Ball Lightning

  • Normal lightning: Lightning is a natural electrical discharge that occurs due to differences in electrical charges within clouds or between clouds and the Earth’s surface during storms.
  • Ball Lightning: Ball lightning has been documented in historical records, with instances dating back to 1638 when a “great ball of fire” entered an English church through a window, hinting at its potential danger.
  • Scientific Recognition: While debates persist, most scientists acknowledge the existence of ball lightning, even though its underlying mechanisms are not fully understood.
  • Chinese Research: A study conducted by researchers from Lanzhou’s Northwest Normal University in 2012 inadvertently captured a ball lightning event during a thunderstorm. Their findings confirmed the presence of elements such as silicon, iron, and calcium in the luminous sphere, matching the composition of local soil.

Possible Causes of Ball Lightning

  • Ground Strike Theory: Some scientists propose that ball lightning may result from ground strikes, initiating chemical reactions between oxygen and vaporized soil elements. This process creates ionized air or plasma, resembling phenomena like St. Elmo’s Fire.
  • Glass-Related Hypothesis: Another theory suggests that ball lightning might form due to the buildup of atmospheric ions on glass surfaces, creating an electrical field capable of generating discharges.
  • Microwave Radiation: An alternative theory posits that ball lightning could be linked to microwave radiation produced when lightning strikes the Earth’s surface, potentially encapsulating it in a plasma bubble.

Association with Earthquakes

  • In rare instances, ball lightning has been observed in connection with earthquakes, displaying as bluish flames, sudden bright flashes from the ground, or floating orbs.
  • A 2014 study exploring earthquake lights proposed that specific rock types release electrical charges during seismic waves, leading to luminous displays.

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Global Geological And Climatic Events

Why are Earthquakes so frequent in Afghanistan?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Pamir Knot, Tectonic Plates

Mains level: Earthquakes

Afghanistan

Central Idea

  • On October 15, Afghanistan was struck by a formidable earthquake with a magnitude of 6.3, adding to the woes of a nation still reeling from a series of devastating quakes just days earlier.
  • This recent seismic activity reflects Afghanistan’s turbulent history of earthquakes, often with catastrophic consequences.

Understanding Earthquakes

  • Tectonic Plate Movement: The Earth’s lithosphere consists of tectonic plates that move due to internal heat energy. Fault lines are formed along the discontinuities where these plates interact.
  • Earthquake Mechanism: Earthquakes occur when these lithospheric plates suddenly slip past one another, releasing energy that propagates as seismic waves. The point where the slip starts is known as the focus or hypocenter, with the epicenter being its surface projection.

earthquake

What exactly causes Earthquakes?

  • As we know, the earth’s outermost surface, crust, is fragmented into tectonic plates.
  • The edges of the plates are called plate boundaries, which are made up of faults.
  • The tectonic plates constantly move at a slow pace, sliding past one another and bumping into each other.
  • As the edges of the plates are quite rough, they get stuck with one another while the rest of the plate keeps moving.
  • Earthquake occurs when the plate has moved far enough and the edges unstick on one of the faults.
  • The location below the earth’s surface where the earthquake starts are called the hypocenter, and the location directly above it on the surface of the earth is called the epicentre.

Afghanistan’s Seismic Vulnerability

  • Tectonic Plate Intersection: Afghanistan’s location atop the convergence of the Indian and Eurasian tectonic plates results in frequent seismic activity.
  • Eurasian Plate: Afghanistan sits on the Eurasian Plate, with the Arabian Plate subducting northward in the west and the Indian Plate doing the same in the east.
  • Complex Geology: The Hindu Kush mountain range and the Pamir Knot add complexity to this geological region, leading to folding, faulting, and earthquakes.
  • Continual Compression: The northward movement of the Indian Plate toward Eurasia causes compression, uplifting the Himalayas, and transmitting tectonic stress. This leads to crustal deformation, faulting, and seismic activity.
  • Active Fault Systems: Afghanistan is intersected by active fault systems like the Chaman Fault and the Main Pamir Thrust, which are prolific sources of earthquakes.

History of Earthquake Afghanistan

  • October 11 Quakes: In October 2023, a series of powerful earthquakes, including a magnitude 6.3 tremor, wreaked havoc in Herat province, claiming the lives of at least a thousand people.
  • June 2022 Tragedy: A magnitude 6.1 earthquake in Khost and Paktika provinces in June 2022 left over 1,000 casualties.
  • 2015 Catastrophe: A major earthquake in northeastern Afghanistan in 2015 claimed over 200 lives in Afghanistan and northern Pakistan.
  • 2002 Devastation: A 6.1-magnitude earthquake in 2002 resulted in approximately 1,000 casualties in northern Afghanistan.
  • 1998 Disaster: In 1998, northeast Afghanistan experienced a catastrophic earthquake and subsequent tremors, causing the loss of at least 4,500 lives.

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Global Geological And Climatic Events

Deadly Earthquake strikes Morocco

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Earthquake

Mains level: NA

morocco earthquake

Central Idea

  • A devastating earthquake struck Morocco, resulting in significant casualties and damage.

Details of the Moroccan Earthquake

  • Shallow Epicenter: The quake’s epicentre was near the town of Ighil, approximately 70 km southwest of Marrakech. It was considered fairly shallow, with varying depth estimates.
  • Higher Energy: Shallow earthquakes are typically more dangerous as they carry more energy, making them more destructive compared to deeper quakes.

Major Causes

  • Tectonic Convergence: The earthquake resulted from the northward convergence of the African plate with the Eurasian plate along a complex plate boundary.
  • Faulting: The USGS attributed the quake to oblique-reverse faulting at a shallow depth within the Moroccan High Atlas Mountain range.
  • Fault Classification: Oblique-slip faults exhibit characteristics of both dip-slip and strike-slip faults, occurring in areas of compression where tectonic plates converge.

Why discuss this?

  • Low Seismicity: Earthquakes are uncommon in North Africa, with low seismicity rates along the northern margin of the continent.
  • Historic Strength: This earthquake was the strongest ever recorded in the mountainous region, catching Morocco unprepared for such an event.
  • Construction Vulnerabilities: Many Moroccan buildings, especially in rural areas and older cities, are not constructed to withstand strong tremors.

What is an Earthquake?

  • An earthquake is an intense shaking of the ground caused by movement under the earth’s surface.
  • It happens when two blocks of the earth suddenly slip past one another.
  • This releases stored-up ‘elastic strain’ energy in the form of seismic waves, which spreads through the earth and cause the shaking of the ground.

morocco earthquake

What exactly causes Earthquakes?

  • As we know, the earth’s outermost surface, crust, is fragmented into tectonic plates.
  • The edges of the plates are called plate boundaries, which are made up of faults.
  • The tectonic plates constantly move at a slow pace, sliding past one another and bumping into each other.
  • As the edges of the plates are quite rough, they get stuck with one another while the rest of the plate keeps moving.
  • Earthquake occurs when the plate has moved far enough and the edges unstick on one of the faults.
  • The location below the earth’s surface where the earthquake starts are called the hypocenter, and the location directly above it on the surface of the earth is called the epicentre.

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Global Geological And Climatic Events

Fujiwhara Effect: When cyclones dance

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Fujiwhara Effect

Mains level: Not Much

fujiwhara

Central Idea

  • In the ever-changing tapestry of Earth’s climate, the Fujiwhara effect has emerged as a captivating and consequential phenomenon.
  • With cyclones intensifying due to global warming, this intricate ‘dance’ between cyclones is garnering attention.

Why in news?

  • Surprising Weather: Recently, a storm named Hurricane Hilary brought a tropical twist to the US west coast. It’s part of a series of odd weather happenings there.
  • Wet Weather: Earlier this year, California had an unexpected rainy season with lots of wet storms, called ‘atmospheric rivers.’
  • Fujiwhara Show: During one of these storms, something special occurred—an effect named after a scientist. Let’s dive into the details.

Decoding the Fujiwhara Effect

  • Cyclone Waltz: Imagine two cyclones (or big storms) spinning in the same direction. When they get close, they begin a kind of dance around a common center.
  • Outcome of the Dance: Depending on the strength of the cyclones, they might merge, spin together, or one might absorb the other.
  • Super Cyclone: Rarely, if both cyclones are super strong, they can become one mega cyclone that causes big trouble.

Historical Context and Impact

  • Origins and Discovery: The Fujiwhara effect got its name from a Japanese scientist who first talked about it in 1921. It was seen happening for real in 1964.
  • Effects Unleashed: This unusual dance can be fierce. It has caused strong winds, broken windows, and power problems in some areas.
  • Guessing Game: The Fujiwhara effect is tricky for weather experts. It’s hard to predict what will happen when two cyclones dance together.

Climate Change Connection

  • More Frequent Moves: The Fujiwhara effect is showing up more often now. Experts believe it’s because our world is getting hotter and ocean waters are warming up.
  • Hotter Waters: Because of global warming, storms are getting stronger. For instance, in Taiwan, typhoons have become 35% stronger since 1977 due to warmer oceans.

Implications

  • Nature’s Symphony: The Fujiwhara effect is like a nature’s concert, showing us how everything is connected in our climate.
  • Future Twist: As storms get more powerful, the Fujiwhara effect could become even more important and harder to understand.
  • Planet’s Dance: The Fujiwhara effect teaches us about our planet’s rhythm and how important it is to take care of our home.

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Global Geological And Climatic Events

Perseid Meteor Shower to be visible soon

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Perseid Metor Shower

Mains level: NA

perseid

Central Idea

  • The Perseid meteor shower is anticipated to peak around August 13.

Perseid Meteor Shower

  • Origin of Phenomenon: The Perseid meteor shower originates from Earth’s passage through debris consisting of ice, rock, and dust, shed by Comet Swift-Tuttle.
  • Orbital details: This comet, with an orbital period of 133 years, last illuminated the skies in 1992 and will not grace Earth’s vicinity until 2125, as confirmed by NASA.
  • Historic Discovery: Astronomers Lewis Swift and Horace Tuttle discovered Comet Swift-Tuttle in 1862, laying the foundation for understanding this celestial spectacle.

Its occurrence

  • Annual Affair: A time-honoured spectacle, the Perseids meteor shower reaches its zenith every mid-August, enchanting both astronomers and laymen with its celestial display.
  • Residual Cosmic Debris: The Perseids meteor shower unfolds as our planet intersects the path of cosmic remnants cast adrift by Comet Swift-Tuttle. This cosmic cloud spans approximately 27 km in width.
  • Dazzling Cascade: Amidst this cosmic choreography, a breathtaking scene emerges as Earth encounters these fragments. During the peak, between 160 and 200 meteors elegantly streak through the atmosphere each hour, leaving behind a luminous trail of splendour.
  • Speed and Splendor: Travelling at a staggering speed of around 214,000 km per hour, these meteors ignite a fiery display as they disintegrate nearly 100 km above the Earth’s surface.

What are Meteoric Showers?

  • Cosmic Origins: Meteors, fragments of rock and ice, are expelled from comets during their celestial orbits around the sun. The Earth’s atmosphere heats these space rocks as they descend, leaving luminous streaks of gas in their wake.
  • A Symphony of Debris: Meteor showers unfold when our planet traverses the debris trail left behind by comets or asteroids during their celestial journey. A cascade of meteorites gracing the skies in unison constitutes a meteor shower.
  • Celestial Tapestry: NASA’s records attest to the existence of over 30 meteor showers annually, painting the skies with celestial beauty observable from our terrestrial vantage point.

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Global Geological And Climatic Events

World past Holocene Epoch: Anthropocene began in 1950

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Anthropocene Epoch

Mains level: Read the attached story

anthropocene

Central Idea

  • AWG’s Proposal: The Anthropocene Working Group (AWG) proposes a new geological epoch called the Anthropocene.
  • Reference Point: The unique reference point for the Anthropocene is Crawford Lake near Toronto in Canada’s Ontario Province.

Understanding the Anthropocene Epoch

  • Coined Term: The Anthropocene epoch was first coined by Nobel Prize-winning chemist Paul Crutzen and biology professor Eugene Stoermer in 2000.
  • Human Impact: The Anthropocene represents the geological time interval characterized by radical changes in the Earth’s ecosystem due to human impact, particularly since the onset of the Industrial Revolution.
  • Environmental Changes: Numerous phenomena associated with the Anthropocene include global warming, sea-level rise, ocean acidification, mass-scale soil erosion, deadly heat waves, and environmental deterioration.
  • Geological Strata: The AWG’s website states that these changes are reflected in a distinctive body of geological strata, with the potential to be preserved into the far future.

Evidence from Crawford Lake

img

  • Selected Site: Crawford Lake in Canada’s Ontario Province was chosen by geologists for examination over 11 other potential sites.
  • Preserved Sediments: The lake’s layers of sediment have preserved the annual impact of human activities on the Earth’s soil, atmosphere, and biology.
  • Shift in Mid-20th Century: The analysis of Crawford Lake’s bottom sediments reveals a clear shift from the mid-20th century, surpassing the bounds of the previous Holocene epoch.
  • Captured Fallout: Over the years, the lake’s sediments have captured the fallouts of large-scale burning of fossil fuels, explosion of nuclear weapons, and dumping of plastic and fertilizers on land and in water bodies.

Debate and Disagreements

  • Scientific Community Disagreements: Not all geologists agree on the reality of the Anthropocene epoch.
  • Debate Points: Disagreements revolve around the precise start of the epoch, whether it has already begun, and the sufficiency of evidence to prove its advent.

The Geological Time Scale

  • Divisions and Categories: The Earth’s geological time scale is divided into five broad categories: eons, eras, periods, epochs, and ages.
  • Fossil-Based Boundaries: Boundaries on the geological time scale correspond to the origination or extinction of specific types of fossils.
  • Current Classification: Currently, we are in the Phanerozoic eon, Cenozoic era, Quaternary period, Holocene epoch, and Meghalayan age.

AWG’s Findings and Next Steps

  • Selection of Crawford Lake: Crawford Lake was chosen due to its preserved sediment layers that provide an annual record of human impact.
  • Overwhelming Effects: Distinct and multiple signals in the lake’s sediments starting around 1950 demonstrate that the effects of human activity overwhelm the Earth system.
  • Unique Global ‘Fingerprint’: The presence of plutonium resulting from nuclear weapon detonations serves as a stark indicator of humanity’s dominant influence on the planet.
  • Approval Process: The AWG plans to present a proposal to the Subcommission on Quaternary Stratigraphy (SQS) and the International Commission on Stratigraphy (ICS) for approval.
  • Final Approval: The final approval is expected to be granted at the 37th International Geological Congress in Busan, South Korea, next year.

Conclusion

  • Compelling Evidence: Geologists’ examination of Crawford Lake provides compelling evidence for the existence of the Anthropocene epoch.
  • Challenging Conventional Timeline: The proposal for the Anthropocene epoch challenges the conventional understanding of the Earth’s official geological timeline.
  • Future Determination: Further discussions and approvals by international geological bodies will determine the recognition and acceptance of the Anthropocene epoch.

Back2Basics: Geological Time Scale

anthropocene

  • The Geological Time Scale is a system used by geologists and palaeontologists to divide Earth’s history into distinct time intervals based on significant geological and biological events.
  • It provides a framework for organizing and understanding the vast expanse of time since the formation of the Earth, approximately 4.6 billion years ago, up to the present day.
  • The Scale is divided into several hierarchical units, including eons, eras, periods, epochs, and ages.

Here is a simplified overview of the major divisions:

(1) Eon: The largest division of time on the Geological Time Scale. The history of Earth is typically divided into four eons:

  • Hadean Eon: Represents the earliest stage of Earth’s history, from its formation to around 4 billion years ago.
  • Archean Eon: Covers the period from around 4 billion to 2.5 billion years ago. It includes the formation of the Earth’s crust, the emergence of life, and the development of the first continents.
  • Proterozoic Eon: Encompasses the time between 2.5 billion and 541 million years ago. It includes significant evolutionary developments, such as the emergence of complex multicellular life.
  • Phanerozoic Eon: The current eon, spanning from 541 million years ago to the present. It is further divided into eras.

(2) Era: The second-largest division of time, encompassing longer periods of geological history within an eon. The Phanerozoic Eon is divided into three eras:

  • Paleozoic Era: Covers the time from 541 million to 252 million years ago. It is known for the diversification of life, including the appearance of complex marine organisms, fish, insects, and the first terrestrial plants.
  • Mesozoic Era: Spans from 252 million to 66 million years ago. It is often referred to as the “Age of Reptiles” and includes the dominance of dinosaurs, as well as the rise of mammals and birds.
  • Cenozoic Era: Extends from 66 million years ago to the present. It is sometimes called the “Age of Mammals” and includes the diversification and proliferation of mammals, the appearance of humans, and the development of modern ecosystems.

(3) Period: A subdivision of an era, representing a distinct interval of time characterized by specific geological and biological events. For example:

  • The Paleozoic Era is divided into periods such as the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
  • The Mesozoic Era is divided into periods including the Triassic, Jurassic, and Cretaceous.
  • The Cenozoic Era is divided into periods such as the Paleogene, Neogene, and Quaternary.

(4) Epoch: A smaller subdivision of a period, representing a shorter interval of time. Epochs are defined by more localized geological and biological changes.

(5) Age: The smallest division of time on the Geological Time Scale. Ages represent relatively brief periods, often defined by specific fossil or rock layers.

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Global Geological And Climatic Events

Evidence of High Rainfall during Deccan Traps Volcanism

Note4Students

From UPSC perspective, the following things are important :

Prelims level: NanoSIMS

Mains level: Not Much

deccan

Central Idea

  • A team of scientists from IIT Kharagpur has discovered evidence of exceptionally high annual rainfall during the volcanic activity that formed the Deccan Traps in India around 66 million years ago.
  • Using a new technique called Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS), the researchers analyzed the isotopic composition of fossil trees from the Cretaceous period.
  • They determined the isotopic composition of the rainfall-derived lake water.

Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS)

  • NanoSIMS is an advanced analytical technique to determine the composition and distribution of elements and isotopes at a microscopic scale.
  • It allows for high-resolution imaging and quantitative analysis of samples.
  • The technique involves bombarding the sample surface with a focused beam of primary ions.
  • This causes the ejection of secondary ions from the sample surface.
  • The secondary ions are collected and analyzed using a mass spectrometer.
  • The mass spectrometer separates the ions based on their mass-to-charge ratio and measures their abundance.

Analysis and Findings

  • New Technique: The team used Nanoscale Secondary Ion Mass Spectrometry to analyze oxygen isotopes in fossil trees and measure the isotopic composition of the lake water derived from rainfall.
  • Depleted Oxygen Isotopes: The analysis revealed depleted oxygen isotope values, indicating higher tropical rainfall in India during the terminal Cretaceous period.
  • Link to Paleoclimatic Changes: The increase in rainfall closely corresponded to changes in paleo-atmospheric carbon dioxide levels, suggesting a potential underlying link between the two.

Implications and Comparison

  • Atmospheric Carbon Dioxide Concentration: The eruption of Deccan Trap lavas released a significant amount of carbon dioxide, raising atmospheric levels to as high as 1,000 ppm.
  • Comparison to Modern Rainfall: The data from fossil trees indicated an annual rainfall of 1,800-1,900 mm, exceeding the average modern rainfall of 1,000-1,200 mm in most parts of peninsular India.
  • Climate Change Predictions: The findings align with predictions made by the Intergovernmental Panel on Climate Change (IPCC) for extreme warming scenarios, suggesting a correlation between high carbon dioxide levels and increased rainfall.

Climate Models and Future Projections

  • Rising Carbon Dioxide Levels: Fossil fuel emissions have raised carbon dioxide levels from 280 ppm to about 420 ppm in 2023.
  • Impact on Rainfall: Climate models indicate that doubling carbon dioxide levels will intensify atmospheric circulation and subsequently increase rainfall.
  • IPCC AR6 Report: The report warns of a significant increase in the wettest day precipitation and tropical cyclone-associated rainfall if carbon dioxide emissions continue to rise unabated.

Conclusion

  • The study provides evidence of high rainfall during the volcanic activity that formed the Deccan Traps in India millions of years ago.
  • The findings suggest a correlation between elevated carbon dioxide levels and increased rainfall, supporting predictions made by climate models for future climate change scenarios.

 

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Global Geological And Climatic Events

Gravity Hole in the Indian Ocean

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Gravity Hole

Mains level: Not Much

gravity hole
The true shape of our Earth

Central Idea

  • One intriguing phenomenon recently discovered is the presence of a significant “gravity hole” in the Indian Ocean, where the gravitational pull is notably weaker.
  • Recent research sheds light on the possible causes behind this anomaly.

What is a Gravity Hole?

  • A “gravity hole” refers to a region on Earth where the gravitational pull is significantly weaker compared to the surrounding areas or the global average.
  • It is characterized by a dip or low gravity anomaly.
  • In such areas, the sea level may be lower than average due to the weaker gravitational force acting upon the water.
  • This term is often used to describe specific locations, such as the Indian Ocean geoid low (IOGL), where the gravitational pull is notably diminished compared to nearby regions.
  • The exact causes of gravity holes can vary and may involve factors such as variations in the Earth’s mass distribution or underlying geological features.

What is Indian Ocean Geoid Low (IOGL)?

  • It is located approximately 1,200 kilometers southwest of the southernmost tip of India.
  • IOGL is an area in the Indian Ocean where the sea level is about 106 meters below the global average.

Unraveling the Causes of IOGL

  • Discovering the Anomaly: Geophysicist Felix Andries Vening Meinesz first identified the IOGL during a survey in 1948. Since then, it has been confirmed by subsequent ship-based experiments and satellite measurements.
  • Ancient Ocean Hypothesis: Researchers from the Indian Institute of Science conducted computer-simulated models spanning 140 million years. They discovered remnants of an ancient ocean, located approximately 965 kilometers below the Earth’s crust, just beneath Africa.
  • Molten Rock Plumes: The simulations revealed molten rock plumes below Africa, potentially caused by tectonic plates subducting into the mantle. These plumes are believed to be a contributing factor to the IOGL.
  • Possible origination: Researchers said that the IOGL comprises slabs from the Tethys Sea, a long-lost sea that plunged into the depths of the planet millions of years ago. Tethys Sea, which once separated the supercontinents of Gondwana and Laurasia is believed to have perturbed the African Large Low Shear Velocity province.

Future Perspectives

  • Lack of Seismic Evidence: While the simulated models suggest the presence of molten rock plumes beneath the Indian Ocean, seismographic evidence has yet to confirm their actual existence.
  • Additional Factors at Play: The researchers emphasize that other factors contributing to the gravitational anomaly in the Indian Ocean need to be further explored before reaching a definitive conclusion.
  • Further Research: Continuation of studies, including seismic surveys and detailed modelling, is necessary to gain a comprehensive understanding of the IOGL and its causes.

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Global Geological And Climatic Events

Places in news: Ubinas Volcano

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Ubinas Volcano

Mains level: NA

Central Idea

  • Peru declared a state of emergency for sixty days in areas around the Ubinas volcano.
  • The volcano has been spewing ash and gas and is probably set to erupt.

Ubinas Volcano

  • Ubinas is an active stratovolcano located in the Moquegua Region of southern Peru, approximately 60 kilometers east of the city of Arequipa.
  • It is part of the Central Volcanic Zone of the Andes and stands at an elevation of 5,672 meters above sea level.

Geological Characteristics

  • Stratovolcano Formation: Ubinas is characterized by its stratovolcano structure, comprising layers of hardened lava, ash, and other volcanic materials.
  • Caldera and Crater: The volcano’s summit contains a 1.4-kilometer-wide and 150-meter-deep caldera, within which lies a smaller crater. This distinct feature adds to the volcano’s geological significance.
  • Ubinas I and Ubinas II: The volcano exhibits an upwards-steepening cone shape, with a notable notch on its southern side. The lower part is referred to as Ubinas I, while the steeper upper section is known as Ubinas II, representing different stages in the volcano’s geological history.

Volcanic Activity

  • Active Volcanic History: Ubinas is recognized as the most active volcano in Peru, displaying a history of small to moderate explosive eruptions and persistent degassing.
  • Notable Eruptions: The volcano has experienced notable eruptions throughout history, including the 2006–2007 event that resulted in eruption columns, ash fall, health concerns, and evacuations in the region.
  • Recent Activity: From 2013 to 2017, Ubinas exhibited lava flow within the crater, accompanied by ash falls, leading to further evacuations in nearby towns.

Eruption and Impact

  • Ash and Gas Emissions: The Ubinas volcano has been actively spewing ash and gas.
  • Smoke Cloud and Affected Areas: The smoke cloud generated by the eruption has reached towns located up to 10 kilometers away from the volcano. This has raised concerns for the well-being of approximately 2,000 people residing in the affected areas.
  • The “Ring of Fire”: The region where Ubinas is situated falls within the “Ring of Fire,” an area around the Pacific Ocean known for its high volcanic and seismic activity.

 

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Global Geological And Climatic Events

Understanding Summer Solstice: Longest Day of the Year

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Summer Solstice

Mains level: Not Much

summer solstice

Central Idea

  • The summer solstice, also known as the longest day of the year, occurs on June 21st for those living north of the Equator.
  • This article explores the significance of the summer solstice, the reasons behind its occurrence, and the effects it has on different parts of the world.

What is Summer Solstice?

  • The summer solstice is the moment when the Earth’s axial tilt is most inclined towards the Sun.
  • It occurs annually on or around June 21st in the Northern Hemisphere.
  • During the summer solstice, the Sun follows its highest and longest path across the sky.
  • This results in an extended duration of daylight hours, making it the longest day of the year.

Factors Influencing the Summer Solstice

  • Earth’s Axial Tilt: The Earth’s axis is tilted relative to its orbit around the Sun, at an angle of approximately 23.5 degrees.
  • Tropic of Cancer: The summer solstice takes place when the Sun is directly over the Tropic of Cancer, located at 23.5 degrees north latitude.
  • Seasonal Variations: The tilt of the Earth’s axis causes different latitudes to receive varying amounts of sunlight throughout the year.

Sunlight Distribution in the Hemispheres

  • The Northern Hemisphere receives the maximum amount of sunlight during the summer solstice, typically on June 20, 21, or 22.
  • In contrast, the Southern Hemisphere experiences its peak sunlight during the winter solstice, which occurs on December 21, 22, or 23.

Cultural Significance and Celebrations

  • The summer solstice holds cultural and religious significance in various civilizations throughout history.
  • Festivals and rituals often commemorate this astronomical event, symbolizing the triumph of light and fertility.
  • People around the world celebrate the summer solstice through festivals, bonfires, music, dancing, and outdoor activities.
  • Notable celebrations include the Summer Solstice Stonehenge Festival in England and the Midnight Sun Festival in Norway.

Back2Basics: Solstices and Equinoxes

Summer Solstice Winter Solstice Equinoxes
Date Around June 21st Around December 21st Around March 20th and September 22nd
Hemisphere Northern Northern Global (Equal duration of day and night)
Day Length Longest day and shortest night Shortest day and longest night Equal day and night duration
Sun’s Path Highest arc in the sky Lowest arc in the sky Intermediate arc in the sky
Season Summer Winter Spring and Autumn
Axial Tilt North Pole tilted towards the Sun South Pole tilted towards the Sun No tilt, relative to the Sun
Daylight Hours Maximum Minimum Approximately equal
Cultural Significance Celebrated as the triumph of light, festivals, and rituals Celebrated as the return of light, festivals, and rituals Symbolizes balance and transition, celebrated by various cultures

 

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Global Geological And Climatic Events

Cyclone Biparjoy and its Naming

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Cyclone Biparjoy

Mains level: Naming of cyclone

Cyclone Biparjoy
PC: windy.com

Central Idea: A cyclonic storm, named Biparjoy, has developed in the Arabian Sea.

Cyclone Biparjoy

  • It was stationed about 850 km west of Goa and 900 km southwest of Mumbai.
  • The cyclone is predicted to gain in strength over the next three days and develop into a very severe cyclonic storm by June 13.
  • It would result in squally weather with wind speeds reaching 35-45 kmph along the coastline of Karnataka, Goa, and Maharashtra
  • The IMD has not yet predicted any major impact on countries adjoining the Arabian Sea, including India, Oman, Iran, and Pakistan.

How it was named?

  • Origin of Cyclone Biparjoy’s Name: ‘Biparjoy’ was suggested by Bangladesh and the word means ‘disaster’ or ‘calamity’ in Bengali. The next cyclone after Biparjoy will be named ‘Tej’ based on India’s suggestion.
  • Rotational Basis for Naming: The naming of cyclones is done by countries on a rotational basis, following certain existing guidelines.
  • Responsibilities of RSMCs and TCWCs: Worldwide, there are six regional specialized meteorological centers (RSMCs) and five regional Tropical Cyclone Warning Centers (TCWCs) mandated for issuing advisories and naming of tropical cyclones.
  • IMD’s Role: IMD is one of the six RSMCs providing tropical cyclone and storm surge advisories to 13 member countries under the WMO/Economic and Social Commission for Asia-Pacific (ESCAP) Panel.
  • Naming Authority of IMD: RSMC, New Delhi, is also mandated to name the tropical cyclones developing over the north Indian Ocean, including the Bay of Bengal and the Arabian Sea.
  • Guidelines for Naming: Some rules are to be followed while naming cyclones, such as being neutral to politics, religious beliefs, cultures, and gender, avoiding offensive or cruel names, and keeping the name short and easy to pronounce.
  • Next Cyclone Name: After Bangladesh, the next cyclone will be named ‘Tej’ based on India’s suggestion.

Cyclones in the Arabian Sea: A quick recap

  • Frequency of Cyclones: It is not rare for cyclones to develop in the Arabian Sea. There are fewer cyclones compared to the Bay of Bengal, but it is not uncommon.
  • Favorable Months: June is one of the favorable months for the formation of cyclones in the Arabian Sea.
  • Factors Influencing Cyclone Formation: Cyclones form due to low-pressure systems over warm waters. The Bay of Bengal is slightly warmer, but the Arabian Sea is also getting warmer due to climate change, leading to an increase in cyclones.
  • Coriolis Effect and Weather Systems: In a depression or low-pressure situation, the air blows in an anticlockwise direction in the northern hemisphere, influenced by the Coriolis Effect.

Role of Climate Change

  • Historical data indicates that the frequency of extremely severe cyclonic storms has increased over the Arabian Sea since 1990, while it has remained the same over the Bay of Bengal.
  • A 2021 study highlighted the increasing intensity, frequency, and duration of cyclonic storms in the Arabian Sea.
  • The warming is indicated by the nearly tripled accumulated cyclone energy, reflecting the extent of warming in recent years.

Back2Basics:

Tropical Cyclones
Definition Intense circular storm over warm oceans with low pressure, high winds, and heavy rain.
Formation Conditions Warm sea surface temperatures, anticlockwise rotation of low-level air, favorable atmospheric conditions.
Conducive Periods April-May and October-December.
Movement and Moisture Cyclones move northwest, gather moist air, and intensify.
Requirements for Cyclogenesis Warm sea temperatures, atmospheric instability, high humidity, Coriolis force, low-level disturbance, low vertical wind shear.
Sea temperatures Temperature of at least 28°C.
Atmospheric instability Allows vertical air movement.
Role of Coriolis Force Required for low-pressure center formation.
Low vertical wind shear Maintains cyclone structure.

 

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Global Geological And Climatic Events

Palghat Gap: A break in the Western Ghats

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Palghat Gap, Western Ghats

Mains level: Not Much

palghat

Central Idea: The article discusses the Palghat (Palakkad) Gap, a significant corridor in the Western Ghats of India. It provides information about the geological origin of the gap.

What is Palghat Gap?

  • The Palghat Gap is a 40 km wide corridor in the Western Ghats, known for its steep hills and serving as a gateway to Kerala.
  • It is a crucial passage for roads and railways connecting Coimbatore and Palakkad.
  • The Bharathappuzha River flows through the Palghat Gap.
  • The vegetation in the gap is classified as dry evergreen forest, different from the tropical rainforests of the Western Ghats.
  • The Palghat Gap marks a distinct divide in the flora and fauna of the region.

Geological origin of the Palghat Gap

  • The Palghat Gap is a geological shear zone running from east to west.
  • Shear zones are weak regions in the Earth’s crust, occasionally causing tremors in the Coimbatore region.
  • The formation of the Palghat Gap occurred when the continental shelves shifted after the separation of Australia and Africa from the Gondwana landmass.
  • India and Madagascar were connected until volcanic activity led to their split, with a similar gap called the Ranotsara Gap in Madagascar.

Biogeographic distinctions and ancient history

  • The biogeographic distinctions in species north and south of the Palghat Gap may be attributed to an ancient river or an incursion of the sea in the distant past.
  • Elephant populations on the Nilgiris side of the gap have different mitochondrial DNA from elephants in the Anamalai and Periyar sanctuaries.
  • DNA analysis of the White-bellied Shortwing, an endemic bird species, shows divergence between populations in the Nilgiris and the Anamalai regions.

Biodiversity south of the Palghat Gap

  • The southern region of the Western Ghats, located south of the Palghat Gap, exhibits high species richness and phylogenetic diversity.
  • A recent study reports over 450 tree species, including ancient species like Magnolia champaca, dating back 130 million years.
  • The warm weather and moist air of the southern Western Ghats support a diverse range of life, making it an island refuge during cycles of ice ages and droughts.
  • The southern Western Ghats receive rainfall more evenly throughout the year compared to the northern region.

Back2Basics: Western Ghats

  • The Western Ghats, also known as the Sahyadri mountain range, is a UNESCO World Heritage Site and one of the 36 biodiversity hotspots in the world.
  • It spans an area of 160,000 sq. km. and stretches for 1,600 km parallel to the western coast of the Indian peninsula, passing through the states of Gujarat, Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu.
Description
Flora and Fauna The Western Ghats are home to a rich diversity of flora and fauna, including over 7,402 species of flowering plants, 1,814 species of non-flowering plants, 139 mammal species, 508 bird species, 227 reptile species, 179 amphibian species, 290 freshwater fish species, and 6,000 insect species.
Geological Significance The Western Ghats, known as the “Great Escarpment of India,” are older than the Himalayas. They influence India’s monsoon weather patterns by intercepting rain-laden monsoon winds from the southwest during late summer.
Geographic Features Stretching north to south along the western edge of the Deccan Plateau, the Western Ghats separate the plateau from the narrow coastal plain called the Western Coastal Plains, which lies along the Arabian Sea.
Catchment Area The Western Ghats cover a vast catchment area for complex riverine drainage systems, contributing to almost 40% of India’s total drainage. The range acts as a barrier, blocking southwest monsoon winds from reaching the Deccan Plateau.

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Global Geological And Climatic Events

Cyclone Mocha developing in Bay of Bengal

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Cyclone Mocha

Mains level: Not Much

cyclone

Central Idea: The Indian Meteorological Department (IMD) has warned of a developing cyclonic or low-pressure area in the Bay of Bengal. It would be named Cyclone Mocha (pronounced ‘Mokha’).

What is a cyclone and how are they formed?

  • A cyclone is a low-pressure system that forms over warm waters.
  • Warm seas present ripe conditions for the development and strengthening of cyclones.
  • The air rises and blows in an anticlockwise direction around the low in the northern hemisphere and in a clockwise direction in the southern hemisphere.
  • As warm air rises and cools, water vapour condenses to form clouds and this can lead to rains.
  • Cyclones can cause significant impacts on life and property, including storm surge, flooding, extreme winds, tornadoes and lightning.

Requirements for a Cyclone to form

There are six main requirements for tropical cyclogenesis:

  1. Sufficiently warm sea surface temperatures
  2. Atmospheric instability
  3. High humidity in the lower to middle levels of the troposphere
  4. Enough Coriolis force to develop a low-pressure centre
  5. A pre-existing low-level focus or disturbance
  6. Low vertical wind shear

How are cyclones named?

  • Cyclones that form in every ocean basin across the world are named by the regional specialized meteorological centres (RSMCs) and Tropical Cyclone Warning Centres (TCWCs).
  • The IMD names the cyclones developing over the north Indian Ocean after following a standard procedure.
  • In 2000, a group of nations called WMO/ESCAP decided to start naming cyclones in the region.
  • After each country sent in suggestions, the WMO/ESCAP Panel on Tropical Cyclones (PTC) finalized the list.
  • This cyclone will be named Mocha (Mokha), a name suggested by Yemen after the Red Sea port city, which is known to have introduced coffee to the world over 500 years ago.

Why is it important to name cyclones?

  • Adopting names for cyclones makes it easier for people to remember, as opposed to numbers and technical terms.
  • It’s easier and less confusing to say “Cyclone Titli” than remember the storm’s number or its longitude and latitude.
  • Apart from the general public, it also helps the scientific community, the media, disaster managers etc.
  • With a name, it is also easy to identify individual cyclones, create awareness of its development, rapidly disseminate warnings to increase community preparedness etc.

 

 

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Global Geological And Climatic Events

Over 19,000 Seamounts discovered

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Seamounts

Mains level: NA

seamount

Central Idea: Scientists have reported finding 19,325 new seamounts after poring through new high-resolution data. A study had already mapped 24,000 seamounts across the world’s oceans.

Why study this?

  • The recent discovery of new seamounts was made possible by advancements in altimetry for gravity-field mapping, which improved spatial coverage.
  • The CryoSat-2, Envisat, Jason-1 geodetic missions, and the SARAL satellite developed by India and France contributed to these advancements.

What are Seamounts?

  • Seamounts are underwater mountains formed through volcanic activity.
  • They are recognised as hotspots for marine life.
  • Most seamounts are formed near mid-ocean ridges, intraplate hotspots, and oceanic island chains with volcanic and seismic activity called island arcs.
  • They can be active, extinct or dormant volcanoes.

Importance of Seamounts

  • Seamounts provide information about the mantle’s composition and how tectonic plates evolve as they are formed when molten rock comes up from below the tectonic plates.
  • Oceanographers study seamounts to understand their influence on how water circulates and absorbs heat and carbon dioxide.
  • Seamounts are home to diverse biological communities as they can cause localised ocean upwelling, which brings nutrient-rich water from deep within the ocean to the surface.

How were they mapped?

  • Surveyors map seamounts using either echo sounders or multibeam sonar on ships for topographic mapping or using satellite altimetry for gravity-field mapping.
  • The hi-res maps produced by multibeam sonar mapping are often incomplete, whereas the low-res maps produced by satellite altimetry have better coverage.

 

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Global Geological And Climatic Events

What is Ningaloo ‘Hybrid’ Solar Eclipse?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Ningaloo ‘Hybrid’ Solar Eclipse

Mains level: Not Much

ningaloo

A ‘hybrid’ solar eclipse called the Ningaloo Eclipse recently happened on April 20, 2023.

Ningaloo ‘Hybrid’ Solar Eclipse

  • It was a rare astronomical event that occurred on April 20, 2023.
  • The Moon passed directly between the Sun and the Earth, casting a shadow on a narrow strip of land in Western Australia.
  • It was a “hybrid” eclipse, starting as an annular eclipse and transitioning into a total eclipse.
  • The path of the eclipse crossed over the Ningaloo Reef, a world heritage site in Western Australia.
  • It offered a unique opportunity to view the eclipse against the backdrop of the reef and the Indian Ocean.

How rare are such events?

  • During a solar eclipse, the Moon passes between the Sun and Earth, casting a shadow on Earth’s surface.
  • However, solar eclipses do not occur every month because the Moon’s orbit is tilted by about 5 degrees relative to Earth’s orbit around the Sun.
  • Therefore, the Moon’s shadow usually misses Earth, but occasionally the alignment is just right for a solar eclipse to occur.
  • In the case of the Ningaloo Hybrid Solar Eclipse, the alignment was such that the Moon was at the right distance from Earth to create both an annular and a total eclipse as it moved across the Sun.
  • This type of eclipse is quite rare, occurring only about once every 400 years.

Back2Basics:

ningaloo

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Global Geological And Climatic Events

Zero Shadow Day: What is it, why does it happen?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Zero Shadow Day

Mains level: Not Much

shadow

Central idea: Many cities across India are experiencing Zero Shadow Day since the sun was directly overhead at that time.

What is Zero Shadow Day?

  • Zero Shadow Day is a phenomenon that occurs twice a year at every point on Earth located between the Tropic of Cancer and the Tropic of Capricorn.
  • During Zero Shadow Day, vertical objects appear to cast no shadow at local noon, when the sun is at its zenith directly above the object.
  • It occurs when the sun’s location moves from 23.5°N to 23.5°S of Earth’s equator and back, causing the shadow to disappear beneath objects at local noon.

Why does it happen?

  • It occurs due to the movement of the sun from south to north during the Uttarayan and back from north to south during Dakshinayan.
  • This movement is caused by Earth’s rotation axis being tilted at an angle of roughly 23.5° to the axis of revolution around the sun.
  • All places whose latitude equals the angle between the sun’s location and the equator on that day experience Zero Shadow Day, with the shadow disappearing at local noon.

Try this PYQ:

On 21st June, the Sun-

(a) Does not set below the horizon at the Arctic Circle

(b) Does not set below the horizon at Antarctic Circle

(c) Shines vertically overhead at noon on the Equator

(d) Shines vertically overhead at the Tropic of Capricorn

 

Post your answers here.
1
Please leave a feedback on thisx

 

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Global Geological And Climatic Events

Africa’s splitting plates could give birth to a new Ocean: Study

Note4Students

From UPSC perspective, the following things are important :

Prelims level: East African Rift, Various lakes

Mains level: Read the attached story

africa

Central idea

  • Scientists predict a new ocean will be created as Africa splits into two separate parts connected to the East African Rift
  • This geological process will inevitably divide the continent resulting in new coastlines and sub-sea internet infrastructure but also will have significant repercussions

What is Rifting?

  • The Earth’s lithosphere, comprising the crust and upper part of the mantle, is divided into tectonic plates that move in relation to each other at varying speeds.
  • Tectonic forces move the plates and can cause them to rupture, resulting in the formation of a rift and potentially leading to the creation of new plate boundaries.
  • Rifting refers to the geological process in which a single tectonic plate is split into two or more plates separated by divergent plate boundaries.
  • In the present day, the gradual separation of the Somali and Nubian tectonic plates is leading to the formation of a rift that could eventually lead to the creation of a new ocean basin.
  • The movement of tectonic plates is a fascinating geological phenomenon.

Rifting in African Continent

  • The African continent is located on the African Plate, which is one of the Earth’s major tectonic plates.
  • The continent is characterized by a number of geological features, including rift valleys.

Most profound feature: The East African Rift System

  • The East African Rift System is the most prominent example of rifting in Africa.
  • It stretches for over 6,000 kilometers from the Red Sea in the north to the Zambezi River in the south.
  • The rift system includes a series of interconnected rift valleys, volcanoes, and lakes.

Causes of the East African Rift System

  • The rift system is caused by the movement of the African Plate away from the Arabian Plate and the Somalian Plate.
  • This movement creates tension in the Earth’s crust, causing it to pull apart and form a rift.

Impact: Lakes Formed by Rifting

  • Over time, the rifting process has led to the formation of several large lakes in the region.
  • These lakes include Lake Victoria, Lake Tanganyika, and Lake Malawi.
  • They are believed to have formed as a result of the sinking of the land between the rift valleys.

Future of Rifting in Africa

  • The rifting process is ongoing and may eventually lead to the splitting of the African continent into two or more separate land masses.
  • However, this process is expected to take millions of years and is not likely to have a significant impact on human populations in the near future.
  • The necessary evacuation of people and potential loss of lives will be an unfortunate cost of this natural phenomenon.
  • The emergence of new coastlines will unlock opportunities for economic growth
  • As the plates continue to split in the future, this phenomenon will result in the displacement of communities, settlements, and various flora and fauna.

Conclusion

  • The movement of tectonic plates has significant implications for the continent’s future.
  • It is important to study and monitor these changes while remembering the power of the Earth’s natural forces and the impact they can have over time.

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Global Geological And Climatic Events

Diyodar meteorite in 2022 was India’s first Aubrite in 170 years

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Diyodar Meteorite

Mains level: Not Much

meteorite

Central idea: A rare and unique meteorite, known as the Diyodar meteorite, was discovered in Banaskantha, Gujarat in December 2022. It is significant because it is the first aubrite to be found in India in 170 years.

What are Aubrites?

  • Aubrites are a type of meteorite that are believed to have formed on a different planet in the early solar system.
  • They are known for their unusual mineralogy and composition and are believed to have originated from a differentiated parent body, such as an asteroid or a planetesimal.
  • They are primarily composed of a mineral called enstatite, which is a magnesium-rich silicate. They also contain other minerals such as nickel-iron, troilite, and chromite.
  • Aubrites are relatively rare, comprising only about 0.1% of all known meteorites.
  • They are believed to have formed under highly reducing conditions, with very little oxygen present.

Meteorite found in Diyodar, Gujarat

  • The Diyodar meteorite is thought to be around 4.5 billion years old, and it is believed to have originated from the asteroid belt between Mars and Jupiter.
  • Its discovery provides scientists with an opportunity to study the composition and structure of these unique meteorites.
  • This, in turn, can help researchers to better understand the early solar system and the processes that led to the formation of planets.

Its composition

  • Around 90% of the meteorite was composed of orthopyroxene.
  • Pyroxenes are silicates consisting of single chains of silica tetrahedra (SiO 4); orthopyroxenes are pyroxenes with a certain structure.
  • Pyroxenes such as diopside and jadeite have been used as gems. Spodumene was historically used as lithium ore.
  • Rocks with pyroxene have also been used to make a crushed stone that is used in construction.

 

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Global Geological And Climatic Events

Earth’s inner core rotating slower than surface: Study

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Earth's interior

Mains level: Read the attached story

earth

Earth’s inner core, a hot iron ball the size of Pluto, has stopped spinning faster than the planet’s surface and might now be rotating slower than it, research suggested.

A quick recap of Earth’s Interior

earth

Structure of earth’s interior is fundamentally divided into three layers – crust, mantle and core.

[A] Crust

  • It is the outermost solid part of the earth, normally about 8-40 kms thick.
  • It is brittle in nature.
  • Nearly 1% of the earth’s volume and 0.5% of earth’s mass are made of the crust.
  • The thickness of the crust under the oceanic and continental areas are different. Oceanic crust is thinner (about 5kms) as compared to the continental crust (about 30kms).
  • Major constituent elements of crust are Silica (Si) and Aluminium (Al) and thus, it is often termed as SIAL(Sometimes SIAL is used to refer Lithosphere, which is the region comprising the crust and uppermost solid mantle, also).
  • The mean density of the materials in the crust is 3g/cm3.
  • The discontinuity between the hydrosphere and crustis termed as the Conrad Discontinuity.

 [B] Mantle

  • The portion of the interior beyond the crust is called as the mantle.
  • The discontinuity between the crust and mantleis called as the Mohorovich Discontinuity or Moho discontinuity.
  • The mantle is about 2900kms in thickness.
  • Nearly 84% of the earth’s volume and 67% of the earth’s mass is occupied by the mantle.
  • The major constituent elements of the mantle are Silicon and Magnesium and hence it is also termed as SIMA.
  • The density of the layer is higher than the crust and varies from 3.3 – 5.4g/cm3.
  • The uppermost solid part of the mantle and the entire crust constitute the Lithosphere.
  • The asthenosphere (in between 80-200km) is a highly viscous, mechanically weak and ductile, deforming region of the upper mantle which lies just below the lithosphere.
  • The asthenosphere is the main source of magma and it is the layer over which the lithospheric plates/ continental plates move (plate tectonics).
  • The discontinuity between the upper mantle and the lower mantleis known as Repetti Discontinuity.
  • The portion of the mantle which is just below the lithosphere and asthenosphere, but above the core is called as Mesosphere.

[C] Core

  • It is the innermost layer surrounding the earth’s centre.
  • The core is separated from the mantle by Guttenberg’s Discontinuity.
  • It is composed mainly of iron (Fe) and nickel (Ni) and hence it is also called as NIFE.
  • It constitutes nearly 15% of earth’s volume and 32.5% of earth’s mass.
  • It is the densest layer of the earth with its density ranges between 9.5-14.5g/cm3.
  • It spins independently because it floats in the liquid metal outer core. One cycle of the swing is about seven decades approximately.
  • It consists of two sub-layers: the inner core and the outer core.
  • The inner core is in solid state and the outer core is in the liquid state (or semi-liquid).
  • The discontinuity between the upper core and the lower core is called as Lehmann Discontinuity.
  • Barysphere is sometimes used to refer the core of the earth or sometimes the whole interior.

What should one understand about the interior of the earth?

  • It is not possible to know about the earth’s interior by direct observations because of the huge size and the changing nature of its interior composition.
  • It is an almost impossible distance for the humans to reach till the centre of the earth (The earth’s radius is 6,370 km).
  • The rapid increase in temperature below the earth’s surface is mainly responsible for setting a limit to direct observations inside the earth.

Sources of Information about the interior of the earth

Direct Sources:

  1. Rocks from mining area
  2. Volcanic eruptions

Indirect Sources

  1. By analyzing the rate of change of temperature and pressurefrom the surface towards the interior.
  2. Meteors, as they belong to the same type of materials earth is made of.
  3. Gravitation, which is greater near poles and less at the equator.
  4. Gravity anomaly, which is the change in gravity value according to the mass of material, gives us information about the materials in the earth’s interior.
  5. Magnetic sources.
  6. Seismic Waves: the shadow zones of body waves (Primary and secondary waves) give us information about the state of materials in the interior.

What is the new study about?

  • Exactly how the inner core rotates has been a matter of debate between scientists— and the latest research is expected to prove controversial.
  • A new research has analyzed seismic waves from repeating earthquakes over the last six decades.
  • It shows that- the inner core started rotating slightly faster than the rest of the planet in the early 1970s, the study said.
  • But it had been slowing down before coming in sync with Earth’s rotation around 2009.

What made the core spin slower?

  • So far there is little to indicate that what the inner core does has many effects on surface dwellers.
  • The researchers said this rotation timeline roughly lines up with changes in what is called the “length of day”— small variations in the exact time it takes Earth to rotate on its axis.
  • But the researchers said they believed there were physical links between all of Earth’s layers, from the inner core to the surface.

 

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Global Geological And Climatic Events

What is Winter Solstice?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Solstice

Mains level: Not Much

solstice

Today, December 21, is Winter Solstice, the shortest day of the year in the Northern Hemisphere. In the Southern Hemisphere, conversely, it was Summer Solstice, the year’s longest day.

What is Winter Solstice?

  • The winter solstice, also called the hibernal solstice, occurs when either of Earth’s poles reaches its maximum tilt away from the Sun.
  • This happens twice yearly, once in each hemisphere.

What are Solstices?

  • Solstices occur because Earth’s axis of rotation is tilted about 23.4 degrees relative to Earth’s orbit around the sun.
  • This tilt drives our planet’s seasons, as the Northern and Southern Hemispheres get unequal amounts of sunlight over the course of a year.
  • From March to September, the Northern Hemisphere is tilted more toward the sun, driving its spring and summer.
  • From September to March, the Northern Hemisphere is tilted away, so it feels like autumn and winter.
  • The Southern Hemisphere’s seasons are reversed.
  • On two moments each year—what are called solstices—Earth’s axis is tilted most closely toward the sun.

Impact on day-time

  • The hemisphere tilted most toward our home star sees its longest day, while the hemisphere tilted away from the sun sees its longest night.
  • During the Northern Hemisphere’s summer solstice—which always falls around June 21—the Southern Hemisphere gets its winter solstice.
  • Likewise, during the Northern Hemisphere’s winter solstice—which always falls around December 22—the Southern Hemisphere gets its summer solstice.

Impact of the tilted axis

  • The Northern Hemisphere spends half the year tilted in the direction of the Sun, getting direct sunlight during long summer days.
  • During the other half of the year, it tilts away from the Sun, and the days are shorter.
  • Winter Solstice, December 21, is the day when the North Pole is most tilted away from the Sun.
  • The tilt is also responsible for the different seasons that we see on Earth.
  • The side facing the Sun experiences day, which changes to night as Earth continues to spin on its axis.

Un-impacted regions

  • On the Equator, day and night are equal. The closer one moves towards the poles, the more extreme the variation.
  • During summer in either hemisphere, that pole is tilted towards the Sun and the polar region receives 24 hours of daylight for months.
  • Likewise, during winter, the region is in total darkness for months.

Celebrations associated with the Winter Solstice

  • For centuries, this day has had a special place in several communities due to its astronomical significance and is celebrated in many ways across the world.
  • Jewish people call the Winter Solstice ‘Tekufat Tevet’, which marks the start of winter.
  • Ancient Egyptians celebrated the birth of Horus, the son of Isis (divine mother goddess) for 12 days during mid-winter.
  • In China, the day is celebrated by families coming together for a special meal.
  • In the Persian region, it is celebrated as Yalda or Shab-e-Yalda. The festival marks the last day of the Persian month of Azar and is seen as the victory of light over darkness.
  • Families celebrate Yalda late into the night with special foods such as ajeel nuts, pomegranates and watermelon, and recite works of the 14th-century Sufi poet Hafiz Shirazi.

In Vedic tradition

  • In Vedic tradition, the northern movement of the Earth on the celestial sphere is implicitly acknowledged in the Surya Siddhanta.
  • It outlines the Uttarayana (the period between Makar Sankranti and Karka Sankranti). Hence, Winter Solstice is the first day of Uttarayana.

 

Try this MCQ:

Q. On 21st June, the Sun

(a) Does not set below the horizon at the Arctic Circle

(b) Does not set below the horizon at Antarctic Circle

(c) Shines vertically overhead at noon on the Equator

(d) Shines vertically overhead at the Tropic of Capricorn

 

Post your answers here.
2
Please leave a feedback on thisx

 

 

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Global Geological And Climatic Events

Mauna Loa: Hawaii’s biggest Volcano set to erupt

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mauna Loa

Mains level: Not Much

mauna

Mauna Loa, the world’s largest active volcano has erupted after 38 years, spewing ash and debris, and covering the sky of Hawaii’s Big Island.

Where is Mauna Loa?

mauna

  • Mauna Loa is one of five volcanoes that together make up the Big Island of Hawaii (biggest being the Mauna Kea).
  • It is the southernmost island in the Hawaiian archipelago.
  • It’s not the tallest (that title goes to) but it’s the largest and makes up about half of the island’s land mass.
  • It sits immediately north of Kilauea volcano, which is currently erupting from its summit crater.

Do you know?

Any volcano that has erupted within the Holocene period (in the last 11,650 years) is considered to be “active” by scientists. “Dormant” volcanoes are those active volcanoes which are not in the process of erupting currently, but have the potential to do so in the future.

Why do volcanoes erupt?

  • The deeper one goes under the surface of the Earth towards its core, the hotter it gets.
  • The geothermal gradient, the amount that the Earth’s temperature increases with depth, indicates heat flowing from the Earth’s warm interior to its surface.
  • At a certain depth, the heat is such that it melts rocks and creates what geologists call ‘magma’.
  • Magma is lighter than solid rock and hence it rises, collecting in magma chambers.
  • Chambers that have the potential to cause volcanic eruptions are found at a relatively shallow depth, between six to ten km under the surface.
  • As magma builds up in these chambers, it forces its way up through cracks and fissures in Earth’s crust. This is what we call a volcanic eruption.
  • The magma that surfaces on the Earth’s crust is referred to as lava.

Why is the eruption of Mauna Loa so explosive?

  • Eruptions vary in intensity and explosiveness, depending on the composition of the magma.
  • In simple terms, runny magma makes for less explosive volcanic eruptions that typically are less dangerous.
  • Since the magma is runny, gasses are able to escape, leading to a steady but relatively gentle flow of lava out of the mouth of the volcano.
  • The eruption at Mauna Loa is of this kind. Since the lava flows out at a slow pace, people typically have enough time to move out of the way
  • . Geologists are also able to predict the flow of the lava depending on the incline and exact consistency it has.

How is vulcanism measured?

  • The Volcanic Explosivity Index (VEI) is a scale used to measure the explosivity of a volcano.
  • It has a range of 1 to 8 with a higher VEI indicating more explosivity.
  • While the VEI of the current eruption at Mauna Loa is not known yet, the previous eruption in 1984 was deemed to have a VEI of 0.

 

Also read about the Pacific Ring of Fire.

 

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Global Geological And Climatic Events

Places in news: Shiveluch Volcano

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Shiveluch Volcano

Mains level: Not Much

shiveluch

The Shiveluch volcano on the Kamchatka Peninsula in the Russian Far East has increased its activity and is now in danger of erupting violently.

About Shiveluch

  • Shiveluch is one of the largest and most active volcanoes in Kamchatka, having erupted at least 60 times in the past 10,000 years.
  • Kamchatka is home to 29 active volcanoes, part of a vast belt of Earth known as the “Ring of Fire” which circles the Pacific Ocean and is prone to eruptions and frequent earthquakes.
  • It has two main parts: Old Shiveluch, which tops 3,283 metres (10,771 ft), and Young Shiveluch – a smaller, 2,800-metre peak protruding from its side.
  • Young Shiveluch lies within an ancient caldera – a large crater-like basin that likely formed when the older part underwent a catastrophic eruption at least 10,000 years ago.
  • It is this part that has become extremely active; the lava dome continues to grow and that stronger “fumarole activity” has been observed.

 

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Global Geological And Climatic Events

What are Eclipses?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Eclipses

Mains level: Read the attached story

eclipse

India recently witnessed a partial solar eclipse. Let’s take a look over all dynamics of Eclipses.

What are Eclipses?

  • An eclipse takes place when one heavenly body such as a moon or planet moves into the shadow of another heavenly body.
  • There are two types of eclipses on Earth: an eclipse of the Moon and an eclipse of the Sun.

[I] A Lunar Eclipse

eclipse

  • The moon moves in an orbit around Earth, and at the same time, Earth orbits the sun. Sometimes Earth moves between the sun and the moon.
  • When this happens, Earth blocks the sunlight that normally is reflected by the moon. (This sunlight is what causes the moon to shine.)
  • Instead of light hitting the moon’s surface, Earth’s shadow falls on it. This is an eclipse of the moon — a lunar eclipse.
  • A lunar eclipse can occur only when the moon is full. (But not every full moon is also a lunar eclipse. Can you guess why?)

Observing a Lunar Eclipse

  • A lunar eclipse can be seen from Earth at night.
  • A lunar eclipse usually lasts for a few hours.
  • At least two partial lunar eclipses happen every year, but total lunar eclipses are rare.

There are two types of lunar eclipses: total lunar eclipses and partial lunar eclipses.

  • A total lunar eclipse occurs when the moon and the sun are on exact opposite sides of Earth. Although the moon is in Earth’s shadow, some sunlight reaches the moon.  The sunlight passes through Earth’s atmosphere, which causes Earth’s atmosphere to filter out most of the blue light. This makes the moon appear red to people on Earth.
  • A partial lunar eclipse happens when only a part of the moon enters Earth’s shadow. In a partial eclipse, Earth’s shadow appears very dark on the side of the moon facing Earth. What people see from Earth during a partial lunar eclipse depends on how the sun, Earth and moon are lined up.
  • In a penumbral lunar eclipse, only the more diffuse outer shadow of Earth – the penumbra – falls on the moon’s face. This third kind of lunar eclipse is much more subtle, and much more difficult to observe than either a total or partial eclipse of the moon.

[II] A Solar Eclipse

eclipse

  • Sometimes when the moon orbits Earth, it moves between the sun and Earth.
  • When this happens, the moon blocks the light of the sun from reaching Earth.
  • This causes an eclipse of the sun or solar eclipse.
  • During a solar eclipse, the moon casts a shadow onto Earth.

There are three types of solar eclipses.

The first is a Total Solar Eclipse

  • A total solar eclipse is only visible from a small area on Earth.
  • The people who see the total eclipse are in the centre of the moon’s shadow when it hits Earth.
  • The sky becomes very dark as if it were night. For a total eclipse to take place, the sun, moon and Earth must be in a direct line.

The second type is a Partial Solar Eclipse

  • This happens when the sun, moon and Earth are not exactly lined up.
  • The sun appears to have a dark shadow on only a small part of its surface.

The third type is an Annular Solar Eclipse

  • An annular eclipse happens when the moon is farthest from Earth. Because the moon is farther away from Earth, it seems smaller. It does not block the entire view of the sun. The moon in front of the sun looks like a dark disk on top of a larger sun-coloured disk. This creates what looks like a ring around the moon.
  • During a solar eclipse, the moon casts two shadows on Earth. The first shadow is called the Umbra. This shadow gets smaller as it reaches Earth. It is the dark centre of the moon’s shadow.
  • The second shadow is called the Penumbra. The penumbra gets larger as it reaches Earth. People standing in the penumbra will see a partial eclipse. People standing in the umbra will see a total eclipse.

Observing a Solar Eclipse

  • Solar eclipses happen once every 18 months.
  • Unlike lunar eclipses, solar eclipses only last for a few minutes.

Why don’t solar eclipses happen at every New Moon?

  • The reason is that the Moon’s orbit tilts 5° to Earth’s orbit around the Sun.
  • Astronomers call the two intersections of these paths nodes.
  • Eclipses only occur when the Sun lies at one node and the Moon is at its New (for solar eclipses) or Full (for lunar eclipses) phase.
  • During most (lunar) months, the Sun lies either above or below one of the nodes, and no eclipse happens.

[III] Planet Transits

  • When a planet comes between Earth and the Sun, it is called a transit.
  • The only 2 planets that can be seen transiting the Sun from Earth are Venus and Mercury because they are the only planets that orbit inside Earth’s orbit.
  • From 2000–2199, there will be 14 transits of Mercury.
  • However, Venus transits are even rarer with only 2 this century, in 2004 and 2012.

 

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Global Geological And Climatic Events

What is Karoo-Ferrar Large Igneous Province?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Karoo-Ferrar Large Igneous Province

Mains level: NA

karoo

A new study shows that a decline in continental plate movement likely controlled the onset and duration of many of the major volcanic events throughout Earth’s history.

Why is the news?

  • Previous studies have linked major volcanic eruptions with past mass extinctions and disturbances in the global climatic, environmental and the carbon cycle.
  • Large igneous province volcanism, formations due to major volcanic eruptions occurring throughout Earth’s history, released large quantities of greenhouse gasses and toxic compounds into the atmosphere.
  • The sea warmed up by 4°C to 10°C, even at low- to mid-latitudes, the study noted.
  • Increased acidic levels and a lack of oxygen drove major ocean extinctions.
  • Large-scale volcanism took place in southern Africa, Antarctica and Australia. This is known as the Karoo-Ferrar Large Igneous Province.

About Karoo-Ferrar Large Igneous Province

  • The Karoo and Ferrar Large Igneous Provinces (LIPs) are two large igneous provinces in Southern Africa and Antarctica respectively, collectively known as the Karoo-Ferrar, Gondwana, or Southeast African LIP associated with the initial break-up of the Gondwana supercontinent.
  • Its flood basalt mostly covers South Africa and Antarctica but portions extend further into southern Africa and into South America, India, Australia and New Zealand.
  • Karoo-Ferrar formed just prior to the breakup of Gondwana in the Lower Jurassic epoch, about 183 million years ago.
  • This time corresponds to the early Toarcian anoxic event and the Pliensbachian-Toarcian extinction.

 

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Global Geological And Climatic Events

In news: Continental Drift Theory

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Lemurs, Continental Drift Theory

Mains level: Continental Drift Theory

This newscard is an excerpt from the original article published in TH which talks about the specie Lemurs who are supposed to jump into seas to find India which got drifted away from the Madagascar.

Study on Lemurs

  • Many life forms in Madagascar have affinities to lineages found in India (3,800 km away) rather than Africa (413 km). This posed a ‘difficult enigma’ to naturalists.
  • One such species is the Lemurs.
  • We most likely see lemurs in a Hollywood animation movie; singing, dancing and playing pranks.
  • Zoologists was perplexed by the presence of lemurs, their relatives, and their fossils in Madagascar and India, but not in nearby Africa or the Middle East.
  • In the 1860s, he proposed that a large island or continent must have once existed between India and Madagascar, serving as a land bridge.
  • Over time, this island had sunk. He called this proposed island Lemuria.

Existence of such Island in Indian legends

  • Tamil revivalists such as Devaneya Pavanar also took up the idea, in the form of a Tamil civilisation, lost to the sea as described in literature and in Pandyan legends.
  • They called this submerged continent Kumari Kandam.

Basis of this legend: Continental Drift Theory

  • In the early 20th century, German geologist Alfred Wegener published a paper on his theory called continental drift.
  • It is a hypothesis that Earth’s continents were moving across Earth, and sometimes, even colliding into one another.
  • According to Wegener’s theory, Earth’s continents were once joined as a single, giant landmass, which he called Pangaea.
  • But over time, Pangaea broke apart and formed the continents as we know them today.
  • Wegener couldn’t explain why this phenomenon was happening, so at the time, his theory was heavily criticized by his colleagues.
  • But over the years, technological advances allowed scientists to study the Earth more closely, and geologists started to build on Wegener’s theory.

Rise over to Plate Tectonics

  • Discoveries like seafloor spreading helped explain the “why” behind continental movement, and eventually, Wegener’s initial continental drift theory morphed into plate tectonic theory.
  • And now, the idea that Earth’s crust is slowly moving beneath our feet is widely accepted.

The Seven Major Tectonic Plates

There are seven major plates, and dozens of minor plates, that make up the outer crust of the Earth. The big seven are:

  1. North American plate
  2. Eurasian plate
  3. Pacific plate
  4. South American plate
  5. African plate
  6. Indo-Australian plate
  7. Antarctic plate

 

The areas between these plates are known as plate boundaries, and their interactions cause some crazy things to happen on Earth’s surface.

There are three types of plate boundaries:

  1. Divergent boundary
  • A divergent boundary is when two plates move away from each other, which creates a fracture in the lithosphere.
  • A well-known divergent boundary is the Mid-Atlantic Ridge, which runs approximately 10,000 miles from the Arctic Ocean all the way down to the south of Africa.
  1. Convergent boundary
  • A convergent boundary is when two plates collide with one another.
  • If the collision is between oceanic crust and continental crust, the denser oceanic crust slides underneath the other plate, which is a process known as subduction.
  • When two continental crusts collide, the rock folds and lifts at the boundary, creating mountains like the Himalayas (where the Indian plate meets the Eurasian plate).
  1. Transform Boundary
  • When two plates move parallel to one another, their meeting point is called a transform boundary. The friction causes tension.
  • Eventually, that tension needs to be released, which can cause earthquakes.
  • The San Andreas Fault is a well-known major transform boundary between the North American and Pacific plates—it caused the infamous San Francisco earthquake of 1906.

How do we apply this theory here?

  • A landmass called Gondwana, split into two 165 million years ago — one containing what is now Africa and South America, the other comprising India, Madagascar, Australia and Antarctica.
  • Around 115 million years ago, Madagascar and India together broke free.
  • Around 88 million years ago, India moved northward, dropping a few parcels of land along the way to form Seychelles.
  • It joined the Eurasian mass 50 million years ago giving rise to the Himalayas and South Asia that we are familiar with.
  • Around 115 million years ago, it was the dinosaurs that ruled. Many life forms had not even evolved.

Substantiation to this study

(1) Fossil study

  • Supporting the Gondwana breakup, dinosaur fossils found in India and Madagascar are closely related and do not resemble species found in Africa and Asia.
  • Fragments of Laplatosaurus madagascarensis have been found in both India and Madagascar.

(2) Molecular clocks

  • A powerful technique, the molecular clock, is used to estimate the time when two forms of life diverged from each other.
  • It is based on the observation that evolutionary changes in the sequence of an RNA or a protein molecule occur at a fairly constant rate.
  • The difference in the amino acids of, say the haemoglobin of two animals can tell you how long ago their lineages diverged.
  • Molecular clocks corroborate well with other evidence, such as the fossil record.
  • South India and Sri Lanka have only two genuses of the cichlid family of freshwater and brackish-water fishes — the Etroplus (a food fish in Kerala, where it is called pallathi) and Pseudetroplus.
  • Molecular comparisons show that the nearest relatives of Etroplus are found in Madagascar, and their common ancestor diverged from African cichlids 160 million years ago.

India’s pivotal position

  • India occupies a pivotal position in the distribution of life forms in Asia, Madagascar and Africa. Gondwana creatures moved out of India.
  • Others crossed over to stay. For example, Asian freshwater crabs (Gecarcinucidae) are now found all over Southeast Asia but their most recent common ancestor evolved in India.
  • Fossil finds in the Vastan lignite mine in Gujarat by researchers have identified the earliest Indian mammal, a species of bat, and the earliest euprimate, a primitive lemur.
  • These were dated 53 million years ago, around the time (or just before) the India-Eurasian plates collided.

What about the lemurs?

  • Madagascar is a large island, with a variety of climatic conditions. Evidence favours an ancestor primate crossing over from Africa.
  • No monkey, ape or large predator managed the crossing, so dozens of lemur species proliferated.
  • In India, we have the lorises, which are the closest extant relatives of the lemurs.
  • These are shy, nocturnal forest dwellers, with large, appealing eyes.
  • They are also believed to have survived oceanic rides from Africa.
  • They are mostly found in the Northeastern States (slow loris), and where Karnataka, Kerala and Tamil Nadu meet (slender loris).

 

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Global Geological And Climatic Events

Summer Solstice 2022: What is it and how is it significant?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Summer Solstice

Mains level: NA

Yesterday, June 21 was the day of the summer solstice in the northern hemisphere.

What is Summer Solstice?

  • Solstice means “sun stands still” in Latin.
  • The longest day of 2021 for those living north of the Equator is June 21.
  • This day is characterized by a greater amount of energy received from the sun.
  • In technical terms, this day is referred to as the summer solstice, the longest day of the summer season.
  • It occurs when the sun is directly over the Tropic of Cancer, or more specifically right over 23.5-degree north latitude.

The Southern Hemisphere receives most sunlight on December 21, 22 or 23 when the northern hemisphere has its longest nights– or the winter solstice.

Why do we have summer solstice?

  • Since Earth rotates on its axis, the Northern Hemisphere gets more direct sunlight between March and September over the course of a day.
  • This also means people living in the Northern Hemisphere experience summer during this time.
  • The rest of the year, the Southern Hemisphere gets more sunlight.
  • During the solstice, the Earth’s axis — around which the planet spins, completing one turn each day — is tilted in a way that the North Pole is tipped towards the sun and the South Pole is away from it.

Answer this PYQ in the comment box:

Q.On 21st June, the Sun (CSP 2019):

 

(a) Does not set below the horizon at the Arctic Circle

(b) Does not set below the horizon at Antarctic Circle

(c) Shines vertically overhead at noon on the Equator

(d) Shines vertically overhead at the Tropic of Capricorn

 

Post your answers here.
10
Please leave a feedback on thisx

Some interesting facts

  • During the June solstice compared to any other time of the year, the North Pole is tipped more directly toward the sun, and the south pole is tipped more directly away from the sun.
  • As a result, all locations north of the equator see days longer than 12 hours and all locations south see days shorter than 12 hours.
  • The sun’s path across the sky is curved—NOT a straight line on the summer solstice.
  • Based on Earth’s current orbit, the summer solstice date rotates between June 20, 21 and 22 and is not fixed since it depends on the physics of our solar system and not on human calendar.

 

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Global Geological And Climatic Events

In news: Tropical Cyclone Asani

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Tropical cyclones

Mains level: Frequent recurrence of Cyclones in India

Severe cyclonic storm ‘Asani’, packing winds above 105 kmph and setting off heavy rain, is likely to make landfall on the eastern coast of India.

What are tropical Cyclones?

  • A tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain.
  • Cyclones are formed over slightly warm ocean waters. The temperature of the top layer of the sea, up to a depth of about 60 meters, need to be at least 28°C to support the formation of a cyclone.
  • This explains why the April-May and October-December periods are conducive for cyclones.
  • Then, the low level of air above the waters needs to have an ‘anticlockwise’ rotation (in the northern hemisphere; clockwise in the southern hemisphere).
  • During these periods, there is an ITCZ in the Bay of Bengal whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west.
  • Once formed, cyclones in this area usually move northwest. As it travels over the sea, the cyclone gathers more moist air from the warm sea which adds to its heft.

Requirements for a Cyclone to form

There are six main requirements for tropical cyclogenesis:

  • Sufficiently warm sea surface temperatures
  • Atmospheric instability
  • High humidity in the lower to middle levels of the troposphere
  • Enough Coriolis force to develop a low-pressure centre
  • A pre-existing low-level focus or disturbance
  • Low vertical wind shear

How are the cyclones named?

  • In 2000, a group of nations called WMO/ESCAP (World Meteorological Organisation/United Nations Economic and Social Commission for Asia and the Pacific) decided to name cyclones.
  • It comprised Bangladesh, India, the Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand, decided to start naming cyclones in the region.
  • After each country sent in suggestions, the WMO/ESCAP Panel on Tropical Cyclones (PTC) finalised the list.
  • The WMO/ESCAP expanded to include five more countries in 2018 — Iran, Qatar, Saudi Arabia, United Arab Emirates and Yemen.

Why is it important to name cyclones?

  • Adopting names for cyclones makes it easier for people to remember, as opposed to numbers and technical terms.
  • It’s easier and less confusing to say “Cyclone Titli” than remember the storm’s number or its longitude and latitude.
  • Apart from the general public, it also helps the scientific community, the media, disaster managers etc.
  • With a name, it is also easy to identify individual cyclones, create awareness of its development, rapidly disseminate warnings to increase community preparedness etc.

 

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Global Geological And Climatic Events

What is Daylight Saving Time (DST)?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Daylight Saving Time (DST), Equinoxes

Mains level: Not Much

The United States Senate unanimously passed a law making daylight saving time (DST) permanent, scrapping the biannual practice of putting clocks forward and back coinciding with the arrival and departure of winter.

What does this imply?

  • With clocks in the US going back an hour, the time difference between New York and India will increase from the current nine and a half hours to ten and a half hours.
  • In the Southern Hemisphere, the opposite has happened, where countries have “sprung forward”, and time difference with India has reduced.

What is DST?

  • DST is the practise of resetting clocks ahead by an hour in spring, and behind by an hour in autumn (or fall).
  • During these months, countries that follow this system get an extra hour of daylight in the evening.
  • Because the spring to fall cycle is opposite in the Northern and Southern Hemispheres, DST lasts from March to October/November in Europe and the US, and from September/October to April in New Zealand and Australia.
  • Dates for this switch, which happens twice a year (in the spring and autumn) are decided beforehand.
  • By law, the 28 member states of the EU switch together — moving forward on the last Sunday of March and falling back on the last Sunday in October.
  • In the US, clocks go back on the first Sunday of November.

Now try this PYQ:

Q.On 21st June, the Sun

(a) Does not set below the horizon at the Arctic Circle

(b) Does not set below the horizon at Antarctic Circle

(c) Shines vertically overhead at noon on the Equator

(d) Shines vertically overhead at the Tropic of Capricorn

How many countries use DST?

  • DST is in practice in some 70 countries, including those in the European Union.
  • India does not follow DST; since countries near the Equator do not experience high variations in daytime hours between seasons.
  • There is, however, a separate debate around the logic of sticking with an only one-time zone in a country as large as India.

What does this system mean to achieve?

  • The key argument is that DST is meant to save energy.
  • The rationale behind setting clocks ahead of standard time, usually by 1 hour during springtime, is to ensure that the clocks show a later sunrise and later sunset — in effect a longer evening daytime.
  • Individuals will wake an hour earlier than usual, complete their daily work routines an hour earlier, and have an extra hour of daylight at the end.

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Global Geological And Climatic Events

What is Bomb Cyclone?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Bomb Cyclone, Bombogenesis

Mains level: Not Much

Major cities such as New York and Boston in US are witnessing a “Bomb Cyclone” characterized by the explosive power of rapid drops in atmospheric pressure.

What is Bomb Cyclone?

  • A bomb cyclone is a large, intense mid-latitude storm that has low pressure at its center, weather fronts and an array of associated weather, from blizzards to severe thunderstorms to heavy precipitation.
  • It becomes a bomb when its central pressure decreases very quickly—by at least 24 millibars in 24 hours.
  • When a cyclone “bombs,” or undergoes bombogenesis, this tells us that it has access to the optimal ingredients for strengthening, such as high amounts of heat, moisture and rising air.

Why is it called a bomb?

  • Most cyclones don’t intensify rapidly in this way.
  • Bomb cyclones put forecasters on high alert, because they can produce significant harmful impacts.

Its etymology

  • The word “bombogenesis” is a combination of cyclogenesis, which describes the formation of a cyclone or storm, and bomb, which is, well, pretty self-explanatory.
  • This can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters.
  • The formation of this rapidly strengthening weather system is a process called bombogenesis, which creates what is known as a bomb cyclone.

How does it occur?

  • Over the warmer ocean, heat and moisture are abundant.
  • But as cool continental air moves overhead and creates a large difference in temperature, the lower atmosphere becomes unstable and buoyant.
  • Air rises, cools and condenses, forming clouds and precipitation.

Where does it occur the most?

  • The US coast is one of the regions where bombogenesis is most common.
  • That’s because storms in the mid-latitudes – a temperate zone north of the tropics that includes the entire continental US – draw their energy from large temperature contrasts.
  • Along the US East Coast during winter, there’s a naturally potent thermal contrast between the cool land and the warm Gulf Stream current.

 

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Global Geological And Climatic Events

What is the Pacific ‘Ring of Fire’?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Active Volcanoes in Pacific ‘Ring of Fire’

Mains level: Pacific ‘Ring of Fire’

The Hunga Tonga-Hunga Ha’apai volcano which massively erupted lies along the Pacific ‘Ring of fire’, and is just over 60 kilometers from the island nation of Tonga.

What is the Pacific ‘Ring of Fire’?

  • The Pacific ‘Ring of Fire’ or Pacific rim, or the Circum-Pacific Belt, is an area along the Pacific Ocean that is characterized by active volcanoes and frequent earthquakes.
  • Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire.
  • It is home to about 75 per cent of the world’s volcanoes – more than 450 volcanoes.
  • Also, about 90 per cent of the world’s earthquakes occur here.

Its spread

  • Its length is over 40,000 kilometres and traces from New Zealand clockwise in an almost circular arc covering Tonga, Kermadec Islands, Indonesia.
  • It is moving up to the Philippines, Japan, and stretching eastward to the Aleutian Islands, then southward along the western coast of North America and South America.

Seismic activity of the region

  • The area is along several tectonic plates including the Pacific plate, Philippine Plate, Juan de Fuca plate, Cocos plate, Nazca plate, and North American plate.
  • The movement of these plates or tectonic activity makes the area witness abundant earthquakes and tsunamis every year.
  • Along much of the Ring, tectonic plates move towards each other creating subduction zones.
  • One plate gets pushed down or is subducted by the other plate.
  • This is a very slow process – a movement of just one or two inches per year.
  • As this subduction happens, rocks melt, become magma and move to Earth’s surface and cause volcanic activity.

What has happened in recent eruption in Tonga?

  • In the case of Tonga, the Pacific Plate was pushed down below the Indo-Australian Plate and Tonga plate, causing the molten rock to rise above and form the chain of volcanoes.
  • Subduction zones are also where most of the violent earthquakes on the planet occur.
  • The December 26, 2004 earthquake occurred along the subduction zone where the Indian Plate was subducted beneath the Burma plate.

 

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Global Geological And Climatic Events

Undersea Volcanic Eruption in Hunga Islands, Tonga

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Hunga Volcano

Mains level: Not Much

A distant undersea volcano has erupted in spectacular fashion near the Pacific nation of Tonga sending large tsunami waves reaching the shore.

Hunga Volcano

  • The Hunga-Tonga-Hunga-Ha’apai volcano has erupted regularly over the past few decades.
  • It consists of two small uninhabited islands, Hunga-Ha’apai and Hunga-Tonga, poking about 100m above sea level 65km north of Tonga’s capital Nuku’alofa.
  • But hiding below the waves is a massive volcano, around 1800m high and 20 kilometres wide.
  • During events in 2009 and 2014/15 hot jets of magma and steam exploded through the waves. But these eruptions were small, dwarfed in scale by the January 2022 events.
  • Researchers suggest this is one of the massive explosions the volcano is capable of producing roughly every thousand years.

Impact of the eruption

  • The ash plume is already about 20km high.
  • Most remarkably, it spread out almost concentrically over a distance of about 130km from the volcano, creating a plume with a 260km diameter, before it was distorted by the wind.
  • The eruption also produced a tsunami throughout Tonga and neighbouring Fiji and Samoa.
  • Shock waves traversed many thousands of kilometres, were seen from space, and recorded in New Zealand some 2000km away.
  • All these signs suggest the large Hunga caldera has awoken.

Why is it so explosive even after being underwater?

Answer: Fuel-coolant interaction

  • If magma rises into sea water slowly, even at temperatures of about 1200 degrees Celsius, a thin film of steam forms between the magma and water.
  • This provides a layer of insulation to allow the outer surface of the magma to cool.
  • But this process doesn’t work when magma is blasted out of the ground full of volcanic gas.
  • When magma enters the water rapidly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water.
  • Volcano researchers call this ‘fuel-coolant interaction’ and it is akin to weapons-grade chemical explosions.

A chain reaction

  • Extremely violent blasts tear the magma apart.
  • A chain reaction begins, with new magma fragments exposing fresh hot interior surfaces to water, and the explosions repeat, ultimately jetting out volcanic particles and causing blasts with supersonic speeds.

How has it emerged out to be so big?

  • The caldera is a crater-like depression around 5km across.
  • Small eruptions (such as in 2009 and 2014/15) occur mainly at the edge of the caldera, but very big ones come from the caldera itself.
  • These big eruptions are so large the top of the erupting magma collapses inward, deepening the caldera.
  • Looking at the chemistry of past eruptions, we now think the small eruptions represent the magma system slowly recharging itself to prepare for a big event.

What next?

  • This latest eruption has stepped up the scale in terms of violence.
  • Researchers are still in the middle of this major eruptive sequence and many aspects remain unclear, partly because the island is currently obscured by ash clouds.

 

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Global Geological And Climatic Events

India’s first open Rock Museum in Hyderabad

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Indian Rock System

Mains level: NA

The Ministry of Science & Technology has inaugurated India’s first open rock museum displaying different types of rocks gathered from different States of ages ranging from 3.3 billion years to around 55 million years.

Rock System in India

Based on this complex and varied geological history, the Geological Survey of India has classified rock systems of the country into 4 major divisions:

  1. Archaean Rock System
  2. Dravidian Rock System
  3. Purana Rock System
  4. Aryan Rock System

[I] Archaean Rock System:

The Archaean group of rocks consists of two systems-(a) Achaean granites and gneisses, and (b) Dharwarian sedimentary:

Archaean Gneisses and Schists (pre-2500 million years)

  • The Archean System contains the first formed rocks of the earth.
  • The rocks are primarily gneisses and granites, having no marks of fossils.
  • They often underlie the strata formed subsequently and the system is generally known as the basement complex or fundamental gneisses.
  • The Archaean rocks cover two-thirds of peninsular India. They also occur in the roots of the mountain peaks all along the Greater Himalayas, trans-Himalayan ranges of Zaskar, Ladakh and Karakoram.

Dharwar System (2500-1800 million years ago)

  • The weathering of the Archaean rocks yielded the earliest sediments and formed the oldest sedimentary strata, the Dharwar system.
  • These are found today in metamorphic forms and do not contain fossils.
  • These rocks occur in scattered patches in parts of Karnataka, Tamil Nadu, central and eastern parts of Chotanagpur plateau, Meghalaya plateau, Aravalis, Himalayan region etc

Mineral contents:

  • They contain gneisses (which range from granite to gabbro) and schists (crystalline rocks such as mica, talc etc.).
  • These rocks have metallic and non-metallic minerals like copper, tin, graphite, lead, zinc, etc.

[II] Dravidian Rock System:

  • This is also known as carboniferous rock system and formed during the Paleozoic era, i.e., from 600- 300 million years ago.
  • They are not much abundant in India.
  • They have plentiful fossils and beginning of coal formation can be seen in this period. The quality of carboniferous coal is high.
  • They are found in extra- Peninsular regions of the Himalayas and the Gangetic plains.

Mineral content

  • This type of rock system comprises of limestones, shale and quartzite and Mount Everest is formed of upper Carboniferous limestones.
  • Most of the coal is not of the Carboniferous period, which is found in India.
  • The meaning of Carboniferous in geology is coal-bearing.

[III] Purana Rock System:

The Purana rock system has two divisions: Cuddapah system and Vindhyan system. The word ‘Purana’ was used in place of a Proterozoic era in India.

Cuddapah Rock system:

  • They are observed in Cuddapah districts of Andhra Pradesh.
  • The non-fossiliferous clay, slates, sandstones and limestones were accumulated in the depression between two-fold mountains which is known as synclinal basins.
  • They also have a large accumulation of building purpose cement grade limestones and quartzites.
  • This type of rock contains ore of iron, cobalt, nickel, manganese etc.

Vindhya Rock System:

  • This type of rock system is also ancient or old sedimentary rocks which are superimposed on the Archaean rock base and derived its name from Vindhya mountains.
  • The recognition of fossils is negligible, only traces of few animal and plant life were found.
  • This rock system has diamond-bearing regions from which Golconda and Panna diamond mined.

[IV] Aryan Rock System

The Aryan rock system in India has the following four subsystems:

  1. Gondwana rock system
  2. Jurassic Rock System
  3. Cretaceous system/ Deccan Trap
  4. Tertiary rock system

(1) Gondwana Rock System:

  • These are found mainly in Raniganj, Jharia regions of Jharkhand, Damodar valley, Pench valley in Chhattisgarh and Madhya Pradesh.
  • They are called so after the name of Gondwana tribe (indigenous people especially residing in Telangana and Andhra Pradesh region).
  • In this type of rock system, you found metallic minerals like iron, manganese, uranium etc. other than coal.
  • They have low carbon content as it is much younger than Carboniferous coal. These rocks have nearly 98% of India’s coal reserve.

(2) Jurassic Rock System

  • During the latter part of Jurrasic when sea level rises as compared to land and shoreline moves towards ground or land which result in a flood. In geology, this phenomenon is called marine transgression.
  • This gives rise to a thick series of shallow-water deposits kin Rajasthan and Kutch. Between the Guntur and Rajamundry, another transgression in the east coast of Peninsula.
  • In Kuchchh, coral limestone, shales and conglomerates are found.

(3) Deccan traps

  • These are formed by the flow of magma over the solidified rock system in layers.
  • Deccan trap gets rise due to volcanic outburst over a major area of Peninsular India from the end of Cretaceous till the beginning of Eocene.
  • The meaning of trap is “stair” or “step” in Swedish and called due to deposition of the volcanic outburst which has a flat top and steep sides.
  • It is mainly found in parts of Kuchchh, Saurashtra, Maharashtra, the Malwa plateau and Northern Karnataka and presently cover near 5 lakh sq. Km.
  • Regur, which is black soil, is formed due to the weathering of these rocks for a long time.

(4) Tertiary rock system

  • The formation of this type of rock system occurs from 60 to 7 million years ago.
  • It is the most noteworthy period in India’s geological history as the Himalayas were born and recent form came in this period.

Also read:

The Geological Structure of India

 

 

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Global Geological And Climatic Events

Earth’s first landmass emerged in Singhbhum: Study

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Emergence of landmass on Earth

Mains level: Not Much

A new study has challenged the widely accepted view that the continents rose from the oceans about 2.5 billion years ago.

About Singhbhum

  • Singhbhum district of Jharkhand is part of the Chhota Nagpur Division.
  • It is one of the leading producers of copper in India.

First landmass to emerge

  • The study suggests that the earliest continental landmass to emerge may have been Jharkhand’s Singhbhum region.
  • Scientists have found sandstones in Singhbhum with geological signatures of ancient river channels, tidal plains and beaches over 3.2 billion years old.
  • They somewhat represent the earliest crust exposed to air.

Studying the sandstones

  • The research studies a sedimentary rock, called granite. They tried to find their age and in which conditions they have formed.
  • They found the age by analysing the uranium and lead contents of tiny minerals.
  • These rocks are 3.1 billion years old, and were formed in ancient rivers, beaches, and shallow seas.
  • All these water bodies could have only existed if there was continental land.
  • Thus, they inferred that the Singhbhum region was above the ocean before 3.1 billion years ago.

How did they analyse?

  • The researchers studied the granites that form the continental crust of Singhbhum region.
  • These granites are 3.5 to 3.1 billion years old and formed through extensive volcanism that happened about 35-45 km deep inside the Earth.
  • This process continued on-and-off for hundreds of millions of years until all the magma solidified to form a thick continental crust in the area.
  • Due to the thickness and less density, the continental crust emerged above surrounding oceanic crust owing to buoyancy.

Back2Basics: Emergence of Landmass

  • In the beginning, more than 4.6-billion years ago, the world was a ball of burning gas, spinning through space.
  • It took hundreds of millions of years for the first land masses to emerge.
  • About 250-million years ago, long, long after the Earth had formed, all the continents of the time had joined together to form a super-continent called Pangaea.
  • This super-continent broke up about 200-million years ago to form two giant continents, Gondwana and Laurasia.
  • Gondwana comprised what is now Africa, South America, Australia, Antarctica and India.
  • The Indian sub-continent lay off the east coast of Africa, before it broke off and moved north rapidly.

Isostacy

  • Huge plates of crustal and upper mantle material (lithosphere) “float” on more dense, plastically flowing rocks of the asthenosphere.
  • The “depth” to which a plate, or block of crust, sinks is a function of its weight and varies as the weight changes.
  • This equilibrium, or balance, between blocks of crust and the underlying mantle is called isostasy.
  • The taller a block of crust is, the deeper it penetrates into the mantle because of its greater mass and weight. Isostasy occurs when each block settles into an equilibrium with the underlying mantle.
  • Blocks of crust that are separated by faults will “settle” at different elevations according to their relative mass.

 

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Global Geological And Climatic Events

What is Leonid’s Meteor Shower?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Leonid Meteor Shower

Mains level: Not Much

The annual Leonid’s Meteor Shower has begun.

Try this question from CSP 2014:

Q.What is a coma, in the content of astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

 

Post your answers here.
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What is Leonid Meteor Shower?

  • Meteor showers are named after the constellation they appear to be coming from.
  • The Leonids originate from the constellation Leo the Lion– the groups of stars that form a lion’s mane.
  • They emerge from the comet Tempel-Tuttle, which requires 33 years to revolve once around the Sun.
  • These meteors are bright and among the fastest moving– travelling at speeds of 71 km per second.
  • During this year’s showers, peaks of around 10 to 15 meteors are expected to be seen every hour.
  • The Leonid showers include fireballs– bright and large meteors than can last longer than average meteors, and “earthgazers”– meteors which appear close to the horizon with colourful and long tails.

What is a meteor shower?

  • On its journey around the Sun, the Earth passes through large swathes of cosmic debris.
  • The debris is essentially the remnants of comets — great frigid chunks of matter that leave behind dirty trails of rocks and ice that linger long after the comets themselves have passed.
  • As the Earth wades through this cloud of comet waste, the bits of debris create what appears from the ground to be a fireworks display in the sky — known as a meteor shower.
  • Several meteor showers can be seen around the year. According to NASA, over 30 meteor showers occur annually and are observable from the Earth.

Back2Basics:

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Global Geological And Climatic Events

Sixth Mass Extinction?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Species Extinction

Mains level: Mass Extinction

A paper published recently has come up with a new reason behind the first mass extinction, also known as the Late Ordovician mass extinction.

Species Extinction

  • Extinction is a part of life, and animals and plants disappear all the time. About 98% of all the organisms that have ever existed on our planet are now extinct.
  • When a species goes extinct, its role in the ecosystem is usually filled by new species, or other existing ones.

What is Mass Extinction?

  • Earth’s ‘normal’ extinction rate is often thought to be somewhere between 0.1 and 1 species per 10,000 species per 100 years.
  • This is known as the background rate of extinction.
  • A mass extinction event is when species vanish much faster than they are replaced.
  • This is usually defined as about 75% of the world’s species being lost in a ‘short’ amount of geological time – less than 2.8 million years.

How many mass extinctions have there been?

Five great mass extinctions have changed the face of life on Earth. We know what caused some of them, but others remain a mystery:

[I] Ordovician-Silurian ME

  • It occurred 443 million years ago and wiped out approximately 85% of all species.
  • Scientists think it was caused by temperatures plummeting and huge glaciers forming, which caused sea levels to drop dramatically.
  • This was followed by a period of rapid warming. Many small marine creatures died out.

[II] Devonian ME

  • It took place 374 million years ago and killed about three-quarters of the world’s species, most of which were marine invertebrates that lived at the bottom of the sea.
  • This was a period of many environmental changes, including global warming and cooling, a rise and fall of sea levels and a reduction in oxygen and carbon dioxide in the atmosphere.
  • We don’t know exactly what triggered the extinction event.

[III] Permian ME

  • It happened 250 million years ago, was the largest and most devastating event of the five.
  • Also known as the Great Dying, it eradicated more than 95% of all species, including most of the vertebrates which had begun to evolve by this time.
  • Some scientists think Earth was hit by a large asteroid which filled the air with dust particles that blocked out the Sun and caused acid rain.
  • Others think there was a large volcanic explosion that increased carbon dioxide and made the oceans toxic.

[IV] Triassic ME

  • It took place 200 million years ago, eliminating about 80% of Earth’s species, including many types of dinosaurs.
  • This was probably caused by colossal geological activity that increased carbon dioxide levels and global temperatures, as well as ocean acidification.

[V] Cretaceous ME

  • It occurred 65 million years ago, killing 78% of all species, including the remaining non-avian dinosaurs.
  • This was most likely caused by an asteroid hitting the Earth in what is now Mexico, potentially compounded by ongoing flood volcanism in what is now India.

What caused first ME?

  • The cooling climate likely changed the ocean circulation pattern.
  • This caused a disruption in the flow of oxygen-rich water from the shallow seas to deeper oceans, leading to a mass extinction of marine creatures.
  • Ordovician Sea has familiar groups like clams and snails and sponges.
  • Many other groups are now very reduced in diversity or entirely extinct like trilobites, brachiopods, and crinoids.

The sixth mass extinction

  • We are currently experiencing a sixth mass extinction as the result of human-induced climate change.
  • There have been several theories behind each mass extinction and with advances in new technologies, researchers have been uncovering more intricate details about these events.

Try this PYQ from CSP 2018

The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of:

 

(a) Widespread monoculture Practices agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.

(b) Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65million years ago that caused the mass extinction of many species including those of dinosaurs.

(c) Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivation in other Parts of the world may cause the disappearance of good native crop plants and the loss of food biodiversity.

(d) Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss, natural habitats, destruction of ecosystems, pollution and global climate change.

 

Post your answers here.
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Global Geological And Climatic Events

Hurricane Ida makes landfall in US

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Hurricane (Tropical Cycolnes)

Mains level: Impact of frequent cyclonic landfalls

Hurricane Ida has made landfall in Louisiana, US as an extremely dangerous Category 4 storm.

What is a Hurricane?

  • A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and the northeastern Pacific Ocean.
  • And a typhoon occurs in the northwestern Pacific Ocean; in the south Pacific or the Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.

What are Tropical Cyclones?

A Tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain.

  • Cyclones are formed over slightly warm ocean waters. The temperature of the top layer of the sea, up to a depth of about 60 meters, need to be at least 28°C to support the formation of a cyclone.
  • This explains why the April-May and October-December periods are conducive for cyclones.
  • Then, the low level of air above the waters needs to have an ‘anticlockwise’ rotation (in the northern hemisphere; clockwise in the southern hemisphere).
  • During these periods, there is an ITCZ in the Bay of Bengal whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west.
  • Once formed, cyclones in this area usually move northwest. As it travels over the sea, the cyclone gathers more moist air from the warm sea which adds to its heft.

Try this question from CSP 2020:

Q.Consider the following statements:

  1. Jet Streams occur in the Northern Hemisphere only.
  2. Only some cyclones develop an eye.
  3. The temperature inside the eye of a cyclone is nearly 10 degree Celsius lesser than that of the surroundings.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3 only

(c) 2 only

(d) 1 and 3 only

 

Post your answers here.
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Destruction caused

  • Strong Winds: Cyclones are known to cause severe damage to infrastructure through high-speed winds.
  • Torrential rains and inland flooding: Torrential rainfall (more than 30 cm/hour) associated with cyclones is another major cause of damages. Unabated rain gives rise to unprecedented floods.
  • Storm Surge: A Storm surge can be defined as an abnormal rise of sea level near the coast caused by a severe tropical cyclone.

Some (unexpected) benefits

Although Tropical cyclones are known for the destruction they cause, when they strike they also bestow certain benefits to the climatic conditions of that area such as

  • Relieve drought conditions
  • Carry heat and energy away from the tropics and transport it towards temperate latitudes
  • Maintain a relatively stable and warm temperature worldwide

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Also read:

[Burning Issue] Tropical Cyclones and India

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Global Geological And Climatic Events

Hawaii’s Kilauea Volcano

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Volanic eruptions in news

Mains level: Volcanic landforms

Geologists have detected a swarm of earthquakes at Hawaii’s Kilauea volcano, though it was not erupting.

Kilauea Volcano

  • Kilauea is about 200 miles south of Honolulu, on the Big Island of Hawaii.
  • It is one of the world’s most active volcanoes, having erupted 34 times since 1952. In Hawaiian tradition, Kilauea is home to the volcano goddess Pele.
  • From 1983 to 2018, it erupted almost continuously, in some cases sending streams of lava that covered farms and homes.
  • At the end of this decades-long eruption, Kilauea spewed lava from vents in a residential neighborhood on its eastern flank and destroyed more than 700 homes.
  • In December, Kilauea erupted at the crater, creating a lake with enough lava to fill 10 Hoover dams. That eruption ended in May.

Do not skip answering this PYQ:

Consider the following statements:

  1. The Barren Island volcano is an active volcano located in the Indian Territory.
  2. Barren Island lies about 140 km east of Great Nicobar.
  3. The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

Which of the statements given above is/are correct? (CSP 2014)

(a) 1 only

(b) 2 and 3 only

(c) 3 only

(d) 1 and 3 only

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Back2Basics: Volcanic Landforms

  • Note the intrinsic and extrinsic types of volcanic landforms

  • A volcano has 3 main characteristics
  1. Cone shaped mountain
  2. Formed by rock or ash thrown from the inside of the earth
  3. At times, opening or depression at top
  • The three main types of volcanos are:

  1. Cinder cone Volcano: The cinder cones are small volcanoes with steep sides. Even though they are small, these are the ones you probably hear about.  They are very explosive and made of ash and rock.  Most of the cinder cones are small and less than 500 meters high.  A famous cinder cone is Sunset Crater Volcano in Arizona.
  2. Shield Volcanoes: A shield is a low and broad volcano that usually has a very wide crater (a dent in the Earth’s surface). It is formed from thin layers of lava after consistent low-grade eruptions.  The largest volcano in the world is a shield volcano.  It is located in Hawaii.
  3. Composite volcanoes: They are the tallest type of volcano. They look very impressive but do usually have quiet and slow lava flows.  They sometimes have small eruptions that cause ash and rock to go flying.  One of the most famous volcanoes in the world is a composite volcano.  It is Mount Fuji in Japan.

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Global Geological And Climatic Events

How the Moon ‘Wobble’ affects rising tides

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Moon wobble

Mains level: Moon wobble and climate change

US coastlines will face increasing flooding in the mid-2030s due to a regular lunar cycle called the wobble effect that will magnify rising sea levels caused by climate change.

What is the Moon Wobble?

  • The moon wobble is nothing but a regular swaying in the moon’s orbit.
  • It was first documented way back in 1728.
  • This wobble takes over an 18.6-year period to complete and continues in a cyclic fashion.

How does this wobble occur?

  • High tides on this planet are caused mostly by the pull of the moon’s gravity on a spinning Earth. On most beaches, you would see two high tides every 24 hours.
  • The moon also revolves around the Earth about once a month, and that orbit is a little bit tilted.
  • moon’s orbital plane around the Earth is at an approximate 5-degree incline to the Earth’s orbital plane around the sun.
  • Because of that, the path of the moon’s orbit seems to fluctuate over time, completing a full cycle — sometimes referred to as a nodal cycle — every 18.6 years.
  • At certain points along the cycle, the moon’s gravitational pull comes from such an angle that it yanks one of the day’s two high tides a little bit higher, at the expense of the other.
  • This does not mean that the moon itself is wobbling, nor that its gravity is necessarily pulling at our oceans any more or less than usual.

What impact does this wobble have on Earth?

  • Influences the ebb and flow of tides: The moon wobbles impacts the gravitational pull of the moon, and therefore, indirectly influences the ebb and flow of tides here on the Earth.
  • One half of the 18.6-year cycle suppresses the tides, which means that the high tides get lower, while the low tides get higher than normal.
  • Once this cycle completes, the situation flips—in the subsequent cycle, the tides are amplified, with high tides getting higher and low tides, lower.
  • The lunar cycle is expected to shift again by mid-2030, and in the coming phase, the tides will amplify once again.

Moon wobble and climate change

  • The upcoming changes in the lunar cycle will pose a serious threat, as the amplified high tides coupled with the rising sea levels will make the risk of flooding far greater across all coastal regions of the globe.
  • The study predicts that the high tide-associated floods—also known as nuisance floods or sunny day floods—may occur in clusters that could last for months or even for longer periods!
  • This surge will be closely associated with the position of the Moon, Earth and the Sun.
  • When the Moon and Earth line up in specific ways with each other and the Sun, the resulting gravitational pull and the ocean’s corresponding response may leave city-dwellers coping with floods every day or two.

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Global Geological And Climatic Events

What is Summer Solstice?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Rotation and Revolution of Earth

Mains level: NA

The summer solstice will happen today around 9:02 am on Monday (Indian Standard Time).

What is Summer Solstice?

  • Solstice means “sun stands still” in Latin.
  • The longest day of 2021 for those living north of the Equator is June 21.
  • This day is characterized by a greater amount of energy received from the sun.
  • In technical terms, this day is referred to as the summer solstice, the longest day of the summer season. It occurs when the sun is directly over the Tropic of Cancer, or more specifically right over 23.5-degree north latitude.

The Southern Hemisphere receives most sunlight on December 21, 22 or 23 when the northern hemisphere has its longest nights– or the winter solstice.

Why do we have summer solstice?

  • Since Earth rotates on its axis, the Northern Hemisphere gets more direct sunlight between March and September over the course of a day.
  • This also means people living in the Northern Hemisphere experience summer during this time.
  • The rest of the year, the Southern Hemisphere gets more sunlight.
  • During the solstice, the Earth’s axis — around which the planet spins, completing one turn each day — is tilted in a way that the North Pole is tipped towards the sun and the South Pole is away from it.

Answer this PYQ in the comment box:

Q.On 21st June, the Sun (CSP 2019):

(a) Does not set below the horizon at the Arctic Circle

(b) Does not set below the horizon at Antarctic Circle

(c) Shines vertically overhead at noon on the Equator

(d) Shines vertically overhead at the Tropic of Capricorn

Some other facts

  • Summer solstice does not mean the earliest sunrise or latest sunset.
  • Although June 21 will be the longest day in 2021, it does not necessarily mean that it brings the earliest sunrise or latest sunset.
  • It depends on the latitudinal location of the country.

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Global Geological And Climatic Events

What is a Supermoon?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Lunar Eclipse

Mains level: Not Much

The Moon will have the nearest approach to Earth on May 26, and therefore will appear to be the closest and largest Full Moon or “supermoon” of 2021.

Tap here to read more about Solar and Lunar Eclipses

What is a Supermoon?

  • A supermoon occurs when the Moon’s orbit is closest to the Earth at the same time that the Moon is full.
  • As the Moon orbits the Earth, there is a point of time when the distance between the two is the least (called the perigee when the average distance is about 360,000 km from the Earth).
  • Also, there is a point of time when the distance is the most (called the apogee when the distance is about 405,000 km from the Earth).
  • Now, when a full moon appears at the point when the distance between the Earth and the Moon is the least, not only does it appear to be brighter but it is also larger than a regular full moon.
  • According to NASA, the term supermoon was coined by astrologer Richard Nolle in 1979.
  • In a typical year, there may be two to four full supermoons and two to four new supermoons in a row.

What is happening today?

  • Two celestial events will take place at the same time.
  • One is the supermoon and the other is a total lunar eclipse, which is when the Moon and Sun are on opposite sides of the Earth.
  • Because of the total lunar eclipse, the moon will also appear to be red.
  • This is because the Earth will block some of the light from the Sun from reaching the moon.
  • The Earth’s atmosphere filters the light, it will soften “the edge of our planet’s shadow” “giving the Moon a deep, rosy glow.”

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Global Geological And Climatic Events

Eruption of Mount Nyiragongo

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mount Nyiragongo

Mains level: Not Much

Thousands have fled a volcanic eruption in the Democratic Republic of Congo from Mount Nyiragongo on the outskirts of Goma City.

These were some volcanoes in news this year:

Mount Vesuvius, Taal Volcano, La Soufriere

Mount Nyiragongo

  • Mount Nyiragongo is an active stratovolcano with an elevation of 3,470 m (11,385 ft) in the Virunga Mountains associated with the Albertine Rift.
  • The main crater is about 2km wide and usually contains a lava lake.
  • The crater presently has two distinct cooled lava benches within the crater walls.
  • It is one of the 16 Decade Volcanoes.
  • Nyiragongo’s lava lake has at times been the most voluminous known lava lake in recent history. The depth of the lava lake varies considerably.
  • Nyiragongo and nearby Nyamuragira are together responsible for 40 percent of Africa’s historical volcanic eruptions.

Answer this PYQ in the comment box:

Q.Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?

  1. Volcanic action
  2. Respiration
  3. Photosynthesis
  4. Decay of organic matter

Select the correct answer using the code given below:

(a) 1 and 3 only

(b) 2 only

(c) 1, 2 and 4 only

(d) 1, 2, 3 and 4

What are Decade Volcanoes?

  • The Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI).
  • They are considered worthy of particular study in light of their history of large, destructive eruptions and proximity to densely populated areas.
  • They are named Decade Volcanoes because the project was initiated in the 1990s as part of the United Nations-sponsored International Decade for Natural Disaster Reduction.

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Global Geological And Climatic Events

Cyclone Tauktae

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Tropical cyclones

Mains level: Frequent landfalls of tropical cyclones in India

Cyclone Tauktae (pronounced Tau-Te), classified as a very severe cyclonic storm (VSCS) and developed in the Arabian Sea, is wreaking havoc all across the Indian Coast.

Don’t you think?

 In recent years, strong cyclones have been developing in the Arabian Sea more frequently than earlier.

Cyclone Tauktae

  • Tauktae is a currently active and strengthening tropical cyclone threatening the state of Gujarat in India and impacting the states Karnataka, Goa and Maharashtra.
  • It is the fourth cyclone in consecutive years to have developed in the Arabian Sea, that too in the pre-monsoon period (April to June).
  • All these cyclones since 2018 have been categorised as either ‘Severe Cyclone’ or above.
  • Once Tauktae makes its landfall, three of these will have hit either the Gujarat or Maharashtra coast.
  • After Cyclone Mekanu in 2018, which struck Oman, Cyclone Vayu in 2019 struck Gujarat, followed by Cyclone Nisarga in 2020 that struck Maharashtra.

What is aiding such rapid intensification?

  • Any tropical cyclone requires energy to stay alive.
  • This energy is typically obtained from the warm water and humid air over the tropical ocean.
  • Currently, seawater up to depths of 50 metres has been very warm, supplying ample energy to enable the intensification of Cyclone Tauktae.
  • The more the heat released through condensation of water vapour, the steeper the drop in pressure.
  • A low-pressure system undergoes multiple stages of intensification to form cyclones.

Not a rare phenomenon

  • Typically, tropical cyclones in the North Indian Ocean region (the Bay of Bengal and the Arabian Sea) develop during the pre-monsoon and post-monsoon (October to December) periods.
  • May-June and October-November are known to produce cyclones of severe intensity that affect the Indian coasts.

Is the Arabian Sea becoming cyclone-friendly?

  • Annually, five cyclones on average form in the Bay of Bengal and the Arabian Sea combined.
  • Of these, four developments in the Bay of Bengal, which is warmer than the Arabian Sea.
  • In the Arabian Sea, cyclones typically develop over the Lakshadweep area and largely traverse westwards, or away from India’s west coast.
  • However, in recent years, meteorologists have observed that the Arabian Sea, too, has been warming. This is a phenomenon associated with global warming.

Back2Basics: Tropical Cyclone

  • A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure centre, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rains.
  • Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone.
  • A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and the northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean.
  • In the south Pacific or the Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.

Also read:

[Burning Issue] Tropical Cyclones and India

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Global Geological And Climatic Events

La Soufriere volcanic eruption

Note4Students

From UPSC perspective, the following things are important :

Prelims level: La Soufriere

Mains level: Not Much

Sulphur dioxide (SO2) emissions from La Soufriere volcano eruption in the Caribbean have reached all the way to India.

Why in news?

  • Its eruption has sparked fear of increased pollution levels in the northern parts of India and acid rain.
  • Volcanic plumes can cause aviation and air quality hazards.

La Soufriere

  • It is an active stratovolcano on the Caribbean island of Saint Vincent in Saint Vincent and the Grenadines.
  • It is the highest peak in Saint Vincent and has had five recorded explosive eruptions since 1718.

Impact of such eruptions

  • Volcanic emissions reaching the stratosphere can have a cooling effect on global temperatures.
  • The most significant climate impacts from volcanic injections into the stratosphere come from the conversion of sulphur dioxide to sulphuric acid, which condenses rapidly in the stratosphere to form fine sulphate aerosols.
  • The aerosols increase the reflection of radiation from the Sun back into space, cooling the Earth’s lower atmosphere or troposphere.

Try this PYQ:

Q.Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?

  1. Volcanic action
  2. Respiration
  3. Photosynthesis
  4. Decay of organic matter

Select the correct answer using the code given below:

(a) 1 and 3 only

(b) 2 only

(c) 1, 2 and 4 only

(d) 1, 2, 3 and 4

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Global Geological And Climatic Events

Indian monsoon 25 million years ago resembled present day Australia’s

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Drift of Indian plate from Gondwanaland

Mains level: History of Indian Monsoon

Using leaf fossils, researchers have found that the Indian monsoon 25 million years ago resembled present-day Australia’s.

Try this PYQ:

Q.Which one of the following is the appropriate reason for considering the Gondwana rocks as the most important rock systems of India?

(a) More than 90% of limestone reserves of India are found in them

(b) More than 90% of India’s coal reserves are found in them

(c) More than 90% of fertile black cotton soils are spread over them

(d) None of the reasons given above is appropriate in this context

India’s drift

  • About 180 million years ago, India separated from the ancient supercontinent Gondwana and took a long northward journey of about 9,000 km to join Eurasia.
  • During this journey, the subcontinent moved from the southern hemisphere, crossed the Equator to reach its current position in the northern hemisphere.
  • Due to these changing latitudes, it experienced different climatic conditions, and a new study has now tried to map these climatic variations using leaf fossils.

Clueless over the evolution of monsoon

  • The evolution of the monsoonal climate in India is still debatable and not fully understood.
  • Though recent data indicates that the monsoon system we experience now dates back to about 25 million years, it is still unclear how the climate was during its long voyage.

Indian research

  • The researchers analysed the morphological characters of fossil leaves collected from Deccan Volcanic Province, East Garo Hills of Meghalaya, Gurha mine in Rajasthan and Makum Coalfield in Assam.
  • The four fossil assemblages were found to be from four different geological ages.
  • It has been observed from across the globe that plant leaf morphological characters such as apex, base and shape are ecologically tuned with the prevailing climatic conditions.
  • The research applied this model to characterize the past monsoon from fossil leaves.

It’s finding

  • The results indicated that the fossil leaves from India were adapted to an Australian type of monsoon and not the current Indian monsoon system during its voyage.
  • The reconstructed temperature data show that the climate was warm (tropical to subtropical) at all the studied fossil sites with temperatures varying from 16.3–21.3 degrees C.
  • All the fossil sites experienced high rainfall, which varied from 191.6 cm to 232 cm.

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Global Geological And Climatic Events

2001 FO32: the largest asteroid passing by Earth

Note4Students

From UPSC perspective, the following things are important :

Prelims level: 2001 FO32

Mains level: Study of asteroids and meteors

On March 21, the largest asteroid predicted to pass by Earth in 2021 will be at its closest. It is called 2001 FO32.

Try this PYQ:

Q.Which of the following is/are cited by the scientists as evidence/evidence for the continued expansion of the universe?

  1. Detection of microwaves in space
  2. Observation of redshirt phenomenon in space
  3. Movement of asteroids in space
  4. Occurrence of supernova explosions in space

Codes:

(a) 1 and 2 only

(b) 2 only

(c) 1, 3 and 4

(d) None of the above can be cited as evidence.

2001 FO32

  • There is no threat of a collision with our planet now or for centuries to come.
  • Scientists know its orbital path around the Sun very accurately since it was discovered 20 years ago and has been tracked ever since.
  • It won’t come closer than 2 million km to Earth, but it will present a valuable scientific opportunity for astronomers who can get a good look at a rocky relic that formed at the dawn of our Solar System.

Proximity to Earth

  • For comparison, when it is at its closest, the distance of 2 million km is equal to 5¼ times the distance from Earth to the Moon.
  • Still, that distance is close in astronomical terms, which is why 2001 FO32 has been designated a “potentially hazardous asteroid”.
  • The reason for the asteroid’s unusually speedy close approach is its highly eccentric orbit around the Sun, an orbit that is tilted 39° to Earth’s orbital plane.
  • This orbit takes the asteroid closer to the Sun than Mercury, and twice as far from the Sun as Mars.
  • Later, the asteroid slows after being flung back out into deep space and swinging back toward the Sun. It completes one orbit every 810 days (about 2¼ years).

Studying the visitor

  • This asteroid will provide an opportunity for astronomers to get a more precise understanding of the asteroid’s size and albedo (i.e. how bright, or reflective, its surface is), and a rough idea of its composition.
  • When sunlight hits an asteroid’s surface, minerals in the rock absorb some wavelengths while reflecting others.
  • By studying the spectrum of light reflecting off the surface, astronomers can measure the chemical “fingerprints” of the minerals on the surface of the asteroid.

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Global Geological And Climatic Events

How long is a year on other planets?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Revolution of Earth and other planets around the Sun

Mains level: NA

For us, 365 days make up a year because Earth takes as many days to complete one orbit of the Sun. But have you ever wondered how many days make up a year on other planets?

What determines the length of a year?

  • The length of a year on any planet depends on where the planet is orbiting.
  • Planets that are closer to the Sun than Earth will have fewer days in a year, while those rotating farther away will take many more days to make up a year.
  • This is because of two reasons – planets that are closer to the Sun will take a shorter time to orbit it than those farther away, and the closer a planet orbits the Sun, the Sun’s gravity can pull on the planet, making the planet orbit faster.

Why should we care?

  • To send a spacecraft to another planet, we need to know where the planet is in orbit.
  • This will help us plan and manoeuvre the spacecraft accordingly.

How long each planet takes to orbit the Sun (in Earth days):

  • Mercury: 88 days
  • Venus: 225 days
  • Earth: 365 days
  • Mars: 687 days
  • Jupiter: 4,333 days
  • Saturn: 10,759 days
  • Uranus: 30,687 days
  • Neptune: 60,190 days

It’s a mean task to consider this PYQ from 2013, Huh!

Q.Which planet was downgraded to dwarf planet status?

(a) Pluto

(b) Mars

(c) Earth

(d) Venus

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Global Geological And Climatic Events

Places in news: Mount Sinabung

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mt Sinabung

Mains level: Pacific ring of fire

Indonesia’s Mount Sinabung volcano sent a cloud of hot ash as high as 3 km today, in its first big eruption since August last year.

Mount Sinabung

  • It is a Pleistocene-to-Holocene stratovolcano in the Karo plateau of Karo Regency, North Sumatra, Indonesia.
  • It is created by the subduction of the Indo-Australian Plate under the Eurasian Plate.
  • It erupted in 2010 after a 400-year-long hiatus and has been continuously active since September 2013.

Why frequent eruptions?

  • Indonesia straddles the “Pacific ring of fire” with nearly130 active volcanoes, more than any other country.
  • Sinabung had been inactive for centuries before it erupted again in 2010.

Try this PYQ:

Q.Consider the following statements:

  1. The Barren Island volcano is an active volcano located in the Indian Territory.
  2. Barren Island lies about 140 km east of Great Nicobar
  3. The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

Which of the statements given above is/are correct? (CSP 2018)

(a) 1 only

(b) 2 and 3 only

(c) 3 only

(d) 1 and 3

What is the Pacific ring of fire?

  • The Pacific Ring of Fire is a region around much of the rim of the Pacific Ocean where many volcanic eruptions and earthquakes occur.
  • It includes the Pacific coasts of South America, North America and Kamchatka, and some islands in the western Pacific Ocean.
  • It is a direct result of plate tectonics: specifically the movement, collision and destruction of lithospheric plates under and around the Pacific Ocean.
  • The collisions have created a nearly continuous series of subduction zones, where volcanoes are created and earthquakes occur.

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Global Geological And Climatic Events

What is Laschamp Excursion?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Laschamp Excursion

Mains level: Mass Extinction

This newscard is an excerpt from the original article published in DownToEarth.

The world experienced a few centuries of apocalyptic conditions 42,000 years ago, triggered by a reversal of the Earth’s magnetic poles combined with changes in the Sun’s behaviour. This event is called as Laschamps Excursion.

Try this PYQ from CSP 2018:

Q.The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of

(a) Widespread monoculture Practices agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.

(b) Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65million years ago that caused the mass extinction of many species including those of dinosaurs.

(c) Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivationin other Parts of the world which may cause the disappearance of good native crop plants and the loss offood biodiversity.

(d) Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss, natural habitats, destructionof ecosystems, pollution and global climate change.

Laschamp Excursion

  • The Laschamp event was a geomagnetic excursion (a short reversal of the Earth’s magnetic field). It occurred 41,400 years ago, during the end of the Last Glacial Period.
  • This event is named after the village where it was discovered in the French Massif Central.
  • It led to series of catastrophic events like the ozone layer was destroyed, electrical storms raged across the tropics, solar winds generated spectacular light shows (auroras), Arctic air poured across North America, ice sheets and glaciers surged and weather patterns shifted violently.
  • During these events, life on earth was exposed to intense ultraviolet light, Neanderthals and giant animals known as megafauna went extinct, while modern humans sought protection in caves.

The Adams Event

  • This last major geomagnetic reversal triggered a series of dramatic events that have far-reaching consequences for our planet.
  • Because of the coincidence of seemingly random cosmic events and the extreme environmental changes found around the world 42,000 years ago, researchers have called this period the “Adams Event”.

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Global Geological And Climatic Events

India and Australia were evolutionary neighbours

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Dickinsonia, Bhimbetka

Mains level: Geological time scale

Bhimbetka, which has yielded a fossil of Dickinsonia dating back about 550 million years, is the first time the particular fossilized organism has been recorded in India.

Why does this fossil matter?

  • It dates back to an era regarded as the precursor to the explosion of life on earth during the Cambrian period.
  • Thus it puts India firmly on the map for studies of the Ediacaran era along with Australia and Russia.

Here’s what makes the discovery a global milestone:

(a) Ediacaran Period

  • The finding gives lead about the earliest living species during a period of the earth’s history known as the Ediacaran, named after the Ediacara Hills in South Australia.
  • This is the period in Earth’s history when Dickinsonia and several multicellular organisms existed.
  • It was approximately 635 million years ago (Ma) and 541 Ma, with the living creatures of the era, called vendobionts.

Now take this opportunity to revise the Geological time scale from your NCERTs. Try differentiating between different era, periods and epoch.

(b) India’s Proximity to Australia

  • Studies of the rock characteristics in and around Bhimbetka show that they share several characteristics with rocks in Australia.
  • Dickinsonia fossils from India were found by the scientists to be identical to the Rawnsley Quartzite in South Australia.
  • This provides evidence of their age and the proximity of the two landmasses in Gondwanaland in that era.
  • The evidence however did not support reconstructions adjusted for the polar wander phenomenon [which involves motion of continents over geologic time and its impacts].

 Use of Zircon dating

  • The age of fossil rock is determined using Zircon isotopes.
  • Zircon dating of the youngest Maihar sandstone in Madhya Pradesh puts its age at 548 Ma.
  • The lower Bhander group in the Son and Chambal valleys yielded an isotope-derived age for limestones ranging from 978 Ma to 1073 Ma, situating it in the older Tonian period.
  • The Ediacaran period was the precursor to the Cambrian (about 541 Ma to 485.4 Ma) when the earth witnessed an explosion of life forms and much of which makes up modern animal life today.

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Global Geological And Climatic Events

What is Winter Solstice?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Winter Solstice

Mains level: Summer and Winter Solstice

Yesterday, December 21, was Winter Solstice, the shortest day of the year in the Northern Hemisphere. In the Southern Hemisphere, conversely, it was Summer Solstice, the year’s longest day.

Try this MCQ:

Q.On 21st June, the Sun

(a) Does not set below the horizon at the Arctic Circle

(b) Does not set below the horizon at Antarctic Circle

(c) Shines vertically overhead at noon on the Equator

(d) Shines vertically overhead at the Tropic of Capricorn

Why are the hours of daylight, not the same every day?

  • The explanation lies in Earth’s tilt.
  • And it’s not just the Earth — every planet in the Solar System is tilted relative to their orbits, all at different angles.
  • The Earth’s axis of rotation is tilted at an angle of 23.5° to its orbital plane.
  • This tilt — combined with factors such as Earth’s spin and orbit — leads to variations in the duration of sunlight than any location on the planet receives on different days of the year.

Impact of the tilted axis

  • The Northern Hemisphere spends half the year tilted in the direction of the Sun, getting direct sunlight during long summer days.
  • During the other half of the year, it tilts away from the Sun, and the days are shorter.
  • Winter Solstice, December 21, is the day when the North Pole is most tilted away from the Sun.
  • The tilt is also responsible for the different seasons that we see on Earth.
  • The side facing the Sun experiences day, which changes to night as Earth continues to spin on its axis.

Un-impacted regions

  • On the Equator, day and night are equal. The closer one moves towards the poles, the more extreme the variation.
  • During summer in either hemisphere, that pole is tilted towards the Sun and the polar region receives 24 hours of daylight for months.
  • Likewise, during winter, the region is in total darkness for months.

Celebrations associated with the Winter Solstice

  • For centuries, this day has had a special place in several communities due to its astronomical significance and is celebrated in many ways across the world.
  • Jewish people call the Winter Solstice ‘Tekufat Tevet’, which marks the start of winter.
  • Ancient Egyptians celebrated the birth of Horus, the son of Isis (divine mother goddess) for 12 days during mid-winter.
  • In China, the day is celebrated by families coming together for a special meal.
  • In the Persian region, it is celebrated as Yalda or Shab-e-Yalda. The festival marks the last day of the Persian month of Azar and is seen as the victory of light over darkness.
  • Families celebrate Yalda late into the night with special foods such as ajeel nuts, pomegranates and watermelon, and recite works of the 14th century Sufi poet Hafiz Shirazi.

In Vedic tradition

  • In Vedic tradition, the northern movement of the Earth on the celestial sphere is implicitly acknowledged in the Surya Siddhanta.
  • It outlines the Uttarayana (the period between Makar Sankranti and Karka Sankranti). Hence, Winter Solstice is the first day of Uttarayana.

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Global Geological And Climatic Events

Christmas-Star Conjunction of Saturn and Jupiter

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Conjunction in space-phenomena

Mains level: Not Much

After nearly 400 years, Saturn and Jupiter – the two largest planets in our solar system – will be brought closest in the night sky by an astronomical event called the “great conjunction” and popularly referred to as the “Christmas Star”.

Try this PYQ:

What is a coma, in the context of Astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

What are the Conjunctions?

  • A conjunction is not unique to Saturn and Jupiter however, it is the name given to any event where planets or asteroids appear to be very close together in the sky when viewed from the Earth.
  • In June 2005 for instance, as a result of the “spectacular” conjunction, Mercury, Venus and Saturn appeared so close together in the sky that the patch of sky where the three planets were could be covered by a thumb.
  • Astronomers use the word “great” for the conjunction of Jupiter and Saturn because of the planets’ sizes.

The “Great Conjunction”

  • It happens once in about 20 years because of the time each of the planets takes to orbit around the Sun.
  • Jupiter takes roughly 12 years to complete one lap around the Sun and Saturn takes 30 years.
  • This is because Saturn has a larger orbit and moves more slowly because it is not as strongly influenced by the Sun’s gravitational force as planets that are closer to the Sun.
  • As the two planets move along their orbits, every two decades, Jupiter catches up with Saturn resulting in what astronomers call the great conjunction.

A ‘rare alignment’

  • Jupiter and Saturn are bright planets and can be typically seen with the naked eye even from cities.
  • But during conjunction, they appear to be close to each other, which is what makes the event noteworthy.
  • The event will coincide with the winter solstice (shortest day of the year in terms of hours of sunlight received) in the Northern Hemisphere and summer solstice in the Southern Hemisphere.
  • This year, however, the event is rare because the planets will come the closest to each other in nearly four centuries; in what astronomer Henry Throop described is a result of a “rare alignment” of the planets.

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Global Geological And Climatic Events

How to measure a Mountain?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mt. Everest

Mains level: Himalayan Orogeny

China and Nepal have announced Mount Everest is 0.86 m taller than the 8,848 m accepted globally so far.

Try this PYQ:

Q.When you travel to the Himalayas, you will see the following:

  1. Deep gorges
  2. U-turn river courses
  3. Parallel mountain ranges
  4. Steep gradients causing land-sliding

Which of the above can be said to be the evidences for the Himalayas being young fold mountains?

(a) 1 and 2 only

(b) 1, 2 and 4 only

(c) 3 and 4 only

(d) 1, 2, 3 and 4

Scaling a mountains’ height

  • The basic principle that was used earlier is very simple and uses  only trigonometry which most of us are familiar with, or at least can recall.
  • There are three sides and three angles in any triangle. If we know any three of these quantities, provided one of them is a side, all the others can be calculated.
  • In a right-angled triangle, one of the angles is already known, so if we know any other angle and one of the sides, the others can be found out.
  • This principle can be applied for measuring the height of any object that does not offer the convenience of dropping a measuring tape from top to bottom.

Accuracy issues

  • For small hills and mountains, whose top can be observed from relatively close distances, this can give quite precise measurements.
  • But for Mount Everest and other high mountains, there are some other complications.
  • These again arise from the fact that we do not know where the base of the mountain is.

Measuring against sea level

  • Generally, for practical purposes, the heights are measured above mean sea level (MSL). Moreover, we need to find the distance to the mountain.
  • This is done through a painstaking process called high-precision levelling. Starting from the coastline, we calculate step by step the difference in height, using special instruments.
  • This is how we know the height of any city from mean sea level.

Adjusting gravitation anomaly

  • But there is one additional problem to be contended with — gravity. Gravity is different in different places. It means that even sea level cannot be considered to be uniform at all places.
  • So, the local gravity is also measured to calculate the local sea level. Nowadays sophisticated portable gravitometers are available that can be carried even to mountain peaks.

Technology solutions

  • These days GPS is widely used to determine coordinates and heights, even of mountains.
  • But, GPS gives precise coordinates of the top of a mountain relative to an ellipsoid which is an imaginary surface mathematically modelled to represent Earth.
  • This surface differs from the mean sea level. Similarly, overhead flying planes equipped with laser beams (LiDAR) can also be used to get the coordinates.

How accurate are China/Nepal’s apprehensions?

  • Considering that during 1952-1954, when neither GPS and satellite techniques were available nor the sophisticated gravimeters, the task of determining the height of Mount Everest was not easy.
  • Nepal and China have said they have measured Mount Everest to be 86 cm higher than the 8,848 m that it was known to be.
  • But these have been explained in terms of geological processes that might be altering the height of Everest. The accuracy of the 1954 result has never been questioned.
  • Most scientists now believe that the height of Mount Everest is increasing at a very slow rate. This is because of the northward movement of the Indian tectonic plate that is pushing the surface up.
  • Big earthquake, like the one that happened in Nepal in 2015, can alter the heights of mountains. Such events have happened in the past.

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Global Geological And Climatic Events

What is Aurora Borealis?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Aurora Borealis

Mains level: Aurora and the science behind

Northern Lights, also known as aurora borealis could be visible in regions such as in the northern parts of Illinois and Pennsylvania in the US.

Try this PYQ:

What is a coma, in the context of Astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

Aurora

  • Auroras occur when charged particles ejected from the Sun’s surface — called the solar wind — enter the Earth’s atmosphere.
  • While flowing toward Earth, the fast-moving solar wind carries with it the Sun’s magnetic field, which disrupts the magnetosphere — the region of space around Earth in which the magnetic field of our planet is dominant.
  • When the Sun’s magnetic field approaches Earth, the protective magnetic field radiating from our planet’s poles deflects the former, thus shielding life on Earth.
  • However, as this happens, the protective fields couple together to form funnels, through which charged solar wind particles are able to stream down to the poles.
  • At the north and south poles, the charged particles interact with different gases in the atmosphere, causing a display of light in the sky.
  • This display, known as an aurora, is seen from the Earth’s high latitude regions (called the auroral oval), and is active all year round.

Behind the name

  • In the northern part of our globe, the polar lights are called aurora borealis or Northern Lights and are seen from the US (Alaska), Canada, Iceland, Greenland, Norway, Sweden and Finland.
  • In the south, they are called aurora australis or southern lights and are visible from high latitudes in Antarctica, Chile, Argentina, New Zealand and Australia.

Where is it observed?

  • Generally, the auroral oval is usually witnessed far up in the Polar Regions or the high latitude regions of Europe, like in Norway.
  • But occasionally, the oval expands, and the lights become visible at lower latitudes.
  • This happens during periods of high solar activity, such as the arrival of solar storms.
  • Solar activities include solar flares, solar energetic particles, high-speed solar wind and Coronal Mass Ejections (CME).

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Global Geological And Climatic Events

Revised height of Mount Everest

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mt. Everest

Mains level: Himalayan Orogeny

Nepal and China jointly announced the new height of Mount Everest as 8,848.86 meters.

8,848 metres — the answer to one of the most widely popular quiz questions, and a number drilled into the minds of school students around the world for decades, is set for a revision.

Mt. Everest

  • Mount Everest or Sagarmatha, Earth’s highest mountain above sea level, is located in the Himalayas between China and Nepal -– the border between them running across its summit point.
  • Its current official elevation – 8,848.86m – places it more than 200m above the world’s second-highest mountain, K2, which is 8,611m tall and located in Pakistan-occupied Kashmir.
  • The mountain gets its English name from Sir George Everest, a colonial-era geographer who served as the Surveyor General of India in the mid-19th century.
  • Considered an elite climbing destination, Everest was first scaled in 1953 by the Indian-Nepalese Tenzing Norgay and New Zealander Edmund Hillary.

Try this PYQ:

Q.When you travel to the Himalayas, you will see the following:

  1. Deep gorges
  2. U-turn river courses
  3. Parallel mountain ranges
  4. Steep gradients causing land-sliding

Which of the above can be said to be the evidences for the Himalayas being young fold mountains?

(a) 1 and 2 only

(b) 1, 2 and 4 only

(c) 3 and 4 only

(d) 1, 2, 3 and 4

Everest’s first survey

  • The mission to measure the world’s highest peak was taken up on a serious note in 1847 and culminated with the finding of a team led by Andrew Waugh of the Royal Surveyor General of India.
  • The team discovered that ‘Peak 15’ — as Mt Everest was referred to then — was the highest mountain, contrary to the then-prevailing belief that Mt Kanchenjunga (8,582 m) was the highest peak in the world.
  • Another belief, prevailing even today, is that 8,840 m is not the height that was actually determined by the 19th-century team.
  • That survey, based on trigonometric calculations, is known as the Great Trigonometric Survey of India.

Why is the height being revised?

  • The height of the summit, however, is known to change because of tectonic activity, such as the 2015 Nepal earthquake.
  • Its measurement over the decades has also depended on who was surveying.
  • Another debate is whether the height should be based on the highest rock point or the highest snow point.

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Global Geological And Climatic Events

Western Disturbances and winters in North

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Western disturbances , Winter rainfall

Mains level: Peculiarities of Indian weather

For the past few days, Chandigarh and its neighbouring states have been experiencing unusually cold days although the night temperatures are normal.

Try this PYQ:

Consider the following statements:

  1. The winds which blow between 30°N and 60°S latitudes throughout the year are known as westerlies.
  2. The moist air masses that cause winter rains in the North-Western region of India are part of westerlies.

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

Temperature anomaly in North

  • Meteorological officials have attributed the trend to the cloud cover in the region which was absent until a few days ago.
  • It is the result of a western disturbance, which has brought about a spell of precipitation in the northwest Himalaya.

Role of clouds

  • During the day, clouds obstruct the heat from the sun from reaching the surface of the earth, reflecting some of it back into space.
  • This lowers the temperature. Cold winds blowing down from snow-bound areas in the mountains also contribute to the cooling effect.
  • At night, however, clouds act like blankets – they help retain some of the heat energy radiated back by the earth’s surface.
  • Overcast weather at night, thus, increases greenhouse warming.

What are western disturbances?

  • In northern India, winter rains and clouds are generally caused by moisture-bearing wind systems called western disturbances.
  • They originate and gather moisture over the Mediterranean region and flow eastwards towards the Indian subcontinent.
  • When some of these winds run into mountains of the northwest Himalaya, they are forced upward.
  • At higher altitudes, the temperatures drop and water vapour gets condensed. This leads to cloud formation and eventually rain and snow.

Other factors for severe winters in North

  • In north India, the huge temperature difference between summers and winters is due to its continentality (distance from seas and oceans).
  • Air from oceans moderates the temperature as it moves onshore, but this effect is missing in continental interiors.
  • As a result, north India has greater seasonal differences as compared to peninsular India.
  • Temperature also reduces rapidly with altitude, and thus, the Himalayan region is colder still.

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Global Geological And Climatic Events

Cyclone Nivar to make landfall in TN

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Tropical cyclones

Mains level: Frequent landfalls of tropical cyclones in India

A developing cyclonic disturbance in the Bay of Bengal is expected to become a ‘severe cyclonic storm’ and make landfall in Tamil Nadu.

Cyclone Nivar

  • The IMD has forecasted the development of a cyclone in the Southwest region of the Bay of Bengal, off Tamil Nadu coast.
  • It has said that it will strengthen into a cyclone. Once intensified, it would acquire its name ‘Nivar’, proposed by Iran.
  • After cyclone Gaja in 2018, this will be the second cyclone to cross Tamil Nadu in the last two years.

Try this PYQ:

In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason?

(a) Sea surface temperatures are low

(b) Inter-Tropical Convergence Zone seldom occurs

(c) Coriolis force is too weak

(d) Absence of land in those regions

Tropical Cyclone

  • A Tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain.
  • Cyclones are formed over slightly warm ocean waters. The temperature of the top layer of the sea, up to a depth of about 60 meters, need to be at least 28°C to support the formation of a cyclone.
  • This explains why the April-May and October-December periods are conducive for cyclones.
  • Then, the low level of air above the waters needs to have an ‘anticlockwise’ rotation (in the northern hemisphere; clockwise in the southern hemisphere).
  • During these periods, there is an ITCZ in the Bay of Bengal whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west.
  • Once formed, cyclones in this area usually move northwest. As it travels over the sea, the cyclone gathers more moist air from the warm sea which adds to its heft.

Must read:

[Burning Issue] Tropical Cyclones and India

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Global Geological And Climatic Events

Places in news: Mount Vesuvius

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mt. Vesuvious, volacanic landforms

Mains level: Not Much

The Italian Culture Ministry announced the discovery of well-preserved remains of two men, who perished during the volcanic eruption of Mount Vesuvius in 79 AD.

Try this PYQ:

Q.Consider the following statements:

  1. The Barren Island volcano is an active volcano located in the Indian Territory.
  2. Barren Island lies about 140 km east of Great Nicobar.
  3. The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3 only

(c) 3 only

(d) 1 and 3 only

Mount Vesuvius

  • Located in southern Italy near the coastal city of Naples, the 4,203-ft (1,281 metres) tall Vesuvius is the only active volcano in mainland Europe.
  • Vesuvius has been classified as a complex volcano (also called a compound volcano), one that consists of a complex of two or more vents.
  • It typically has explosive eruptions and pyroclastic flows –– defined as a high-density mix of hot lava blocks, pumice, ash and volcanic gas.
  • It has erupted more than 50 times and is considered among the most dangerous volcanoes in the world due to its proximity to Naples and surrounding towns.
  • Its last serious eruption, lasting two weeks, was in 1944 during World War II, which left 26 Italian civilians dead and around 12,000 displaced.

The eruption of 79 AD

  • In 79 AD, the Roman Empire-era sister cities of Pompeii and Herculaneum were destroyed and buried during a catastrophic eruption of Vesuvius.
  • It was a catastrophic event that destroyed the ancient Roman city of Pompeii and killed around 16,000 people.
  • Pompeii, 8 km away from Vesuvius, served as a resort town on the Bay of Naples for Rome’s elite citizens, consisting of villas, cafes, marketplaces and a 20,000-seat arena.
  • In 63 AD, a major earthquake rattled the city, serving as a warning for the eruption to come. However, few residents bothered to abandon the region, known for its volatility.

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Global Geological And Climatic Events

Leonid Meteor Shower

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Meteor terminology

Mains level: Not Much

The Leonid meteor showers are currently making their yearly appearance and will reach their peak in India on November 17 and 18.  In August this year, there was another meteor called Perseids Shower.

Try this question from CSP 2014:

Q.What is a coma, in the content of astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

What is Leonid Meteor Shower?

  • Meteor showers are named after the constellation they appear to be coming from.
  • The Leonids originate from the constellation Leo the Lion– the groups of stars which form a lion’s mane.
  • They emerge from the comet Tempel-Tuttle, which requires 33 years to revolve once around the Sun.
  • These meteors are bright and among the fastest moving– travelling at speeds of 71 km per second.
  • During this year’s showers, peaks of around 10 to 15 meteors are expected to be seen every hour.
  • The Leonid showers include fireballs– bright and large meteors than can last longer than average meteors, and “earthgazers”– meteors which appear close to the horizon with colourful and long tails.

What is a meteor shower?

  • On its journey around the Sun, the Earth passes through large swathes of cosmic debris.
  • The debris is essentially the remnants of comets — great frigid chunks of matter that leave behind dirty trails of rocks and ice that linger long after the comets themselves have passed.
  • As the Earth wades through this cloud of comet waste, the bits of debris create what appears from the ground to be a fireworks display in the sky — known as a meteor shower.
  • Several meteor showers can be seen around the year. According to NASA, over 30 meteor showers occur annually and are observable from the Earth.

Back2Basics:

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Global Geological And Climatic Events

Cyclonic storms during October

Note4Students

From UPSC perspective, the following things are important :

Prelims level: MJO, Cyclones

Mains level: Frequent landfalls of tropical cyclones in India

October to December period is among the favourable months for the development of cyclones in the Bay of Bengal and the Arabian Sea. This year, however, October passed without witnessing a cyclonic storm.

Must read: [Burning Issue] Tropical Cyclones and India

https://www.civilsdaily.com/burning-issue-tropical-cyclones-and-india/

When do cyclones form and hit Indian coasts?

  • About 80 cyclones are formed around the world annually, out of which five are formed in the Bay of Bengal and the Arabian Sea, together known as the North Indian Ocean.
  • India’s east and west coasts are prone to cyclones with the maximum associated hazards—rain, heavy winds and storm surge— faced by coastal districts of West Bengal, Odisha and Andhra Pradesh.
  • Cyclones in the North Indian Ocean are bi-modal in nature, that is, they occur during two seasons— April to June (pre-monsoon) and October to December (post-monsoon).
  • Of these, May and November remain the most conducive for the development of cyclones.

When have cyclones skipped October, previously?

  • Cyclonic disturbances— either in the form of a well-marked low pressure, depression or a deep depression— are common in October.
  • Ocean disturbances enter the Bay of Bengal from the South China seaside and head towards the Indian coast.
  • IMD officials have attributed it to the weak La Nina conditions along the equatorial Pacific Ocean.
  • Cooler than normal sea surface temperatures over this region—termed as La Nina— has been prevailing since August this year.

Madden Julian Oscillation (MJO)

  • Because Madden Julian Oscillation (MJO) was positioned in a favourable phase, the low-pressure systems intensified maximum up to a deep depression.
  • MJO is kind of an eastward-moving cyclic weather event along the tropics that influences rainfall, winds, sea surface temperatures and cloud cover. They have a 30 to 60-day cycle.
  • Most importantly, there was the high wind shear noted between the different atmospheric levels, last month.
  • The vertical wind shear— created due to significant wind speed difference observed between higher and lowers atmospheric levels— prevented the low-pressure systems and depression from strengthening into a cyclone.

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Global Geological And Climatic Events

What are Western Disturbances?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Polar Vortex

Mains level: Not Much

With the approaching winter, minimum temperatures in the national capital have trended downward over the last due to the arrival of northwesterly winds called Western Disturbances.

Try this PYQ:

Q.Westerlies in the southern hemisphere is stronger and persistent than in northern hemisphere. Why?

  1. The southern hemisphere has less landmass as compared to the northern hemisphere.
  2. Coriolis force is higher in the southern hemisphere as compared to the northern hemisphere

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

Western Disturbances

  • A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.
  • It is a non-monsoonal precipitation pattern driven by the westerlies.
  • The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea.
  • Extratropical storms are global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere.
  • In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.
  • Western disturbances are more frequent and strong in the winter season.

Their significance

  • Western disturbances, specifically the ones in winter, bring moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.
  • They are the cause of most winter and pre-monsoon season rainfall across northwest India.
  • Precipitation during the winter season has great importance in agriculture, particularly for the rabi crops.
  • Wheat among them is one of the most important crops, which helps to meet India’s food security. An average of four to five western disturbances forms during the winter season.
  • The rainfall distribution and amount vary with every western disturbance.

Also read: Polar Vortex 

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Global Geological And Climatic Events

Ladakh Fault in Indus Suture Zone (ISZ)

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Himalayan orogeny

Mains level: Not Much

A recent survey has found that a tectonic fault line that runs through Ladakh, all along the Indus river, is not inactive as was previously thought and is, in fact, moving northward.

Tap here to read more about Himalayan orogeny:

Indus Suture Zone (ISZ)

  • A suture zone is a linear belt of intense deformation, where distinct terranes, or tectonic units with different plate tectonic, metamorphic, and paleogeographic histories, join together.
  • The ISZ represents a belt of tectonic compression caused by the underthrusting of the Indian shield/ plate against the Tibetan mass.
  • It marks the boundary between the Indian and Eurasian plates.
  • The suture zone stretches from the North-Western Himalayan syntaxis bordering the Nanga Parbat to the East as far as the Namche Barwa Mountain.

Its tectonic activity

  • The Karakoram Range and the Ladakh plateau lie to the north of ISZ and originally formed a part of the European plate.
  • The zone has been neo-tectonically active for the past 78,000-58,000 years.
  • While the frontal and central parts of the Himalayas — the Shivaliks, Himachal Pradesh, Uttarakhand, Jammu and Kashmir and Sikkim — are still known to be active and moving.
  • The fault line runs all along the Indus river, from China through India and Pakistan.
  • The study was conducted in Ladakh from the north of Ladakh’s capital, Leh, to the Tso Moriri lake, a distance of 213 kilometres.

Why the Ladakh region is more vulnerable?

  • Fault lines weaken the rock formation in the region through which it runs, making the area vulnerable to excessive erosion and landslides.
  • What makes the Ladakh region vulnerable is that unlike other areas in the Himalayas and the rest of the country, there is very little vegetation here and very few trees that can root the soil down.
  • So, in the case of a flash flood or a cloud burst, this can have a widespread impact.

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Global Geological And Climatic Events

What are Medicanes?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Medicanes

Mains level: Frequent landfalls of tropical cyclones in India

Very recently, a medicane named Ianos made landfall along the coast of Greece and caused heavy rainfall and flooding on the islands of Zakynthos, Kefalonia and Ithaca.

Try this PYQ:

In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason?

(a) Sea surface temperatures are low

(b) Inter-Tropical Convergence Zone seldom occurs

(c) Coriolis force is too weak

(d) Absence of land in those regions

What are Medicanes?

  • Medicanes are extra-tropical hurricanes observed over the Mediterranean Sea.
  • Medicanes occur more in colder waters than tropical cyclones, hurricanes and typhoons.
  • Hence, the cores of these storms are also cold, as compared to the warm cores of tropical cyclones.
  • Warmer cores tend to carry more moisture (hence rainfall), are bigger in size and have swifter winds.
  • The main societal hazard posed by Medicanes is not usually from destructive winds but through life-threatening torrential rains and flash floods.

Why in news?

  • This year is a mild La Niña, according to the World Meteorological Organization.
  • La Niña is the cooling phase of the El Niño Southern Oscillation (ENSO) cycle in the equatorial Pacific Ocean, as opposed to the warming El Niño phase.
  • It is characterized by the unusual cooling of the central and east-central equatorial Pacific Ocean.
  • A La Niña produces more rain in the central-eastern part, where most of the Mediterranean cyclones develop.

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Global Geological And Climatic Events

Re-scaling the height of Mt Everest

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Himalayan orogeny

Mains level: NA

China and Nepal are expected to announce the latest official height of Mt. Everest.

Try this PYQ:

Q.When you travel to the Himalayas, you will see the following:

  1. Deep gorges
  2. U-turn river courses
  3. Parallel mountain ranges
  4. Steep gradients causing land-sliding

Which of the above can be said to be the evidences for the Himalayas being young fold mountains?

(a) 1 and 2 only

(b) 1, 2 and 4 only

(c) 3 and 4 only

(d) 1, 2, 3 and 4

Mt. Everest

  • Mount Everest or Sagarmatha, Earth’s highest mountain above sea level, is located in the Himalayas between China and Nepal -– the border between them running across its summit point.
  • Its current official elevation – 8,848m – places it more than 200m above the world’s second-highest mountain, K2, which is 8,611m tall and located in Pakistan-occupied Kashmir.
  • The mountain gets its English name from Sir George Everest, a colonial-era geographer who served as the Surveyor General of India in the mid-19th century.
  • Considered an elite climbing destination, Everest was first scaled in 1953 by the Indian-Nepalese Tenzing Norgay and New Zealander Edmund Hillary.

Everest’s first survey

  • The mission to measure the world’s highest peak was taken up on a serious note in 1847 and culminated with the finding of a team led by Andrew Waugh of the Royal Surveyor General of India.
  • The team discovered that ‘Peak 15’ — as Mt Everest was referred to then — was the highest mountain, contrary to the then-prevailing belief that Mt Kanchenjunga (8,582 m) was the highest peak in the world.
  • Another belief, prevailing even today, is that 8,840 m is not the height that was actually determined by the 19th-century team.
  • That survey, based on trigonometric calculations, is known as the Great Trigonometric Survey of India.

Why is the height being measured again?

  • Everest’s current official height– 8,848m– has been widely accepted since 1956, when the figure was measured by the Survey of India.
  • The height of the summit, however, is known to change because of tectonic activity, such as the 2015 Nepal earthquake.
  • Its measurement over the decades has also depended on who was surveying.
  • Another debate is whether the height should be based on the highest rock point or the highest snow point.

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Global Geological And Climatic Events

What is the Hangenberg Crisis?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Hangenberg Crisis

Mains level: Mass Extinction

The explosion of a nearby star — occurred at between Devonian and Carboniferous periods — could have caused a mass extinction event that took place 359 million years ago.

Try this question from CSP 2018:

Q.The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of

(a) Widespread monoculture Practices agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.

(b) Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65million years ago that caused the mass extinction of many species including those of dinosaurs.

(c) Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivationin other Parts of the world which may cause the disappearance of good native crop plants and the loss offood biodiversity.

(d) Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss, natural habitats, destructionof ecosystems, pollution and global climate change.

Hangenberg crisis

  • The Earth suffered an intense loss of species diversity that lasted for at least 300,000 years.
  • The event is thought to have been caused by long-lasting ozone depletion, which would have allowed much more of the Sun’s ultraviolet (UV) radiation to reach and harm life on Earth.
  • It was called the Hangenberg crisis.

What did researchers find?

  • Extensive volcanism and global warming can also rupture the ozone layer but shreds of evidence for these are indefinite as far as the time period is concerned.
  • So, they up that one or more supernovae explosions, at a distance of 65 light-years away from the Earth, may have caused a prolonged loss of ozone.
  • Betelgeuse, a supernova, around 600 light-years away and present outside the kill distance of 25 light-years poses a danger today.
  • Events like gamma-ray bursts, solar eruptions and meteorite collisions end up very soon. As such, they cannot pave the way for gradual ozone depletion that took place at the close of the Devonian aeon.
  • A supernova event can be powerful enough to bathe its galaxy in light for days and months alike. It can be spotted across the universe as well.

Why Supernovae are considered dangerous?

  • Supernovae (SNe) are quick sources of ionizing photons that include fatal X-rays, UV and gamma rays.
  • Over a longer period of time, the bang clashes with the nearby gas, resulting in a shockwave that causes particle acceleration.
  • As such, cosmic rays are generated by SNe. These charged particles with high energies get magnetically confined on the inside of SN remains.
  • The fossil evidence shows a 300,000-year shrink in biodiversity leading the way to Devonian-Carboniferous Boundary (DCB) mass extinction.
  • This puts forward the possibility of multiple catastrophes or multiple supernovae explosions.

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Global Geological And Climatic Events

Tornado’s dynamics and its India connection

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Tornado, Cyclones difference

Mains level: Rising events of Tropical Cyclone in India

Babu ChunderSikur Chatterjee’s paper was the earliest record of a tornado’s dynamics in the history of meteorology, according to a study.

Try this PYQ:

Q. In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason? (CSP 2015)

(a) Sea surface temperatures are low

(b) Inter-Tropical Convergence Zone seldom occurs

(c) Coriolis force is too weak

(d) Absence of land in those regions

What is a Tornado?

  • A tornado is a rapidly rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud.
  • The windstorm is often referred to as a twister, whirlwind or cyclone winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern.
  • Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it.
  • It is generally accompanied by extreme weather such as heavy downpours, hail storms, and lightning.

Who was Babu ChunderSikur Chatterjee?

  • Chatterjee was an Indian scientist employed with the Surveyor General of India during the British colonial era.
  • He was likely the first person to scientifically document a tornado’s path in 1865, a study from the Indian Institute of Tropical Meteorology (IITM), Pune, has claimed.
  • Chatterjee had published his findings in a journal named Proceedings of the Asiatic Society of Bengal, in a paper titled ‘Note on a whirlwind at Pundooah’, near Hooghly.
  • The paper described a tornado’s dynamics in meticulous detail and was accompanied by a sketch that mathematically depicted its scale, track and rotation.

His work

 

  • Chatterjee quantitatively mapped the entire trail of á tornado’s destruction.
  • He benefited from the rare opportunity to observe a tornado passing through a railway track where there were conveniently placed markers at predefined locations.
  • This enabled him to observe and make clear measurements of the tornado’s direction, dynamics and path.

Back2Basics

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Global Geological And Climatic Events

Death Valley records the highest temperature on Earth

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Death Valley, Mojave Desert

Mains level: Not Much

California’s Death Valley registered a temperature of 54.4 degrees Celsius or 129.9 degrees Fahrenheit on August 16, 2020, which, once verified, could be the hottest temperature ever recorded on Earth.

Some years back, there was a question in the mains:

Major hot deserts in the northern hemisphere are located between 20-30 degree north and on the western side of the continents. Why?

Death Valley and its location

  • Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert.
  • It is one of the hottest places on Earth, along with deserts in the Middle East and the Sahara.
  • The valley is extremely dry because it lies in the rain shadow of four major mountain ranges (including the Sierra Nevada and the Panamint Range).
  • Moisture moving inland from the Pacific Ocean must pass eastward over the mountains to reach Death Valley; as air masses are forced upward by each range, they cool and moisture condenses, to fall as rain or snow on the western slopes.
  • When the air masses reach Death Valley, most of the moisture has already been lost and there is little left to fall as precipitation.

Key factors leading to its high temperature

  • Solar heating: The valley’s surface (consisting of soil, rocks, sand, etc.) undergoes intense solar heating because the air is clear and dry, and the land is dark and sparsely vegetated. This is especially noticeable in summer when the sun is nearly directly overhead.
  • Trapping of warm air: Warm air naturally rises and cools; in Death Valley, this air is subject to continual reheating as it is trapped by high, steep valley walls and recycled back to the valley floor.
  • Migration of warm air from other areas (advection): Warm desert regions adjacent to Death Valley, especially to the south and east, often heat air before it arrives in Death Valley.
  • Warm mountain winds: As winds are forced up and over mountains (e.g., the numerous ranges west of Death Valley), the winds can be warmed in several ways. The resulting dry, warm winds are known as foehn winds.

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Global Geological And Climatic Events

Perseids Meteor Shower

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Meteor terminology

Mains level: Not Much

The Perseids meteor shower is going to be active from August 17-26.

Try this question from CSP 2014:

Q.What is a coma, in the content of astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

What is the Perseids meteor shower?

  • The Perseids meteor shower peaks every year in mid-August. It was first observed over 2,000 years ago.
  • The Perseids occur as the Earth runs into pieces of cosmic debris left behind by the comet Swift-Tuttle.
  • The cloud of debris is about 27 km wide, and at the peak of the display, between 160 and 200 meteors streak through the Earth’s atmosphere every hour as the pieces of debris.
  • They travel at the speed of some 2.14 lakh km per hour; burn up a little less than 100 km above the Earth’s surface.

What are Meteor Showers?

  • Meteors are bits of rock and ice that are ejected from comets as they manoeuvre around their orbits around the sun.
  • As meteors fall towards the Earth, the resistance makes the space rocks extremely hot and, as meteorites pass through the atmosphere, they leave behind streaks of glowing gas that are visible to the observers and not the rock itself.
  • Meteor showers, on the other hand, are witnessed when Earth passes through the trail of debris left behind by a comet or an asteroid.
  • When a meteor reaches the Earth, it is called a meteorite and a series of meteorites, when encountered at once, is termed as a meteor shower.
  • According to NASA, over 30 meteor showers occur annually and are observable from the Earth.

Where do the Perseids come from?

  • The comet Swift-Tuttle, which was discovered in 1862 by Lewis Swift and Horace Tuttle, takes 133 years to complete one rotation around the sun.
  • The last time it reached its closest approach to the sun was in 1992 and will do so again in 2125.
  • Every time comets come close to the sun, they leave behind dust that is essentially the debris trail, which the Earth passes through every year as it orbits around the Sun.

Back2Basics:

 

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Global Geological And Climatic Events

In news: Mount Sinabung

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mount Sinabung

Mains level: Not Much

The Mount Sinabung volcano in Indonesia has erupted spouting ash at least 5,000 metres high into the sky.

In the Philippines, a volcano called Taal on the island of Luzon; 50 km from Manila has recently erupted in January. Note all such recent eruption in news.

Also, try this PYQ:

Consider the following statements:

  1. The Barren Island volcano is an active volcano located in the Indian Territory.
  2. Barren Island lies about 140 km east of Great Nicobar
  3. The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

Which of the statements given above is/are correct? (CSP 2018)

(a) 1 only

(b) 2 and 3 only

(c) 3 only

(d) 1 and 3

Mount Sinabung

  • It is a Pleistocene-to-Holocene stratovolcano in the Karo plateau of Karo Regency, North Sumatra, Indonesia.
  • It is created by the subduction of the Indo-Australian Plate under the Eurasian Plate.
  • It erupted in 2010 after a 400-year-long hiatus and has been continuously active since September 2013.

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Global Geological And Climatic Events

What is Seismic Noise?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Seismic noise

Mains level: Seismic activity and thier monitoring

The seismic noise level has dropped by as much as 50 per cent between March and May due to lockdowns this year, according to researchers.

Ever heard of space-based monitoring of seismic activities?  This topic creates a scope for potential prelims question…

What is Seismic Noise?

  • Seismic noise refers to vibrations within the Earth, which are triggered by natural and man-made phenomena like earthquakes, volcanoes and bombs.
  • Seismometers, specialised devices that record ground motions, also capture seismic noise.
  • Everyday human activity — such as road traffic, manufacturing in factories, the sound produced by planes roaring overhead, or simply people walking down the street.
  • The sound signals created by human beings are often referred to as anthropogenic seismic noise.
  • Seismic noise acts almost like background sound for seismologists — it is the unwanted component of signals recorded by a seismometer.

Variations in noise levels

  • The level of anthropogenic seismic noise recorded varies based on a number of factors.
  • Highly-populated urban areas will generate more vibrations from human activity than less densely populated regions.
  • Timing too plays an important role. The degree of seismic noise is found to be much lower during public holidays.

Why is this important to record this noise?

  • Due to this, scientists will be able to spot weaker signals.
  • Such small signals tell us about a geological fault making seismic hazard assessment more accurate.
  • This means that scientists will have a better shot at monitoring a whole range of seismogenic behaviour, including the smallest earthquakes or the early signs of a volcanic eruption.

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Global Geological And Climatic Events

[pib] Ravines of Chambal-Gwalior Region

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Ravines, Chambal River

Mains level: Features of badland topography

Union Minister of Agriculture & Farmers’ Welfare held a meeting with World Bank representatives to bring large Ravines of Gwalior–Chambal region under agriculture.

Try this question for mains:

Q.What is Badland Topography? Discuss the scope of their utilization as arable land in India.

What are Ravines?

  • Badland topography is a major feature of the Chambal valley is characterized by an undulating floodplain, gullies and ravines.
  • Ravines are a type of fluvial erosional feature and are formed as a result of constant vertical erosion by streams and rivers flowing over semi-arid and arid regions.

How are they formed?

  • Researchers consider the regional climate as a major factor in the formation of ravines.
  • Climate indeed plays a huge role by supplying the water in the form of rain or snow as well as providing the temperature variations.
  • However, the ravines of Chambal are a bit difficult to be explained solely on climatic terms.
  • The region through which the Chambal River flows does not receive enough rainfall to create ravines that are 60–80 m deep.
  • Researchers have attributed neotectonic activities to the Chambal ravines genesis.

Other factors

  • It is well known that rivers are full of energy and actively erode in their initial phases and progressively become passive as they attain their base levels.
  • But sometimes, due to tectonic movements, the base level may be lowered further thus energizing the river and reactivating the erosion. This is known as River Rejuvenation.
  • Moreover, wind erosion has also contributed to the formation of Chambal ravines.

Back2Basics: What are Badlands?

  • Badlands are erosional landforms of highly dissected morphology that are created on soft bedrock in a variety of climate conditions.
  • They develop in arid to semiarid areas where the bedrock is poorly cemented and rainfall is generally heavy and intermittent.
  • The dry, granular surface material and light vegetation are swept from the slopes during showers, leaving the gullies bare.

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Global Geological And Climatic Events

Lonar Lake turned pink due to ‘Haloarchaea’ microbes

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Lonar Crater Lake, Pleistoscene epoch

Mains level: Not Much

The colour of Lonar lake water in Maharashtra’s Buldhana district turned pink due to a large presence of the salt-loving ‘Haloarchaea’ microbes, a probe carried out by a Pune-based institute has concluded.

Make a note of all saltwater lakes in India. Few of them are Pulicat, Pangong Tso, Chilika, and Sambhar Lakes etc.

Haloarchaea’ microbes

  • Haloarchaea or halophilic archaea is a bacteria culture which produces pink pigment and is found in water saturated with salt.
  • The increased salinity and pH facilitated the growth of halophilic microbes, mainly Haloarchaea.
  • Basically, it is the biomass of these microbes and because of that, the surface of the water turned red or pink and as soon as the biomass subsided, the colour disappeared.
  • The scientist said the colour of the lake is now returning to original as the rainy season has kicked in, allowing dilution of the water.
  • Initially, it was thought for the red-pigmented Dunaliella algae due to which the water might have turned pink.
  • Because of that, the salinity and pH/alkalinity levels have also come down and green algae have started growing in the water body.

About Lonar Lake

  • Lonar Lake, also known as Lonar crater, is a notified National Geo-heritage Monument, saline (pH of 10.5), Soda Lake, located at Lonar in Buldhana district, Maharashtra.
  • It was created by an asteroid collision with earth impact during the Pleistocene Epoch.
  • It is one of the four known, hyper-velocity, impact craters in basaltic rock anywhere on Earth.
  • It sits inside the Deccan Plateau—a massive plain of volcanic basalt rock created by eruptions some 65 million years ago.
  • Its location in this basalt field suggested to some geologists that it was a volcanic crater.

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Global Geological And Climatic Events

‘Churachandpur Mao Fault’ in Mizoram

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Churachandpur Mao Fault

Mains level: Plate tectonics and continental drift theories

Mizoram’s zone of “scary” earthquakes is caught between two subterranean faults called the ‘Churachandpur Mao Fault’.

Try this question from CSE Mains 2014:

Q.Why are the world’s fold mountain systems located along the margins of continents? Bring out the association between the global distribution of Fold Mountains and the earthquakes and volcanoes.

Churachandpur-Mao Fault (CMF)

  • The CMF is named after two places in Manipur and runs north-south into Myanmar along the border of Champhai.
  • The Mat Fault runs northwest-southeast across Mizoram, beneath river Mat near Serchhip.
  • It is defined by straight valleys; most prominent being between Kangpokpi and Maram region of Mizoram.
  • The fault takes a north-easterly trend from Maram where the fault zone is characterized by active landslides during the monsoon.

Why study CMF?

  • Faults are discontinuities or cracks that are the result of differential motion within the earth’s crust.
  • Vertical or lateral slippage of the crust along the faults causes an earthquake.

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Global Geological And Climatic Events

Rapid Intensification of Cyclones

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Marsupial theory, MJO , MISO, El-Nino, La-Nina

Mains level: Tropical Cyclones

Tropical cyclones remain the deadliest natural climate hazard that causes an unacceptably high loss of life, property and infrastructure.  Global warming has already resulted in a detectable increase in the number of higher intensity cyclones as well as their intensification.

Also read:

[Burning Issue] Tropical Cyclones and India

Try this question:

Q. The Marsupial Theory often seen in news is related to which of the climatic phenomena?

a) Heatwaves b) Monsoon Variability c) Formation of Cyclones d) Thunderstorms

What is Rapid Intensification of Cyclones?

  • RI is defined as an increase in maximum sustained winds by at least 55 km/hour in a 24-hour period.
  • Such acceleration can only come with a rapid drop in the pressure in the eye of the cyclone.
  • Rapid intensification (RI) is making cyclone forecasts harder and intense cyclones with RI are expected to grow in number.
  • The lack of understanding of the transition from a seedling of a cyclone, like a low-pressure system to a tropical storm, limits extending the forecast lead times.

Factors causing RI

The most important environmental factors for cyclone genesis are-

  • the rotation or vorticity of a low-pressure system at the surface;
  • sea surface temperatures or the volume of warm water available;
  • the vertical motion of air in this low-pressure system;
  • the amount of humidity available in the middle atmosphere and
  • the vertical shear or the change in winds from the surface to the upper atmosphere.

MJO and Cyclones

  • Madden-Julian Oscillations as they are known, dominate the tropics during October-April by propagating from the western Indian Ocean into the eastern Indian Ocean, across the Indonesian seas into the Pacific Ocean.
  • Referred to as MJOs, these Madden-Julian Oscillations throw seeds of rotational low-pressure systems over the Indian and the Pacific Oceans.
  • And thus, MJOs show a strong association with cyclogenesis, especially for the post-monsoon season.

Impacts of MISO

  • Monsoon Intraseasonal Oscillations (MISO) are alternating periods of heavy and minimal rainfall, each lasting for about a month or so and tending to follow a cyclical, northward shifting pattern from the equator to southern Asia.
  • While the strong vertical shear suppresses cyclones during the monsoon season, MISOs influence cyclone genesis during the pre-monsoon season.

Other factors

  • At longer timescales, phenomena like the El Niño and La Niña influence not only the number of cyclone seeds but also the location and the expanse of warm water.
  • For example, during the pre-monsoon season of La Niña year, the region of warm water over the Bay of Bengal increases. This leads cyclones to travel longer and grow stronger than during an El Niño year.
  • Over the Pacific Ocean, on the other hand, it is the El Niño that provides a larger swath of warm water and more intense cyclones.
  • West Africa produces waves called easterly waves that propagate west from land onto the tropical Atlantic Ocean and sow the seeds for most hurricanes.
  • Extensive analysis has produced theories that are evocatively called the Marsupial Theory — a wave pouch that allows cyclones to grow, or waves interacting to produce a Kelvin cat’s eye, which is a ‘sweet-spot’ for the birth of a cyclone.

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Global Geological And Climatic Events

The lost continent of Zealandia

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Zealandia

Mains level: Zealandia and its features

A new map has revealed the lost continent of Zealandia.

The ocean relief can be divided into various parts such as Continental Shelf, Continental Slope, Continental Rise or Foot, Deep Ocean basins, Abyssal plains & Abyssal Hills, Oceanic Trenches, Seamounts and Guyots.

Revise these ocean bottom relief features from your basic references.

Also revise India’s Deep Ocean Mission.

About Zealandia

  • Zealandia — or Te Riu-a-Māui, as it’s referred to in the indigenous Māori language — is a 2 million-square-mile (5 million square kilometres) continent east of Australia, beneath modern-day New Zealand.
  • Scientists discovered the sprawling underwater mass in the 1990s, then gave it formal continent status in 2017.
  • Still, the “lost continent” remains largely unknown and poorly studied due to its Atlantean geography.

Its formation

  • It is a group of submerged pieces of crust that separated from the ancient supercontinent Gondwana about 85 million years ago.
  • Gondwana was formed when Earth’s ancient supercontinent, Pangea, split into two fragments.
  • Laurasia was transformed into North America, Asia, and Europe, while Gondwana became Africa, South America, Australia, and Antarctica.
  • But land masses continued to be rearranged afterwards, with Zealandia breaking off Gondwana.

Data revealed by the new map

  • The new maps reveal Zealandia’s bathymetry (the shape of the ocean floor) as well as its tectonic history, showing how volcanism and tectonic motion have shaped the continent over millions of years.
  • Data for the bathymetric map was provided by the Seabed2030 project — a global effort to map the entire ocean floor by 2030.

Why call it a continent?

  • Zealandia was classified as a “microcontinent,” as the island of Madagascar, until 2017.
  • But according to Mortimer, it has all the requirements to be classified as a continent.
  • It has defined boundaries; it occupies an area of over one million square kilometres and is elected above the ocean crust.

Also read: https://www.civilsdaily.com/news/seabed-2030-project/

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Global Geological And Climatic Events

What is ‘Last Glacial Maximum’?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Last Glacial Maximum

Mains level: Nature induced Climate Change

Researchers analysed simulations of this past climate and predicted that the ongoing climate change could reawaken an ancient climate pattern of the Indian Ocean Region (IOR).

Try this question from CSP 2017:

Q.With reference to ‘Indian Ocean Dipole (IOD)’, sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?

1. IOD phenomenon is characterized by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.

2. An IOD phenomenon can influence El Nino’s impact on the monsoon.

Select the correct Option using the code given below:

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

The Last Glacial Maximum

  • The Last Glacial Maximum (LGM) was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent.
  • Vast ice sheets covered much of North America, Northern Europe, and Asia and profoundly affected Earth’s climate by causing drought, desertification, and a large drop in sea levels.
  • Growth of ice sheets commenced 33,000 years ago and maximum coverage was between 26,500 years and 19–20,000 years ago, when deglaciation commenced in the Northern Hemisphere.
  • It caused an abrupt rise in sea level.

Shells predict IOR climate variability

  • By studying microscopic zooplankton called foraminifera, the team had published a paper in 2019 which first found evidence from the past of an Indian Ocean El Niño.
  • Foraminifera builds a calcium carbonate shell, and studying these can tell us about the properties of the water in which they lived.
  • The team measured multiple individual shells of foraminifera from ocean sediment cores and was able to reconstruct the sea surface temperature conditions of the past.
  • The Indian Ocean has the capacity to harbour much larger climate variability than observed during the last few decades or a century.

Lessons to learn

  • There are many lessons to be learnt from this cooler period about our warmer future.
  • As it is, under present-day conditions, changes in the Indian Ocean Dipole and the El Niño–Southern Oscillation strongly affect Indian Monsoon variability from year to year.
  • If the hypothesized ‘equatorial mode’ emerges in the near future, it will pose another source of uncertainty in rainfall prediction and will likely amplify swings in monsoon rainfall.
  • It could bring more frequent droughts to East Africa and southern India and increased rainfall over Indonesia.

Back2Basics

What is the Indian Ocean Dipole? Explain its connection with the Indian monsoons

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Global Geological And Climatic Events

What is the Anthropause Period?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Anthropause, Anthropocene

Mains level: Human impact on gelological time scale

Researchers in the UK are set to study the “Anthropause”, a term they have coined to refer to the coronavirus-induced lockdown period and its impact on other species.

Practice question for mains:

Q. What is the significance of declaring Anthropocene epoch? Discuss how it is different from any geological events. Discuss the Anthropause Period.

Anthropause Period

  • Researchers have suggested the lockdown period, which is also being referred to as the “Great Pause”, be referred to with a more precise term.
  • It is referred specifically to a considerable global slowing of modern human activities, notably travel.
  • The unprecedented curbs imposed on millions of people around the world, mainly due to restrictions in travel, led to reports of unusual animal behaviour.
  • For instance, there were pumas sighted in Chile’s Santiago, jackals in the parks of Tel Aviv in Israel, dolphins in the waters of Italy and even a monkey fight on the streets of Thailand.
  • The researchers believe studying this period will provide valuable insights into the relationship between human-wildlife interactions in the 21st century.

What do the researchers hope to find?

  • As a result of the lockdown, nature appears to have changed, especially in urban environments, since not only are there now more animals, but also some “unexpected visitors.”
  • In their outline, researchers mention how the scientific community can use these “extraordinary circumstance” provided by global lockdowns to understand how human activity affects wildlife.
  • On the other hand, there are some animals for which the lockdown may have made things more challenging.
  • For instance, for various urban-dwelling animals, such as rats, gulls and monkeys who depend on food provided or discarded by humans, the lockdown would have made life more difficult.

Why is studying the lockdown important?

  • Expanding human populations continue to transform their environments at unprecedented rates.
  • Further, because the reduction in human activity during the lockdown on both land and sea has been “unparalleled” in recent history, the effects have been “drastic, sudden and widespread”.
  • Essentially, this gives them a chance to study the extent to which modern human mobility affects wildlife.
  • The study can be linked can help provide insights that may be useful in preserving global biodiversity, maintaining the integrity of ecosystems and predicting global zoonoses and environmental changes.

Back2Basics

Anthropocene as Earth’s new epoch

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Global Geological And Climatic Events

‘Ring of Fire’ Solar Eclipse

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Solar Eclipse and related terms, Summer Solstice

Mains level: Not Much

A rare celestial event, an annular solar eclipse popularly called as the ‘ring of fire’ eclipse, will be visible on June 21, 2020 from some parts of Northern India. The first solar eclipse of this year takes place on the summer solstice, which is the longest day in the Northern Hemisphere.

Try this question from CSP 2019:

Q. On 21st June, the Sun

(a) Does not set below the horizon at the Arctic Circle

(b) Does not set below the horizon at Antarctic Circle

(c) Shines vertically overhead at noon on the Equator

(d) Shines vertically overhead at the Tropic of Capricorn

What is the Solar Eclipse?

  • A Solar Eclipse happens when the moon while orbiting the Earth comes in between the sun and the Earth, due to which the moon blocks the sun’s light from reaching the Earth, causing an eclipse of the sun or a solar eclipse.
  • According to NASA, people who are able to view the total solar eclipse are in the centre of the moon’s shadow as and when it hits the Earth.
  • There are three types of eclipses: one is a total solar eclipse, which is visible only from a small area on Earth. A total solar eclipse happens when the sun, moon and Earth are in a direct line.
  • The second type of a solar eclipse is a partial solar, in which the shadow of the moon appears on a small part of the sun.

Annular Solar Eclipse

  • The third kind is an annular solar eclipse, which happens when the moon is farthest from the Earth, which is why it seems smaller.
  • In this type of an eclipse, the moon does not block the sun completely, but looks like a “dark disk on top of a larger sun-coloured disk” forming a “ring of fire”.
  • Furthermore, during a solar eclipse, the moon casts two shadows on the Earth; the first one is called the umbra, which gets smaller as it reaches the Earth.
  • The second one is called the penumbra, which gets larger as it reaches the Earth.
  • According to NASA, people standing in the umbra see a total eclipse and those standing in the penumbra see a partial eclipse.

Why the study of solar eclipse is crucial?

  • One of the reasons that NASA studies solar eclipses is to study the top layer of the sun called the corona.
  • During an annular eclipse, NASA uses ground and space instruments to view this top layer when the sun’s glare is blocked by the moon.

Back2Basics: Summer Solstice

  • The summer solstice occurs when one of the Earth’s poles has its maximum tilt toward the Sun.
  • It happens twice yearly, once in each hemisphere (Northern and Southern).
  • For that hemisphere, the summer solstice is when the Sun reaches its highest position in the sky and is the day with the longest period of daylight.
  • Within the Arctic circle (for the northern hemisphere) or Antarctic circle (for the southern hemisphere), there is continuous daylight around the summer solstice.
  • On the summer solstice, Earth’s maximum axial tilt toward the Sun is 23.44°. Likewise, the Sun’s declination from the celestial equator is 23.44°.

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Global Geological And Climatic Events

Lonar Lake colour changes to pink

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Lonar Crater Lake, Pleistoscene epoch

Mains level: NA

The colour of water in Maharashtra’s Lonar Lake, formed after a meteorite hit the Earth some 50,000 years ago, has changed to glaring.

Make a note of all saltwater lakes in India. Few of them are Pulicat, Pangong Tso, Chilika, and Sambhar Lakes etc.

About Lonar Lake

  • Lonar Lake, also known as Lonar crater, is a notified National Geo-heritage Monument, saline (pH of 10.5), Soda Lake, located at Lonar in Buldhana district, Maharashtra.
  • It was created by an asteroid collision with earth impact during the Pleistocene Epoch.
  • It is one of the four known, hyper-velocity, impact craters in basaltic rock anywhere on Earth.
  • It sits inside the Deccan Plateau—a massive plain of volcanic basalt rock created by eruptions some 65 million years ago.
  • Its location in this basalt field suggested to some geologists that it was a volcanic crater.

Why there’s a color change?

  • The salinity and algae can be responsible for this change.
  • There is no oxygen below one meter of the lake’s water surface.
  • There is an example of a lake in Iran, where water becomes reddish due to increase in salinity.
  • The level of water in the Lonar Lake is currently low as compared to the few past years and there is no rain to pour fresh water in it.
  • The low level of water may lead to increased salinity and change in the behaviour of algae because of atmospheric changes.

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Global Geological And Climatic Events

Permafrost and the hazards of its Thawing

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Permafrost

Mains level: Paper 1-Permafrost thaw.

The principal reason that led to the recent 20,000-tonne oil leak at an Arctic region power plant in Russia that is now being recognised is the sinking of ground surface due to permafrost thaw.

Try this question from Mains 2017:
Q. What is Cryosphere? How does the Cryosphere affect global climate?

What is Permafrost?

  • Permafrost is ground that remains completely frozen at 0 degrees Celsius or below for at least two years.
  • It is defined solely based on temperature and duration.
  • The permanently frozen ground, consisting of soil, sand, and rock held together by ice, is believed to have formed during glacial periods dating several millennia.

Where are they found?

  • These grounds are known to be below 22 per cent of the land surface on Earth, mostly in polar zones and regions with high mountains.
  • They are spread across 55 per cent of the landmass in Russia and Canada, 85 per cent in the US state of Alaska, and possibly the entirety of Antarctica.
  • In northern Siberia, it forms a layer that is 1,500 m thick; 740 m in northern Alaska.
  • At lower latitudes, permafrost is found at high altitude locations such as the Alps and the Tibetian plateau.

How climate change is eating away at these grounds?

  • The Earth’s polar and high altitude regions — its principal permafrost reservoirs — are the most threatened by climate change.
  • Arctic regions are warming twice as fast compared to the rest of the planet, its current rate of temperature change being the highest in 2,000 years.
  • In 2016, Arctic permafrost temperatures were 3.5 degrees Celsius higher than at the beginning of the 20th century.
  • A study has shown that every 1 degree Celsius rise in temperature can degrade up to 39 lakh square kilometre due to thawing.
  • This degradation is expected to further aggravate as the climate gets warmer, putting at risk 40 per cent of the world’s permafrost towards the end of the century– causing disastrous effects.

The threat to infrastructure

  • Thawing permafrost is also ominous for man-made structures overhead.
  • The Russian oil leak occurred recorded temperatures in Siberia at more than 10 degrees Celsius above average, and called them “highly anomalous” for the region where the power plant is located.
  • As temperatures rise, the binding ice in permafrost melts, making the ground unstable and leading to massive potholes, landslides, and floods.
  • The sinking effect causes damage to key infrastructure such as roads, railway lines, buildings, power lines and pipelines.
  • These changes also threaten the survival of indigenous people, as well as Arctic animals.

A ticking time bomb

  • Beneath its surface, permafrost contains large quantities of organic leftover from thousands of years prior — dead remains of plants, animals, and microorganisms that got frozen before they could rot.
  • It also holds a massive trove of pathogens.
  • When permafrost thaws, microbes start decomposing this carbon matter, releasing greenhouse gases like methane and carbon dioxide.
  • Researchers have estimated that for every 1 degree Celsius rise in temperature, these grounds could release GHGs to the tune of 4-6 years’ of emissions from coal, oil, and natural gas.
  • Along with greenhouse houses, these grounds could also release ancient bacteria and viruses into the atmosphere as they unfreeze.

Back2Basics
https://www.civilsdaily.com/news/thawing-of-permafrost/

Also read:

Ambarnaya River Oil spill in Russia

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Global Geological And Climatic Events

What is Lunar Eclipse?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Lunar and Solar Eclipse

Mains level: Not Much

A penumbral lunar eclipse will be observed today midnight. The Earth will imperfectly align itself between the Sun and the moon, casting a shadow on the latter, marking the second lunar eclipse of the year.

Solar and Lunar eclipse has been quite frequent this year. Mark the major differences between them.

Lunar Eclipse

  • A lunar eclipse occurs when the Moon moves into the Earth’s shadow.
  • This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned with Earth between the other two.
  • A lunar eclipse can occur only on the night of a full moon. The type and length of a lunar eclipse depend on the Moon’s proximity to either node of its orbit.
  • Any object that obstructs light will produce two shadows: one which will be dark and dense, is called the umbra; and the other which is light and diffused is called the penumbra.
  • The only light reflected from the lunar surface has been refracted by Earth’s atmosphere.
  • This light appears reddish for the same reason that a sunset or sunrise does: the Rayleigh scattering of bluer light. Due to this reddish colour, a totally eclipsed Moon is sometimes called a blood moon.

Types

  • In a total eclipse of the moon, the inner part of Earth’s shadow, called the umbra, falls on the moon’s face. At mid-eclipse, the entire moon is in shadow, which may appear blood red.
  • In a partial lunar eclipse, the umbra takes a bite out of only a fraction of the moon. The dark bite grows larger and then recedes, never reaching the total phase.
  • In a penumbral lunar eclipse, only the more diffuse outer shadow of Earth – the penumbra – falls on the moon’s face. This third kind of lunar eclipse is much more subtle and much more difficult to observe than either a total or partial eclipse of the moon.

How it is different from Solar Eclipse?

  • A solar eclipse happens when the moon passes in between the earth and the sun. A lunar eclipse happens when the earth passes in between the moon and the sun.
  • During a solar eclipse, the moon partially or fully hides the sun’s rays for a few minutes.
  • Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth.
  • Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the full Moon.

What’s special this time?

  • This eclipse is also called a strawberry moon eclipse — the term, interestingly, originates from an American concept and has little to do with the Euro-Asia region.
  • June’s full moon usually coincides with the harvesting season of wild strawberries in America and the phenomenon was often addressed in reference to that.
  • India had already witnessed an eclipse earlier this year, in January.
  • The strawberry moon eclipse is going to be its second and probably the last visible lunar one in 2020.

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Global Geological And Climatic Events

The Sixth Mass Extinction

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Sixth Mass Extinction

Mains level: Mass Extinction

Click here for high resolution of the image: National Geographic

The ongoing sixth mass extinction may be one of the most serious environmental threats to the persistence of civilization, according to new research published in an American journal.

Try this question from CSP 2018:

The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of

(a) Widespread monoculture Practices agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.

(b) Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65million years ago that caused the mass extinction of many species including those of dinosaurs.

(c) Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivationin other Parts of the world which may cause the disappearance of good native crop plants and the loss offood biodiversity.

(d) Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss, natural habitats, destructionof ecosystems, pollution and global climate change.

Highlights of the research

  • The study analysed 29,400 species of terrestrial vertebrates and determined which of these are on the brink of extinction because they have fewer than 1,000 individuals.
  • The disappearance of their component populations has been occurring since the 1800s.
  • Most of these 515 species are from South America (30 per cent), followed by Oceania (21 per cent), Asia (21 per cent) and Africa (16 per cent) among others.

The Anthropocene Extinction

  • Mass extinction refers to a substantial increase in the degree of extinction or when the Earth loses more than three-quarters of its species in a geologically short period of time.
  • So far, during the entire history of the Earth, there have been five mass extinctions.
  • The sixth, which is ongoing, is referred to as the Anthropocene extinction.
  • The five mass extinctions that took place in the last 450 million years have led to the destruction of 70-95 per cent of the species of plants, animals and microorganisms that existed earlier.
  • These extinctions were caused by “catastrophic alterations” to the environment, such as massive volcanic eruptions, depletion of oceanic oxygen or collision with an asteroid.
  • After each of these extinctions, it took millions of years to regain species comparable to those that existed before the event.

So what is the sixth mass extinction then?

  • Researchers have described it as the “most serious environmental problem” since the loss of species will be permanent.
  • Even though only an estimated 2% of all of the species that ever lived are alive today, the absolute number of species is greater now than ever before.
  • The research claims that this extinction is human-caused and is more immediate than climate destruction.

Major drivers of mass extinction

  • Significantly, the study calls for a complete ban on wildlife trade as many of the species currently endangered or on the brink of extinction are being decimated by legal and illegal wildlife trade.
  • The current COVID-19 pandemic, while not fully understood, is also linked to the wildlife trade.
  • There is no doubt that there will be more pandemics if man continues destroying habitats and trading wildlife for own consumption as food and traditional medicines.

What happens when species go extinct?

  • When species go extinct, the impact can be tangible such as in the form of a loss in crop pollination and water purification.
  • Further, if a species has a specific function in an ecosystem, the loss can lead to consequences for other species by impacting the food chain.
  • The effects of extinction will worsen in the coming decades as the resulting genetic and cultural variability will change entire ecosystems.
  • If the number of individuals in a population or species drops, their contributions to ecosystem services become unimportant.
  • Their genetic variability and resilience is reduced, and its contribution to human welfare may be lost.” the study says.

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Global Geological And Climatic Events

What is South Atlantic Anomaly?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Van Allen Radiation Belt, South Atlantic Anomaly

Mains level: South Atlantic Anomaly and its impact

New data obtained by the European Space Agency (ESA) Swarm satellites has revealed the existence of a mysterious anomaly weakening the Earth’s magnetic field. Termed as ‘South Atlantic Anomaly’, it extends all the way from South America to southwest Africa.

The term ‘South Atlantic Anomaly’ at its first sight looks similar to any climate/oceanic current related phenomena. But it’s not! This is where you can end up losing 2.66 marks in the prelims!

What is South Atlantic Anomaly (SAA)?

  • The SAA is referred to the behaviour of Earth’s Geo-Magnetic field in an area between Africa and South America.
  • The SAA is an area where the Earth’s inner Van Allen radiation belt comes closest to the Earth’s surface, dipping down to an altitude of 200 kilometres.
  • This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher-than-usual levels of radiation.
  • The effect is caused by the non-concentricity of the Earth and its magnetic dipole.
  • The SAA is the near-Earth region where the Earth’s magnetic field is weakest relative to an idealized Earth-centered dipole field.

Weakening of the magnetic field

  • Over the last 200 years, the magnetic field has lost around 9% of its strength on a global average.
  • A large and rapid shrink has been observed in the SAA region over the past 50 years just as the area itself has grown and moved westward.
  • The weakening of the magnetic field is also causing technical difficulties for the satellites and spacecraft orbiting the planet.
  • The study conducted between 1970 and 2020, said that the magnetic field weakened considerably in a large region stretching from Africa to South America, known as the ‘SAA’.
  • This area has grown and moved westward at a rate of around 20 km per year.

Its impact

  • The magnetic shield has an important role to play in keeping unwanted radiation away as well as helping determine the location of magnetic poles.
  • Even though unlike global warming or any weather change, this anomaly doesn’t directly impact human lives, it could actually bring on a change in the way we access technology.
  • The reversal and apparent shift, which could keep extending could actually impact satellite and telecommunication system, which means that some of the internet and mobile phone functioning which depend on satellite signals can possibly get disrupted.
  • It could also affect the mapping and navigation systems in smartphones.
  • The weakening of earth’s magnetic field could also impact migratory movement.
  • Birds, animals- all those who migrate with the change in season depend on the earth’s mapping to move about can find it a little difficult.
  • This is only a possibility, but we don’t know the extent of the damage till now.

About the Van Allen Radiation Belt

  • A Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet’s magnetic field.
  • The belts are located in the inner region of Earth’s magnetosphere. The belts trap energetic electrons and protons.
  • Earth has two such belts and sometimes others may be temporarily created.
  • Most of the particles that form the belts are thought to come from solar wind and other particles by cosmic rays.
  • By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.

Also read:

Shifting north magnetic pole forces urgent navigation fix


Back2Basics: Swarm  Constellation

  • Swarm is a European Space Agency (ESA) mission to study the Earth’s magnetic field.
  • It is ESA’s first constellation of satellites for Earth observation.
  • The Swarm constellation consists of three satellites (Alpha, Bravo and Charlie) placed in two different polar orbits, two flying side by side at an altitude of 450 km and a third at an altitude of 530 km.

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Global Geological And Climatic Events

What is Solar Minimum?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Solar minima and maxima

Mains level: Solar minima and maxima, its impact on space weather and earth

The sun is said to have gone into a state called the ‘solar minimum’ and is about to enter the deepest period of ‘sunshine recession’ as sunspots are virtually not visibly at all.

Practice question for Mains:

Q. What are Solar minima and maxima? Discuss its impact on space weather and the Earth.

What is a solar minimum and why is it happening now?

  • Sun has a cycle that lasts on average 11 years, and right now we are at the peak of that cycle.
  • Every 11 years or so, sunspots fade away, bringing a period of relative calm.
  • This is called the solar minimum. And it’s a regular part of the sunspot cycle.
  • While intense activity such as sunspots and solar flares subside during solar minimum, that doesn’t mean the sun becomes dull. Solar activity simply changes form.

What about Solar Maximum?

  • Solar minima and maxima are the two extremes of the Sun’s 11-year and 400-year activity cycle.
  • At a maximum, the Sun is peppered with sunspots, solar flares erupt, and the Sun hurls billion-ton clouds of electrified gas into space.
  • Sky watchers may see more auroras, and space agencies must monitor radiation storms for astronaut protection.
  • Power outages, satellite malfunctions, communication disruptions, and GPS receiver malfunctions are just a few of the things that can happen during a solar maximum.

What are its effects on Earth?

a) On space weather

  • The Solar wind from coronal holes will temporarily create disturbances in the Earth’s magnetosphere, called geomagnetic storms, auroras, and disruptions to communications and navigation systems.
  • The space weather during solar minimum will also affect Earth’s upper atmosphere on satellites in low Earth orbit changes.
  • This means that the Earth’s upper atmosphere will cool down which is generally heated and puffed up by ultraviolet radiation from the sun.
  • However, the heat at the upper atmosphere of our planet helps Earth to drag debris and keep the low Earth orbit clear of manmade space junk.
  • Apart from this, the solar minimum will change the space weather significantly which will lead to an increase in the number of galactic cosmic rays that reach Earth’s upper atmosphere.
  • These Galactic cosmic rays are high energy particles which are a result of distant supernova explosions and other violent events in the galaxy.

b) On astronauts

  • According to NASA the sun’s magnetic field weakens and provides less shielding from these cosmic rays during a solar minimum which will directly increase the threat to astronauts travelling through space.
  • This may cause health risks to astronauts travelling through space as the sun’s magnetic field weakens and provides less shielding from these cosmic rays.

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Global Geological And Climatic Events

Super Cyclone Amphan and its threats

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Tropical Cyclones

Mains level: Rising events of Tropical Cyclone in India

The storm system in the Bay of Bengal, Amphan, developed into a super cyclone and is expected to make landfall along the West Bengal-Bangladesh coast very soon.

Realted PYQ:

Q. In the South Atlantic and South Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason? (CSP 2015)

(a) Sea Surface temperature are low
(b) Inter Tropical Convergence Zone seldom occurs
(c) Coriolis force is too weak
(d) Absence of land in those regions

Super Cyclone Amphan

  • Cyclone Amphan is a tropical cyclone formed over the Bay of Bengal that has intensified and likely to turn into a “super cyclonic storm (maximum wind speed is 224 kmph)”.
  • It has been named by Thailand.
  • Amphan is the equivalent of a Category 5 hurricane on the Saffir-Simpson Hurricane Wind Scale.
  • By the time it makes landfall in West Bengal, Amphan is expected to tone down into a category 4 Extremely Severe Cyclonic (ESC) storm with a wind speed of 165-175 kmph and gusting to 195 kmph.

What makes it a nightmare?

  • This is the first super cyclone to form in the Bay of Bengal after the 1999 super cyclone that hit Odisha and claimed more than 10,000 lives.
  • It is the third super cyclone to occur in the North Indian Ocean region after 1999 which comprises of the Bay of Bengal, the Arabian Sea and the northern part of the Indian Ocean.
  • The other two super cyclones were Cyclone Kyarr in 2019 and Cyclone Gonu in 2007.

Recent cyclones in the region

  • From 1965 to 2017, the Bay of Bengal and the Arabian Sea collectively registered 46 ‘severe cyclonic storms’.
  • More than half of them occurred between October and December.
  • Seven of them occurred in May and only two (in 1966 and 1976) were recorded in April, according to data from the IMDs cyclone statistics unit.
  • Cyclone Phailin in 2013 and the super cyclone of 1999 — both of which hit coastal Odisha — have been the most powerful cyclones in the Bay of Bengal in the past two decades in terms of wind speed.
  • Last year, Fani, which was an ESC made landfall in Odisha and ravaged the State, claiming at least 40 lives.

Back2Basics: Tropical Cyclones

  • Cyclones are formed over slightly warm ocean waters.
  • The temperature of the top layer of the sea, up to a depth of about 60 metres, need to be at least 28°C to support the formation of a cyclone.
  • This explains why the April-May and October-December periods are conducive for cyclones.
  • Then, the low level of air above the waters needs to have an ‘anticlockwise’ rotation (in the northern hemisphere; clockwise in the southern hemisphere).
  • During these periods, there is an ITCZ in the Bay of Bengal whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west.
  • This induces the anticlockwise rotation of the air.
  • Once formed, cyclones in this area usually move northwest. As it travels over the sea, the cyclone gathers more moist air from the warm sea and adds to its heft.

What strengthens them?

  • A thumb rule for cyclones is that the more time they spend over the seas, the stronger they become.
  • Hurricanes around the US, which originate in the vast open Pacific Ocean, are usually much stronger than the tropical cyclones in the Bay of Bengal, a relatively narrow and enclosed region.
  • The cyclones originating here, after hitting the landmass, decay rapidly due to friction and absence of moisture.

Grading of Cyclones

  • Tropical cyclones in the Bay of Bengal are graded according to maximum wind speeds at their centre.
  • At the lower end are depressions that generate wind speeds of 30 to 60 km per hour, followed by:
  1. cyclonic storms (61 to 88 kmph)
  2. severe cyclonic storms (89 to 117 kmph)
  3. very severe cyclonic storms (118 to 166 kmph)
  4. extremely severe cyclonic storms (167 to 221 kmph) and
  5. super cyclones (222 kmph or higher)

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Global Geological And Climatic Events

[pib] River erosion in Ladakh Himalayas

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Himalayan rivers, Zanskar Padam

Mains level: Read the attached story

Indian researchers have studied rivers in Ladakh Himalaya, bringing out 35 thousand-year histories of river erosion and identified hotspots of erosion and wide valleys that act buffer zones.

Click here to read more about the Himalayan river systems and its orogeny

Erosion hotspot: Ladakh region

  • The Ladakh Himalaya forms a high altitude desert between Greater Himalayan ranges and Karakoram Ranges.
  • The Indus and its tributaries are major rivers flowing through the terrain.
  • The Zanskar River is one of the largest tributaries of the upper Indus catchment, draining orthogonally through highly deformed Zanskar ranges.

Zanskar: A major river in Ladakh

  • Two prominent tributaries of Zanskar River are the Doda and Tsrap Lingti Chu, which confluence at Padam village in the upper valley to form the Zanskar River.
  • Zanskar catchment was explored to understand the landform evolution in the transitional climatic zone, using morpho-stratigraphy and study of landforms like valley fill terraces, alluvial fans (triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt).

Zanskar Padam

  • Zanskar river makes a deep gorge in its lower reaches with the headwaters in upper Zanskar makes wide basin called as Padam.
  • The basin stores large amount of sediments in form of fans and river terrace deposits
  • The research suggested that the wide valley of Padam, with an area of 48 square km, in the upper Zanskar, has stored a vast amount of sediments in these landforms.
  • Thus Padam valley is a hotspot of sediment buffering in the Zanskar.

Sediment study reveals the erosion

  • The study suggested that most sediments were derived from Higher Himalayan crystalline that lies in the headwater region of Zanskar.
  • It was found out that dominant factors responsible for sediment erosion were deglaciation and Indian Summer Monsoon derived precipitation in the headwaters despite the presence of a geomorphic barrier (the deep, narrow gorge).

Significance of the study

  • The scientists have traced where the rivers draining Himalaya and its foreland erode the most and identify the zones that receive these eroded sediments and fill up.
  • The study will help understand river-borne erosion and sedimentation, which are the main drivers that make large riverine plains, terraces, and deltas that eventually become the cradle to evolving civilizations.
  • It will also help study the dynamics of devastating floods created by these Himalayan rivers in recent times.
  • Thus, the understanding of water and sediment routing becomes crucial while developing infrastructure and for other development works in the river catchment area.

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Global Geological And Climatic Events

New list of names of tropical cyclones over north Indian Ocean

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Naming of Tropical Cyclones

Mains level: Tropical Cyclones

The India Meteorological Department (IMD) has released a new list containing 169 names of future tropical cyclones that would emerge in the Bay of Bengal and the Arabian Sea.

When is the name of a Tropical Cyclone declared?

  • Names are declared when TCs are diagnosed with maximum sustained surface wind-speed of 34 knots (62 kmph) or more as per Global Data Processing and Forecasting System (GDPFS) Manual of WMO.
  • Panel Members’ names will be listed alphabetically country-wise.

We can expect a statement based prelim question like – Which of the following criterion are followed while naming a tropical cyclone?

Who is involved in the naming of Tropic Cyclone?

  • Worldwide there are six regional specialised meteorological centres (RSMCs) and five regional Tropical Cyclone Warning Centres (TCWCs) mandated for issuing advisories and naming of tropical cyclones.
  • IMD is one of the six RSMCs to provide tropical cyclone and storm surge advisories to 13 member countries under WMO/ESCAP Panel.
  • The panel countries include Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, United Arab Emirates and Yemen.
  • RSMC, New Delhi is also mandated to name the Tropical Cyclones developing over the North Indian Ocean (NIO) including the Bay of Bengal and the Arabian Sea.

Since when did naming begin?

  • The WMO/ESCAP Panel on Tropical Cyclones (PTC) at its twenty-seventh Session held in 2000 in Muscat, agreed in principle to assign names to the tropical cyclones in the Bay of Bengal and the Arabian Sea.
  • After long deliberations among the member countries, the naming of the tropical cyclones over the north Indian Ocean commenced from September 2004.
  • This list contained names proposed by the eight member countries of WMO/ESCAP PTC, viz., Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand.

Why name Cyclones?

The naming of Tropical Cyclones (TC) helps the scientific community, disaster managers, media and general masses to-

  • identify each individual cyclone.
  • create awareness of its development.
  • remove confusion in case of simultaneous occurrence of TCs over a region
  • remember a TC easily
  • rapidly and effectively disseminate warnings to a much wider audience

Major criteria adopted for naming

  • The proposed name should be neutral to (a) politics and political figures (b) religious believes, (c) cultures and (d) gender
  • The name should be chosen in such a way that it does not hurt the sentiments of any group of the population over the globe
  • It should not be very rude and cruel in nature
  • The maximum length of the name will be eight letters
  • The Panel reserves the right to reject any name if any of the criteria above are not satisfied
  • The names of tropical cyclones over the north Indian Ocean will not be repeated. Once used, it will cease to be used again.

Back2Basics

Explained: Naming of cyclones

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Global Geological And Climatic Events

Earth’s seismic noise levels

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Seismic noise

Mains level: Seismic activity and thier monitoring

Scientists at the British Geological Survey (BGS) reported a change in the Earth’s seismic noise and vibrations amid the coronavirus lockdown. This change has been monitored through a space-based seismograph.

Ever heard of space-based monitoring of seismic activities?  This topic creates a scope for potential prelims question…

What is seismic noise?

  • In geology, seismic noise refers to the relatively persistent vibration of the ground due to a multitude of causes.
  • It is the unwanted component of signals recorded by a seismometer– the scientific instrument that records ground motions, such as those caused by earthquakes, volcanic eruptions, and explosions.
  • This noise includes vibrations caused due to human activity, such as transport and manufacturing, and makes it difficult for scientists to study seismic data that is more valuable.
  • Apart from geology, seismic noise is also studied in other fields such as oil exploration, hydrology, and earthquake engineering.

How are vibrations generated?

  • We measure ground vibrations from earthquakes using seismometers.
  • These are incredibly sensitive so they also pick up other sources of vibration too, including human activity, such as road traffic, machinery and even people walking past.
  • All these things generate vibrations that propagate as seismic waves through the Earth.

Reasons for the decline

  • Due to the enforcement of lockdown measures around the world to tackle the novel coronavirus pandemic, the Earth’s crust has shown reduced levels of vibration.

How do the reduced noise levels help scientists?

  • The seismic noise vibrations caused by human activity are of high frequency (between 1-100 Hz), and travel through the Earth’s surface layers.
  • Usually, to measure seismic activity accurately and reduce the effect of seismic noise, geologists place their detectors 100 metres below the Earth’s surface.
  • However, since the lockdown, researchers were able to study natural vibrations even from surface readings, owing to lesser seismic noise.
  • Due to lower noise levels, scientists are now hoping that they would be able to detect smaller earthquakes and tremors that had slipped past their instruments so far.

 

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Global Geological And Climatic Events

What are Primordial Black Holes (PBH)?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Primordial Black Holes, Big Bang

Mains level: Black Holes

A scientist duo from Pune has studied primordial black holes that were born as a result of a tiny bump in the potential energy levels of the universe, at a time when it was expanding rapidly.

Strange space events are known to be the favourites of UPSC 🙂

Primordial Black Holes (PBH)

  • PBH are a hypothetical type of black hole that formed soon after the Big Bang
  • It is believed that they are formed as a result of collapsing radiations as opposed to the collapse of massive stars, which is the case of any other black holes.
  • PBH can be massively large as 3000kms or be extremely tiny like nucleus of an atom.

What did the study conclude?

  • The study has confirmed that this marginal rise in potential energy resulted in birth of several PBHs and also emitted very powerful gravitational waves.
  • Approximately 14 billion years ago before the commencement of the Hot Big Bang phase, the very young universe was found to be active and expanding at a highly accelerated rate.
  • This exponential growth in its size was fuelled by the presence of uniform energy field and density as the universe passed through the Cosmic Inflation phase.
  • According to the scientists, as time passes, this uniform energy prevailing in the Inflation Field wanes out.
  • As a result, the universe resumes its normal decelerating rate.

Expansion of universe

  • Gravity is normally attractive in nature. The PBH did undergo rapid expansion due to the Inflation field which contrarily possessed repulsive gravity.
  • This pushed the universe to expand at a much faster rate than normal.
  • The universe had expanded to nearly 10^27 times its original size, that too, within just fraction of a second by the time Cosmic Inflation phase concluded.
  • Thereafter, the remnant energy possessed by this gravitational force got converted mainly into photons (light) in addition to protons, electrons, neutrons and other particles.
  • As the universe continued to grow exponentially during the Cosmic Inflation phase, it sent across tiny quantum jitters.
  • These fluctuations, released in a specific fashion, when sufficiently large, slowly give birth to galaxies and stars. Among those that were significantly large, helped form PBHs.

 

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Global Geological And Climatic Events

[pib] Ionospheric based monitoring of large earthquakes

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Ionosphere, CIP

Mains level: Relation between atmosphere and seismic activity

Scientists of Indian Institute of Geomagnetism (IIG) an autonomous institution of the DST have extensively studied the signatures of recent large earthquakes into the ionosphere with an ambitious aim to derive the seismic source characteristics from the ionosphere.

CLAIMS

  • The research is a part of the interdisciplinary program ‘Coupled Lithosphere-Atmosphere- Ionosphere-Magnetosphere System (CLAIMS)’ of IIG.
  • CLAIMS focuses on energy transfer to the atmosphere during solid Earth processes such as earthquakes as well as tsunamis.

Key terms: Co-seismic Ionospheric Perturbations (CIP)

  • In general, the Earth crust uplift during an earthquake produces compressional (i.e. pressure) waves in the overlying atmosphere.
  • These waves propagate upward in the region of exponentially decreasing atmospheric neutral density, and thus, wave amplitude increase with atmospheric heights.
  • On arrival at ionospheric heights, the waves redistribute ionospheric electron density and produce electron density perturbations (disruption) known as CIP.

Objective of CLAIMS

  • The spatial distribution of near field co-seismic Ionospheric perturbations (CIP) associated with this event could reflect well the ground deformation pattern evolved around the epicentre.
  • These CIPs were derived using the Global Positioning System (GPS) measured Total Electron Content (TEC).
  • The CIP distribution was estimated at Ionospheric piercing point (IPP) altitude.

Other factors affecting CIP

The major effective non-tectonic forcing mechanisms at ionospheric altitudes are the-

  1. orientation between the ambient geomagnetic field and seismic induced neutral wave perturbations.
  2. orientation between the moving satellite line of sights and the wave perturbations.
  3. ambient ionospheric electron density gradient.

Back2Basics

Ionosphere

  • The ionosphere is the ionized part of Earth’s upper atmosphere, from about 60 km to 1,000 km altitude.
  • It is a region that includes the thermosphere and parts of the mesosphere and exosphere.
  • It is ionized by solar radiation.

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Global Geological And Climatic Events

Pink Supermoon/ Paschal Moon

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Pink Supermoon

Mains level: NA

A supermoon is all scheduled to show up in the sky on April 7. It would be the biggest and brightest full moon of 2020.

Pink Supermoon

  • According to NASA, a supermoon takes place when a full moon is at its closest to the Earth.
  • When the full moon appears at perigee (closest point from the earth) it is slightly brighter and larger than a regular full moon — and that is what we call a “supermoon.”
  • They are called Supermoons because they are 7 per cent bigger and 15 per cent brighter, compared to an average full Moon.
  • The moon will not be originally pink in colour. It got its name from the pink wildflowers – Wild Ground Phlox – that bloom in the spring and are native to North America.
  • It is also called Paschal moon because, in the Christian calendar, this is used to calculate the date for Easter – the first Sunday after the Paschal Moon is Easter Sunday.

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Global Geological And Climatic Events

Earth’s spin has slowed over time

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Torreites sanchezi, Leap Year

Mains level: Evolution in the spin of earth and various factors affecting it

 

Earth spun 372 times a year 70 million years ago, compared to the current 365. This means the day was 23½ hours long, compared to 24 today.

Faster Earth in the olden days

  • It has long been known that Earth’s spin has slowed over time.
  • Previous climate reconstructions, however, have described long-term changes over tens of thousands of years.
  • The new study looked at daily and annual variations in the mollusc shell.

About the Mollusc

  • A mollusc is an invertebrate of a large phylum which includes snails, slugs, mussels, and octopuses. They have a soft unsegmented body and live in aquatic or damp habitats, and most kinds have an external calcareous shell.
  • The ancient mollusc, Torreites Sanchez, belonged to an extinct group called rudist clams.
  • At 70 million years ago, it belonged to the Late Cretaceous — it was around the time this epoch ended, some 65 million years ago, that dinosaurs went extinct.

How did researchers conclude this variation?

  • Torreites sanchezi grew very fast, laying down daily growth rings.
  • Using lasers on a single individual, scientists sampled tiny slices and counted the growth rings accurately.
  • This allowed them to determine the number of days in a year 70 million years ago, and more accurately calculate the length of a day.

Significance of the research

  • It is important to note that the period of Earth’s orbit has remained the same. In other words, one year 70 million years ago was as long as one year today.
  • However, if there were a calendar then, the year would have been 372 “days” long, with each “day” half-an-hour shorter than one day today.
  • Today, Earth’s orbit is not exactly 365 days, but 365 days and a fraction, which is why our calendars have leap years, as a correction.

The Moon’s retreat

  • Friction from ocean tides, caused by the Moon’s gravity, slows Earth’s rotation and leads to longer days.
  • And as Earth’s spin slows the Moon moves farther away at 3.82 cm per year.
  • If this rate is projected back in time, however, the Moon would be inside the Earth only 1.4 billion years ago.
  • This new measurement, in turn, informs models of how the Moon formed and how closes it has been to Earth over their 4.5-billion-year gravitational relationship.

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Global Geological And Climatic Events

[pib] Effects of Himalayan slip on its Hydrology

Researchers from the Indian Institute of Geomagnetism have found the mighty Himalayas subside and move up depending on the seasonal changes in groundwater.

Tectonic activity and groundwater

  • The Himalayan foothills and the Indo-Gangetic plain are sinking because its contiguous areas are rising due to tectonic activity associated with landmass movement or continental drift.
  • The new study shows that subsidence and uplift are found to be associated with seasonal changes in groundwater, apart from the normal, common reasons.
  • Water acts as a lubricating agent, and hence when there is water in the dry season, the rate of the slip of the fault in this region is reduced.
  • In the Himalaya, seasonal water from glaciers, as well as monsoon precipitation, plays a key role in the deformation of the crust and the seismicity associated with it.
  • The subsidence rate is associated with groundwater consumption.

Findings of the study

  • The researchers have made the combined use of GPS and Gravity Recovery And Climate Experiment (GRACE) data, which has made it possible for them to quantify the variations of hydrologic mass.
  • The GRACE satellites, launched by the US in 2002, monitor changes in water and snow stores on the continents.
  • The combined data suggest a 12% reduction in the rate of the subsurface slip. This slip refers to how fast the fault is slipping relative to the foot and hanging wall.
  • The slip occurs at the Main Himalayan Thrust (MHT), due to hydrological variations and human activities, over which there is the periodic release of accumulated strain.

About GRACE Mission

  • The Gravity Recovery and Climate Experiment (GRACE) was a joint mission of NASA and the German Aerospace Center.
  • Twin satellites took detailed measurements of Earth’s gravity field anomalies from its launch in March 2002 to the end of its science mission in October 2017.
  • By measuring gravity anomalies, GRACE showed how mass is distributed around the planet and how it varies over time.

 

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Global Geological And Climatic Events

Explained: Cycle 25/ Solar Cycle

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Solar Cycle, Sunspots, Solar Dynamo

Mains level: Read the attached story

 

 

The sunspots identified by researchers from IISER Kolkata herald the start of a new solar cycle called Cycle 25.

What are Sunspots?

  • Sunspots are temporary phenomena on the Sun’s photosphere that appear as spots darker than the surrounding areas. They are relatively cooler spots on the Sun’s surface.
  • They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection.
  • Sunspots usually appear in pairs of opposite magnetic polarity with a leader and a follower.

What is Solar Cycle?

  • From our safe distance of about 148 million km, the Sun appears to be sedate and constant. However, huge solar flares and coronal mass ejections spew material from its surface into outer space.
  • They originate from sunspots, an important phenomenon that people have been following for hundreds of years. They originate deep within the Sun and become visible when they pop out.
  • Their number is not constant but shows a minimum and then rises up to a maximum and then falls again in what is called the solar cycle.
  • Every 11 years or so, the Sun’s magnetic field completely flips. This means that the Sun’s north and south poles switch places. Then it takes about another 11 years for the Sun’s north and south poles to flip back again.
  • So far, astronomers have documented 24 such cycles, the last one ended in 2019.

How do they occur?

  • Given the high temperatures in the Sun, matter exists there in the form of plasma, where the electrons are stripped away from the nuclei.
  • The Sun is made of hot ionized plasma whose motions generate magnetic fields in the solar interior by harnessing the energy of the plasma flows.
  • This mechanism is known as the solar dynamo mechanism (or magnetohydrodynamic dynamo mechanism).
  • Simply stated, it is a process by which kinetic energy of plasma motions is converted to magnetic energy, which generates the magnetised sunspots, giving rise to the solar cycle..
  • Because of the nature of the solar dynamo, the part of its magnetic field that gives rise to sunspots reverses direction when it moves from one solar cycle to another.
  • This can be inferred by observing when the relative orientation of the sunspot pairs flips.

Features

  • The solar cycle affects activity on the surface of the Sun, such as sunspots which are caused by the Sun’s magnetic fields. As the magnetic fields change, so does the amount of activity on the Sun’s surface.
  • One way to track the solar cycle is by counting the number of sunspots.
  • The beginning of a solar cycle is a solar minimum, or when the Sun has the least sunspots. Over time, solar activity—and the number of sunspots—increases.
  • The middle of the solar cycle is the solar maximum, or when the Sun has the most sunspots. As the cycle ends, it fades back to the solar minimum and then a new cycle begins.
  • Giant eruptions on the Sun, such as solar flares and coronal mass ejections, also increase during the solar cycle. These eruptions send powerful bursts of energy and material into space.

Impacts of Solar Cycle

  • This activity has effects on Earth. For example, eruptions can cause lights in the sky, called aurora, or impact radio communications. Extreme eruptions can even affect electricity grids on Earth.
  • Solar activity can affect satellite electronics and limit their lifetime.
  • Radiation can be dangerous for astronauts who do work on the outside of the International Space Station.
  • Forecasting of the solar cycle can help scientists protect our radio communications on Earth, and help keep satellites and astronauts safe.

Start of cycle 25

  • Following a weakening trend in activity over the last few cycles, there were predictions that the Sun would go silent into a grand minimum in activity, with the disappearance of cycles.
  • However, a team from IISER Kolkata has shown that there are signs that cycle 25 has just begun.
  • They used the data from the instrument Helioseismic and Magnetic Imager aboard NASA’s space-based Solar Dynamics Observatory for their calculations.

Why is this so important to us on earth?

  • After all the sunspots look small and are hardly even visible to us. Contrary to this, sunspot activity may be correlated with climate on earth.
  • In the period between 1645 and 1715, sun spot activity had come to a halt on the Sun – a phenomenon referred to as the Maunder minimum.
  • This coincided with extremely cold weather globally. So sunspots may have a relevance to climate on earth.
  • Such links are tenuous, but definitely solar activity affects space weather, which can have an impact on space-based satellites, GPS, power grids and so on.

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Global Geological And Climatic Events

Solar Storms

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Solar Storms

Mains level: Solar storms and their impact on Earth

 

According to a research, sudden releases of high-energy particles from the sun, called solar storms, can mess with the navigational ability of gray whales, causing them to strand on land.

Solar storms

  • Solar storms are a variety of eruptions of mass and energy from the solar surface.
  • Flares, prominences, sunspots, coronal mass ejections are the common harbingers of solar activity, as are plages and other related phenomena seen at other wavelengths.

Impact on Whales

  • Solar storms have the potential to modify geomagnetic field and disrupt magnetic orientation behaviour of animals, hampering their navigation during long periods of migration.
  • They disrupt earth’s magnetic field — and the whales’ navigational sense.
  • The radio frequency noise created by the solar outburst affects the whales’ senses in a way that prevents them from navigating at all.

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Global Geological And Climatic Events

Yongle Blue Hole (YBH)

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Yongle Blue Hole (YBH)

Mains level: Signifcance of Blue Holes

 

Carbon more than 8,000 years old has been found inside the world’s deepest blue hole — the Yongle Blue Hole (YBH).

Yongle Blue Hole (YBH)

  • The deepest known marine cavern is the Yongle blue hole, which measures roughly 300 metres from top to bottom.
  • Blue holes are marine caverns filled with water and are formed following dissolution of carbonate rocks, usually under the influence of global sea level rise or fall.
  • Its waters are mostly isolated from the surrounding ocean and receive little fresh water from rainfall, making it a rare spot to study the chemistry of oxygen-deprived marine ecosystems.
  • What distinguishes them from other aquatic caverns is that they are isolated from the ocean and don’t receive fresh rainwater.
  • They are generally circular, steep-walled and open to surface.

Significance of YBH

  • YBH has a depth of 300 metres, far deeper than the previously recorded deepest blue hole, Dean’s Blue Hole in Bahamas, which had a depth of 202 metres.
  • However, like most blue holes, it is anoxic i.e. depleted of dissolved oxygen below a certain depth. This anaerobic environment is unfavorable for most sea life.
  • Such anoxic ecosystems are considered a critical environmental and ecological issue as they have led to several mass extinctions.
  • Concentrations of carbon, usually found in deep marine holes like YBH, provide a natural laboratory to study carbon cycling and potential mechanisms controlling it in the marine ecosystem.
  • The transition from aerobic to anaerobic environment adversely affects the biogeo-chemistry of the ocean.

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Global Geological And Climatic Events

Why do we have Leap Years?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Leap Year and the science behind it

Mains level: Not Much

 

The year 2020 is a ‘leap year’, meaning the month of February will have 29 days instead of 28, and the total number of days will be 366 instead of 365. This was also the case in 2016, and 2024 will again be a leap year.

Leap Years

  • A calendar is meant to correspond to the Earth’s seasons.
  • For this, the number of days in a calendar needs to match the time required by the Earth to orbit the Sun.
  • The time required by the Earth to complete its orbit around the Sun is approximately 365.242 days. But years are usually only 365 days.
  • To adjust for the extra 0.242 days in the orbital period, which becomes almost one full day in four years, the calendar adds an extra day once every four years.
  • This approximates the time to 365.25 days, which is close to the actual 365.242 days.

But is that not inaccurate?

  • Yes, it is. And further adjustments are made to the Gregorian calendar, the calendar we follow today.
  • The Gregorian calendar was introduced in 1582. Before that, the calendar followed was the Julian calendar, introduced in 45 BC.
  • The calendars were different in their treatment of leap years.
  • The Julian calendar had leap days every four years, but since it still did not accurately conform to the Earth’s precise orbit time, it kept falling behind with respect to natural seasons over the centuries.
  • By the 16th century, the Julian calendar had fallen out of tune with the natural seasons by almost 10 days.
  • To correct this discrepancy, Pope Gregory XIII in 1582 decreed that the day of October 4 that year would be followed directly by October 15 – thus covering up the error.
  • The Pope also modified the leap year system in the Julian calendar. That new system came to be known as the Gregorian calendar.

What is the new system?

  • In the Gregorian calendar, a century year (a year ending with 00) is not a leap year, even though it is a multiple of 4. Thus, the year 2100 will not be a leap year.
  • But even this does not provide total accuracy. To ensure that, some century years remain leap years. In the Gregorian calendar, leap years include those century years which are exactly divisible by 400.
  • Thus, 2000 remained a leap year even though it ended with 00.
  • The Gregorian calendar reduces the margin of error under the Julian calendar, thus keeping days more in tune with seasons.

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Global Geological And Climatic Events

Eruption of Taal Volcano

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Taal Volcano

Mains level: Volcanism and its impact

 

In the Philippines, a volcano called Taal on the island of Luzon; 50 km from Manila has recently erupted.

Taal Volcano

  • Taal is classified as a “complex” volcano. Taal has 47 craters and four maars (a broad shallow crater).
  • It is situated at the boundaries of two tectonic plates — the Philippines Sea Plate and the Eurasian plate — it is particularly susceptible to earthquakes and volcanism.
  • A complex volcano, also called a compound volcano, is defined as one that consists of a complex of two or more vents, or a volcano that has an associated volcanic dome, either in its crater or on its flanks.
  • Examples include Vesuvius, besides Taal.
  • The Taal volcano does not rise from the ground as a distinct, singular dome but consists of multiple stratovolcanoes (volcanoes susceptible to explosive eruptions), conical hills and craters of all shapes and sizes.

Threats posed

  • Taal’s closeness to Manila puts lives at stake. Manila is a few tens of kilometres away with a population of over 10 million.
  • The volcano is currently at alert level 4, which means that a “hazardous eruption” could be imminent within a few hours to a few days.
  • Hazardous eruptions are characterised by intense unrest, continuing seismic swarms and low-frequency earthquakes.

Earlier records of eruption

  • Taal has erupted more than 30 times in the last few centuries. Its last eruption was on October 3, 1977.
  • An eruption in 1965 was considered particularly catastrophic, marked by the falling of rock fragments and ashfall.
  • Before that, there was a “very violent” eruption in 1911 from the main crater. The 1911 eruption lasted for three days, while one in 1754 lasted for seven months.
  • Because it is a complex volcano with various features, the kinds of eruption too have been varied. An eruption can send lava flowing through the ground, or cause a threat through ash in the air.

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Global Geological And Climatic Events

Private: Iron-snow on Earth’s innermost layer

  • The Earth’s deepest layer, the inner core, is capped by snow made of tiny particles of iron, which are much heavier than the snowflakes seen in the atmosphere.
  • According to the study the iron-snow falls from the molten outer core and piles up on top of the inner core, creating stacks up to 200 miles thick which cover the innermost layer of the planet.
  • Based on these findings, the study proposed the iron snow-capped core as an explanation for these aberrations.
  • With new data from experiments on core-like materials, the scientists found that crystallisation was possible and that about 15 per cent of the lowermost outer core could be made of iron-based crystals.
  • Researchers said these could eventually fall down the liquid outer core and settle on top of the solid inner core.
  • The slurry-like composition of the snow pack slows the seismic waves in such a way that the variation in snow pile size — thinner in the eastern hemisphere and thicker in the western — affected the speed of the waves.

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