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GS Paper: Salient Features Of World’S Physical Geography

  • A Good Monsoon

    Why in the News?

    This May has been unusually wet, with India getting 68.4% more rain than normal. Also, there have been no extreme temperatures or major heatwaves across most parts of the country.

    What caused the wet and cool May in India?

    • Above-Normal Rainfall: India received 68.4% more rainfall than usual for May, making it one of the wettest months in recent times. Eg: 27 out of 36 meteorological subdivisions saw over 20% surplus rain.
    • Frequent Moisture-Laden Winds: Western disturbances from the Mediterranean and incursions from the Bay of Bengal and Arabian Sea brought continuous showers. Eg: These weather systems caused intermittent thunderstorms across northern and eastern India.
    • Suppression of Heatwaves: Each thunderstorm cooled temperatures, preventing the buildup of heatwaves. Eg: No major heatwave was reported across central and north India during May.

    Why is the formation of heat lows over northwest India important for the monsoon?

    • Creates Suction for Moist Winds: Heat lows act like a vacuum, pulling moisture-laden southwesterly winds from the Indian Ocean into the Indian subcontinent. Eg: Strong heat lows over Rajasthan help trigger early monsoon onset over central India.
    • Drives Monsoon Circulation: These low-pressure areas initiate and sustain the monsoon trough, which is essential for widespread rainfall. Eg: Absence of heat lows can delay or weaken the monsoon across northwest and central India.
    • Influences Rainfall Intensity and Spread: Proper heat low development ensures uniform and timely rainfall, crucial for agriculture. Eg: Weak heat lows in 2015 contributed to a patchy and deficient monsoon season.

    How do El Niño and IOD affect the monsoon?

    • El Niño Weakens Monsoon Winds: El Niño leads to warmer Pacific Ocean waters, which suppresses the Indian monsoon by weakening the low-pressure system over the subcontinent. Eg: The 2015 El Niño caused a 14% rainfall deficit in India.
    • Positive IOD Strengthens Monsoon: A positive Indian Ocean Dipole (IOD) brings warmer waters near Africa and cooler waters near Indonesia, enhancing monsoon winds and rainfall over India. Eg: In 2019, a strong positive IOD offset El Niño’s impact, resulting in above-normal rainfall.

    What would be the impact of monsoon on food inflation? 

    • Good Monsoon Boosts Crop Yields: Adequate rainfall ensures timely sowing and healthy harvests, leading to better food availability and stable prices. Eg: A normal monsoon in 2022 helped moderate cereal price rise.
    • Reduces Dependency on Imports: Sufficient domestic production of staples like wheat and pulses lowers the need for costly imports, helping control food inflation. Eg: In 2024, surplus wheat stock due to good rainfall reduced price pressure.
    • Stabilises Rural Demand and Supply Chains: A healthy monsoon supports rural incomes, improving supply consistency and reducing volatility in food prices. Eg: Strong kharif output in 2021 led to a drop in vegetable prices.

    Way forward: 

    • Strengthen Climate-Responsive Agriculture: Promote drought- and flood-resistant crop varieties and expand irrigation to reduce dependence on erratic monsoons.
    • Enhance Weather Forecasting and Storage Infrastructure: Improve real-time weather alerts and expand warehousing to minimize post-harvest losses and stabilize food prices.

    Mains PYQ:

    [UPSC 2024] What are the causes of persistent high food inflation in India? Comment on the effectiveness of the monetary policy of the RBI to control this type of inflation.

    Linkage: Understanding the dynamics of food inflation, as required by this question, is essential for appreciating the significant positive economic contribution that a favorable monsoon can make by potentially increasing agricultural output and stabilizing food prices.

  • Davis Strait Proto-Microcontinent

    Why in the News?

    A hidden landmass, called the Davis Strait proto-microcontinent, has been discovered beneath the icy waters between Canada’s Baffin Island and Greenland.

    About the Davis Strait Proto-Microcontinent:

    • The Davis Strait Proto-Microcontinent is a hypothesised landmass located in the Davis Strait, believed to have existed during the Paleozoic era.
    • It is composed of 19–24 km thick thinned continental crust, surrounded by two narrow bands of 15–17 km thick continental crust.
    • It is thought to have broken apart due to tectonic movements.
    • Geological evidence, including similarities in rock formations and tectonic features found in Greenland and parts of the Canadian Arctic, supports the idea of this ancient landmass.
    • While its exact nature and extent remain debated, the proto-microcontinent is crucial for understanding the tectonic processes that shaped the Atlantic Ocean and surrounding regions.

    About Davis Strait:

    • The Davis Strait is a large body of water located between southeastern Baffin Island (Canada) and southwestern Greenland, serving as part of the Northwest Passage.
    • It separates the Baffin Bay (to the north) from the Labrador Sea (to the south), and it connects the Atlantic Ocean and Arctic Ocean through the Canadian Arctic Archipelago.
    • It is an important maritime route for shipping and trade.
    • Named after John Davis, the English explorer who navigated the area in the late 16th century, the Davis Strait plays a significant role in the tectonic evolution of the Arctic region.
    [UPSC 2013] Consider the following:

    (1). Electromagnetic radiation (2). Geothermal energy (3). Gravitational force (4). Plate movements (5). Rotation of the earth (6). Revolution of the earth

    Which of the above are responsible for bringing dynamic changes on the surface of the earth?

    Options: (a) 1 only (b) 2 and 3 only (c) 1, 2 and 3 (d) None*

     

  • Delamination of the Indian Plate

    Why in the News?

    Recent studies reveal that the Indian Plate is splitting into two, with the lower part detaching and sinking into the Earth’s mantle, a process called delamination, as published by the American Geophysical Union.

    About Delamination:

    • Delamination in tectonic plates refers to the process where the lower part of a continental plate, including the lower crust and/or lithospheric mantle, splits and sinks into the Asthenosphere.
    • This process is driven by density differences and can lead to rapid uplift, changes in stress regimes, and altered magmatism.
    • It can occur in various tectonic settings, including compressional zones, subduction zones, and intraplate regions. 
    • The denser lower part of the plate, including the lower crust and/or lithospheric mantle, is less buoyant than the less dense asthenosphere, leading to sinking.
    • High temperatures can also weaken the lithosphere and facilitate delamination.

    Delamination of the Indian Plate

    Indian Plate and Its Splitting:

    • The Indian Plate has been colliding with the Eurasian Plate for about 60 million years, causing the formation of the Himalayas and influencing regional seismic activity.
    • It is shifting northward at a rate of approximately 5 cm per year..
    • The lower, denser part of the Indian Plate is detaching and sinking into the Earth’s mantle.
    • This may lead to increased seismic activity due to shifts in tectonic stress.
    • In regions like the Himalayan collision zone, delamination results in fractures that increase stress in the Earth’s crust, raising the likelihood of seismic events.
    [UPSC 2004] Consider the following geological phenomena:

    1. Development of a fault 2. Movement along a fault 3. Impact produced by a volcanic eruption 4. Folding of rocks Which of the above cause earthquakes?

    Options:

    (a) 1, 2 and 3 (b) 2 and 4 (c) 1, 3 and 4 (d) 1, 2, 3 and 4

     

  • What is Atmospheric River?

    Why in the News?

    Earlier this month, severe weather in the United States, including heavy rainfall, strong winds, and thunderstorms, was caused by an Atmospheric River.

    What is an Atmospheric River?

    • An atmospheric river is a narrow, fast-moving band of moisture and wind that transports large amounts of water vapor across vast distances.
    • They form when large-scale weather patterns align, creating channels of moisture transport from tropical oceans, guided by low-level jet streams toward the coast.
    • They typically span 402-606 km in width and can extend over 1600 km in length.
    • The most powerful atmospheric rivers transport moisture equivalent to the Mississippi River’s flow.
    • Example: The Pineapple Express, a well-known atmospheric river, transports moisture from Hawaii to the West Coasts of the U.S. and Canada.
    • The intense rainfall from atmospheric rivers leads to flooding, mudslides, and infrastructure damage, with wind speeds comparable to hurricanes.

    Impact and Climate Change:

    • Rising global temperatures cause more water to evaporate, and warmer air can hold more moisture.
    • For every 1°C increase, the atmosphere can hold 7% more moisture, leading to stronger storms.
    • Research indicates such events will likely grow longer and more intense.
    [UPSC 2023] With reference to the Earth’s atmosphere, which one of the following statements is correct?

    (a) The total amount of insolation received at the equator is roughly about 10 times of that received at the poles.

    (b) Infrared waves are largely absorbed by carbon dioxide that is concentrated in the upper atmosphere.

    (c) Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.  

    (d) Ultraviolet rays are absorbed by the ozone layer lying in the ionosphere.

     

  • What are Mesoscale Convective System (MCS)?

    Why in the News?

    A recent study in Nature Geoscience suggests that soil moisture levels could help predict severe thunderstorms, like mesoscale convective systems (MCSs), especially in regions like India.

    About Mesoscale Convective Systems (MCS):

    • MCSs are larger than individual thunderstorms but smaller than larger weather systems like cyclones.
    • They typically cover areas between 100 to 1,000 km in diameter.
    • They form when warm, moist air rises, creating storms that feed off each other, growing in size and intensity as they move across the region.
    • They can cause flash floods, damaging winds, and severe thunderstorms, and are often responsible for large-scale weather events.
    • In tropical regions, MCSs account for 50 to 90 % of total rainfall, making them a major cause of severe weather-related damage.
    • A notable example is the March 2024 thunderstorm in West Bengal, which caused significant property damage and loss of life.

    Soil Moisture’s Role in MCS as per the Study:

    • Shifts in soil moisture can be detected two to five days before the formation of storms, providing critical lead time for early warnings in vulnerable regions.
    • Contrasting soil moisture levels over large areas (hundreds of kilometers) lead to changes in atmospheric conditions, including A notable example is the March 2024 thunderstorm in West Bengal, which caused significant property damage and loss of life.
    • Larger contrasts in moisture content between dry and wet regions cause greater temperature differences, which in turn lead to changes in wind direction and speed.
    • These variations contribute to turbulence, making storms more intense and spreading rainfall over a wider area.
    [UPSC 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

     

  • Hadean Protocrust

    Why in the News?

    A study from Macquarie University, Australia, suggests that plate tectonics may have started earlier than previously thought, with signs of it possibly existing in the Hadean protocrust even before the plates began to move.

    What is Hadean Protocrust?

    • The Hadean protocrust is the Earth’s first crust, formed within the first 200 million years of the planet’s creation.
    • During this time, the surface was mostly molten and constantly hit by space rocks, making it very hot and unstable.
    • Over time, parts of the molten surface began to cool and solidify, creating the first crust.

    Hadean Protocrust

    Back2Basics: Hadean Aeon

    • The Hadean Aeon is the earliest geological eon in Earth’s history, lasting from about 4.6 billion to 4 billion years ago.
    • The surface was incredibly hot and volcanic activity was widespread, often described as “hellish.”
    • It was followed by the Archean Eon (about 4 billion to 2.5 billion years ago), characterized by the formation of Earth’s first stable crust, the beginning of plate tectonics, and the earliest known forms of life.
    • As the surface cooled, the thick parts of the crust formed the first continents, which moved on the hot, semi-fluid layer beneath them called the asthenosphere.

    Key Findings of the Recent Study:

    • The researchers found that the chemical signatures linked to plate tectonics might have appeared earlier, even when the Earth’s crust was still forming in the Hadean protocrust.
    • This discovery suggests that early movements of the Earth’s crust, similar to plate tectonics, could have happened before plates began to move as we know them today.
    • The study used models and experiments to support these ideas, but further research is needed to confirm these findings.
    [UPSC 2013] Which of the following are responsible for bringing dynamic changes on the surface of the earth?

    1. Electromagnetic radiation 2. Geothermal energy 3. Gravitational force 4. Plate movements 5. Rotation of the earth 6. Revolution of the earth

    Which of the above are responsible for bringing dynamic changes on the surface of the earth?

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

     

  • Spring Equinox, 2025

    Why in the News?

    March 20 marks the arrival of the vernal equinox in the Northern Hemisphere, signaling the beginning of the spring season.

    What are Equinoxes?

    • An equinox occurs when the Earth’s axis is not tilted toward or away from the Sun, resulting in equal length of day and night across the planet.
    • Equinoxes occur twice a year:
      • Vernal Equinox: Around March 20-21, marking the beginning of spring in the Northern Hemisphere and fall in the Southern Hemisphere.
      • Autumnal Equinox: Around September 22-23, marking the beginning of fall in the Northern Hemisphere and spring in the Southern Hemisphere.
    • On an equinox, the Sun is directly above the Equator, leading to almost equal distribution of sunlight between the Northern and Southern Hemispheres.
    • The equal length of day and night is observed, with each lasting approximately 12 hours.

    What are Solstices?

    • A solstice occurs when the Earth’s tilt is most extreme either towards or away from the Sun. This results in the longest or shortest day of the year in each hemisphere.
    • Solstices occur twice a year:
      • Summer Solstice (Northern Hemisphere): Around June 20-22, marking the longest day and shortest night of the year, as the Northern Hemisphere is tilted toward the Sun.
      • Winter Solstice (Northern Hemisphere): Around December 20-23, marking the shortest day and longest night of the year, as the Northern Hemisphere is tilted away from the Sun.
    • Solstices create unequal distribution of sunlight, with one hemisphere receiving significantly more or less sunlight than the other.

    Cultural Significance of the Equinox:

    • Nowruz, celebrated on the vernal equinox, marks the beginning of the Persian New Year.
      • The festival has been celebrated for over 3,000 years by the Zoroastrian community, including the Parsi community in India.
    • Vernal Equinox Day is a national holiday in Japan, celebrating the arrival of spring.
    • Easter, one of the most significant days in Christianity, is determined based on the first Sunday after the first full moon following the vernal equinox.
    • Passover, the Jewish festival, begins on the first full moon after the vernal equinox.

     

    PYQ:

    [UPSC 2019] 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 Wallace Line?

    Why in the News?

    In the 19th century, English naturalist Alfred Russel Wallace observed a sharp shift in biodiversity as he moved from Asia to Australia, leading him to propose the Wallace Line—an imaginary boundary separating species from both regions.

    wallace line

    About the Wallace Line:

    • It is a bio-geographical boundary separating Asia and Australia’s eco-zones.
    • It was identified by Alfred Russel Wallace in 1863 during his explorations.
    • It is an imaginary line running through the Lombok Strait (between Bali and Lombok) and the Makassar Strait (between Borneo and Sulawesi).
    • Distinct evolutionary histories:
      • West of the line (Asia): Tigers, elephants, and orangutans.
      • East of the line (Australia): Kangaroos, marsupials, and cockatoos.
    • A very few species cross the line, particularly birds and mammals.
    • This is a barrier for land species but not marine life.
    • Its formation:
      • Continental drift: Australia separated from Antarctica and moved toward Asia (~35 million years ago). This created a deep-water channel, preventing species migration.
      • Pleistocene Epoch Influence: Lower sea levels exposed land bridges but deep waters maintained the boundary.

    Scientific Relevance:

    • Wallace Line is more of a gradient than a strict boundary.
    • Understanding biogeography helps predict species adaptation to climate change.

    Note: 

    Weber Line more accurately defines the balance point where the influence of Asian and Australian species is nearly equal, whereas the Wallace Line marks a sharper divide.

     

  • Delhi Earthquake

    Why in the News?

    A magnitude 4 earthquake struck New Delhi with epicentre near Dhaula Kuan. The quake was shallow (5 km depth), highlighting Delhi’s seismic vulnerability due to its location in Zone IV of India’s earthquake hazard map.

    Possible Causes of the Earthquake

    • Tectonic Activity along the Delhi-Hardwar Ridge:
      • Delhi sits on the Delhi-Hardwar Ridge, an active seismic fault.
      • Continuous collision of the Indian and Eurasian plates builds tectonic stress, leading to earthquakes when stress is released.
    • Groundwater Extraction as a Seismic Trigger: Excessive exploitation alters rock pressure, potentially inducing fault movements.
    • Anthropogenic (Human-Induced) Activity:
      • Urbanization, metro construction, and large-scale infrastructure projects alter subsurface stress.
      • Vibrations from construction activities can contribute to localized seismic instability.

    About the Aravalli-Delhi Fold Belt

    • The Aravalli-Delhi Fold Belt is a major geological formation that extends from southern Rajasthan to Haryana and Delhi.
      • It consists of ancient folded rock formations that have undergone millions of years of geological transformation.
    • This region has several pre-existing faults, meaning seismic activity can occur without direct tectonic subduction.
    • Although historically more active, tectonic movements in the belt have slowed over time.
    • These earthquakes occur due to fault reactivation and local stress accumulation rather than large-scale tectonic shifts.
      • Himalayan earthquakes are caused by subduction, where the Indian plate moves under the Eurasian plate.

    PYQ:

    [2021] Discuss about the vulnerability of India to earthquake related hazards. Give examples including the salient features of major disasters caused by earthquakes in different parts of India during the last three decades.

    [2015] The frequency of earthquakes appears to have increased in the Indian subcontinent. However, India’s preparedness for mitigating their impact has significant gaps. Discuss various aspects.

     

  • “One Nation, One Time” in the country

    Why in the News?

    To ensure uniform timekeeping, the government has proposed new rules requiring Indian Standard Time (IST) to be used exclusively for all official and business purposes. The Consumer Affairs Ministry is inviting public feedback on these rules.

    What are the  Draft Legal Metrology (Indian Standard Time) Rules of 2025?

    • Mandatory Use of IST: The rules establish IST as the sole time reference for legal, administrative, commercial, and official documents across various sectors including commerce, transport, public administration, legal contracts, and financial operations.
    • Prohibition on Alternative Time References: The draft prohibits any time references other than IST for official and commercial purposes. Exceptions are allowed for specialised fields like astronomy and navigation but require prior government approval.
    • Display and Synchronization Requirements: Government offices and public institutions must prominently display IST. Additionally, time-synchronization systems will be necessary to ensure accuracy, reliability, and cybersecurity.
    • Collaboration with Scientific Institutions: The Department of Consumer Affairs is working with the National Physical Laboratory (NPL) and the Indian Space Research Organisation (ISRO) to develop a robust mechanism for time generation and dissemination.
    • Penalties and Compliance Monitoring: Violations of these rules will incur penalties. Regular audits will be conducted to ensure compliance across sectors.

    How the New Draft Rules are significant?

    • Standardisation Across Sectors: The rules mandate the exclusive use of Indian Standard Time (IST) as the sole time reference for all official and commercial activities, including commerce, transport, public administration, and legal contracts. This uniformity is essential for ensuring consistency in operations across diverse sectors.
    • Enhancement of Critical Infrastructure: The initiative aims to improve precision in critical national infrastructure such as telecommunications, banking, defence, and emerging technologies like 5G and artificial intelligence.
    • Support for Technological Advancements: The rules will facilitate the integration of advanced technologies by ensuring that all systems operate on a synchronized time basis. This is particularly important for digital governance, navigation systems, and real-time applications that rely on precise timing.
    • National Security Implications: By synchronizing critical infrastructure, the rules contribute to national security. It will enhance time accuracy and support operations in defense and emergency response scenarios, where timely coordination is crucial.
    • Regulatory Framework and Compliance: The draft establishes a robust regulatory framework, including provisions for penalties and periodic audits to ensure compliance. This will help maintain high standards of timekeeping across all sectors and promote accountability among entities using IST.

    What challenges exist in transitioning to a unified time system?

    • Technological Integration: Upgrading existing systems to synchronise with IST will require significant technological investments and modifications, particularly in sectors like finance and stock exchanges that depend on precise time-stamping for transactions.
    • Coordination Across Sectors: Ensuring compliance across diverse industries such as commerce, transport, and public administration will be complex and resource-intensive, requiring adjustments in scheduling and communication systems, especially for public transportation networks like railways and airlines.
    • Public and Business Awareness: Raising awareness and educating businesses and the public about the new rules is essential for smooth implementation, as smaller enterprises may need additional support to align their operations with IST requirements.

    How will compliance be monitored? (Way forward) 

    • Periodic Audits: Regular inspections will be conducted to ensure compliance with IST regulations across various sectors with government auditors verifying proper implementation in public institutions and commercial enterprises.
    • Penalties for Violations: Non-compliance will result in penalties acting as a deterrent with entities found using alternative time references in official documents facing fines or legal consequences.
    • Collaborative Efforts and Public Feedback: Partnerships with institutions like the National Physical Laboratory and ISRO will support a reliable time dissemination system while stakeholder feedback will help refine the rules and address practical challenges.

    Mains PYQ:

    Q What do you understand by “Standard Positioning System” and “Precision positioning system” in the GPS era? Discuss the advantage India perceives from its ambitious IRNSS programme employing just seven satellites. (UPSC IAS/2015)