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GS Paper: GS1-15.Geographical features and their location- Changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.

  • Places in news: Sulina Channel

    sulina

    Central Idea

    • As Russia threatens ships in the Black Sea, a Romanian route ‘Sulina Channel’ provides a lifeline for Ukraine’s grain exports.

    Sulina Channel

    • The Sulina Channel is located in the southeastern part of Romania, specifically within the Danube Delta region.
    • It connects the Danube River, one of Europe’s major rivers, with the Black Sea, providing a direct route for maritime transportation.
    • The channel is approximately 64 km long, making it a significant watercourse for shipping and navigation.
    • It is a vital trade route for cargo vessels, commercial ships, and other maritime traffic entering or leaving the Black Sea region.
    • The construction of the Sulina Channel dates back to the 19th century when it was developed to improve the navigation of large ships and vessels in and out of the Danube Delta.

    Significance for Ukraine

    • The Sulina Channel, the only deep and wide channel among the Danube’s branches, serves as a crucial “riverine expressway” for transporting goods from inland Ukrainian ports to the Black Sea.
    • Ukrainian grain ships sail from ports like Izmail and Reni on the Chilia Channel to Sulina, where the cargo is transferred to larger vessels.
    • These vessels proceed to Constanta, Romania’s major seaport, for further transport into the Mediterranean.
    • This route falls under NATO’s surveillance and protection, ensuring a degree of security against Russian aggression.

  • Places in news: Kuril Islands

    kuril

    Central Idea

    • Russia’s invasion of Ukraine is ongoing, leading to challenges in resource allocation along its western border.
    • Japan sees a chance to reclaim the Kuril Islands, also known as the Northern Territories in Japan, which were seized by Soviet forces during WWII.

    About Kuril Islands

    • The Kuril Islands, also known as the Kurile Islands, are a volcanic archipelago situated in the northern Pacific Ocean.
    • They stretch from the northeastern tip of Hokkaido, Japan, to the southernmost tip of Russia’s Kamchatka Peninsula.
    • It consist of 56 islands, with Iturup, Kunashir, Shikotan, and Habomai being the most significant.
    • The Kuril Islands are part of the Pacific Ring of Fire, an area with intense volcanic and seismic activity, due to the movement of tectonic plates.
    • The islands are home to several active volcanoes, with some of the notable ones being Alaid, Ebeko, and Chikurachki.

    What is the dispute?

    • The islands have been a subject of territorial dispute between Russia and Japan since the end of World War II.
    • After the war, the Soviet Union took control of the Kuril Islands, leading to the displacement of around 17,000 Japanese residents who were living there.
    • Japan claims the southernmost islands (Iturup, Kunashir, Shikotan, and Habomai) and refers to them as the “Northern Territories.”
    • Russia maintains sovereignty over the islands and considers them an integral part of its territory.
    • The territorial dispute has hindered the signing of a formal peace treaty between Russia and Japan to officially end World War II hostilities.

  • World past Holocene Epoch: Anthropocene began in 1950

    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.

  • Evidence of High Rainfall during Deccan Traps Volcanism

    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.

     

  • Gravity Hole in the Indian Ocean

    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.

  • Places in news: Ubinas Volcano

    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.

     

  • Indian Ocean Dipole : What is it, how it can limit El Nino effects?

    Central Idea

    • With the El Nino phenomenon set to affect the Indian monsoon this year, there is growing optimism surrounding the development of a positive Indian Ocean Dipole (IOD) and its ability to mitigate the effects of El Nino. The IOD, a weaker ocean-atmosphere interaction in the Indian Ocean, has demonstrated limited impacts in the past but holds potential in offsetting the adverse effects of El Nino, particularly in neighbouring regions.

    *Relevance of the topic*

    *Questions on Indian ocean dipole and El nino and its impact on Indian monsoon have been asked multiple times in previous years.

    *Relate this topic with Indian monsoon, and its impact on Indian agriculture as, Rainfed agriculture occupies about 51 percent of country’s net sown area and accounts for nearly 40 percent of the total food production.

    The current status of the Indian Ocean Dipole (IOD) and El Nino

    • IOD:
    • The IOD is currently in a neutral phase. This means that there is no significant temperature difference between the western and eastern sides of the Indian Ocean along the equator.
    • However, international climate models suggest the possibility of a positive IOD event developing in the coming months.
    • The India Meteorological Department (IMD) has also reported an 80% chance of a positive IOD during the June-August 2023 season. The development of a positive IOD would have implications for weather patterns in the Indian Ocean region.
    • El Nino:
    • El Nino has already established itself in the Pacific Ocean this year. El Nino occurs when the prevailing wind systems weaken, resulting in reduced displacement of warm waters in the eastern side of the Pacific.
    • This abnormal warming of the eastern Pacific can have impacts on global weather patterns, including the Indian monsoon. The presence of El Nino raises concerns about its potential impact on the Indian monsoon rainfall.

    Understanding El Nino and IOD

    Phenomenon El Nino Indian Ocean Dipole (IOD)
    Definition Warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean Ocean-atmosphere interaction in the Indian Ocean
    Cause Weakening or reversal of trade winds Temperature difference between the western and eastern parts of the Indian Ocean along the equator
    Impact on Weather Disrupts atmospheric circulation patterns globally, leading to droughts, floods, and changes in temperature and precipitation patterns Influences regional weather patterns in the Indian Ocean basin and its surrounding landmasses
    Indian Monsoon Suppresses rainfall, leading to drought conditions in some regions Positive IOD enhances rainfall along the African coastline and over the Indian subcontinent; negative IOD suppresses rainfall in affected regions
    Opposite Phase La Nina (cooling of sea surface temperatures in the central and eastern equatorial Pacific) Opposite effects based on the temperature gradient between the western and eastern parts of the Indian Ocean
    Relative Impact Significantly affects global weather patterns Weaker impacts compared to El Nino and La Nina, but still influences local weather patterns

    The interplay between the El Nino Southern Oscillation (ENSO) and IOD

    • Triggering Mechanism: ENSO events, specifically El Nino, can trigger the development of a positive IOD in the Indian Ocean.
    • External Drivers: While external factors such as ENSO can initiate IOD events in some cases, there is evidence to suggest that IOD events can also occur due to local circulations or subsurface processes within the equatorial Indian Ocean.
    • Internal Dynamics: IOD events largely develop and mature through internal dynamics, even when triggered by external drivers. They have the potential to exhibit independent existence and can impact weather patterns in the Indian Ocean region.
    • Impact on IOD: During El Nino, the Pacific side of Indonesia tends to be cooler than normal, which influences the Indian Ocean side, leading to the development of a positive IOD.
    • Mutual Interaction: The circulation patterns of IOD and ENSO can impact each other when both events are strong. The interaction between the two phenomena can influence the intensity and duration of each event.
    • Contrasting Associations: Positive IOD events are often associated with El Nino, while negative IOD events are sometimes linked to La Nina. However, this association is not absolute, and IOD events can occur independently or have different associations depending on the specific conditions.
    • Combined Impacts: Strong IOD and ENSO events can have combined effects on weather patterns, as their circulation patterns can interact and influence each other.

    The impacts of Indian Ocean Dipole

    • Rainfall Distribution: IOD significantly influences rainfall patterns in the Indian Ocean region. During a positive IOD, there is increased convection and rainfall along the African coastline and over the Indian subcontinent. Conversely, a negative IOD leads to suppressed rainfall in these regions.
    • Drought and Floods: Positive IOD events can bring above-average rainfall to the affected regions, which can alleviate drought conditions and replenish water resources. However, this increased rainfall can also result in flooding and water-related disasters in certain areas.
    • Agricultural Productivity: IOD has implications for agriculture as it affects the availability and distribution of rainfall. Positive IOD events can enhance agricultural productivity in the affected regions, while negative IOD events may lead to reduced crop yields and agricultural challenges.
    • Fisheries: IOD impacts the productivity of marine ecosystems. During positive IOD, increased upwelling of nutrient-rich waters occurs, which promotes higher fish stocks and benefits fisheries. In contrast, negative IOD can disrupt the marine food chain and impact fish populations.
    • Coral Bleaching: IOD influences sea surface temperatures, and prolonged positive IOD events can contribute to increased sea surface temperatures in the affected regions. This can lead to coral bleaching, negatively impacting coral reefs and marine biodiversity.
    • Indian Monsoon: IOD can influence the strength and distribution of the Indian monsoon rainfall. Positive IOD events are generally associated with enhanced monsoon rainfall over the Indian subcontinent, while negative IOD events can lead to reduced monsoon rainfall.
    • Weather Extremes: IOD can contribute to the occurrence of extreme weather events such as heatwaves, storms, and tropical cyclones in the Indian Ocean region.
    • Economic and Social Impacts: The impacts of IOD on rainfall, agriculture, fisheries, and other sectors have direct economic and social implications. These impacts can affect livelihoods, water availability, food security, and overall economic development in the affected regions.

    Impacts of El Nino on the Indian monsoon

    • Weakened Monsoon Winds: During El Nino, the trade winds that blow from the east across the Indian Ocean weaken. These winds are responsible for carrying moisture-laden air towards the Indian subcontinent, facilitating the monsoon rainfall. With weakened winds, the supply of moisture is reduced, leading to a decrease in rainfall.
    • Delayed Onset: El Nino can cause a delayed onset of the Indian monsoon. The normal onset of monsoon rainfall in India is around June, but during El Nino years, the monsoon arrival may be delayed, resulting in a late start to the rainy season.
    • Deficient Rainfall: El Nino events often lead to below-average rainfall during the monsoon season in India. The reduced moisture transport and altered atmospheric circulation associated with El Nino result in deficient rainfall across various parts of the country.
    • Regional Variations: The impact of El Nino on the Indian monsoon is not uniform throughout the country. Certain regions, particularly central and northern India, are more prone to experiencing below-average rainfall during El Nino years. However, some areas in southern India may receive near-normal or even above-normal rainfall during these periods.
    • Drought Conditions: El Nino-induced deficient rainfall can result in drought conditions in affected regions. This can have adverse effects on agriculture, water availability, and livelihoods, leading to crop failures, reduced agricultural productivity, and water scarcity.
    • Temperature Extremes: El Nino can contribute to increased temperatures during the monsoon season in some parts of India. The reduced cloud cover and rainfall can lead to heatwaves and higher temperatures, posing health risks and impacting human well-being.

    Conclusion

    • While the IOD’s ability to counterbalance the effects of El Nino is limited, there is hope that a positive IOD event may develop in the coming months. Past instances, such as the strong IOD event in 2019, have demonstrated the potential of IOD in compensating for monsoon rainfall deficits. As researchers continue to study the interplay between ENSO and IOD, the development of a positive IOD this year would be welcomed, offering some respite from the anticipated impacts of El Nino on the Indian monsoon.

    Also read:

    What is El Nino and How it impacts the Monsoon?

     

  • Understanding Summer Solstice: Longest Day of the Year

    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

     

  • Places in news: Brahmani Natural Arch

    brahmani arch

    Central Idea

    • The Geological Survey of India (GSI) plans to declare the ‘Brahmani Natural Arch’ in Kanika range of Sundargarh forest division of Odisha as a Geo Heritage Site.
    • This natural arch is believed to date back to the Jurassic period and would be the largest natural arch in India with the Geo Heritage tag.

    Brahmani Natural Arch

    • The oval-shaped arch has a base length of 30 meters and a height of 12 meters.
    • The alcove of the arch has a maximum height of 7 meters and a width of 15 meters.
    • India currently has two other natural arches, located at Tirumala hills in Tirupati and Andaman and Nicobar, but both are smaller than the one in Sundargarh.

    Its formation

    • The natural arch is composed of ferruginous sandstone from the Upper Kamthi formation.
    • It dates back to the lower to middle Jurassic age, approximately 184 to 160 million years old.
    • Research on the geological significance of the site began in 2017 after its discovery during coal exploration in the district.

    Awareness and Preservation Efforts

    • The GSI state unit and Sundargarh forest division conducted an awareness drive in the district to promote the protection of the natural arch.
    • Steps are being taken to promote the proposed geo-heritage site as a cultural pride and potentially name it ‘Brahmani natural arch.’
    • The site could be promoted and preserved as an eco-tourism destination.

    Back2Basics:

    Geological Heritage Sites in India
    Andhra Pradesh Mangampeta Volcanogenic bedded Barytes (Cuddapah Dist.), Eparchaean Unconformity (Chittor Dist.), Natural Geological Arch in Tirumala Hills (Chittor Dist.), Erra Matti Dibbalu located between Vishakhapatnam and Bhimunipatnam.
    Maharashtra Lonar Lake (Buldana Dist.)
    Kerala Laterite near Angadipuram PWD rest house premises (Malapuram Dist.), Varkala Cliff Section (Thiruvanatapuram Dist.)
    Chattisgarh Lower Permian Marine bed at Manendragarh (Surguja Dist.)
    Tamil Nadu Fossil wood near Tiruvakkarai (South Arcot Dist.), National fossil wood park in Sattanur (Tiruchirapalli Dist.), Charnockite in St. Thomas Mount (Madras), Badlands of Karai Formation with Cretaceous fossils along Karai – Kulakkalnattam Section (Perambalur District)
    Karnataka Columnar Lava in St. Mary Island (Udupi Dist.), Pillow lavas near Mardihalli (Chitradurga Dist.), Peninsular Gneiss in Lalbagh (Bangalore), Pyroclastics & Pillow lavas in Kolar Gold fields (Kolar Dist.)
    Gujarat Sedimentary Structures – Eddy Markings in Kadan Dam (Panch Mahals Dist.)
    Himachal Pradesh Siwalik Fossil Park (Saketi, Sirmur dt.)
    Rajasthan Sendra Granite (Pali Dist.), Barr Conglomerate (Pali Dist.), Stromatolite Fossil Park near Jharmarkotra Rock Phosphate deposit (Udaipur Dist.), Gossan in Rajpura-Dariba Mineralised belt (Udaipur Dist.), Akal Fossil Wood Park (Jaisalmer Dist.)
    Odisha Pillow Lava in iron ore belt at Nomira (Keonjhar dist.)
    Jharkhand Plant Fossil bearing Inter-trappean beds of Rajmahal Formation around Mandro (Sahibganj dist.)
    Nagaland Nagahill Ophiolite Site near Pungro
    Sikkim Stromatolite bearing Dolomite/Limestone of Buxa Formation at Mamley, near Namchi (South district), Stromatolite bearing Dolomite / Limestone of Buxa Formation, Sikkim

     

     

    https://www.newindianexpress.com/cities/bhubaneswar/2023/jun/11/gsi-proposes-geo-heritage-tag-for-jurassic-age-natural-arch-in-odisha-2583901.html

  • Monsoon onset in Kerala on June 4

    monsoon

    Central Idea: The monsoon is likely to set in over Kerala with a “slight delay” on June 4, the India Meteorological Department (IMD) said. The usual onset date over Kerala is June 1, within a seven-day window.

    What does the “Onset of Monsoon” mean?

    • The onset of the monsoon over Kerala marks the beginning of the four-month, June to September southwest monsoon season over India.
    • It brings more than 70 per cent of the country’s annual rainfall.
    • It marks a significant transition in the large-scale atmospheric and ocean circulations in the Indo-Pacific region.
    • The IMD announces it only after certain newly defined and measurable parameters, adopted in 2016, are met.
    • The onset is a significant day in India’s economic calendar.

    How does IMD predict the monsoon?

    • Broadly, the IMD checks for the consistency of rainfall over a defined geography, its intensity, and wind speed:
    1. Rainfall: The IMD declares the onset of the monsoon if at least 60% of 14 designated meteorological stations in Kerala and Lakshadweep record at least 2.5 mm of rain for two consecutive days at any time after May 10.
    2. Wind field: The depth of westerlies should be upto 600 hectopascal (1 hPa is equal to 1 millibar of pressure) in the area bound by the equator to 10ºN latitude, and from longitude 55ºE to 80ºE. The zonal wind speed over the area bound by 5-10ºN latitude and 70-80ºE longitude should be of the order of 15-20 knots (28-37 kph) at 925 hPa.
    3. Heat: The INSAT-derived Outgoing Longwave Radiation (OLR) value (a measure of the energy emitted to space by the Earth’s surface, oceans, and atmosphere) should be below 200 watt per sq m (wm2) in the box confined by 5-10ºN latitude and 70-75ºE latitude.
    • The onset is not officially declared until the prescribed conditions (above) are met.

    Factors considered by IMD

    • The IMD uses a specialised model that forecasts the arrival dates within a four-day window.
    • It uses six predictors:
    1. Minimum temperatures over northwest India
    2. Pre-monsoon rainfall peak over south Peninsula
    3. Outgoing long-wave radiation (OLR) over the South China Sea
    4. Lower tropospheric zonal wind over the southeast Indian Ocean
    5. Upper tropospheric zonal wind over the east equatorial Indian Ocean, and
    6. OLR over the southwest Pacific region

    Back2Basics: Long Period Average (LPA)

    • The IMD predicts a “normal”, “below normal”, or “above normal” monsoon in relation to a benchmark “long period average” (LPA).
    • The LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30 years, 50 years, etc.
    • LPA refers to the average rainfall recorded from June to September for the entire country, the amount of rain that falls every year varies from region to region and from month to month.
    • The IMD’s prediction of a normal monsoon is based on the LPA of the 1971-2020 period, during which India received 87 cm of rain for the entire country on average.
    • It has in the past calculated the LPA at 88 cm for the 1961-2010 period, and at 89 cm for the period 1951-2000.

    Why LPA is needed?

    • The IMD records rainfall data at more than 2,400 locations and 3,500 rain-gauge stations.
    • Because annual rainfall can vary greatly not just from region to region and from month to month, but also from year to year within a particular region or month.
    • An LPA is needed to smooth out trends so that a reasonably accurate prediction can be made.
    • A 50-year LPA covers for large variations in either direction caused by freak years of unusually high or low rainfall, as well as for the periodic drought years.
    • It also takes into account the increasingly common extreme weather events caused by climate change.

    Range of normal rainfall

    The IMD maintains five rainfall distribution categories on an all-India scale. These are:

    1. Normal or near normal, when the percentage departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA;
    2. Below normal, when departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA;
    3. Above normal, when actual rainfall is 104-110% of LPA;
    4. Deficient, when departure of actual rainfall is less than 90% of LPA; and
    5. Excess, when the departure of actual rainfall is more than 110% of LPA.

     

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