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Subject: Geography

  • Cuvette Centrale: World’s Largest Tropical Peatland Complex

    Why in the News?

    The Democratic Republic of the Congo (DRC) has launched oil exploration over 124 million hectares of the Cuvette Centrale peatlands raising global ecological risk.

    About the Cuvette Centrale Peatland Complex:

    • Location: Central Congo Basin, spanning the Democratic Republic of the Congo and the Republic of Congo.
    • Size: Covers approximately 145,000–167,600 sq. km—larger than England and about 10% of the Congo Basin.
    • Peat Coverage: Around 40% of the region is underlain by peat—formed over 10,000 years due to flat terrain, rainforest climate, and slow-moving water.
    • Landscape: Features a mosaic of seasonal lakes, floating prairies, swamp forests, rivers, and grasslands.
    • Global Status: The world’s largest near-contiguous tropical peatland complex.

    Ecological Significance:

    • Carbon Storage: Holds about 30–30.6 gigatonnes of carbon—
      • Equal to 3 years of global fossil fuel emissions.
      • Nearly 15 years of U.S. emissions.
      • About 28% of global tropical peat carbon stock.
    • Climate Impact: Acts as a major carbon sink, critical for regulating global temperatures and mitigating climate change.
    • Biodiversity: Habitat for forest elephants, lowland gorillas, and rare plant species.
    • Local Importance: Sustains indigenous livelihoods and maintains regional water cycles.
    • Conservation Status: Recognized as a transnational Ramsar wetland site, highlighting its international ecological value.
    [UPSC 2024] One of the following regions has the world’s largest tropical peatland, which holds about three years’ worth of global carbon emissions from fossil fuels, and the possible destruction of which can exert a detrimental effect on the global climate. Which one of the following denotes that region?

    Options: (a) Amazon Basin (b) Congo Basin* (c) Kikori basin (d) Rio De La Plata Basin

     

  • Places in news: Bitra Island

    Why in the News?

    The Lakshadweep administration has proposed the acquisition of Bitra Island, the smallest inhabited island in the archipelago, for national defence purposes.

    bitra

    About Bitra Island:

    • Location: Situated in the Arabian Sea; part of the Amindivi subgroup of the Lakshadweep archipelago
    • Distance from Mainland: ~483 km west of Kochi  
    • Land Area: 0.10–0.18 square kilometres
    • Population: ~271–350 (as of 2025)
    • Language and Livelihood
      • Languages Spoken: Malayalam, Mahl, and English
      • Economic Activities: Fishing, coconut farming, and emerging ecotourism (birdwatching, snorkeling, diving)
    • Climate:
      • Type: Tropical monsoon (similar to Kerala)
      • Temperature Range: 25–35°C
      • Annual Rainfall: ~1600 mm
      • Monsoon Season: Mid-May to mid-September; sea access is limited
    • Historical and Cultural Significance:
      • History: Populated around 1945
      • Pilgrimage Site: Hosts a shrine to Arab saint Malik Mulla

    Strategic Importance:

    • Location: Close to key international shipping lanes in the Arabian Sea
    • Surveillance Advantage: Ideal point for maritime monitoring
    • Military Utility: Suitable for naval installations and coastal defence
    • Maritime Awareness: Enhances India’s preparedness in the western seaboard
    [UPSC 2014] Which one of the following pairs of islands is separated from each other by the ‘Ten Degree Channel’?

    Options: (a) Andaman and Nicobar* (b) Nicobar and Sumatra (c) Maldives and Lakshadweep (d) Sumatra and Java

     

  • Wind Stilling Effect in the Indo-Gangetic Plain (IGP)

    Why in the News?

    A satellite-based study (2003–2020) of 141 Indian cities revealed a surprising aerosol pattern — southern cities act as pollution hotspots, while many northern cities form ‘clean islands’ due to a phenomenon called the Wind Stilling Effect.

    Key Highlights of the Study:

    • Conducted by: The Indian Institute of Technology Bhubaneswar.
    • Method: Used high-resolution aerosol optical depth data to track pollution.
    • Focus: Examined how urbanisation interacts with natural and transported pollution.
    • Surprising Insight: Many northern cities were not major aerosol hotspots, contrary to assumptions.
    • Classification of Cities: Two categories based on aerosol levels relative to surrounding areas:
      • Urban Aerosol Pollution Islands-
        • Location: Predominantly in southern and southeastern India.
        • Characteristics: Cities had higher aerosol levels than nearby rural surroundings.
        • Pollution Source: Mostly local emissions from vehicles, construction, and industries.
        • Absence of External Influence: Minimal contribution from long-range dust or biomass burning.
      • Urban Aerosol Clean Islands-
        • Location: Observed in northwestern India and the Indo-Gangetic Plain.
        • Pattern: Cities had lower aerosol levels than nearby upwind (southwest) areas.
        • Mechanism: Incoming pollutants were blocked or deflected, creating a “clean island” effect.
        • Downwind Evidence: Northeast (downwind) sides showed equal or lower aerosol levels compared to city centres.

    About the Wind Stilling Effect:

    • Overview: A phenomenon where dense urban infrastructure reduces surface wind speed, altering local airflow.
    • Barrier Formation: Slowed winds create atmospheric stagnation zones, especially on the upwind side.
    • Pollution Blocking: Long-range pollutants like Thar Desert dust or biomass smoke are slowed or blocked.
    • Misleading Cleanliness: Cities appear cleaner not due to lower emissions, but due to pollution deflection.
    • Seasonality: Most evident during the pre-monsoon season, when dust transport is high and cloud cover is minimal.
    [UPSC 2010] If there were no Himalayan ranges, what would have been the most likely geographical impact on India ?

    1. Much of the country would experience the cold waves from Siberia. 2. Indo-gangetic plain would be devoid of such extensive alluvial soils. 3. The pattern of monsoon would be different from what it is at present.

    Which of the statements given above is/are correct ?

    Options: (a) 1 only (b) 1 and 3 only (c) 2 and 3 only (d) 1, 2 and 3*

     

  • [22nd July 2025] The Hindu Op-ed: Water, energy demand spotlights risk of human-induced quakes 

    PYQ Relevance:

    [UPSC 2020] Discuss the geophysical characteristics of Circum-Pacific Zone.

    Linakge: This question is about a region known for earthquakes and volcanoes. The article mainly talks about quakes caused by human activity but also mentions that these usually happen in places already on fault lines or where tectonic plates are shifting—areas like the Circum-Pacific. So, it’s important to understand these natural zones when looking at how human actions might trigger earthquakes.

     

    Mentor’s Comment:  Human-induced earthquakes are increasingly drawing scientific and public attention, as research shows that human activities like groundwater extraction, dam construction, and fracking can trigger or accelerate seismic activity, particularly in tectonically sensitive regions such as Delhi-NCR, the Western Ghats, and parts of Maharashtra and Kerala.

    Today’s editorial analyses the Issues related to Human-induced earthquakes in India. This topic is important for GS Paper I (Geography), GS Paper II (Governance) and  GS Paper III (Disaster Management) in the UPSC mains exam.

    _

    Let’s learn!

    Why in the News?

    Recent studies in India have highlighted a correlation between excessive groundwater depletion and increased seismic events, especially in Delhi.

    What are human-induced earthquakes?

    • These are earthquakes triggered by human activities rather than natural tectonic movements. Activities like mining, groundwater extraction, building dams, and fracking disturb the earth’s crust, causing seismic activity. Over 700 human-induced quakes have been recorded globally in the last 150 years.

     

    How do activities like groundwater extraction and dams trigger quakes in India?

    • Groundwater Depletion Weakens Crustal Stability: Excessive extraction of groundwater reduces pore pressure, leading to a shift in stress within the earth’s crust. Eg: In Delhi-NCR, increased seismic activity between 2003–2012 has been linked to excessive groundwater loss.
    • Reservoir-Induced Seismicity (RIS): The weight of large reservoirs exerts additional pressure on underlying faults, triggering quakes. Eg: The 1967 Koynanagar earthquake (magnitude 6.3) was linked to the Koyna Dam in Maharashtra.
    • Water Infiltration into Fault Zones: Water from reservoirs or excessive irrigation can seep deep into fault lines, lubricating them, and making them more likely to slip. Eg: Seismic tremors near Mullaperiyar Dam in Kerala are suspected to be induced due to water infiltration in a seismically sensitive region.
    • Load Variation Due to Filling and Emptying of Dams: Rapid filling or draining of reservoirs changes the stress distribution, causing small or moderate tremors. Eg: In the Himalayan region, such stress changes are a concern for dams like Tehri Dam.
    • Ground Subsidence from Overuse of Aquifers: Excessive groundwater extraction leads to land subsidence, altering the natural equilibrium of stress in the crust. Eg: Regions in North Gujarat have experienced subsidence, making them more vulnerable to fault reactivation and quakes.

    Why is Delhi-NCR prone to quakes from groundwater loss?

    • Rapid Groundwater Depletion Alters Stress Fields: Excessive groundwater extraction reduces the hydrostatic pressure underground, disturbing the natural stress balance in fault zones. This stress redistribution can reactivate dormant faults, triggering seismic activity. Eg: Studies from 2003–2012 show increased microseismic activity in parts of Gurgaon and Faridabad, correlated with falling water tables.
    • Aquifer-Related Land Subsidence: Continuous overuse of aquifers causes the land to sink (subsidence), which can strain the Earth’s crust and disturb nearby fault lines. In Delhi-NCR, land sinking has been recorded in Dwarka, Kapashera, and parts of Noida, increasing quake risk. Eg: A 2021 study by IIT-Kanpur showed that excessive aquifer use led to ground subsidence and elevated seismic hazard.
    • Built-Up Pressure on Seismically Active Faults: Delhi-NCR sits near the Mahendragarh-Dehradun fault and Delhi-Haridwar ridge, making it naturally earthquake-prone. When groundwater is extracted, it weakens the structural resistance of rocks, making nearby active faults more vulnerable. Eg: Minor tremors in Rohini and West Delhi (2020-21) were suspected to be linked to combined stress from tectonics and human activity.

    How does climate change contribute to seismic risks?

    • Melting Glaciers Increase Uplift Pressure: Rapid glacial melt in the Himalayas (due to rising temperatures) reduces surface weight. This triggers isostatic rebound — the crust rises and shifts, which can activate faults beneath. Eg: In Uttarkashi (Uttarakhand), increased seismic activity has been observed near retreating Gangotri Glacier, linked to glacial thinning and uplift.
    • Changing Rainfall Patterns Cause Landslides and Crustal Stress: Intense rainfall and flash floods (exacerbated by climate change) cause rapid groundwater recharge and erosion, disturbing fault stability. Eg: In Kodagu (Karnataka), unusually heavy rains in 2018 triggered landslides and minor tremors due to destabilized slopes and crustal shifts.
    • Sea-Level Rise and Coastal Seismic Pressure: Rising sea levels increase water load on coastal plates, especially in delta regions. This can suppress or activate tectonic stresses near coastlines. Eg: In Sundarbans (West Bengal), changes in sediment load and sea-level rise have raised concerns of future seismic risks in this low-lying, tectonically sensitive zone.
    What are the steps taken by the Indian Government?

    •  Seismic Zoning and Monitoring: India is divided into four seismic zones (II to V) to prioritize risk-based planning. The National Centre for Seismology (NCS) monitors seismic activity across the country in real-time.
    • Implementation of Earthquake-Resistant Building Codes: The Bureau of Indian Standards (BIS) has issued IS codes for earthquake-resistant construction.
    • Capacity Building and Public Awareness: NDMA and NDRF conduct training, mock drills, and awareness programs in vulnerable areas.

    Way forward: 

    • Integrated Land and Water Management: Promote sustainable groundwater use, recharge practices, and land-use planning to reduce land subsidence and seismic vulnerability.
    • Expand Monitoring and Preparedness: Enhance seismic monitoring networks and public awareness programs to improve early warning systems and disaster resilience.

  • In news: Kamchatka Peninsula

    Why in the News?

    Five strong offshore earthquakes hit Russia’s Kamchatka Peninsula, the strongest measuring 7.4 in magnitude.

    Kamchatka Peninsula

    About Kamchatka Peninsula:

    • Location: Situated in Far Eastern Russia, bordered by the Sea of Okhotsk (west) and the Pacific Ocean and Bering Sea (east).
    • Size and Shape: Stretches about 1,200 km north to south and 480 km at its widest point.
    • Area: Covers approximately 370,000 square kilometers—comparable in size to New Zealand.
    • Ethnic Composition: Majority are ethnic Russians; around 13,000 belong to the indigenous Koryak community.
    • Climate: Harsh with long, snowy winters and wet, cool summers.
    • Topography: Highest peak is Klyuchevskaya Sopka, an active volcano in the Eastern Mountain Range.
    • Global Recognition: Hosts the “Volcanoes of Kamchatka,” a UNESCO World Heritage Site.

    Tectonic Significance:

    • Geological Setting: Lies on the Pacific Ring of Fire, making it a global hotspot for seismic and volcanic activity.
    • Volcanic Density: Contains over 150 volcanoes, 29 of which are currently active.
    • Kuril–Kamchatka Trench: Located just offshore, reaches depths of about 10,500 meters and drives regional seismicity.
    • Tectonic Cause: Caused by subduction of the Pacific Plate beneath the Eurasian Plate.
    [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*

     

  • Disputes over Grand Ethiopian Renaissance Dam (GERD)

    Why in the News?

    The completion of Ethiopia’s Grand Ethiopian Renaissance Dam (GERD) has reignited tensions over Nile water rights, with Egypt and Sudan fearing reduced water flows.

    Disputes over Grand Ethiopian Renaissance Dam (GERD)

    About Grand Ethiopian Renaissance Dam (GERD):

    • Overview: Gravity dam on the Blue Nile near Ethiopia–Sudan border.
    • Construction Timeline: Under construction since 2011, led by Ethiopian Electric Power Corporation.
    • Capacity: Set to become Africa’s largest hydropower plant with 6.45 GW output.
    • Reservoir Size: Holds 74 billion cubic metres; filling may take 5–15 years.
    • Key Features: 145 m tall dam, 16 turbines, and a supporting saddle dam.
    • Purpose: Aims to power Ethiopia (65% population lacks electricity) and export surplus to neighbouring countries.
    • Disputes Around GERD:
      • Egypt’s Concern: Fears reduced water flow; Relies 90% on Nile; demands a binding filling agreement.
      • Sudan’s Worry: Concerns over flood risks and water regulation.
      • Ethiopia’s Stand: Asserts sovereign rights; began filling without consensus.
      • Stalled Talks: Tripartite negotiations have failed; Egypt warns of possible conflict.

    Back2Basics: Nile River

    • Overview: North-flowing, longest river in Africa at ~6,650 km.
    • Drainage Basin: Covers 11 countries—Tanzania, Uganda, Rwanda, Burundi, DRC, Kenya, Ethiopia, Eritrea, South Sudan, Sudan, and Egypt.
    • Main Tributaries:
      • White Nile: Recognized as the headstream, its most remote source is the Kagera River in Burundi, flowing through Rwanda into Lake Victoria. It officially begins at Jinja, Uganda, where it exits Lake Victoria.
      • Blue Nile: Originates from Lake Tana in Ethiopia and merges with the White Nile at Khartoum, Sudan.  Supplies over 80% of total Nile flow by the time it reaches Egypt.
    • Lifeline Status: Vital for Egypt and Sudan’s drinking water, irrigation, and energy needs.

     

    [UPSC 2008] Ogaden region has been a source of conflict between which countries?

    Options: (a) Morocco and Algeria (b) Nigeria and Cameroon (c) Angola and Zambia (d) Ethiopia and Somalia*

     

  • In news: Reykjanes Peninsula

    Why in the News?

    Recently a volcano erupted in south-west Iceland, continuing a pattern of recurring geological activity on the Reykjanes Peninsula.

    In news: Reykjanes Peninsula

    About the Reykjanes Peninsula:

    • Location: Situated in southwest Iceland along the Mid-Atlantic Ridge where tectonic plates diverge.
    • Volcanic Reawakening: Dormant for centuries until 2021; now sees recurring eruptions.
    • Eruption Type: Known for fissure eruptions—lava flows from cracks, not a central crater.
    • Key Sites: Includes Grindavik (evacuated), Blue Lagoon spa, and Svartsengi power plant.
    • Volcanic Importance: Part of Iceland’s 30+ active volcanic zones.

    Key Features:

    • Eruption Style: Produces steady lava flows with minimal ash output.
    • Flight Safety: Air traffic remains unaffected due to lack of stratospheric ash.
    • Evacuation Impact: Grindavik largely abandoned after 2023 lava threat.
    • Long-Term Activity: Eruptions may persist for decades or longer.
    • Iceland Snapshot: Population ~400,000; similar in size to Kentucky.
    • Tourism Appeal: Attracts visitors like other volcanic hotspots—Mexico, Indonesia, Sicily, and New Zealand.
    [UPSC 2014] 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*

     

  • [17th July 2025] The Hindu Op-ed: A tectonic shift in thinking to build seismic resilience

    PYQ Relevance:

    [UPSC 2015] Earthquakes along the plate margins are still a cause of concern. India’s preparedness for mitigating their impact has significant gaps. Discuss various aspects.

    Linkage: The article emphasizes that India’s seismic risk is rooted in the northward drift of the Indian Plate colliding with the Eurasian Plate, which shaped the Himalayas and makes the region “overdue for a ‘Great Himalayan Earthquake’.  The question specifically mentions “earthquakes along the plate margins” and critically highlights “India’s preparedness for mitigating their impact has significant gaps.

     

    Mentor’s Comment:  The 4.4 magnitude tremor in Delhi on July 10, 2025, though moderate, exposed the critical fragility of India’s infrastructure, especially in Delhi, where over 80% of buildings violate seismic safety norms. This event is part of a wider pattern of seismic activity across Asia, underlining the urgent need for earthquake preparedness. India, particularly northern and northeastern regions, lies in high-risk seismic zones (IV & V) due to the collision of tectonic plates, making a massive quake imminent. Urbanisation, outdated construction, and poor enforcement of seismic codes like IS 1893:2016 worsen the risk.

    Today’s editorial analyses the vulnerability to earthquakes in India. This topic is important for GS Paper I (Geography) and  GS Paper III (Disaster Management) in the UPSC mains exam.

    _

    Let’s learn!

    Why in the News?

    On July 10, 2025, a 4.4 magnitude earthquake struck near Delhi, exposing the fragile state of infrastructure.

    Why is Delhi vulnerable to earthquakes?

    • High Seismic Risk Zone: Delhi lies in Seismic Zone IV, indicating a severe seismic hazard with a peak ground acceleration (PGA) of around 0.24g. Eg: Similar Zone IV cities like Srinagar and Patna have experienced strong tremors in the past.
    • Poor Structural Compliance: Over 80% of buildings in Delhi, especially those constructed before 2000, do not comply with seismic safety codes. Eg: Unregulated high-rise apartments in East Delhi lack ductile detailing or shear walls, making them prone to collapse.
    • Liquefaction-Prone Areas: Areas like East Delhi and Yamuna floodplains are built on soft alluvial soils, which are susceptible to liquefaction during earthquakes. Eg: In the 2001 Bhuj earthquake, structures on soft soil experienced severe tilting and collapse.
    • Rapid Urbanisation Without Planning: Delhi’s urban sprawl and dense population (over 33 million) have led to haphazard construction, often violating zoning and structural norms. Eg: Many illegal colonies like those in outer Delhi lack any seismic design considerations.

    What are the vulnerable areas in India? 

    • Himalayan Region: The Himalayan belt is highly prone to earthquakes due to the collision of the Indian and Eurasian tectonic plates. Eg: Regions like Jammu & Kashmir, Himachal Pradesh, Uttarakhand, and parts of Northeast India fall under Seismic Zone V.
    • Indo-Gangetic Plain: This region experiences significant seismic activity due to the tectonic stress transfer from the Himalayan region. Eg: Parts of Bihar, Uttar Pradesh, Delhi, and West Bengal lie in Seismic Zones III and IV.
    • Peninsular India Fault Zones: Though considered geologically stable, intraplate faults in Peninsular India can still trigger strong earthquakes. Eg: Areas like Latur (Maharashtra), Koyna (Maharashtra), and Bhuj (Gujarat) have witnessed major quakes in the past.

    What are the steps taken by the Indian Government? 

    • Building Code Reforms: The government enforces Earthquake-Resistant Building Codes to ensure structural safety in seismic zones. Eg: The Bureau of Indian Standards (BIS) revised IS 1893 and IS 4326 to include updated seismic design norms across construction sectors.
    • National Seismic Zoning: India has been zoned into seismic risk areas to guide planning and construction based on earthquake vulnerability. Eg: The country is divided into Zone II to Zone V, with Zone V (like parts of Uttarakhand, Kashmir) being most earthquake-prone.
    • Disaster Management Framework: The government has established a dedicated institutional framework to coordinate disaster preparedness and response. Eg: The National Disaster Management Authority (NDMA) issues guidelines for earthquake risk mitigation and conducts regular mock drills and capacity-building programs.

    What are the steps taken at the international level?

    • Sendai Framework for Disaster Risk Reduction (2015–2030): The United Nations adopted this global framework to strengthen disaster preparedness, promote resilient infrastructure, and reduce disaster losses. Eg: Countries like Japan and Chile have aligned their national disaster policies with Sendai priorities, emphasizing risk governance and early warning.
    • Global Seismic Hazard Assessment Program (GSHAP): Led by the International Lithosphere Program, this initiative provides seismic hazard maps to help countries plan safer infrastructure. Eg: Italy and other European nations use GSHAP data to revise building codes and zoning laws in earthquake-prone zones.
    • Early Warning Systems and Technology Sharing: Countries are collaborating to develop earthquake early warning systems and share real-time seismic data across borders. Eg: The Pacific Tsunami Warning Center and Japan’s Earthquake Early Warning System help neighbouring nations prepare faster for seismic events.

    What global lessons can India adopt from other countries? (Way forward)

    • Building Code Enforcement: Strong and regularly updated building codes ensure that infrastructure can withstand seismic shocks, reducing casualties and damage. Eg: After the 1995 Kobe earthquake, Japan revised its seismic building codes, which helped limit destruction during the 2011 Tōhoku earthquake.
    • Early Warning Systems: Timely alerts enable people to take quick protective actions, such as evacuation or shutting down utilities, before the shaking begins. Eg: In 2017, Mexico City’s SASMEX system gave a 20-second alert before the quake struck, allowing residents to prepare.
    • Retrofitting Incentives: Providing financial support for retrofitting older buildings motivates citizens to strengthen structures against earthquakes. Eg: The Earthquake Brace + Bolt program in California offers funds to homeowners, promoting structural safety in vulnerable areas.

  • In news: Great Trigonometric Survey (GTS)

    Why in the News?

    This newscard highlights the role of Indian assistants in completing the Great Trigonometric Survey (GTS), which began in 1802 to map India’s geography.

    About the Great Trigonometrical Survey (GTS):

    • Launch and Objective: The GTS was a massive scientific and cartographic initiative launched in 1802 by the British to map India with unprecedented precision using trigonometry and geodesy.
    • Initiator: It was conceptualised by William Lambton, a British army officer, and carried out under the East India Company.
    • Purpose: It aimed to measure Earth’s curvature, create accurate maps, and support colonial administration, scientific research, and military planning.
    • Survey Method: It used triangulation, involving a network of interconnected triangles built from a known baseline to calculate distances and angles over large areas.
    • First Baseline: The initial baseline was measured in 1802 at St. Thomas Mount near Madras (Chennai) and extended over 2,600 km up to the Himalayas.
    • Instruments Used: The survey used massive theodolites (weighing up to half a ton) and measuring chains, requiring large teams for operation and transport.
    • Scientific Outcome: It led to the formulation of the Everest Spheroid, a geodetic reference model still used for mapping in South Asia.
    • Duration and Leadership: Although planned to take 5 years, the project lasted nearly 70 years (until 1871) and was led by successors such as George Everest (after whom Mt. Everest was named), Andrew Scott Waugh, and James Walker.

    How did the GTS led to the Mapping of India?

    • First Accurate Maps: It provided scientific maps that corrected earlier errors, enabling modern geodetic frameworks for administration and infrastructure.
    • Survey Range: It mapped from southern India to the Himalayas, supporting large-scale development and scientific measurement.
    • Great Arc Measurement: It measured the Great Arc (Chennai to Dehradun), a significant geodetic arc that helped calculate Earth’s curvature.
    • Himalayan Heights: Using triangulation data, the survey measured 79 Himalayan peaks, including Mount Everest, K2, and Kangchenjunga.
    • Mount Everest Identification: In 1852, Peak XV was identified as the world’s highest mountain, later named Mount Everest in honour of George Everest.
    • Latitude-Longitude System: It produced precise longitude and latitude coordinates, crucial for navigation, military logistics, and administration.
    • Infrastructure Impact: Survey benchmarks supported railways, roads, canals, and earthquake studies, many of which remain relevant today.

    Contribution of Indians to the GTS:

    • Syed Mir Mohsin Husain: A jeweller from Arcot who repaired critical instruments and was later appointed as an instrument maker in the Surveyor General’s office.
    • Radhanath Sikdar: An Indian mathematician who calculated the height of Mount Everest in 1852, confirming it as the tallest peak globally.
    • Indian Field Workers: Thousands of Indian flagmen, khalasis, and labourers undertook challenging tasks like carrying heavy equipment, setting markers, and working in hazardous environments.
    • Logistical Support: Indian artisans and technicians repaired, calibrated, and adapted instruments, making the project feasible under Indian conditions.
    • Role of Pundits: Trained Indian “pundits” conducted secret surveys in Tibet and politically sensitive regions, where British officers were restricted.
    [UPSC 2018] Among the following cities, which one lies on a longitude closest to that of Delhi?

    Options: (a) Bengaluru* (b) Hyderabad (c) Nagpur (d) Pune

     

  • [pib] Fossils reveal Kashmir Valley’s Climatic Past

    Why in the News?

    Researchers from Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow, have found strong evidence that the Kashmir Valley, now cool and temperate, was once a warm, humid subtropical region.

    About the Study on Fossils:

    • Site of Fossil Discovery: The fossils were recovered from the Karewa sediments of the Kashmir Valley, known for preserving ancient plant remains.
    • Analysis: Researchers used CLAMP (Climate Leaf Analysis Multivariate Program) to analyze fossil leaf shape, size, and margins to estimate past temperature and rainfall patterns.
    • Coexistence Approach: It was also used, comparing fossil plants with their modern relatives to reconstruct the region’s ancient climate.

    Key Findings:

    • Past Climate Type: The Kashmir Valley once had a warm, humid subtropical climate, very different from the cool, Mediterranean-type climate it experiences today.
    • Vegetation Evidence: Fossilized leaves showed diverse subtropical plant types no longer found in the region’s current vegetation.
    • Role of Tectonic Uplift: The tectonic uplift of the Pir Panjal Range was identified as a key factor that blocked the Indian summer monsoon from entering the valley.
    • Climatic Transition: This led to gradual drying of the region and a shift from subtropical forests to temperate ecosystems.
    • Impact of Mountain-Building: The study shows that mountain-building (tectonic uplift) can directly affect climate patterns by altering monsoon routes.
    • Relevance to Climate Change: The findings provide insight into natural climate shifts over millions of years, helping contextualize modern climate change.
    • Ecological Vulnerability: It also highlights the fragility of mountain ecosystems like the Himalayas, which are vulnerable to both natural and human-induced environmental changes.

    Back2Basics:

    • Karewa Sediments: They are plateau-like terraces in the Kashmir Valley, made up of lacustrine (lake) and fluvio-glacial deposits; They are known to preserve ancient fossils, especially of plants.
    • Subtropical Climate: A warm and humid climate with moderate to high rainfall, supporting dense vegetation. Ex: Climate of northeastern India.
    • Mediterranean-Type Climate: Characterized by mild, wet winters and hot, dry summers; Ex: Current climate of parts of the Kashmir Valley.

     

    [UPSC 2025] Which of the following are the evidence of the phenomenon of continental drift?

    I. The belt of ancient rocks from Brazil coast matches with those from Western Africa. II. The gold deposits of Ghana are derived from the Brazil plateau when the two continents lay side by side. III. The Gondwana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere.

    Options: (a) I and III only (b) I and II only (c) I, II and III * (d) II and III only