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Subject: Geographical Features

  • What are Flying Rivers/ Atmospheric Rivers?

    Why in the News?

    Droughts and fires in South America highlight the importance of “flying rivers” — rain-bearing vapor streams disrupted by Amazon deforestation.

    What are Atmospheric Rivers?

    • Overview: Long, narrow bands of concentrated water vapour in the lower atmosphere, often termed “rivers in the sky.”
    • Dimensions: Typically 2,000–5,000 km long, 400–500 km wide, and about 3 km deep.
    • Water Transport: Carry nearly 90% of water vapour across Earth’s mid-latitudes — almost double the Amazon River’s flow.
    • Formation: Warm tropical seawater evaporates, and winds transport this moisture; upon encountering land or mountains, vapour condenses into heavy rainfall or snow.
    • Role: Unlike short-term weather systems, Atmospheric Rivers (ARs) shape long-term hydrological cycles and trigger extreme precipitation events.

    Global Impacts of Atmospheric Rivers:

    • Flooding & Extreme Weather: Cause 80% of flood-related damages along the US West Coast; also linked to devastating floods in Europe, Africa, South America, and Australia.
    • South America: Amazon’s “flying rivers” disrupted by deforestation, leading to droughts in Peru, Bolivia, and Ecuador; threatens Amazon rainforest’s survival and risks savannisation.
    • East Asia: Up to 80% of heavy rainfall events in China, Korea, and Japan during early monsoon linked to ARs.
    • Climate Connection: Warming oceans are making ARs longer, wider, and more intense, increasing risks of catastrophic floods and landslides.
    • Positive Role: Contribute 30–50% of annual precipitation in some regions (e.g., US West Coast) and help end 33–74% of droughts.

    Atmospheric Rivers in India’s Context:

    • Interaction: ARs combine with cyclonic circulations and the Himalayan ranges, causing extreme rainfall and flash floods.
    • Case Studies:
      • 2010 Leh cloudburst (Ladakh) – flash floods and mudslides.
      • 2011 Kupwara floods (J&K) – severe AR-driven rainfall.
    • Study (1951–2020): Identified 574 AR events during the monsoon season in India.
    • Recent Trends: Nearly 80% of India’s most severe floods (1985–2020) linked to AR activity.
    • Cause: Rapid Indian Ocean warming intensifies evaporation, moisture transport, and AR-driven floods.
    • Impact: Leads to short, intense rainfall spells, landslides, flash floods, crop loss, and mass displacement of communities.
    [UPSC 2024] With reference to “water vapour,” which of the following statements is/are correct?

    1. It is a gas, the amount of which decreases with altitude.

    2. Its percentage is maximum at the poles.

    Select the answer using the code given below:

    Options: (a) 1 only* (b) 2 only (c) Both 1 and 2 (d) Neither 1 and 2

     

  • Climate Models and Their Accuracy

    Why in the News?

    The US President Donald Trump called climate change the “greatest con job ever,” disgusted with the predictions based on climate models central to climate science.

    Climate Models and Their Accuracy

    What are Climate Models?

    • Overview: Climate models are computer simulations using mathematical equations to represent the Earth’s climate system, including the atmosphere, oceans, land surface, and ice.
    • Basis: Built on physics, chemistry, and biology, they simulate interactions among Earth’s components.
    • Purpose: Forecast temperature, rainfall, humidity, sea-level rise, and extreme weather under scenarios like high greenhouse gas emissions.
    • Difference from Weather Models: Weather models predict short-term local events, while climate models analyze long-term regional and global patterns.

    How do Climate Models work?

    • Grid System: Earth divided into a 3D grid of cells across land, atmosphere, and oceans.
    • Equations: Each cell governed by equations on energy movement, air, ice, and land processes.
    • Data Input: Observational data (greenhouse gases, ocean conditions, land use) fed into the model.
    • Interactions: Equations simulate changes in each cell and their effects on neighboring cells.
    • Outputs: Provide projections for temperature, precipitation, sea levels, ice cover, and extreme climate events.

    Evolution of Climate Models:

    Model Type What is it? Strengths Limitations
    Energy Balance Models (EBMs) 

    (1960s)
    • The earliest climate models.
    • They treat Earth like a single box system, calculating surface temperature by balancing incoming solar radiation vs outgoing infrared radiation.
    • Essentially, they answer: “How warm should Earth be if X amount of energy comes in and Y amount goes out?”
    • Very simple; first to link CO₂ emissions with global warming.
    • Computationally inexpensive.
    • Oversimplified — ignores atmosphere, oceans, and circulation.
    • Cannot simulate rainfall, winds, or regional climate.
    Radiative Convective Models (RCMs) 

    (1960s–70s)
    • Introduced the vertical structure of the atmosphere.
    • They divide the atmosphere into layers and simulate how radiation (solar + infrared) and convection move heat upward and downward.
    • Show how greenhouse gases trap heat and alter temperatures at different heights.
    • Capture greenhouse effect more realistically;
    • Explain vertical temperature profiles;
    • Useful for studying stratospheric cooling.
    • Still ignore oceans and global circulation;
    • Cannot project regional variations or weather patterns.
    General Circulation Models (GCMs) (Global Climate Models)

    (1970s onwards)
    • The first 3D models of Earth’s climate.
    • Divide the planet into grid cells (100–250 km), each with equations for atmosphere, oceans, ice, and land.
    • Simulate winds, currents, rainfall, temperature, and pressure by solving physical equations of motion, energy, and mass.
    • Comprehensive representation of climate;
    • Simulate monsoon, El Niño, ocean currents; reproduce past climate trends.
    • Very resource-intensive; grid too coarse to capture local detail (cities, villages);
    • Uncertainty in clouds and aerosols.
    Earth System Models (ESMs)

    (1990s–present)
    • Advanced GCMs that integrate biogeochemical cycles (carbon cycle, vegetation, ocean chemistry, aerosols, land-use changes).
    • Show how human activities (deforestation, fossil fuels, pollution) interact with natural systems, feedback loops, and long-term climate.
    • Holistic view of climate–biosphere interactions;
    • Essential for IPCC reports and policy projections.
    • Extremely complex;
    • Uncertainties in carbon feedbacks, aerosols, and long-term ecological processes.
    Regional Climate Models (RCMs)

    (1990s–present)
    • High-resolution versions of GCMs, zoomed into specific regions (25–50 km grids).
    • Use downscaling techniques to provide localised forecasts of rainfall, temperature, droughts, and monsoons.
    • Useful for city- or country-level policy (flood risk, agriculture, urban heat);
    • Capture Indian monsoon and Himalayan glaciers better.
    • Dependent on GCM input;
    • Projections limited to chosen region;
    • Computationally intensive.

    How accurate are Climate Models?

    • Strengths: Modern models predict sea-level rise, polar ice loss, temperature increases, and rainfall trends with high accuracy.
    • Validation: Predictions are compared with historical climate records to confirm reliability.

    • Limitations:

      • Lack of precise data on clouds, volcanic activity, El Niño events.
      • Limited accuracy for regional variations (e.g., urban floods, Indian monsoon extremes).
      • Less accuracy in Global South due to data scarcity and complex climate systems.
      • Grid resolution (100–250 km per cell) causes oversimplification of land–atmosphere interactions.
    [UPSC 2025] The World Bank warned that India could become one of the first places where wet-bulb temperatures routinely exceed 35°C. Which of the following statements best reflect(s) the implication of the above-said report?

    I. Peninsular India will most likely suffer from flooding, tropical cyclones and droughts.

    II. The survival of animals including humans will be affected as shedding of their body heat through perspiration becomes difficult.

    Select the correct answer using the code given below:

    (a) I only      (b) II only      (c) Both I and II      (d) Neither I nor II

     

  • South-west Monsoon: Its Onset and Retreat

    Why in the News?

    According to the India Meteorological Department (IMD), the southwest monsoon began its earliest withdrawal in a decade on September 14 from western Rajasthan, three days before the usual date of September 17.

    What is Monsoon? 

    • Overview: A seasonal reversal of winds, southwest winds (wet) in summer and northeast winds (dry) in winter.
    • Onset Date: Officially begins June 1 over Kerala, advances northwards, covering entire India by mid-July.
    • Importance: Accounts for ~75% of India’s annual rainfall, critical for Kharif crops, water storage, and ecosystems.

    Mechanism of Monsoon Onset:

    • Differential Heating: Indian landmass heats faster than the Indian Ocean, creating low pressure over NW India that pulls in moist winds.
    • Mascarene Highs:
      • Located near Mascarene Islands (east of Madagascar).
      • Strengthen during May–June winter in Southern Hemisphere.
      • Push strong cross-equatorial winds from the SE Indian Ocean towards India.
    • Cross-Equatorial Flow:
      • Southeast trades from Mascarene High cross the equator.
      • Deflected by Coriolis, they become southwest monsoon winds, feeding both Arabian Sea branch and Bay of Bengal branch.
    • ITCZ (Intertropical Convergence Zone) Shift: Moves northwards over Ganga plains, anchoring the monsoon trough.
    • Tibetan Plateau Heating: Acts as an elevated heat source, deepening low pressure.
    • Jet Stream Influence:
      • Subtropical Westerly Jet (STWJ) shifts north of Himalayas, allowing the monsoon trough.
      • Tropical Easterly Jet (TEJ) develops, enhancing moisture flow.
    • Local Triggers: Orographic uplift along Western Ghats, NE Hills, and Indo-Gangetic plains causes heavy rains.

    What is Retreat/Withdrawal of Monsoon?

    • Earliest Withdrawal (2025): Began Sept 14 from western Rajasthan — earliest in a decade (normal = Sept 17).
    • Withdrawal Process: Gradual, completes by mid-October.
    • IMD Withdrawal Criteria:
      1. Development of anti-cyclonic circulation at lower troposphere.
      2. No rainfall for 5 consecutive days over the region.
      3. Prevalence of dry weather conditions.
    • Seasonal Marker: IMD fixes Sept 30 as the official end of SW monsoon.
    • Agricultural Role: Retreat moisture crucial for Rabi crop sowing.

    Influencing Factors for Monsoon Retreat:

    • Seasonal Cooling: Reduced solar heating over land in September weakens low pressure.
    • Pressure Gradient Reversal: High pressure redevelops over NW India, collapsing SW winds.
    • ITCZ Shift: Moves back southwards towards the equator, reversing wind patterns.
    • Jet Stream Role: TEJ weakens, westerlies return, pushing out moist winds.
    • Topography & Seas: Coastal and mountainous regions (e.g., SE peninsula, Bay of Bengal) may still receive residual/post-monsoon showers.
    • Mascarene Highs: As SH winter ends, Mascarene highs weaken, cross-equatorial inflow diminishes, aiding withdrawal.

    Climatic Phenomena affecting the Indian Monsoon:

    1. ENSO (El Niño–Southern Oscillation):

    • ENSO originates in the equatorial Pacific Ocean and strongly influences the Pacific Walker Circulation (PWC).
      1. El Niño years: The eastern and central Pacific waters warm up. This weakens the Walker circulation and reduces the flow of moisture-laden winds from the Mascarene Highs towards India. As a result, the monsoon becomes weak or deficient, often leading to droughts.
      2. La Niña years: The opposite happens; Pacific waters cool, the Walker circulation strengthens, and strong cross-equatorial winds from the Mascarene Highs bring more moisture into India. Monsoon rainfall is usually above normal, sometimes leading to floods.
    • Key point: ENSO acts like a “remote controller” sitting in the Pacific but directly influencing the strength of the Indian monsoon winds.

    2. Indian Ocean Dipole (IOD):

    • The Indian Ocean itself has its own seesaw pattern of sea surface temperatures.
      • Positive IOD: Western Indian Ocean (near Africa) is warmer, and eastern Indian Ocean (near Indonesia) is cooler. This strengthens cross-equatorial winds from the Mascarene Highs, feeding more moisture into India. Result: Good rainfall, strong monsoon, even if El Niño is present.
      • Negative IOD: Western Indian Ocean is cooler, eastern side is warmer. This pulls away monsoon winds from India and weakens the rainfall.
    • Key point: IOD is a “local driver” sitting in the Indian Ocean, which can either amplify or cancel out ENSO’s effect.

    3. ENSO–IOD Interaction:

    • Monsoon outcome is not decided by ENSO or IOD alone, but by how they combine:
      • El Niño + Positive IOD: IOD can cancel El Niño’s bad effect (1997 monsoon was near normal).
      • El Niño + Negative IOD: Worst-case combo, often brings severe droughts.
      • La Niña + Positive IOD: Both reinforce each other, leading to very heavy rainfall and flood risk.
      • ENSO Neutral + Positive/Negative IOD: IOD becomes the deciding factor.

    The Big Picture:

    • Pacific Walker Circulation is the “conveyor belt” moving rising and sinking air across the Pacific and Indian Oceans.
      • When it shifts east (El Niño): India gets less rain.
      • When it strengthens west (La Niña): India gets more rain.
    • IOD modifies this system locally in the Indian Ocean-  it can either buffer or worsen ENSO’s impact.
    • The Mascarene Highs act as the main “engine room” for cross-equatorial winds, but the Walker circulation and IOD decide how strong that engine runs.
    • Madden–Julian Oscillation (MJO): An eastward-moving pulse of cloud and rainfall that travels around the equator every 30–60 days.
      • MJO decides the intra-seasonal variability: when it rains heavily (active phase) and when dry breaks occur.

     

    [UPSC 2012] Consider the following statements:

    1. The duration of the monsoon decreases from southern India to northern India.

    2. The amount of annual rainfall in the northern plains of India decreases from east to west.

    Which of the statements given above is/are correct?

    Options: (a) 1 Only (b) 2 Only (c) Both 1 and 2* (d) Neither 1 nor 2

     

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

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

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

    Select the correct answer using the code given below:

    (a) 1 only  (b) 2 only * (c) Both 1 and 2  (d) Neither 1 nor 2

     

  • India’s only active volcano in Andaman’s Barren Island erupts

    Why in the News?

    Barren Island, which is not only India’s but South Asia’s only active volcano, has erupted twice in a span of eight days.

    barren island

    About Barren Island:

    • Location: In the Andaman Sea, about 138–140 km northeast of Port Blair, within the Andaman and Nicobar Islands (India).
    • Unique Status: The only confirmed active volcano in the Indian subcontinent and South Asia, lying on the volcanic arc between Sumatra (Indonesia) and Myanmar.
    • Geophysical Features: Roughly circular island (~3 km diameter); volcanic crater located 0.5 km from shore, rising to 354 m above sea level and classified as a stratovolcano made of lava, volcanic ash, and rock fragments.
    • Volcanic Activity
      • First Recorded Eruption: 1787.
      • Notable Eruptions: 1789, 1795, 1803–04, 1852, 1991, 2017, and minor eruptions in 2025.
      • 1991 Eruption: Lasted ~6 months, destructive to local fauna.
      • Volcanic Explosivity Index (VEI): Generally low, around 2.
    • Geological Significance:
      • Age of Flows: Oldest subaerial lava flows dated to 1.6 million years ago.
      • Crust: Built on 106 million-year-old oceanic crust.
      • Tectonics: Part of the subduction zone where the Indian Plate meets the Burmese Plate.
      • Research Value: Critical for geological and volcanic studies as India’s only active volcano.

    Note:

    Although there are no active volcanoes in mainland India, there are some extinct and dormant volcanoes in the country. These are: Narcondam Island (dormant, A&N Islands); Deccan Plateau (18.51°N 73.43°E; extinct, Maharashtra); Baratang Island (mud volcanoes; active, A&N Islands); Dhinodhar Hills (extinct, Gujarat); Dhosi Hill (extinct, Haryana–Rajasthan border); Tosham Hills (extinct, Haryana); and Loktak Lake (Supervolcanic caldera, Manipur).

    [UPSC 2018] Consider the following statements:

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

    Which of the statements given above is/are correct?

    (a) 1 only*

    (b) 2 and 3

    (c) 3 only

    (d) 1 and 3

  • Commissioning of Oju Hydel Project

    Why in the News?

    The Union Environment Ministry has cleared the 2,220 MW Oju Hydroelectric Project on the Subansiri River in Taksing, Upper Subansiri district, near the China border.

    About the Oju Hydroelectric Project:

    • Capacity & Location: A 2,220 MW run-of-river hydro project on the Subansiri River at Taksing, Upper Subansiri district, Arunachal Pradesh, near the China border.
    • Infrastructure:
      • Dam: 93 m high, 355 m long concrete gravity dam.
      • Tunnels: Two diversion tunnels, 14.17 km headrace tunnel.
      • Powerhouse: Underground, with 8 turbines of 231.25 MW each.
    • Hydrology: Catchment area 9,827 sq. km; average annual yield 11,339 million cubic meters.

    Significance of the Project:

    • Hydro Cascade: Largest in Subansiri basin, upstream of projects like Niare, Naba, Nalo, Dengser, Upper & Lower Subansiri, making it vital for basin-wide energy planning.
    • Border Security: Strengthens India’s strategic presence near China border through infrastructure development.
    • Energy Security: Provides clean power at ~₹5.65/kWh, supporting renewable targets and reducing fossil dependence.

    Back2Basics: Subansiri River

    Commissioning of Oju Hydel Project

    • Also called the Gold River, it is the largest tributary of the Brahmaputra, about 518 km long with a 32,640 sq. km basin.
    • It originates in Lhuntse County, Tibet, flows through Upper Subansiri district (Arunachal Pradesh), and enters India via the Miri Hills.
    • The Upper Subansiri refers to its Himalayan origin stretch, while the Lower Subansiri marks its descent into the Assam Valley through Lower Subansiri district.
    • It joins the Brahmaputra at Jamurighat/Majuli Island in Assam; key tributaries are Rangandi, Dikrong, Kamle, Char Chu, and Tsari Chu.
    • Known for floods, rapids, and hydropower projects like the Lower Subansiri, the river also carries cultural importance in Tibet’s Tsari region.

  • Earth gains new tiny ‘Quasi-Moon’ 2025 PN7

    Earth gains new tiny 'Quasi-Moon' 2025 PN7

    Why in the News?

    Astronomers have confirmed the discovery of asteroid 2025 PN7, Earth’s latest quasi-moon.

    About Quasi-Moon 2025 PN7:

    • Discovery: First detected on 2 August 2025 by the Pan-STARRS 1 telescope in Hawaii; confirmed in September 2025 as Earth’s newest quasi-satellite.
    • Orbit: Circles the Sun, not Earth, but remains near Earth due to a 1:1 orbital resonance – meaning it completes one solar orbit in the same time as Earth.
    • Distance from Earth: At closest, ~299,000 km, similar to the Moon’s distance.
    • Physical Traits: Roughly 19 metres wide, very faint (magnitude 26.4), requiring large telescopes to track.
    • Orbital Parameters: Semi-major axis 1.003 AU (same as Earth), eccentricity 0.108 (slightly oval), inclination just under 2°.
    • Arjuna Nature: Fits the Arjuna asteroid class criteria – extremely Earth-like orbit, low eccentricity, and low inclination, making it appear as a temporary companion.
    • Stability: Expected to remain a quasi-satellite for ~128 years before shifting into another orbital configuration.

    What is the Arjuna Asteroid Class?

    • Overview: A rare group of near-Earth objects (NEOs) with orbits closely matching Earth’s path around the Sun.
    • Etymology: Originated with the discovery of asteroid 1991 VG by astronomer Robert H. McNaught at the Siding Spring Observatory in Australia in 1991.
    • Name Origin: Inspired by Arjuna from the Mahabharata – symbolising fast-moving and elusive objects.
    • Special Traits:
      • Can approach Earth more closely than most asteroid families.
      • Sometimes become temporary mini-moons or quasi-satellites.
      • Have relatively low relative velocities, making them attractive for spacecraft missions.
    • Scientific Importance:
      • Offer natural laboratories for studying orbital resonance and gravitational effects.
      • Useful for testing asteroid mining and redirection technologies.
      • Significant for planetary defence, since tracking their movements refines collision risk predictions.
    [UPSC 2023] Consider the following pairs:

    Object in space – Description

    1. Cepheids – Giant clouds of dust and gas in space

    2. Nebulae – Stars which brighten and dim periodically

    3. Pulsars – Neutron stars that, are formed when massive stars run out of fuel and collapse

    How many of the above pairs are correctly matched?

    (a) Only one * (b) Only two (c) All three (d) None

     

  • 7 Natural Heritage Sites from India added to UNESCO’s Tentative List

    Why in the News?

    Seven natural heritage sites from India were added to UNESCO’s Tentative List of World Heritage Sites, raising India’s tally from 62 to 69 places.

    About the 7 newly added UNESCO Tentative List Sites:

    Site

    Detailed Facts
    Deccan Traps (Panchgani & Mahabaleshwar, Maharashtra) • One of the world’s largest volcanic provinces (~66 mya)
    • Basalt lava flows covering ~500,000 sq. km
    • Step-like “trap” topography, fossil beds, red bole layers
    • Linked to end-Cretaceous mass extinction
    • Part of Western Ghats; within Koyna Wildlife Sanctuary
    St. Mary’s Island Cluster (Udupi, Karnataka) • Four islands in Arabian Sea near Udupi
    • Famous for hexagonal/polygonal rhyolitic lava columns (~85–88 mya)
    • Formed during breakup of India–Madagascar
    • Declared National Geo-heritage Monument (2016)
    • Rare acidic lava formations, unique in India
    Meghalayan Age Caves (East Khasi Hills, Meghalaya) • Mawmluh Cave is type locality for Meghalayan Age (~4,200 years ago)
    • Records global drought event in late Holocene
    • Meghalaya has longest sandstone cave (Krem Puri – 24.5 km)
    • Karst systems preserve stalagmites, paleoclimate archives
    • Culturally significant to Khasi tribes; threatened by mining
    Naga Hill Ophiolite (Nagaland) • 200 km belt of uplifted oceanic crust & mantle rocks
    • Composed of gabbro, peridotite, basalt
    • Formed at supra-subduction / mid-ocean ridge zones
    • Later thrust onto Indian continental plate
    • Only major ophiolite exposure in India; National Geological Monument
    Erra Matti Dibbalu (Red Sand Hills, Andhra Pradesh) • Quaternary-age coastal red sand mounds (~12,000–18,500 years old)
    • Spread over 5 km near Visakhapatnam
    • Derived from ancient Khondalite rocks
    • Record climate shifts, sea-level oscillations, monsoon history
    • Mesolithic–Neolithic artefacts found; National Geo-heritage Monument
    Tirumala Hills (Tirupati, Andhra Pradesh) • Famous for Eparchaean Unconformity (1.5 billion-year gap)
    • Boundary between Archaean gneiss & Proterozoic quartzites
    • Hosts Silathoranam natural arch, rare erosional landform
    • Hills rise to ~900 m; part of Cuddapah Basin
    • Combines geological, tectonic, and spiritual significance
    Varkala Cliff (Kerala) • Coastal cliff escarpment up to 80 m high
    • Exposes Mio-Pliocene Warkalli Formation (1.3–25 mya)
    • Fossiliferous sedimentary rocks beside sea (rare in India)
    • Natural springs and aquifers emerge from cliff face
    • Declared National Geological Monument; major tourism hub (Papanasam Beach)

    Back2Basics: UNESCO’s Tentative List

    • What is it: An inventory of cultural and natural sites that a member country plans to nominate for future World Heritage status.
    • Requirement: A site must stay on this list for at least one year before nomination.
    • Purpose: Allows UNESCO to assess Outstanding Universal Value (OUV) and plan conservation.
    • Note: Not all sites on the Tentative List become World Heritage Sites.
    • World Heritage Sites (WHS): Cultural, natural, or mixed sites recognised under the 1972 World Heritage Convention for their OUV.
    • Categories of WHS:
      • Cultural: Temples, monuments, forts, archaeological remains.
      • Natural: National parks, caves, biodiversity zones.
      • Mixed: Sacred landscapes with both cultural and natural value.
    • 10 Criteria for Selection: A site must satisfy at least one of these:
      • Cultural (i–vi): Masterpiece of human genius; interchange of values; unique cultural testimony; outstanding architecture/landscape; example of settlement/land use; linked to events, traditions, or ideas of universal significance.
      • Natural (vii–x): Exceptional natural beauty; example of Earth’s history; ecological or biological processes; key habitats for in-situ biodiversity conservation and threatened species.
    • India: It is currently a member of the UNESCO World Heritage Committee (2021–2025 term); Has 42 World Heritage Sites (34 cultural, 7 natural, 1 mixed).
    [UPSC 2024] Consider the following properties included in the World Heritage List released by UNESCO:

    1. Shantiniketan 2. Rani-ki-Vav 3. Sacred Ensembles of the Hoysalas 4. Mahabodhi Temple Complex at Bodhgaya

    How many of the above properties were included in 2023?

    Options: (a) Only one (b) Only two* (c) Only three (d) All four

     

  • In news: Cauvery River Dispute

    Why in the News?

    On the Cauvery dispute, Karnataka CM has said that water will be released to Tamil Nadu since the rainfall is adequate, while stressing the Mekedatu Dam’s role in water balance and clean energy.

     

    Back2Basics: Cauvery River

    • Origin & Course: Rises at Talakaveri, Brahmagiri range (Kodagu, Karnataka); flows ~800 km through Karnataka & Tamil Nadu into the Bay of Bengal.
    • Catchment: Spreads across Karnataka, Tamil Nadu, Kerala, Puducherry.
    • Tributaries: Harangi, Hemavati, Kabini, Suvarnavathi, Bhavani.
    • Nature: Perennial river, sustained by both advancing & retreating monsoons.
    • Protected Areas: Cauvery WLS, Biligirirangan Hills, Pushpagiri, Muthathi, Ranganathittu, Bhimeshwari, Nagarhole, Bandipur.

    About Cauvery Water Sharing Dispute:

    • Colonial Origins: Began in 1892 (Madras Presidency vs Mysore); 1924 Agreement (50 years, expired 1974).
    • Post-Independence: Disputes arose with dam projects by Karnataka (1960s–80s); Supreme Court referred to Cauvery Water Disputes Tribunal (CWDT).
    • Interim Phase: Cauvery River Authority (CRA, 1998) issued temporary orders.
    • CWDT Final Award (2013): Tamil Nadu 419 TMC, Karnataka 270, Kerala 30, Puducherry 7.
    • Karnataka’s Obligation: In normal years, release 177.25 TMC to TN, including 123.14 TMC in SW monsoon.
    • Challenges: Disputes sharpen in weak monsoons, triggering use of a “distress formula”.
    • Legal Basis: Governed by Article 262, Inter-State River Water Disputes Act, 1956; Seventh Schedule entries 17 (State List) & 56 (Union List).

    cauvery

    About Mekedatu Dam Project:

    • Location: Deep gorge at Cauvery–Arkavathi confluence near Kanakapura, Karnataka.
    • Design: Balancing reservoir of ~66 TMC capacity.
    • Objectives: Provide Bengaluru drinking water, generate 400 MW hydropower, regulate flows to TN in drought years.
    • Importance: Karnataka argues it benefits both states by ensuring regulated water release.
    • Opposition: Tamil Nadu objects, fearing reduced downstream availability.
    • Current Status: Karnataka insists on moving ahead, requiring Centre & TN’s clearance.
    [UPSC 2022] Gandikota canyon of South India was created by which one of the following rivers?

    Options: (a) Cauvery (b) Manjira (c) Pennar* (d) Tungabhadra

     

  • Places in news: Erra Matti Dibbalu

    Why in the News?

    This newscard is an excerpt from a photo published in ‘The Hindu’.

    About Erra Matti Dibbalu:

    • Location: Found between Visakhapatnam and Bheemunipatnam in Andhra Pradesh, stretching 5 km along the coast, with widths ranging from 200 m to 2 km.
    • Meaning: In Telugu, “Erra Matti” means red soil and “Dibbalu” means mounds, describing the reddish sand dunes.
    • Geological Heritage: Listed among the 34 National Geological Heritage Monument Sites of India by the Geological Survey of India (GSI).
    • Formation: Created around 12,000–18,500 years ago through the combined effect of tectonic activity (2.5 million–11,000 years ago), sea-level changes, monsoonal variability, and global climatic shifts.
    • Composition: Derived mainly from Khondalite rocks of the Eastern Ghats hinterland, with the red colour due to oxidation of iron-rich sediments.

    Significance:

    • Geological Value: Acts as a paleo-environment indicator, providing evidence of climate change, sea-level fluctuations, and coastal evolution during the late Quaternary period.
    • Archaeological Importance: Artefacts from Mesolithic and Neolithic periods and sediment layers dating back to the Late Pleistocene epoch have been found here.
    • Conservation Status: Declared a National Geo-heritage Monument (2016) and included in UNESCO’s Tentative List of World Heritage Sites (2025) for global recognition and protection.
    • Unique Landscape: Features badland topography with sand dunes, buried channels, gullies, and dendritic drainage patterns.
    • Rare Formation: Only two other similar red sand dune systems exist globally—the Teri dunes in Tamil Nadu and one site in Sri Lanka.
    [UPSC 2014] When you travel in Himalayas, you will see the following:

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

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

    Options: (a) 1 and 2 only (b) 1, 2 and 4 only (c) 3 and 4 only (d) 1, 2, 3 and 4*

     

  • Freshwater Aquifers found beneath the Atlantic Ocean

    Why in the News?

    The recent discovery of a massive freshwater aquifer beneath the Atlantic shelf opens new possibilities for addressing future global water shortages.

    About the Aquifer:

    • Location: Offshore northeastern U.S., stretching possibly from New Jersey to Maine.
    • Expedition 501: Drilled up to 400 m beneath the seabed, retrieving nearly 50,000 liters of water and thousands of sediment cores.
    • Findings: Fresh and nearly fresh water discovered at both shallower and deeper depths than expected, confirming a vast, pressurized aquifer.
    • Global Context: Similar offshore aquifers are suspected or identified near South Africa, Hawai‘i, Jakarta, and Canada’s Prince Edward Island.

    Possible Origins of the Freshwater:

    • Glacial Meltwater Hypothesis: Ancient ice sheets during lower sea levels allowed meltwater to seep into porous sediments.
    • Connected Aquifer Hypothesis: Modern terrestrial groundwater may still slowly flow offshore through geologic formations.
    • Significance: Determining whether the aquifer is finite fossil water or a renewable source is critical for deciding its usability.

    Significance of the Discovery:

    • Water Security: Could supply a metropolis the size of New York City for centuries, if managed sustainably.
    • Climate Change Resilience: Offers backup options as coastal aquifers face saltwater intrusion and urban demand rises (e.g., Cape Town’s “Day Zero” crisis in 2018).
    • Scientific Impact: First direct, systematic drilling of offshore freshwater for mapping and salinity profiling.
    [UPSC 2021] With reference to the water on the planet Earth, consider the following statements:

    1.The amount of water in the rivers and lakes is more than the amount of groundwater.

    2.The amount of water in polar ice caps and glaciers is more than the amount of groundwater.

    Which of the statements given above is/are correct?

    Options: (a) 1 only (b) 2 only* (c) Both 1 and 2 (d) Neither 1 nor 2