BharatNotes Why this chapter matters for UPSC: Landform types, their formation via plate tectonics, and their economic/environmental significance form a recurring strand in GS1 Physical Geography. India is a textbook case — it has the world's youngest high fold mountains (Himalayas), ancient residual mountains (Aravalli, Eastern Ghats), a classic horst-graben system (Satpura–Narmada–Tapi), the world's largest alluvial plain (Indo-Gangetic), and multiple plateau types (Deccan, Chota Nagpur, Malwa). This chapter also links to disaster management (GLOFs, cyclones) and environmental geography.
PART 1 — Quick Reference Tables
Types of Mountains
| Type | Formation Mechanism | India Examples | Global Examples | Key Trait |
|---|---|---|---|---|
| Fold Mountains | Two tectonic plates collide (convergent boundary); rock strata buckle and fold upward | Himalayas (young fold), Aravalli (old fold) | Alps, Andes, Rockies, Atlas | Highest mountains; folded rock strata visible; young = steep peaks |
| Block Mountains (Horst) | Rock block uplifted between two parallel faults; adjacent blocks sink as grabens | Satpura (horst); Vindhyas; Western Ghats (escarpment) | Vosges (France), Sierra Nevada (USA), Black Forest (Germany) | Flat/gentle top; steep scarp faces; flanked by rift valleys |
| Volcanic Mountains | Successive lava/ash accumulation from volcanic vents | Barren Island (Andaman — India's only active volcano) | Kilimanjaro (Africa), Fujiyama (Japan), Mauna Loa (Hawaii), Mt St Helens (USA) | Conical shape; can be active, dormant, or extinct |
| Residual (Relict) Mountains | Ancient mountains worn down by millions of years of erosion; only hard rock remains | Aravalli, Eastern Ghats, Nilgiris | Sierras of Spain, Catskills (USA), Highlands of Scotland | Old, rounded, low-elevation; composed of hard crystalline rock |
Note: The Aravalli appears in both fold (old fold mountain — it was folded during the Proterozoic) and residual (it is now a heavily eroded, worn-down remnant) categories. NCERT Class 6 treats it as a residual mountain; UPSC sources classify it as an ancient fold mountain.
Landforms — Comparative Overview
| Landform | Definition | India Example | Global Example | Key Relevance |
|---|---|---|---|---|
| Mountain | Elevated land > 600 m; narrow, steep summit | Himalayas, Karakoram | Alps, Andes, Rockies | River source; orographic rainfall; biodiversity corridors |
| Hill | Elevated land < 600 m; gentler, rounded top | Shivalik Hills, Nilgiris (lower parts) | South Downs (UK) | Tourism; moderate agriculture |
| Plateau | Elevated, broad, relatively flat land with steep sides (tableland) | Deccan Plateau, Chota Nagpur Plateau | Tibetan Plateau, Colorado Plateau | Rich in minerals; pastoralism; ancient geology |
| Plain | Flat, low-lying land; formed by alluvial/glacial/fluvial deposition | Indo-Gangetic Plain | Amazon Basin, Mississippi Valley, Eurasian Steppe | Agriculture; high population density; transport corridors |
| Valley | Low-lying land between mountains/hills; carved by rivers or glaciers | Kashmir Valley, Brahmaputra Valley | Rhine Valley, Rift Valley (Africa) | Settlement, agriculture, tourism |
| Glacier | Slow-moving river of ice formed by compacted snow | Gangotri, Siachen, Zemu | Antarctic ice sheet, Greenland ice sheet, Franz Josef Glacier | Freshwater reservoir; source of glacial rivers |
Types of Plateaus
| Plateau Type | Definition | India Example | Global Example |
|---|---|---|---|
| Intermontane Plateau | Completely surrounded by mountains on all sides; highest & most extensive | Ladakh Plateau (between Great Himalayas & Karakoram) | Tibetan Plateau ("Roof of the World"), Bolivian Altiplano |
| Piedmont Plateau | Lies at the foot of mountains; only one side borders mountains | Malwa Plateau (India); Patagonian Plateau (Argentina) | Piedmont Plateau (eastern USA) |
| Continental Plateau | Far from mountains; formed by broad uplift or lava outpouring | Deccan Plateau (partly); Arabian Plateau | Colorado Plateau (USA), Australian Shield |
| Dissected Plateau | Heavily eroded by rivers; looks mountainous; sharp relief | Chota Nagpur Plateau (cut by Damodar, Subarnarekha) | Ozark Plateau (USA) |
| Volcanic (Lava) Plateau | Formed by repeated horizontal lava flows covering original topography | Deccan Plateau (Deccan Traps basalt flows) | Columbia Plateau (USA), Ethiopian Highlands |
PART 2 — Detailed Notes
2.1 Fold Mountains — Formation Mechanism
Step-by-step formation of fold mountains:
- Two continental tectonic plates approach each other (convergent plate boundary)
- Sedimentary rocks accumulated at the bottom of ancient seas between the plates (geosynclines) are subjected to immense lateral compressional forces
- These rocks buckle, fold, and thrust upward over millions of years, building mountain ranges
- Rock strata show visible folding — synclines (downward folds) and anticlines (upward folds)
Case Study — The Himalayas:
- ~80 million years ago (mya), India was ~6,400 km south of Asia, moving north at ~9 m per century (~9 cm/year)
- The Tethys Sea (an ancient ocean) lay between the Indian and Eurasian plates
- ~50 mya: The Indian plate collided with the Eurasian plate (Eocene); Tethys Sea sediments were compressed and folded upward → the Himalayas began rising; the Tethys Sea closed ~50 mya as the two plates met
- Himalayan building continued after the initial collision; northward speed dropped by ~half (~4–5 cm/year today)
- The Indian plate is still moving north at ~4–5 cm per year → the Himalayas are still rising at 5–6 mm per year (GPS-measured; some sections up to 10 mm/year)
- Marine fossils (sea shells, ammonites) are found in Himalayan rocks — direct evidence of the Tethys Sea floor origin
Divisions of fold mountains — old vs young:
| Category | Age | India Example | Global Example | Characteristics |
|---|---|---|---|---|
| Young Fold | < 65 mya | Himalayas (~40–50 mya) | Alps, Andes, Rockies | Still high, rugged, seismically active |
| Old Fold | > 250 mya | Aravalli (~1.8 bya), Eastern Ghats (Archean) | Appalachians (USA), Urals (Russia) | Worn down, low-elevation, geologically stable |
Other young fold mountain ranges worldwide:
- Alps (Europe): African plate + Eurasian plate collision; ~30–40 mya
- Andes (South America): Nazca oceanic plate subducting under South American plate; highly active volcanically
- Rockies (North America): Pacific plate subduction; forms the continental divide
2.2 Block Mountains (Horsts) and Rift Valleys (Grabens)
Formation mechanism:
- When tensional (pulling apart) forces act on the Earth's crust, parallel faults develop
- The land between two faults may be uplifted → forms a horst (block mountain)
- The land between two faults may subside/sink → forms a graben (rift valley)
- The horst has a relatively flat top and steep escarpment (scarp) faces
India's classic horst–graben system:
- Satpura Range = horst (block mountain); forms an east-west wall
- Narmada Valley (north of Satpura) = graben (rift valley); Narmada flows west through it
- Tapi Valley (south of Satpura) = graben (rift valley); Tapi flows west through it
- Both Narmada and Tapi are west-flowing rivers because they follow the graben topography — they do NOT form deltas (unlike most peninsular rivers); they form estuaries
- Seismic refraction data confirms the horst nature of Satpura and the graben character of the Narmada and Tapi valleys
Western Ghats: The escarpment of the Western Ghats (steep west-facing cliff) has a block mountain character — formed partly by faulting when the Indian subcontinent separated from the African continent (~130–150 mya, Gondwana breakup). The abrupt western face and gentle eastern slope (towards the Deccan Plateau) is characteristic of block-faulted topography.
Global examples:
- Rhine Valley (Germany/France) = graben; Vosges Mountains and Black Forest = horsts on either side
- East African Rift System = series of grabens; Lake Tanganyika, Lake Malawi, Lake Turkana lie in these grabens
- Jordan Valley / Dead Sea = classic graben; Dead Sea is ~430–440 m below sea level (dropping ~1 m/year due to water extraction; ~440 m as of 2025) — the lowest land surface on Earth
2.3 Volcanic Mountains
Formation: Magma rises from the mantle through vents; successive eruptions accumulate lava and ash layers building conical mountains ("mountains of accumulation").
Types by activity:
| Type | Definition | India Example | Global Example |
|---|---|---|---|
| Active | Erupts regularly | Barren Island (Andaman) — major eruption 2022–23; thermal activity through 2024–25 | Kilauea (Hawaii), Stromboli (Italy), Etna (Sicily) |
| Dormant | Not erupted in historical times but not extinct | Narcondam Island (Andaman) | Fujiyama (Japan — last erupted 1707), Vesuvius (Italy) |
| Extinct | No recorded eruption; no volcanic activity | Many old volcanic cones | Ben Nevis (Scotland), Mount Kenya |
India: Barren Island (Andaman & Nicobar) is India's only confirmed active volcano; it has repeated eruptive phases — a major eruption occurred in 2022–2023 (ash plumes up to 15,000 ft) with continued thermal and eruptive activity documented through 2024–2025 (Smithsonian Global Volcanism Program).
Deccan Traps ≠ volcanic mountain: The Deccan Plateau is a lava plateau (flood basalt), not a volcanic mountain. It formed from massive, relatively low-viscosity lava flows over ~600,000–800,000 years, ~66 mya. The link to the Chicxulub asteroid impact remains scientifically debated — one hypothesis is that the impact seismic shockwaves re-energized the Deccan eruptions.
2.4 Residual (Relict) Mountains
Formation: These are remnants of ancient mountains (originally fold or other types) that have been worn down by millions of years of erosion by wind, water, glaciers, and weathering. Only the hardest, most resistant rocks survive.
Characteristics: Low elevation; rounded summits; ancient crystalline (Precambrian) rock; geologically stable; no seismic risk.
India Examples:
| Mountain | Age | State(s) | Composed of |
|---|---|---|---|
| Aravalli Range | Rocks: ~3.3–2.5 bya (Banded Gneissic Complex — Paleoarchean to Neoarchean); range formed ~1.8 bya (Paleoproterozoic Aravalli Orogeny) | Rajasthan, Gujarat, Haryana, Delhi | Quartzite, schist, marble, granite |
| Eastern Ghats | ~2.9 bya (Archean) | AP, Telangana, Odisha, TN | Khondalites, charnockites, granites |
| Nilgiris | ~2.5 bya | Tamil Nadu–Kerala border | Ancient gneisses and schists |
Aravalli — Key UPSC Facts:
- India's oldest mountain range; one of the world's oldest fold mountain systems (by age of rocks: ~3.3–2.5 billion years; by mountain-building event: ~1.8 bya — Precambrian Aravalli Orogeny)
- Longest in India: ~692 km (Gujarat to Delhi)
- Ecological function: Acts as a natural barrier preventing the Thar Desert from expanding eastward; recharge zone for Delhi's groundwater
- Average elevation today: ~300–900 m (originally comparable to the Alps — heavily eroded)
2.5 India's Major Landform Regions
A. The Himalayan Region (Young Fold Mountains)
Age: ~40–50 million years old (young fold mountains)
Three parallel ranges (north to south):
Range Local name Average altitude Key features Greater Himalayas Himadri > 6,000 m Highest; continuous; Mt Everest, K2 region; permanent snow/glaciers Lesser Himalayas Himachal 1,500–4,500 m Most famous hill stations (Shimla, Mussoorie, Nainital, Darjeeling); Pir Panjal, Dhaula Dhar, Mahabharat range Outer Himalayas Shivaliks 600–1,500 m Youngest & outermost; dun valleys (Dehradun, Patli Dun); highly erosion-prone Highest peaks:
Peak Height Location Note Mt Everest 8,848.86 m (official, Dec 8, 2020 — joint Nepal-China survey) Nepal–China border World's highest; 3rd highest in the world by some older counts due to rounding K2 (Godwin-Austen) 8,611 m Pakistan-administered Kashmir (PoK) World's 2nd highest; technically in Pakistan-controlled territory Kangchenjunga 8,586 m Sikkim–Nepal border Highest peak entirely within/bordering India; world's 3rd highest; sacred to Sikkimese people Nanda Devi 7,816 m Uttarakhand Highest peak entirely within India's undisputed territory (if K2 is excluded) Still rising: 5–6 mm per year (GPS-measured); Indian plate moves north at ~4–5 cm/year
Earthquake zone: Himalayas are in Seismic Zone IV–V; major earthquakes occur regularly (2015 Nepal, 2005 Kashmir)
B. Indo-Gangetic Plain (Alluvial Plain)
- Formation: Alluvial deposits from Himalayan rivers (Indus, Ganga, Brahmaputra systems) accumulated in a tectonic foredeep (depression) between the Himalayas and the Peninsular plateau
- Extent: ~3,200 km long (Punjab to Assam); widths vary — narrow in Punjab, wider in UP/Bihar
- Alluvium depth: 1,300–1,400 m on the southern margins; increases towards the Himalayan foothills; in some parts of the Gangetic trough the sediment column is several kilometres deep
- Soil: Two types:
- Khadar (newer alluvium): near river channels; renewed by floods annually; more fertile; lighter in colour
- Bhangar (older alluvium): above flood level; contains kankar (calcite nodules); slightly less fertile
- Population density: Exceeds 800–1,000 persons per sq km in core areas (UP density: 828/sq km per 2011 census; Bihar: >1,100/sq km); among world's most densely populated agricultural regions
- Population supported: ~500–700 million people across the Indo-Gangetic–Brahmaputra alluvial belt
- Agriculture: Wheat (Rabi), rice (Kharif), sugarcane, pulses; irrigation from canals and groundwater (Punjab–Haryana canal network is one of the world's largest)
- "Granary of India": Punjab, Haryana, UP combined produce ~50% of India's wheat
C. Deccan Plateau
- Type: Continental plateau (partly volcanic/lava plateau); one of the world's oldest geological formations
- Age: Archaean shield (~3 billion years old); overlaid by Deccan Traps basalt flows (~66 mya)
- Deccan Traps: Massive flood basalt event lasting ~600,000–800,000 years (spanning ~66.3–65.5 mya); produced ~2 million km² of basalt covering much of peninsular India; formed during roughly the same time as the Chicxulub asteroid impact (~66.052 mya)
- Tilt: Slopes gently from west to east → most peninsular rivers (Godavari, Krishna, Mahanadi, Cauvery) flow east into Bay of Bengal
- Rock and soil: Basalt → weathers into black cotton soil (regur) — ideal for cotton cultivation; high clay content; moisture-retentive
- Cotton belt: Maharashtra, Gujarat, Telangana, MP — entire cotton-growing belt sits on Deccan Traps basalt
D. Chota Nagpur Plateau
- Type: Dissected plateau; heavily eroded by Damodar, Subarnarekha, and other rivers
- Location: Primarily Jharkhand; extends into Chhattisgarh, Odisha, West Bengal, Bihar
- Minerals (key UPSC fact):
Mineral Significance Coal (Damodar Valley) India's largest metallurgical + thermal coal belt; Jharia, Raniganj, Bokaro coalfields Iron ore (Singhbhum) High-grade hematite + magnetite; basis of Jamshedpur (Tata Steel) Manganese ~50%+ of India's manganese reserves Mica Hazaribagh = global mica hub; used in electrical insulators, cosmetics Bauxite, Chromite, Copper Additional significant deposits - Industrial hub: Jamshedpur (steel), Bokaro (steel), Dhanbad (coal), Rourkela (steel in Odisha)
- "Ruhr of India" — analogous to Germany's industrial coal–steel belt
E. Coastal Plains
| Feature | Western Coastal Plain | Eastern Coastal Plain |
|---|---|---|
| Width | 10–65 km (narrow; 10–25 km in some stretches, wider in north/south extremes) | 100–120 km average; up to 200 km in delta regions |
| Between | Western Ghats and Arabian Sea | Eastern Ghats and Bay of Bengal |
| States | Kerala, Karnataka, Goa, Maharashtra | Tamil Nadu, Andhra Pradesh, Odisha, West Bengal |
| Rivers | Short; west-flowing; form estuaries (Narmada, Tapi, Periyar) | Form large deltas (Mahanadi, Godavari, Krishna, Cauvery, Ganga–Brahmaputra) |
| Rainfall | Very heavy (orographic; 2,000–4,000 mm on windward/Western Ghats side) | Moderate; depends on NE monsoon in Tamil Nadu |
| Hazards | Coastal erosion, Arabian Sea cyclones (less frequent) | Bay of Bengal cyclones (more frequent and intense); storm surge; delta sinking |
| Special names | Konkan (Maharashtra–Goa), Malabar (Karnataka–Kerala) | Coromandel (Tamil Nadu), Northern Circar (AP) |
PART 3 — Analysis Frameworks
3.1 Significance of Landforms
| Landform | Benefits | Environmental Challenges |
|---|---|---|
| Himalayas | Water towers (feed Indus, Ganga, Brahmaputra); orographic rainfall; biodiversity hotspot; India's northern barrier | Glacial retreat; GLOFs (Glacial Lake Outburst Floods — Chamoli 2021); seismic risk (Zone IV–V); landslides |
| Aravalli / Old Mountains | Groundwater recharge (Delhi's lifeline); biodiversity corridor; check Thar expansion | Mining and urbanisation destroying the range; Delhi NCR encroachment |
| Indo-Gangetic Plain | Agricultural heartland; most fertile soil; transport corridor | Groundwater depletion (Punjab "dark zones"); air pollution; floods; land subsidence |
| Deccan Plateau | Black cotton soil (cotton, soybean); mineral wealth; power generation (rivers for hydro) | Drought vulnerability (low rainfall variability); mining displacement |
| Chota Nagpur Plateau | Mineral–industrial base ("Ruhr of India"); forests; tribal cultural heritage | Tribal displacement (mines); deforestation; river pollution (Damodar — once India's most polluted river) |
| Western Coastal Plain | Fisheries; spices; ports (JNPT, Cochin, Mangalore); tourism; rubber, coconut | Coastal erosion; sea-level rise; salinity intrusion; urbanisation |
| Eastern Coastal Plain | Major deltas (rice bowl); aquaculture; ports (Chennai, Visakhapatnam, Paradip) | Cyclones (super cyclone Amphan 2020, Fani 2019); delta erosion; coastal flooding |
3.2 Plate Tectonics and India's Landforms
| Plate Boundary Type | Geological Result | India/South Asia Example |
|---|---|---|
| Convergent (continent–continent) | Fold mountains; no subduction; both plates buckle | Himalayas (India–Eurasia) |
| Convergent (oceanic–continental) | Subduction; volcanic arc; trench | Andaman–Nicobar arc (subduction of Indian plate under Eurasian — Burma microplate) |
| Divergent | Rift valleys; new ocean crust | Arabian Sea formation (when India separated from Africa ~130 mya) |
| Transform | Horizontal movement; earthquakes | Sagaing Fault (Myanmar) — affects NE India |
PART 4 — Prelims Checklist
| # | Fact | Why It Matters |
|---|---|---|
| 1 | Himalaya = young fold mountains; ~40–50 mya | Most common MCQ |
| 2 | Aravalli = India's oldest mountain range, one of the world's oldest; rocks ~3.3–2.5 billion years old (BGC); range formed ~1.8 bya | Say "India's oldest" not "world's oldest" — African greenstone belts are older |
| 3 | Aravalli is also classified as a residual mountain (NCERT Class 6) | Dual classification — context matters |
| 4 | Satpura = horst (block mountain); Narmada + Tapi valleys = grabens | Classic pair; rift valley rivers |
| 5 | Narmada and Tapi flow west through grabens → form estuaries, NOT deltas | High-frequency trap |
| 6 | Deccan Plateau = lava plateau (Deccan Traps basalt); ~66 mya; NOT formed by plate collision | Common confusion with fold mountains |
| 7 | Black cotton soil (regur) = derived from Deccan Traps basalt weathering; moisture-retentive; ideal for cotton | Economic geography link |
| 8 | Everest height = 8,848.86 m (official, Dec 8, 2020 — Nepal–China joint survey) | "8,849 m" is a common rounding; "2023 revised" is wrong |
| 9 | Kangchenjunga = 8,586 m; 3rd highest in world; highest peak bordering India (Sikkim–Nepal) | Often confused with Nanda Devi |
| 10 | K2 = 8,611 m; world's 2nd highest; in Pakistan-administered Kashmir (PoK) — NOT within India | Sovereignty nuance |
| 11 | Nanda Devi = 7,816 m; highest peak entirely within undisputed Indian territory | Distinction from Kangchenjunga (Nepal border) |
| 12 | Indo-Gangetic Plain: Khadar (new alluvium, near river) vs Bhangar (old alluvium, above flood level, kankar nodules) | Direct prelims MCQ |
| 13 | Chota Nagpur Plateau: ~50% of India's manganese; Hazaribagh = global mica hub; Jharia = largest coalfield | Mineral geography |
| 14 | Damodar River valley = India's largest coal-bearing region; was once India's most polluted river | Environmental geography |
| 15 | Western Coastal Plain is narrower than Eastern Coastal Plain (10–65 km vs 100–200 km) | Direct comparison MCQ |
| 16 | Western coast rivers → estuaries; Eastern coast rivers → deltas (because West coast rivers are short, fast, little sediment) | Critical rivers concept |
| 17 | Barren Island (Andaman) = India's only active volcano; major eruption 2022–2023; activity ongoing through 2024–2025 | Unique geography fact; update from older "2017–2018" phrasing |
| 18 | Dead Sea = lowest land on Earth (~430–440 m below sea level, dropping ~1 m/year) = graben | Global geography |
| 19 | Tibetan Plateau = intermontane plateau; Malwa Plateau = piedmont plateau; Deccan = continental/lava plateau | Plateau type classification |
| 20 | Indian plate moves north at ~4–5 cm/year; Himalayas rise at ~5–6 mm/year | Plate tectonics data |
| 21 | Tethys Sea sediments → folded → Himalayas; Tethys Sea closed ~50 mya (Eocene); marine fossils found in Himalayan rocks | Direct evidence concept; avoid "20 mya" — correct is ~50 mya |
| 22 | East African Rift System = series of grabens; Dead Sea, Red Sea also rift-related | Global comparison |
| 23 | Gondwana breakup ~130 mya → India separated from Africa → Western Ghats escarpment formed | Geological history |
| 24 | Orographic rainfall: Mountains force winds to rise → condensation on windward side → rain shadow on leeward | Applied climate–landform link |
| 25 | Bhangar soil contains kankar (impure calcium carbonate nodules) | Direct NCERT MCQ |
[Additional] 6a. Chamoli Disaster 2021 — Rock-Ice Avalanche and Himalayan Hazard Cascades
The chapter mentions GLOFs and landslides in the context of the Himalayas but has no coverage of the Chamoli disaster of February 7, 2021 — the most studied Himalayan hazard event in recent decades. Crucially, it was NOT a glacier burst or GLOF (as widely misreported), but a rock-and-ice avalanche. The disaster and subsequent events (Joshimath 2023, Sikkim GLOF 2023) define the current UPSC GS3 Disaster Management + GS1 Physical Geography intersection.
Key Terms — Himalayan Hazard Events:
| Term | Meaning |
|---|---|
| Rock-and-ice avalanche | A mass of rock and glacier ice that detaches from a steep mountain face and descends at high speed; frictional heat from the long fall can melt all ice instantly, creating a high-volume debris flow; this is what happened at Chamoli 2021 — NOT a GLOF |
| GLOF (Glacial Lake Outburst Flood) | A rapid discharge of water from a glacial lake when the ice/moraine dam fails, is overtopped, or breached by calving ice; can release millions of cubic metres of water in minutes; caused by rockfall into the lake creating a wave (seiche) or by moraine instability |
| Moraine | Debris (rock, sediment) deposited by a glacier; a moraine dam holds water in a glacial lake; as glaciers retreat, more moraine-dammed lakes form and moraine dams can become unstable |
| Seiche | An internal wave created inside a lake when a mass (ice, rock) falls into it; can be large enough to overtop and breach a moraine dam → triggers a GLOF |
| Debris flow | A fast-moving slurry of rock, soil, and water; more mobile and destructive than a landslide; can travel tens of kilometres; what the Chamoli rock-ice avalanche became after descending into the valley |
| Run-of-river hydropower | A hydropower plant that uses river flow directly (without large reservoir storage); requires tunnels to divert water to turbines; Rishiganga and Tapovan-Vishnugad projects were run-of-river projects |
[Additional] Chamoli Disaster 2021 — What Actually Happened, Cascading Damage, and Policy Response (GS3 — Disaster Management / GS1 — Physical Geography):
What happened — scientific verdict:
Published in Science (Shugar et al., July 16, 2021, DOI: 10.1126/science.abh4455 — 52 co-authors from institutions in 16 countries):
| Parameter | Verified Fact |
|---|---|
| Date | February 7, 2021 |
| Location | Chamoli district, Uttarakhand |
| Source | Steep north face of Ronti Peak (~5,600 m) above Ronti Gad |
| What fell | ~27 million cubic metres of rock and glacier ice (~80% rock, ~20% ice) |
| Mechanism | Rock-ice mass descended ~3,200 m; frictional heat converted all ice to water instantly; transformed into a massive debris flow |
| Path | Ronti Gad → Rishiganga River → Dhauliganga River |
| Scour height | Debris scoured valley walls up to 220 metres above the valley floor |
| What it was NOT | NOT a GLOF; NOT a "glacier burst" — the early media description was incorrect; peer-reviewed consensus = rock-and-ice avalanche |
Infrastructure destroyed:
| Project | Capacity/Value | Status |
|---|---|---|
| Rishiganga Hydroelectric Project (private) | 13 MW | Completely swept away |
| Tapovan-Vishnugad NTPC Project | 520 MW; ~₹1,500 crore estimated damage | Severely damaged; tunnels blocked; 140 workers trapped |
| Dhauliganga Dam | — | Washed away |
Casualties:
- ~83 bodies recovered + 36 body parts; ~204 people missing
- Approximately 140 workers at the Tapovan site at the time; rescue teams penetrated only ~100 m into the 2 blocked tunnels (debris inflow continued)
- NDRF, SDRF, Indian Army, and ITBP deployed; rescue operations continued for weeks
Key follow-up Himalayan hazard events (2023):
Joshimath land subsidence (January 2023):
- Joshimath town (Chamoli district, Uttarakhand) — gateway to Badrinath and Hemkund Sahib — began visibly sinking in January 2023
- Over 1,400 houses affected (of 2,152 total); 181 buildings critically unsafe and evacuated
- Ground cracks up to 2 feet wide and half a kilometre long appeared; subsidence of 5–30+ cm
- Causes: Joshimath sits on ancient landslide debris (sand and stone, NOT bedrock); unplanned construction; inadequate drainage; suspected contribution from NTPC Tapovan-Vishnugad tunnel passing ~1 km from town
- ISRO/SAC InSAR remote sensing monitoring confirmed subsidence
Sikkim GLOF — October 4, 2023 (South Lhonak Lake):
- A multihazard cascade: ~14.7 million cubic metres of frozen lateral moraine collapsed into South Lhonak Lake → generated a 20-metre seiche wave → breached the moraine dam → released ~50 million cubic metres of lake water
- Floodwaters reached Teesta III Dam (Chungthang Dam, ₹16,000 crore) at midnight before gates could be opened → dam destroyed in minutes
- ~25,900 buildings inundated/damaged/destroyed; 31 major bridges lost; ~270 km² agricultural land affected
- 92 confirmed dead by October 18, 2023; additional missing persons
- Downstream Teesta River levels rose by up to 20 feet (6.1 m) — floods reached Bangladesh
NDMA policy response — National GLOF Risk Mitigation Programme (NGRMP):
- Targets 195 high-risk glacial lakes out of ~7,500 glacial lakes identified within India (part of ~28,000 across the broader Himalayas)
- Programme integrates: high-resolution satellite mapping, SAR interferometry, Automated Weather and Water Stations (AWWS), glacier-lake surveys, and early warning systems
- Accelerated after the 2023 Sikkim GLOF
UPSC synthesis: Chamoli 2021 = GS3 Disaster Management + GS1 Physical Geography. Key exam facts: February 7, 2021; Chamoli district Uttarakhand; rock-and-ice avalanche (NOT GLOF/glacier burst) from Ronti Peak; ~27 million cubic metres of rock + ice; Ronti Gad → Rishiganga → Dhauliganga; 220 m scour height; Rishiganga Project (13 MW) swept away; Tapovan-Vishnugad NTPC (520 MW) severely damaged; ~200 killed/missing; NDRF + SDRF + Army + ITBP deployed; Science paper = Shugar et al. 2021 = 52 co-authors; Joshimath subsidence = January 2023 = landslide debris foundation + unplanned development; Sikkim GLOF = October 4 2023 = South Lhonak Lake = moraine breach = Teesta III Dam destroyed; NDMA NGRMP = 195 high-risk glacial lakes. Prelims trap: Chamoli 2021 was NOT a GLOF (it was a rock-ice avalanche that was widely misidentified in early media reports); GLOF = glacial lake outburst (Sikkim 2023 WAS a GLOF); Joshimath is in Chamoli district (NOT Rudraprayag or Uttarkashi); Tapovan-Vishnugad project = NTPC (NOT private; Rishiganga was the private 13 MW project).
[Additional] 6b. Western Ghats UNESCO World Heritage Site 2012 — Gadgil vs Kasturirangan
The chapter covers the Western Ghats as a physiographic and biodiversity region but has no UNESCO WHS coverage and no mention of the landmark Gadgil Committee vs Kasturirangan Committee debate — the most contested environmental governance question in modern India, directly linked to GS3 Environment & Biodiversity and GS2 Governance.
Key Terms — Western Ghats UNESCO and ESA:
| Term | Meaning |
|---|---|
| Western Ghats UNESCO WHS | Official name: "Western Ghats"; WHL No. 1342; inscribed 2012 at the 36th WHC session (Saint Petersburg); serial nomination across 39 component sites in 4 states (Kerala, Karnataka, Tamil Nadu, Maharashtra); criteria (ix)(x) — two natural criteria |
| ESA (Ecologically Sensitive Area) | A category under the Environment (Protection) Act 1986 to restrict activities that could damage fragile ecosystems; can prohibit quarrying, mining, large construction; declared by MoEF&CC by central notification |
| WGEEP (Gadgil Report) | Western Ghats Ecology Expert Panel — chaired by Prof. Madhav Gadgil (IISc ecologist); report submitted August 31, 2011; recommended designating 100% of the Western Ghats as ESA with three ecological sensitivity zones |
| HLWG (Kasturirangan Report) | High-Level Working Group — chaired by Dr. K. Kasturirangan (former ISRO Chairman); report submitted April 15, 2013; recommended designating only 37% (~60,000 sq km) of Western Ghats as ESA — the "natural landscape" only |
| Natural vs Cultural Landscape | Kasturirangan's distinction: "natural landscape" = 90%+ forested area (protected); "cultural landscape" = human-dominated, largely non-forest (development allowed) |
[Additional] Western Ghats UNESCO WHS 2012 — Criteria, Serial Sites, and ESA Controversy (GS1 — Art & Culture/Physical Geography / GS3 — Environment / GS2 — Governance):
UNESCO inscription facts:
| Parameter | Detail |
|---|---|
| Official name | Western Ghats |
| WHL Number | 1342 |
| Inscription year | 2012 |
| WHC Session | 36th session — Saint Petersburg, Russia |
| Type | Serial natural heritage nomination |
| Component sites | 39 sites in 7 sub-clusters |
| States | 4 states — Kerala (20 sites), Karnataka (10 sites), Tamil Nadu (6 sites), Maharashtra (4 sites) |
| Total area | 795,315 hectares |
| UNESCO criteria | Natural criteria (ix) and (x) |
UNESCO criteria — what each means:
| Criterion | What it recognises |
|---|---|
| (ix) — Geological/biological processes | Gondwanaland breakup; Indian plate isolation and northward drift; monsoon formation after Himalayan collision; speciation processes over 130+ million years of isolation |
| (x) — Biodiversity and endemism | One of the world's 8 "hottest" biodiversity hotspots; ≥325 globally threatened species; exceptional plant and animal endemism; finest non-equatorial tropical evergreen forests |
Note: The UNESCO inscription covers 4 states (Kerala, Karnataka, Tamil Nadu, Maharashtra). The 2024 MoEF&CC draft ESA notification covers 6 states (adding Gujarat and Goa) — these are different frameworks with different geographies.
WGEEP (Gadgil) vs HLWG (Kasturirangan) — core comparison:
| Parameter | WGEEP — Gadgil (2011) | HLWG — Kasturirangan (2013) |
|---|---|---|
| Area assessed | 1,29,037 sq km (142 taluks) | 1,64,280 sq km (188 taluks) |
| ESA extent recommended | 100% of Western Ghats | 37% (~60,000 sq km) — "natural landscape" only |
| High-priority zone | ESZ-1 = ~60% (strict protection) | All proposed ESA treated uniformly |
| Mining / quarrying | Banned in ESZ-1 and ESZ-2 | Restricted only in natural landscape |
| Hydropower | Decommissioning recommended in highest zones | More permissive |
| Governance model | Gram sabha-level decentralisation | Central/state regulatory approach |
| Fate | Rejected by state governments (livelihood and development concerns); mining and plantation industry opposition | Adopted as basis for MoEF notification process; still not fully notified |
ESA notification status — August 2024 draft:
- MoEF&CC issued a fresh draft ESA notification on August 3, 2024 (the latest in a long series of draft notifications going back to 2014)
- Proposed area: 56,825 sq km across all 6 Western Ghats states (Gujarat, Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu)
- Prohibited: quarrying, mining, large infrastructure development in proposed ESA
- Public objection deadline: September 29, 2024
- As of 2025–26: the ESA notification remains in DRAFT form — NOT finalised
- Resistance from state governments (especially Goa, Kerala, Karnataka, Maharashtra), farming communities, and mining/plantation industries
Why the Gadgil–Kasturirangan debate matters for UPSC:
The Western Ghats ESA debate encapsulates core GS2-GS3 governance tensions:
- Development vs conservation: State governments argue strict ESA restrictions would make millions of farmers, plantation workers, and miners jobless; environmentalists argue without protection the hotspot will collapse
- Centre vs States: Environment (Protection) Act 1986 allows MoEF to declare ESAs centrally, overriding state preferences — a federal tension
- Science vs politics: Gadgil = pure ecological science; Kasturirangan = attempt to balance science with socioeconomic realities; both criticised — Gadgil for ignoring 50 million people who live in the Western Ghats, Kasturirangan for inadequate ground verification
UPSC synthesis: Western Ghats = GS1 Physical Geography + GS1 Art & Culture + GS3 Environment + GS2 Governance. Key exam facts: WHL No. 1342; inscribed 2012 at 36th WHC (Saint Petersburg); 39 component sites in 7 sub-clusters; 4 states = Kerala (20) + Karnataka (10) + Tamil Nadu (6) + Maharashtra (4); area = 795,315 ha; criteria = (ix)(x) — two natural criteria; one of world's 8 "hottest" biodiversity hotspots; ≥325 globally threatened species; Gadgil Report (WGEEP, 2011) = 100% ESA → rejected; Kasturirangan Report (HLWG, 2013) = 37% (~60,000 sq km) ESA → adopted as basis; 2024 draft notification = 56,825 sq km (6 states) = NOT yet finalised. Prelims trap: Western Ghats WHS criteria = (ix)(x) — NATURAL criteria (NOT cultural); UNESCO inscription = 4 states (Gujarat and Goa are NOT part of the 2012 inscription but ARE in the 2024 ESA draft notification — different documents); WHL = 1342 (NOT same as Ajanta 242 or Ellora 243); Gadgil report = rejected by states (Kasturirangan = accepted for notification process); ESA notification = NOT finalised as of 2026.
PART 5 — PYQ-Style Questions
Prelims:
Which of the following is the correct order of the Himalayan ranges from north to south? (a) Shivaliks → Lesser Himalayas → Greater Himalayas (b) Greater Himalayas → Lesser Himalayas → Shivaliks (c) Lesser Himalayas → Shivaliks → Greater Himalayas (d) Greater Himalayas → Shivaliks → Lesser Himalayas
The Narmada river flows in a rift valley between which two landforms? (a) Vindhyas and Eastern Ghats (b) Satpura and Vindhyas — forming a graben between the two horsts (c) The Narmada flows in a graben (rift valley) north of the Satpura horst (d) Western Ghats and the Deccan Plateau
Kangchenjunga, the highest peak bordering India, is located on the border between: (a) India and China (b) India (Sikkim) and Nepal (c) India and Bhutan (d) India and Pakistan
The black cotton soil found in Maharashtra and Gujarat is derived from the weathering of: (a) Granite of the Archaean shield (b) Basalt of the Deccan Traps (c) Alluvium deposited by Himalayan rivers (d) Laterite formed under heavy rainfall conditions
Which of the following pairs is correctly matched? (a) Chota Nagpur Plateau — Intermontane plateau (b) Malwa Plateau — Dissected plateau (c) Tibetan Plateau — Piedmont plateau (d) Chota Nagpur Plateau — Dissected plateau
"Khadar" and "Bhangar" refer to which of the following? (a) Types of black soil in the Deccan Plateau (b) Types of alluvium in the Indo-Gangetic Plain (c) Two types of coastal landforms (d) Wind-deposited and river-deposited soil types in Rajasthan
Barren Island, India's only active volcano, is located in: (a) Lakshadweep (b) Andaman and Nicobar Islands (c) Gujarat coast (d) Off the coast of Goa
Consider the following statements about the Aravalli Range: I. It is the oldest mountain range in India. II. It prevents the Thar Desert from expanding eastward. III. Its rocks date to approximately 2.5 billion years ago. IV. It is classified as a young fold mountain. Which statements are correct? (a) I and IV only (b) I, II and IV only (c) I, II and III only (d) All of the above
Mains:
"The physiographic diversity of India is both a boon and a challenge." Elaborate with reference to the Himalayan region, the Indo-Gangetic Plain, and the Deccan Plateau. (250 words)
Discuss the formation of the Himalayas and explain how their continued uplift is linked to natural hazard risk in the Indian subcontinent. (150 words)
"Plateau regions of India are mineral-rich but environmentally fragile." Examine this statement with reference to the Deccan and Chota Nagpur plateaus. (250 words)
