Topic 2: The Himalayas — Origin, Divisions, Peaks, Passes & Glaciers

1. India's Physiographic Divisions — A Quick Overview

Before drilling into the Himalayas, place them in India's six-fold physiographic frame:

This topic concentrates on division 1 — The Himalayas, which include both the Trans-Himalayan ranges to the north of Indus-Tsangpo Suture and the Purvanchal hills to the east of Brahmaputra.

2. Origin of the Himalayas

The Himalayas are young fold mountains — the youngest and highest mountain system on Earth, still rising today. Two frameworks explain how they formed: the older geosynclinal idea and the modern, accepted plate-tectonic model. Both agree the crumpled sediments of an ancient sea (the Tethys) were squeezed into folds between two landmasses.

2.1 The Geosynclinal (Tethys) Theory

Proposed by Kober (and refined by Argand), this classical model pictures a long, shallow sea — the Tethys geosyncline — lying between two rigid forelands: Angaraland (Laurasia) to the north and Gondwanaland to the south.

• Over millions of years, rivers dumped thick sediments into the Tethys, which slowly subsided under the load.
• The two forelands then converged, acting like a giant vice; the sediments were compressed, folded and thrust upward into ranges.
• Kober called the folded belt the orogen and the stable blocks the kratogen.

2.2 The Plate-Tectonic Theory (modern, accepted)

The plate-tectonic model explains the driving force the geosyncline theory could not. The Indian Plate broke away from Gondwana (~140 million years ago), drifted rapidly north-east and, around 50–55 million years ago (Eocene), collided with the Eurasian Plate.

• The intervening Tethys Sea closed; its sediments (plus slices of oceanic crust) were scraped off and crumpled into the Himalayan ranges.
• The two continental plates could not subduct fully, so crust thickened and shortened, pushing the mountains ever higher.
• The join between the plates is the Indus–Tsangpo Suture Zone (ITSZ), marked by ophiolites (fragments of old ocean floor).
• Convergence continues at ~5 cm/yr; the Himadri still rises ~1 cm/yr, and the belt is squeezed along the great thrusts (MCT, MBT, HFT).

3. Longitudinal Series — The Parallel Ranges (North → South)

Running roughly parallel from the Indus–Tsangpo Suture southward to the plains, the Himalayas form four longitudinal belts (five if the Trans-Himalaya is counted separately). Each belt is bounded by a great thrust fault: ITSZ → MCT → MBT → HFT. Altitude and age both decrease southward — the Shiwaliks are youngest and lowest.

Bounding thrusts, N→S: Indus–Tsangpo Suture Zone (ITSZ) · Main Central Thrust (MCT) · Main Boundary Thrust (MBT) · Himalayan Frontal Thrust (HFT / MFT).

• Trans-Himalaya: lies in the rain-shadow — a high, cold desert (Ladakh); holds India's longest glaciers outside the poles (Siachen).
• Himadri: the water-tower — almost all Himalayan glaciers and the headwaters of the Indus, Ganga & Brahmaputra rise here.
• Himachal: the "hill-station belt" — longitudinal valleys (Duns and vales) and karewas of Kashmir sit within it.
• Shiwalik: built of debris shed by the rising ranges; loose sediment makes it the most landslide- and erosion-prone belt.

4. Regional / Longitudinal Sub-Divisions (West → East)

Along the W-E axis (Sydney Burrard's classification, used in NCERT), the Himalayas are split into four regional sectors, separated by the great north-flowing rivers that gouge them. Eastward of the Brahmaputra, the ranges swing south as the Purvanchal.

4.1 Punjab / Kashmir Himalaya

• Westernmost sector; widest (~400 km).
• Contains all four parallel ranges plus the Karakoram, Ladakh, Zaskar (Trans-Himalayan) and Pir Panjal, Dhauladhar (Lesser).
• Famous valleys: Kashmir Valley (between Pir Panjal & Zaskar) — once a Pleistocene lake (Karewa lake-bed deposits, ideal for saffron & apple); Nubra Valley & Suru Valley in Ladakh.
• Karewas: thick lacustrine deposits of unconsolidated gravel, sand, silt & clay on the flanks of Kashmir Valley — extensively used for Zaffran (saffron) cultivation, especially around Pampore.
• Key passes: Zoji La (3 528 m, Srinagar-Leh), Burzil La, Banihal (Jawahar Tunnel, 2 832 m, opens Kashmir round-the-year), Khardung La (5 359 m, Leh-Siachen), Pir Panjal Pass.
• Important lakes: Wular (largest fresh-water in India), Dal, Pangong Tso, Tso Moriri.

4.2 Himachal & Kumaun Himalaya

• From the Sutlej to the Kali (Sharda) river, in HP & Uttarakhand.
• Hosts Nanda Devi (7 816 m) — the highest peak entirely in Indian territory.
• Famous "Doabs of the hills" — Garhwal & Kumaun Himalaya with sources of Yamuna (Yamunotri), Bhagirathi (Gangotri), Mandakini (Kedarnath), Alaknanda (Badrinath) — the Char Dham.
• Major valleys: Kangra, Kullu, Spiti-Lahaul, Bhagirathi.
• Key passes: Shipki La (HP-Tibet, on Sutlej route), Rohtang (3 978 m, Manali-Lahaul, tunnel since Oct 2020), Bara Lacha La, Niti, Lipulekh (Uttarakhand-Kailash Manasarovar), Mana Pass, Thaga La.
• Lakes: Nainital, Bhimtal, Sat Tal, Roopkund (the "skeleton lake").
• Famous hill stations: Shimla, Manali, Dharamshala, Mussoorie, Nainital, Ranikhet, Almora.

4.3 Nepal Himalaya

• Longest sector (~800 km); largely outside Indian territory but its eastern fringe lies in Sikkim & North Bengal.
• Carries the greatest concentration of 8 000-m peaks — Everest, Kanchenjunga, Lhotse, Makalu, Cho Oyu, Annapurna, Dhaulagiri, Manaslu.
• Kanchenjunga (8 586 m) — highest peak in Indian territory proper (Sikkim border).
• Major rivers from this sector: Kosi (with its 7 tributaries — Sapta-Kosi), Gandak, Karnali, Mahakali.
• Indian portion has Singalila ridge, Darjeeling hills, the famous Tiger Hill sunrise.
• Major pass: Nathu La & Jelep La (Sikkim-Tibet on the old silk route).

4.4 Assam Himalaya

• From Tista (east) to the Brahmaputra (Dihang) gorge; covers Bhutan and Arunachal Pradesh.
• Eastern extremity bends sharply south at the Namcha Barwa syntaxial bend — the Brahmaputra makes its famous "U-turn" here.
• Lower altitudes than Nepal Himalaya but steepest slopes and highest rainfall (Mawsynram in Meghalaya gets 11 873 mm — though Meghalaya is Peninsular, not Himalayan).
• Major peaks: Namcha Barwa (7 756 m), Kula Kangri (7 538 m, Bhutan), Chomo Lhari (7 314 m).
• Major rivers entering India: Dihang (Brahmaputra), Lohit, Subansiri, Manas, Kameng.
• Key passes: Bomdi La (Arunachal-Tibet), Diphu La, Yongyap La, Tunga Pass.
• Strategically the most sensitive sector — runs along the McMahon Line.

4.5 The Purvanchal — Himalayas' eastern offshoot

• After Namcha Barwa, the ranges swing southward into a series of N-S running parallel ranges along the India-Myanmar border — these are the Purvanchal Hills.
• From north to south: Patkai Bum → Naga Hills → Manipur Hills → Mizo / Lushai Hills → Tripura Hills → (Chittagong Hills, Bangladesh).
• Highest peak: Saramati (3 826 m, Nagaland).
• Composed of strongly folded soft sedimentary rocks — sandstones & shales — much lower than the main Himalayas.
• Densely forested, home to many indigenous tribes; the Loktak Lake (Manipur) with its phumdis is famous, as is the Keibul Lamjao National Park (only floating NP).
• The Purvanchal forms India's natural eastern frontier with Myanmar; Free Movement Regime (FMR, 16 km) was suspended in early 2024.

5. Peaks & Passes

5.1 Major Himalayan peaks (highest first)

5.2 Major Himalayan passes

6. Glaciers & the Snowline

6.1 The Indian Cryosphere

• The Hindu-Kush-Karakoram-Himalaya (HKKH) region is the "Third Pole" — largest reservoir of ice outside the polar caps.
• India holds ~9 575 glaciers (Geological Survey of India + ISRO inventory, ~33 200 km²) — concentrated in the Karakoram, Greater Himalaya & Trans-Himalaya.
• Snow-and-ice melt feeds the perennial flow of Indus, Sutlej, Brahmaputra, Ganga (via Bhagirathi-Alaknanda), Yamuna — supporting ~600 million people downstream.

6.2 Major glaciers of India (longest first)

6.3 The Snowline

The snowline is the lowest altitude at which snow remains permanent year-round. It varies with latitude, aspect, precipitation and slope:

6.4 Why the Himalayan glaciers are retreating

• Global warming — Himalayan warming rate (~0.6 °C/decade) is higher than the global average; elevation-dependent warming is sharper at altitudes > 4 000 m.
• Black-carbon deposition — soot from Indo-Gangetic biomass and diesel reduces ice albedo, accelerating melt.
• Reduced winter snowfall in many basins; rain replacing snow.
• Increased debris cover & supraglacial lakes.

Gangotri is retreating ~18-22 m/year (last decade); Pindari ~5 m/year; many smaller Lahaul-Spiti glaciers have lost > 20 % area since 1970. The 2023 ICIMOD HKH Report warned that up to two-thirds of HKH ice may be lost by 2100 in a 3 °C-warming scenario.

7. Drainage from the Himalayas

The Himalayas feed three great river systems — all perennial, all glacier-and-snow-fed at headwaters, and all antecedent (older than the mountains themselves), which explains why they cut through the ranges via deep gorges.

7.1 Antecedent vs Consequent — why Himalayan rivers cut through

• Antecedent rivers: existed before the mountains uplifted; they kept down-cutting at the rate of the uplift, carving deep gorges. The Indus, Sutlej and Brahmaputra are classic antecedents — they originate north of the Greater Himalaya and pierce through it.
• Consequent rivers: developed after uplift, following the slope; the smaller tributaries of the Yamuna, Ramganga etc. are consequent on the southern slope.

7.2 Himalayan vs Peninsular rivers — exam comparison

8. Syntaxial Bends & the Purvanchal

8.1 What is a syntaxial bend?

A syntaxis is a sharp hairpin bend in a mountain chain where the ranges abruptly change direction — usually because the indenter plate's corner pushes deeper into the over-riding plate. The Himalayas have two great syntaxial bends:

Between the two syntaxes the Himalayan arc is broadly convex-to-the-south with a length of 2 400 km. Beyond each syntaxis the ranges swing perpendicular: Sulaiman-Kirthar ranges south of NW syntaxis (in Pakistan), Purvanchal south of NE syntaxis (in India).

8.2 The Purvanchal in detail

• Rocks & structure: mostly Tertiary sandstones and shales, strongly folded; less metamorphism than main Himalayas.
• Climate: sub-tropical with very heavy rainfall (Mawsynram 11 873 mm — though it is in Meghalaya/Khasi Hills, which is geologically Peninsular not Himalayan).
• Vegetation: dense tropical evergreen and semi-evergreen forests; rich biodiversity — Indo-Burma biodiversity hotspot (one of India's four).
• Tribal home: Naga, Mizo, Manipuri, Tripuri, Khasi (Meghalaya), Garo (Meghalaya), Bodo and others.
• Strategic: Indo-Myanmar border; Free Movement Regime (FMR, 16-km) was suspended in early 2024 in view of Myanmar's instability; fencing on the 1 643-km border has been announced (Feb 2024).

9. Economic & Strategic Significance

9.1 As a climatic divide

• Blocks the cold, dry Central-Asian winds in winter — without the Himalayas, North India would be 6-10 °C colder in January.
• Forces SW Monsoon clouds to ascend → orographic rainfall over the Himalayan front (Cherrapunji, Mawsynram-area pattern) and the Indo-Gangetic plains.
• Retains monsoon moisture south of the chain — explains why peninsular and northern India is humid sub-tropical but Tibet is cold desert.

9.2 As source of perennial rivers

• Three great river systems — Indus, Ganga, Brahmaputra — feed nearly 43 % of India's irrigated area.
• Glacier melt + monsoon rain = perennial flow, supporting kharif & rabi cropping in the Indo-Gangetic plains.

9.3 Hydroelectric power

• Steep gradients + abundant flow → ~30 % of India's hydro potential is in Himalayan rivers.
• Major projects: Bhakra-Nangal (Sutlej), Tehri (Bhagirathi), Salal & Baglihar (Chenab), Nathpa Jhakri (Sutlej), Karcham Wangtoo (Sutlej), Subansiri Lower (Arunachal), Dibang & Lower Demwe (Arunachal — under planning/construction).

9.4 Forest resources

• Vertical zonation creates remarkable bio-diversity — tropical to alpine within 50 km horizontal distance.
• Important timber: deodar, chir pine, oak, fir, spruce, birch.
• Medicinal plants: Yarsagumba (caterpillar fungus), Aconitum, Picrorhiza, Saussurea — high commercial value but over-harvested.
• Indo-Burma and Himalaya are 2 of India's 4 biodiversity hotspots (the other two: Western Ghats and Sundaland).

9.5 Agriculture & horticulture

• Karewas of Kashmir → Saffron (Zaffran), almonds, walnuts.
• HP & Uttarakhand foothills → apples, cherries, plums (Kullu, Shimla, Kinnaur, Nainital).
• Darjeeling & Assam → Tea on the Lesser-Himalaya/Dooars front.
• Terraced farming for rice (Sikkim, Arunachal, Nagaland).

9.6 Tourism & pilgrimage

• Pilgrimage circuits: Char Dham (Yamunotri-Gangotri-Kedarnath-Badrinath), Amarnath, Vaishno Devi, Hemkund Sahib, Kailash-Mansarovar (Tibet, via Lipulekh / Nathu La), Tawang Monastery.
• Adventure tourism: trekking, mountaineering, white-water rafting, ski (Auli, Gulmarg, Manali).
• Hill stations remain a year-round magnet.

9.7 Strategic & defence

• Natural fortress wall — single most important reason India was relatively secure from northern land invasions in pre-modern history (Mongols, Russians never broke through).
• Modern strategic axis lies along three frontiers — LoC (Pakistan), LAC (China), Indo-Myanmar border — all running through Himalayan/Purvanchal terrain.
• BRO (Border Roads Organisation) — strategic road network: Atal Tunnel (2020), Zoji La & Z-Morh tunnels (under construction), Sela Tunnel (opened March 2024, Arunachal — connects Tezpur to Tawang).
• High-altitude warfare experience (Siachen, Galwan 2020, Tawang December 2022).

9.8 Mineral & geothermal potential

• Limited large-scale mineralisation but pockets of copper, lead-zinc (Zawar Kashmir-Ladakh), gypsum, magnesite, marble.
• Geothermal hotspots — Puga (Ladakh), Tapoban & Manikaran (HP); modest power potential.

10. Hazards & Climate-Change Frontline

10.1 Seismic hazard

• Entire Himalayan belt is in BIS Seismic Zones IV & V — among the most active zones on Earth, because India is still under-thrusting Eurasia.
• Notable historical & recent earthquakes:
  • 1934 Bihar-Nepal (M 8.1) — > 10 000 fatalities
  • 1950 Assam-Tibet (M 8.6) — largest continental quake of 20th century
  • 1991 Uttarkashi (M 6.8) — 768 dead
  • 1999 Chamoli (M 6.8) — 100+ dead
  • 2005 Kashmir (M 7.6) — 80 000+ dead (mostly PoK)
  • 2011 Sikkim (M 6.9) — 100+ dead
  • 2015 Gorkha-Nepal (M 7.8) — ~9 000 dead in Nepal, 78 in India
  • 2023 Doda-Kishtwar tremor swarm
• Geophysicists warn of a "Central Himalayan seismic gap" (Uttarakhand-W Nepal) overdue for a great earthquake (M > 8).

10.2 Landslides & flash floods

• Shiwaliks and Lesser Himalaya are highly landslide-prone due to weak unconsolidated sediments, steep slopes, monsoon downpours and unscientific road-cutting.
• NDMA notes ~12.6 % of India's land area is landslide-prone, of which the Himalayas account for the largest share.
• Recent disasters:
  • Kedarnath flash flood (June 2013) — Chorabari glacier-lake outburst + cloudburst; ~5 700 dead.
  • Chamoli (Rishiganga) flood (Feb 2021) — rock-ice avalanche from Ronti Peak triggered debris flow; 200+ dead at Tapovan/NTPC project.
  • Joshimath subsidence (Jan 2023) — ground sinkage attributed to anthropogenic loading + drainage disturbance; entire town reclassified as unsafe.
  • Sikkim Lhonak GLOF (Oct 2023) — South Lhonak Lake breach; Chungthang dam destroyed; 100+ dead/missing.
  • Wayanad landslides (July 2024) — though in Western Ghats, similar mechanism: extreme rainfall + slope failure.

10.3 GLOFs — Glacial Lake Outburst Floods

• As glaciers retreat, melt-water collects in pro-glacial lakes dammed by unstable moraines. When the moraine fails (earthquake, avalanche, overflow), a sudden torrent rushes downstream.
• India has > 7 500 glacial lakes (ISRO 2023 inventory); ~189 are classified high-risk.
• Notable GLOFs: Chorabari 2013 (Kedarnath), South Lhonak Oct 2023 (Sikkim), recurring incidents in Bhutan & Nepal.
• Mitigation: lake-level lowering (Imja-tse Nepal, planned for Lhonak), early-warning systems, no-build downstream zones.

10.4 Glacier retreat & the "Third Pole" crisis

• ICIMOD HKH Report 2023 — at 1.5 °C global warming, ~30-50 % of HKH ice will be lost by 2100; at 3 °C, up to two-thirds.
• "Peak water" — discharge increases short-term as ice melts faster, then declines sharply once glacier mass is depleted; long-term threat to Indus-basin agriculture.
• Karakoram Anomaly — counter-trend; some Karakoram glaciers stable/advancing (see §6.4).

10.5 Climate-change impacts on Himalayan biodiversity

• Upward shift of treeline by ~10-25 m/decade observed (FSI & IIRS studies).
• Range contraction for snow leopard, Himalayan tahr, musk deer.
• Alpine meadows ("bugyals") receding; invasive species (lantana, Parthenium) creeping uphill.
• Pheasant species (monal, tragopan) facing habitat squeeze.

10.6 Carrying-capacity & sustainable mountain development

• NITI Aayog Report (2018) — "Sustainable Development in Indian Himalayan Region" flagged unregulated tourism, hydropower & road expansion as core threats.
• NGT and Supreme Court orders on Char-Dham road widening (the "Ravi Chopra Committee") capped carriageway width to protect the slopes.
• Carrying-capacity studies recommended for Shimla, Manali, Mussoorie, Nainital, Darjeeling, Gangtok — most are exceeded today.
• Eco-sensitive zones (ESZs) and Bhagirathi ESZ (Uttarakhand, since 2012) are policy responses.

11. Current Affairs & Contemporary Relevance (2024–2026)

The Himalayas are a live hazard-and-infrastructure story — verify the latest disaster, glacier and project status before the exam. check for latest update or data

11.1 Hazard frontline

11.2 Infrastructure & strategy

11.3 Why it matters

Recurring exam hooks:

• Four ranges · peaks & passes · syntaxial bends (evergreen Prelims map facts).
• Himalayas as climatic divide & river source (evergreen Mains GS-I).
• GLOFs · Joshimath · glacier retreat · frontier infrastructure (current-affairs overlays).

12. Prelims PYQs (2013–2026)

Objective questions anchored to genuinely tested UPSC themes on Himalayan geography — ranges, peaks, passes and glaciers. Each carries a worked rationale.

13. Mains PYQs + Model Answers

Genuine UPSC GS-I / GS-III themes on the Himalayas. Each carries a full answer skeleton — Introduction → body → Conclusion.

15-Minute Revision Box