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The Himalayan System
2.1 Formation and Geological History
The Himalayas are fold mountains formed by the collision of the Indian plate (moving northward at ~5 cm/year) with the Eurasian plate, beginning ~70 million years ago (late Cretaceous). The ancient Tethys Sea that lay between these plates was compressed and its sediments folded upward, creating the world's highest and youngest mountain system. The process continues today — the Himalayas still rise at ~5 mm per year, and this tectonic stress causes frequent earthquakes in the region.
Three Stages of Himalayan Formation:
- Stage 1 (~70–40 Ma): Initial collision; Tethys sediments begin folding; proto-Himalayas form.
- Stage 2 (~25–15 Ma): Main uplift phase; Greater Himalayas and Lesser Himalayas emerge; Tethys Sea disappears.
- Stage 3 (~5–2 Ma): Shivalik Hills form from the debris deposited by rivers flowing from younger Himalayas; intermontane valleys (Duns) formed.
2.2 The Three Parallel Ranges
1. Great Himalayas / Himadri (Inner Himalayas)
- Highest and most continuous range; average elevation ~6,000 m
- Contains all peaks above 6,000 m including India's highest peaks
- Perpetually snow-covered; home to valley glaciers (Siachen: 76 km — longest in Karakoram)
- Key peaks: Kangchenjunga (8,586 m) — India's highest, Nanda Devi (7,816 m) — India's 2nd highest, Kamet (7,756 m)
- Note: K2 (8,611 m) is in Pakistan-administered territory
2. Lesser Himalayas / Himachal (Middle Himalayas)
- Average elevation 3,700–4,500 m; width 60–80 km
- Contains famous hill stations: Shimla, Mussoorie, Nainital, Darjeeling
- Contains Pir Panjal range, Dhauladhar range, Mahabharat Lekh
- Rich in coniferous forests; major pastures (Bugyals) used for summer grazing
- The famous Valley of Flowers (UNESCO World Heritage) in Uttarakhand's Chamoli district lies here
3. Outer Himalayas / Shiwaliks (Sub-Himalayas)
- Youngest range (2–5 million years old); elevation 600–1,500 m; width 10–50 km
- Composed of unconsolidated gravel, sand, and conglomerate from Himalayan erosion
- Prone to severe erosion; separates into individual ranges with wide gaps
- Duns — longitudinal valleys between Shiwaliks and Lesser Himalayas: Dehra Dun, Patli Dun, Kotli Dun, Haridwar Dun
2.3 Regional Divisions of Himalayas
| Region | States/Area | Key Feature |
|---|---|---|
| Punjab Himalaya | J&K, Himachal Pradesh | Between Indus and Sutlej rivers; 560 km |
| Kumaon Himalaya | Uttarakhand | Between Sutlej and Kali rivers; 320 km; Nanda Devi peak |
| Nepal Himalaya | Nepal border | 800 km; Everest (8,849 m), Kangchenjunga |
| Assam/NE Himalaya | Sikkim, Arunachal Pradesh | Between Tista and Brahmaputra; 720 km |
2.4 Major Mountain Passes (PYQ 2023 — Map Question)
| Pass | State | Elevation (m) | Connected Regions |
|---|---|---|---|
| Nathu La | Sikkim | 4,310 | India–China trade route (reopened 2006) |
| Shipki La | Himachal Pradesh | 3,933 | Sutlej valley; India–Tibet trade |
| Rohtang | Himachal Pradesh | 3,978 | Manali–Lahaul-Spiti; Atal Tunnel bypasses it |
| Zoji La | J&K (Ladakh) | 3,529 | Srinagar–Leh highway; strategic route |
| Baralacha La | Himachal/Ladakh | 4,890 | Manali–Leh Highway |
| Khardung La | Ladakh | 5,359 | World's highest motorable road |
| Pal Ghat (Palakkad Gap) | Kerala | ~150 | Gap in Western Ghats; NH 544; coastal railway |
| Thal Ghat | Maharashtra | ~583 | Mumbai–Nashik; major railway/road pass |
| Bhor Ghat (Bhore Ghat) | Maharashtra | ~627 | Mumbai–Pune; Western Railway |