78. Physiography of India

CORE Key Points at a Glance

1. 1

   Six Major Physiographic Divisions

   • Himalayan Mountains, Indo-Gangetic Plain, Peninsular Plateau
   • Great Indian Desert (Thar), Coastal Plains, Islands
   • Each division differs in geological age, origin, and economic use
   • Together they cover all of India's 32.87 lakh sq km
2. 2

   Himalayas — Stretch and Dimensions

   • Extend 2,500 km from Indus Gorge (west) to Brahmaputra Gorge (east)
   • Average width 150–400 km
   • India's highest peak is Kangchenjunga (8,586 m) on the Sikkim-Nepal border
   • Still rising at ~5 mm per year due to ongoing plate collision
3. 3

   Three Parallel Himalayan Ranges

   • Greater Himalayas (Himadri) — avg height 6,000 m; perpetually snow-covered
   • Lesser Himalayas (Himachal) — avg 3,700–4,500 m; hill stations and forests
   • Outer Himalayas (Shiwaliks) — 600–1,500 m; youngest; prone to erosion
4. 4

   Indo-Gangetic Plain — World's Largest Alluvial Plain

   • 2,400 km long, 150–300 km wide, covering ~7.5 lakh sq km
   • Divided into four zones: Bhabar, Terai, Bangar (old alluvium), Khadar (new alluvium)
   • Khadar is the most fertile — renewed annually by Himalayan rivers
   • Supports over 40% of India's food grain output
5. 5

   Peninsular Plateau — Ancient Gondwana Origin

   • One of the oldest and most stable landmasses (Gondwanaland origin)
   • Composed mainly of Deccan Trap basalts and Archaean gneisses and schists
   • Average elevation 600–900 m; covers ~16 lakh sq km (half of India)
   • Source of India's richest coal, iron ore, bauxite, and manganese deposits
6. 6

   Western Ghats (Sahyadri) — Key Facts

   • Run 1,600 km from the Tapi River (north) to Kanyakumari (south)
   • Highest peak Anamudi (2,695 m) in Kerala — highest south of the Himalayas
   • Form a continuous watershed separating the narrow Konkan coast from Deccan Plateau
   • UNESCO World Heritage biodiversity hotspot (2012)
7. 7

   Eastern Ghats — Discontinuous Range

   • Discontinuous, averaging 600 m height
   • Cut across by Mahanadi, Godavari, Krishna, and Kaveri rivers
   • Highest peak Jindhagada (1,690 m) in Andhra Pradesh
   • Rich in bauxite (Visakhapatnam) and iron ore deposits
8. 8

   Shivaliks and Dun Valleys

   • Shivalik Hills (Outer Himalayas) are geologically youngest
   • Intermontane valleys between Shivaliks and Lesser Himalayas are called Duns
   • Key Duns: Dehra Dun (85 km long, 25 km wide), Patli Dun, Kotli Dun
   • Formed ~5–2 million years ago from debris eroded from younger Himalayas
9. 9

   Coastal Plains — East vs West

   • Eastern coastal plain is wider (100–120 km) with major deltas of Mahanadi, Godavari, Krishna, and Kaveri
   • Western coastal plain is narrower (10–80 km)
   • Western plain divided into Konkan (north), Goa, and Malabar (south) sections
   • Total coastline: 7,516 km (including island territories)
10. 10

    India's Two Island Groups

    • Andaman & Nicobar (Bay of Bengal) — 572 islands, 8,249 sq km
    • Southern tip Indira Point at 6°45'N is India's southernmost point
    • Lakshadweep (Arabian Sea) — 36 coral atolls, 32 sq km (smallest UT)
    • A&N commands the Malacca Strait; strategically vital
11. 11

    Important Mountain Passes (PYQ 2023)

    • Nathu La (Sikkim, 4,310 m), Shipki La (Himachal, 3,933 m)
    • Rohtang Pass (Himachal, 3,978 m), Zoji La (J&K, 3,529 m)
    • Pal Ghat (Kerala, 150 m) — lowest gap in Western Ghats
12. 12

    Thar Desert — Key Characteristics

    • Lies west of the Aravallis in Rajasthan; area ~2.09 lakh sq km in India
    • Extends into Pakistan as the Cholistan Desert
    • Landforms: sandy plains (Erg), barren rocky plateaus (Reg), shifting barchan dunes
    • Salt lakes: Sambhar, Didwana, Pachpadra; India's highest solar energy potential
13. 13

    Shivalik Formation — PYQ 2021 Q3

    • Formed through continental collision of Indian and Eurasian plates
    • Tethys Sea sediments were folded and uplifted
    • Shivaliks are the youngest range, formed 5–2 million years ago
    • Debris eroded from the younger Himalayas built up the Shivalik structure