Key Points at a Glance

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

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

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

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

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

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)

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

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

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)

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

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

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

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