RAS Mains Topic 78: Physiography of India

Q: How were the Himalayas formed? Distinguish between Himadri, Himachal, and Shiwaliks.

The Himalayas are **fold mountains** formed by the collision of the Indian and Eurasian plates, compressing Tethys Sea sediments upward (~70–40 million years ago). **Himadri** (Inner Himalayas) is the highest range, averaging 6,000 m, with perpetual snow. **Himachal** (Middle Himalayas) averages 3,700–4,500 m; contains hill stations like Shimla. **Shiwaliks** (Outer Himalayas) are youngest, 600–1,500 m, formed from eroded debris; Duns (like Dehra Dun) lie between them and Himachal.

Study Material

Paper Paper II

Unit 3

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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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

Key facts

Six Major Physiographic Divisions — Himalayan Mountains, Indo-Gangetic Plain, Peninsular Plateau — Great Indian Desert (Thar), Coastal Plains, Islands
Himalayas — Stretch and Dimensions — Extend 2,500 km from Indus Gorge (west) to Brahmaputra Gorge (east) — Average width 150–400 km
Three Parallel Himalayan Ranges — Greater Himalayas (Himadri) — avg height 6,000 m; perpetually snow-covered — Lesser Himalayas (Himachal)
Indo-Gangetic Plain — World's Largest Alluvial Plain — 2,400 km long, 150–300 km wide, covering ~7.5 lakh sq km
Peninsular Plateau — Ancient Gondwana Origin — One of the oldest and most stable landmasses (Gondwanaland origin)

Key Points at a Glance

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
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
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
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
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
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
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
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
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
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
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
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
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

Why does India's physiography matter for RPSC geography?

India's physiography matters for RPSC geography because it explains the country's climate, drainage, agriculture, population distribution, economy, and strategic geography through the physical structure of the land. The National Portal of India describes the Himalayan mountain wall as extending about 2,400 km.

Overview of India's Physical Landscape

India's physiography — the study of its physical landscape — forms the structural foundation for understanding its climate, drainage, agriculture, population distribution, and strategic geography. India's total area is 32.87 lakh sq km (7th largest country; 2.4% of world's land area), hosting 17.5% of the world's population.

The country spans from 37°6'N (J&K) in the north to 8°4'N (Kanyakumari) in the south, and from 68°7'E (Gujarat) in the west to 97°25'E (Arunachal Pradesh) in the east. This latitudinal range of 29° creates remarkable physiographic diversity.

Geological Time Periods

India's land boundary is 15,200 km, while its coastline measures 7,516.6 km (including island territories). This vast territory is structured into six physiographic divisions spanning three fundamentally different geological periods:

Ancient Gondwana Peninsular Shield — over 600 million years old
Recent alluvial Indo-Gangetic trough — Quaternary age
Geologically youngest Himalayan fold mountains — formed through Cenozoic orogeny, 70–2 million years ago

Why Physiography Matters for RPSC

The physical structure of India determines everything from monsoon patterns (Western Ghats force orographic rainfall) to agricultural potential (Indo-Gangetic Plain's fertile alluvium). It also shapes economic activity (coal in Gondwana formations, oil in western coast), strategic corridors (mountain passes), and settlement patterns. RPSC has tested Shiwalik formation, Western Ghats, mountain passes, peninsular plateau features, and coastal plains consistently since 2013.

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PREDICTED Predicted RAS Questions

Based on PYQ trends and 2026 syllabus analysis

1 5M How were the Himalayas formed? Distinguish between Himadri, Himachal, and Shiwaliks. 5 marks · 50 words

Model Answer

The Himalayas are fold mountains formed by the collision of the Indian and Eurasian plates, compressing Tethys Sea sediments upward (~70–40 million years ago). Himadri (Inner Himalayas) is the highest range, averaging 6,000 m, with perpetual snow. Himachal (Middle Himalayas) averages 3,700–4,500 m; contains hill stations like Shimla. Shiwaliks (Outer Himalayas) are youngest, 600–1,500 m, formed from eroded debris; Duns (like Dehra Dun) lie between them and Himachal.

~50 words • 5 marks