Physical Geography of India Questions for UPSC CSE

Physiographic Divisions of India

India is divided into six major physiographic units, each with distinct geological origin and economic importance. Think of India as a layered sandwich from north to south: mountains on top, plains in the middle, and peninsular rock at the base, with coasts and islands as the edges. The Himalayas are young fold mountains formed by the collision of the Indian plate with the Eurasian plate. The Northern Plains are formed by alluvial deposits of the Indus, Ganga, and Brahmaputra river systems. The Peninsular Plateau is the oldest and most stable landmass, made of hard igneous and metamorphic rocks.

• Six divisions: The Himalayan Mountains, Northern Plains, Peninsular Plateau, Indian Desert (Thar), Coastal Plains, Islands
• Himalayas have three parallel ranges: Greater Himalayas (Himadri), Lesser Himalayas (Himachal), Outer Himalayas (Shivaliks) — mnemonic GLS
• Northern Plains extend 2400 km long, 240-320 km wide — formed by three river systems
• Bhabar (porous gravel belt), Terai (waterlogged), Bhangar (old alluvium), Khadar (new alluvium) — plains sub-zones from north to south
• Peninsular Plateau tilts westward — so most rivers flow east toward Bay of Bengal
• Central Highlands north of Narmada, Deccan Plateau south of Narmada — separated by Satpura range

The Himalayas — Structure and Passes

The Himalayas are geologically young, weak, and still rising — this makes them prone to earthquakes and landslides. They run roughly 2500 km from the Indus Gorge in the west to the Brahmaputra Gorge in the east. Passes through the Himalayas are strategically critical and frequently tested in UPSC. A simple way to remember major passes is to go state by state from west to east.

• Karakoram Pass — Ladakh (highest motorable road nearby)
• Zoji La — connects Srinagar to Leh (J and K)
• Rohtang Pass — Himachal Pradesh (connects Manali to Lahaul-Spiti)
• Shipki La — Himachal Pradesh (Sutlej enters India here)
• Nathu La and Jelep La — Sikkim (trade route to China)
• Bomdi La — Arunachal Pradesh
• Trans-Himalayan ranges include Karakoram, Ladakh, Zaskar — lie north of Greater Himalayas

Drainage Systems — Rivers of India

Indian rivers are classified as Himalayan rivers (perennial, snow-fed) and Peninsular rivers (seasonal, rain-fed). Himalayan rivers are antecedent — they existed before the mountains rose and cut through them. Peninsular rivers have reached maturity with graded profiles. The Indus system flows west, the Ganga-Brahmaputra flows east — both drain the northern plains. Peninsular rivers like Krishna, Godavari, Cauvery flow east into the Bay of Bengal. Only Narmada and Tapi flow west into the Arabian Sea through rift valleys.

• Indus, Ganga, Brahmaputra — three main Himalayan drainage systems
• Brahmaputra is called Tsangpo in Tibet, Dihang when it enters India
• Ganga is longest river entirely within India (2525 km)
• Narmada and Tapi are rift valley rivers — flow west, no delta, form estuaries
• East-flowing peninsular rivers form deltas — Mahanadi, Godavari (largest peninsular river), Krishna, Cauvery
• Inland drainage — Luni river in Rajasthan drains into Rann of Kutch (saline lake)

Western Ghats vs Eastern Ghats

These two ranges are often tested as a comparison. Western Ghats run continuously for 1600 km from Gujarat to Kanyakumari and act as a water divide. They are a UNESCO World Heritage biodiversity hotspot. Eastern Ghats are discontinuous, lower in height, and cut through by rivers like Godavari, Krishna, and Mahanadi. Western Ghats get heavy orographic rainfall on their windward western side; Eastern Ghats are in the rain shadow of Western Ghats for southwest monsoon.

• Western Ghats: continuous, average height 900-1600 m, Agasthyamalai, Anai Mudi (2695 m) is highest peak in South India
• Eastern Ghats: discontinuous, average height 600 m, cut by rivers
• Palakkad Gap (Palghat Gap) in Western Ghats — important passage between Kerala and Tamil Nadu
• Nilgiri Hills — junction of Western and Eastern Ghats
• Cardamom Hills, Anaimalai Hills, Palni Hills — sub-ranges of Western Ghats
• Shillong Plateau — only plateau in India northeast, made of ancient rocks

Coastal Plains and Islands

India has two types of coastline: the western coast (narrow, rocky, straight, with lagoons like Vembanad and Chilika near Kerala and Odisha respectively) and the eastern coast (broader, with deltas and sandy beaches). The eastern coast is also called the Coromandel Coast in the south and Northern Circars in the north. India has two groups of islands — Andaman and Nicobar in the Bay of Bengal (volcanic and raised coral origin, over 500 islands) and Lakshadweep in the Arabian Sea (coral atolls, only 36 islands, smallest UT by area).

• West Coast from north to south: Konkan (Maharashtra-Goa), Kannad (Karnataka), Malabar (Kerala)
• East Coast: Northern Circars (north), Coromandel Coast (south)
• Chilika Lake — largest coastal lagoon in India, Odisha, Ramsar site
• Andaman and Nicobar — separated by 10 Degree Channel; Indira Point (southernmost tip of India) is here
• Lakshadweep — separated from Maldives by 8 Degree Channel (also called Minicoy Channel)
• Barren Island in Andaman — only active volcano in South Asia

Indian Desert and Central Highlands

The Thar Desert in Rajasthan is the world's most populated desert. It forms a natural boundary with Pakistan. The Aravallis — among the world's oldest fold mountains — run across Rajasthan and separate the desert from the plains. The Central Highlands include the Malwa Plateau north of the Vindhyas, Bundelkhand, and Chhota Nagpur Plateau (rich in minerals — called the mineral heartland of India). The Deccan Trap in Maharashtra is made of volcanic lava and is excellent for cotton cultivation (black/regur soil).

• Aravallis: oldest fold mountains, run NE-SW, protect Ganga plains from desert winds
• Vindhya and Satpura — two ranges that historically divided North India from South India
• Chhota Nagpur Plateau — made of ancient rocks, rich in coal, iron, manganese
• Deccan Trap covers Maharashtra, MP, Gujarat — basaltic lava, black cotton soil
• Luni river — only significant river of Rajasthan desert, saline after Balotara

• Confusing Chilika Lake (Odisha, east coast) with Vembanad Lake (Kerala, west coast) — both are Ramsar sites but on opposite coasts
• Thinking all peninsular rivers flow east — Narmada and Tapi are exceptions, flowing west through rift valleys, not over plateau edges
• Mixing up mountain passes: Nathu La is in Sikkim, Zoji La is in J and K — a very common MCQ trap
• Calling the Brahmaputra an east-flowing river in India — it enters from the east, curves westward (makes a U-turn at Namcha Barwa) and flows west through Assam before joining the Bay of Bengal
• Assuming Eastern Ghats are south of Western Ghats — they are parallel ranges on the east and west coasts respectively, meeting at the Nilgiris

• GLS for Himalayan ranges: Greater (Himadri) — Lesser (Himachal) — Shivaliks, from north to south
• BTKB for alluvial plain zones north to south: Bhabar — Terai — Khadar — Bhangar (remember: BaTuKa Bhangar)
• NT flows West, others East: Narmada and Tapi are the two west-flowing peninsular rivers — NT Goes West
• 10 Degree Channel separates Andaman from Nicobar; 8 Degree Channel separates Lakshadweep islands (8 is less than 10, Lakshadweep is smaller and further south-west)

• UPSC Prelims frequently asks about rivers and the seas they drain into — always link a river to its source, the states it passes through, and its mouth (delta or estuary)
• Mountain passes have been asked in Prelims multiple times — especially Nathu La (trade), Zoji La (strategic), Shipki La (river entry). Make a state-wise pass list
• In Mains GS1, questions like 'Discuss the role of Western Ghats as a biodiversity hotspot and water tower of peninsular India' require linking physical geography to ecology and water resources
• Islands questions in Prelims focus on channels (8 Degree, 10 Degree), active volcanoes (Barren Island), and southernmost/northernmost points — these are direct factual MCQs
• Avoid over-reading maps in revision — focus on relative positions (which is east of what, which river is longer) since UPSC tests conceptual spatial awareness, not exact coordinates