Geography

1

Physical Geography

Interior of the Earth

Earth's Layers

Crust: Sial (Silicon + Aluminium) — 30 km continental, 5 km oceanic
Mantle: Sima (Silicon + Magnesium) — 2900 km; source of magma
Core: Nife (Nickel + Iron) — Outer core liquid, Inner core solid; 6371 km centre

Plate Tectonics

Lithosphere divided into 7 major + several minor tectonic plates. Types of boundaries: Convergent (collision — mountains, trenches), Divergent (spreading — mid-oceanic ridges), Transform (sliding — earthquakes).

Indian Plate

Indian plate colliding with Eurasian plate → Himalayas forming. This is a convergent boundary. The Himalayas are still rising ~5mm per year.

Atmospheric Phenomena

Feature	Description
Jet Streams	High-velocity winds at tropopause (~9–12 km); westerly; influence Indian monsoon
El Niño	Warming of Pacific Ocean surface → weakens Indian monsoon
La Niña	Cooling of Pacific → strengthens Indian monsoon
Indian Ocean Dipole	Positive IOD (warm west, cool east) → good monsoon for India

2

Indian Geography — Physical Divisions

Six Physiographic Divisions

Physical Divisions

1. Himalayan Mountains — Trans (Karakoram), Greater (Himadri), Lesser (Himachal), Outer (Shiwalik)
2. Northern Plains — Bhabar (pebbles), Terai (marshy), Bhangar (old alluvium), Khadar (new alluvium)
3. Peninsular Plateau — Deccan Plateau; Malwa, Chotanagpur, Shillong plateaus
4. Coastal Plains — Western (steep, short rivers), Eastern (wide, deltaic rivers)
5. Islands — Andaman & Nicobar (Bay of Bengal), Lakshadweep (Arabian Sea — coral atolls)
6. Indian Desert — Thar Desert (Rajasthan); hot, arid; Barchans (crescent-shaped dunes)

Mountain Passes

Pass	State/Region	Significance
Nathu La	Sikkim	India-China trade route, LAC
Banihal Pass	J&K	Connects Jammu to Srinagar (Jawaharlal Tunnel)
Zoji La	J&K	Connects Srinagar to Leh
Shipki La	Himachal Pradesh	India-Tibet; Sutlej enters India
Lipulekh	Uttarakhand	India-China; Kailash Mansarovar route
Bomdi La	Arunachal Pradesh	India-China border

3

Climate of India

Monsoon System

India has a monsoon climate. Southwest Monsoon (June–September) brings 75–90% of India's annual rainfall. Northeast Monsoon (October–December) is important for Tamil Nadu and SE coastal areas.

Factors Controlling Indian Monsoon

1. Differential heating of land and sea (thermal low over Rajasthan)
2. Position of ITCZ (shifts northward in summer)
3. Jet Streams (Subtropical westerly jet retreats northward; Somali Jet strengthens)
4. Tibetan Plateau (acts as elevated heat source)
5. El Niño/La Niña effect on monsoon strength

Rainfall Distribution

Region	Rainfall	Notes
Cherrapunji/Mawsynram	>1000 cm/year	Wettest places in India (Meghalaya)
Western Ghats (windward)	200–400 cm	Heavy orographic rain
Leeward side of W. Ghats	50–100 cm	Rain shadow effect
Thar Desert	<25 cm	Driest region
NE India	200–400 cm	Assam, Meghalaya

4

Rivers & Lakes

Himalayan Rivers (Perennial)

Indus System

Indus → Jhelum → Chenab → Ravi → Beas → Sutlej (tributaries left to right of Indus in Punjab)

Ganga System

Ganga originates at Gangotri; joins Yamuna at Allahabad (Prayagraj Sangam); major tributaries: Yamuna, Ghaghara, Gandak, Kosi (sorrow of Bihar), Son, Chambal
Ganga-Brahmaputra delta = Sundarbans (world's largest mangrove)

Brahmaputra System

Originates in Mansarovar lake as Tsangpo; enters India at Arunachal Pradesh; called Dihang, then Brahmaputra; joins Ganga in Bangladesh (called Meghna)

Peninsular Rivers (Rain-fed, seasonal)

River	Origin	Flows Into
Mahanadi	Raipur, Chhattisgarh	Bay of Bengal
Godavari	Nasik, Maharashtra (longest peninsular river)	Bay of Bengal
Krishna	Mahabaleshwar, Maharashtra	Bay of Bengal
Kaveri	Coorg (Kodagu), Karnataka	Bay of Bengal
Narmada	Amarkantak, MP (west-flowing — rift valley)	Arabian Sea
Tapi	Betul, MP (west-flowing — rift valley)	Arabian Sea

5

Agriculture

Cropping Seasons

Season	Sowing	Harvest	Crops
Kharif	June–July (monsoon onset)	September–October	Rice, Maize, Cotton, Groundnut, Sugarcane, Jute
Rabi	October–November	March–April	Wheat, Barley, Mustard, Gram, Peas
Zaid	March–April	June–July	Watermelon, Cucumber, Muskmelon

Green Revolution

1960s: High-Yielding Varieties (HYV) of wheat (by Norman Borlaug, India adapted by M.S. Swaminathan); chemical fertilisers, irrigation, mechanisation. Punjab, Haryana, UP benefited most. Second Green Revolution focuses on pulses, coarse cereals, eastern India.

6

Economic Geography

Mineral Distribution

Mineral	Leading States
Coal	Jharkhand (Jharia), Odisha, Chhattisgarh, WB
Iron Ore	Odisha (largest reserves), Jharkhand, Chhattisgarh, Goa
Manganese	Odisha (largest producer), MP, Maharashtra
Bauxite	Odisha, Jharkhand, Gujarat, Maharashtra
Mica	Jharkhand, Rajasthan, AP (India = world's largest producer)
Copper	Rajasthan (Khetri), Jharkhand (Singhbhum)
Petroleum	Rajasthan (largest), Assam, Gujarat, Bombay High (offshore)

Important Straits Near India

Palk Strait (India-Sri Lanka) • Ten Degree Channel (Andaman & Nicobar) • Eight Degree Channel (Lakshadweep) • Nine Degree Channel (Lakshadweep) • Malacca Strait (SE Asia — connects Indian & Pacific Oceans)

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