Physical Geography of India

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Physical Geography of India maps the country’s natural framework — its landforms, drainage, climate, soils, and vegetation — and is a recurring 3%-weight area in UPPSC PCS General Studies.

Six physiographic divisions: Northern & North-Eastern Mountains, Northern Plains, Peninsular Plateau, Indian Desert, Coastal Plains, and Islands.
Himalayan ranges (west to east, highest to lowest): Himadri (Greater) → Himachal (Lesser) → Shivaliks (Outer).
Drainage: Himalayan rivers are perennial (antecedent/dendritic); Peninsular rivers are seasonal with radial patterns.
Monsoon onset: 1 June over Kerala, driven by ITCZ shift, differential land-sea heating, and Somali jet cross-equatorial flow.
Soil trap: Black (Regur) soil forms from Deccan Trap basalt, not alluvium.

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Physiographic Framework

India is conventionally split into six physiographic divisions. The Northern Plains are an alluvial/depositional plain built by the Indus, Ganga, and Brahmaputra river systems, not a structural bench. The Peninsular Plateau is the oldest landmass of India, composed of igneous and metamorphic rocks, with an average elevation of 600–900 m — far from low-lying.

Himalayas and Ghats

The Greater Himalayas (Himadri) average ~6,000 m and contain K2 (8,611 m) and Kanchenjunga (8,586 m); the Lesser Himalayas (Himachal) host valleys like Kashmir, Kullu, and Kangra; the Shivaliks are the newest, lowest, and most fragile. Western Ghats are continuous and higher; Eastern Ghats are discontinuous, lower, and broken by Godavari, Krishna, and Cauvery — both meet at the Nilgiri Hills.

Monsoon Mechanism

The Indian monsoon arises from differential heating of land and sea, the seasonal shift of the ITCZ over the Ganga plain (July), and Somali jet cross-equatorial flow. IMD recognises four seasons: cold-weather (Dec–Feb), hot-weather (Mar–May), advancing SW monsoon (Jun–Sep), and retreating NE monsoon (Oct–Nov).

River Discharge

Use Q = A × v for river discharge questions, where A = cross-sectional area (m²), v = mean velocity (m/s), giving Q in m³/s.

UPPSC Question Patterns

Format	Typical Ask
Map-based MCQ	Locate passes (Rohtang, Shipki La, Nathu La)
Statement pair	Identify correct Himalayan range sequence
Assertion–Reason	Monsoon onset vs withdrawal dates
Match-the-following	Soil parent material vs region

Trap: Eastern Ghats are not a single continuous chain — most UPPSC answer keys penalise this confusion.

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Comprehensive coverage for students on a longer study timeline.

Drainage Systems and Patterns

Himalayan rivers (Indus, Ganga, Brahmaputra) are perennial, antecedent, and drain in dendritic to trellis patterns shaped by young, folded structures. Peninsular rivers are mostly rain-fed, seasonal, and display radial drainage (e.g., around Amarkantak) because rivers flow outward from the central plateau crest. Godavari (1,465 km) and Krishna (1,401 km) are the longest Peninsular rivers; Kaveri is shorter but deltaic.

Climate Dynamics — Quantitative Hooks

The pressure gradient force per unit mass is PGF = −(1/ρ)(Δp/Δn), with Δp in Pa, Δn in metres, ρ ≈ 1.2 kg/m³ near the surface. Combined with Coriolis acceleration a_c = 2Ωv sinφ (Ω = 7.2921 × 10⁻⁵ rad/s), this yields the geostrophic wind approximation. For orographic rainfall, a useful empirical form is R = R₀(1 + 0.0023 h), where h is altitude in metres — useful when a question gives base-station rainfall and elevation gain.

Soils and Vegetation Linkages

Soil	Parent Material	Typical Region
Alluvial	River deposits	Indo-Gangetic plain
Black/Regur	Deccan Trap basalt	Maharashtra, Gujarat
Red	Crystalline igneous	Eastern Deccan
Laterite	Leaching under heavy rain	Western Ghats, NE
Desert/Arid	Aeolian sand	Western Rajasthan

Tropical Evergreen forests occur where rainfall exceeds 200 cm; Tropical Deciduous (Moist/Dry) is the most widespread; Sundarbans is the largest mangrove tract.

Common Mistakes

Calling Andaman & Nicobar coral islands — they are volcanic arc islands; Lakshadweep is the coral atoll group.
Stating the Thar Desert receives moderate rainfall — actual average is <150 mm/year.
Treating the Indo-Gangetic plain as structural — it is depositional alluvium.

Practice Prompts

Explain how the ITCZ shift and Somali jet interact to drive the SW monsoon onset over Kerala on 1 June.
Compare the drainage and flow regime of a Himalayan river (e.g., Ganga) with a Peninsular river (e.g., Godavari), citing three diagnostic differences.

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Physical Geography of India