Physical Features of India — Class 9 (CBSE)

India has every major physical feature on Earth — the world's highest mountains, vast alluvial plains, ancient plateaus, hot deserts, long coastlines, and tropical islands. This chapter explains why: India is the result of one of the most dramatic continental collisions in Earth's history, between the Indian Plate and the Eurasian Plate. The result is six distinct physiographic divisions, each with its own geological story.

1. The story — plate tectonics and India

About 140 million years ago, India was part of the supercontinent Gondwanaland — connected to Africa, South America, Australia, and Antarctica. The breakup of Gondwanaland began ~ 65 million years ago.

The Indian Plate drifted northward at the unusually fast rate of ~ 15 cm/year (most plates move 1-5 cm/year). It crashed into the Eurasian Plate around 50 million years ago. The collision continues today, lifting the Himalayas by ~ 5 mm/year.

This single tectonic event explains India's geography:

• Himalayas formed by collision-induced uplift.
• Northern Plains formed by sediment deposition from rivers draining the Himalayas.
• The Peninsular Plateau is the ancient Indian Plate from Gondwanaland.
• The Indian Ocean and the Arabian Sea are the seas around the moving continent.

2. The six physiographic divisions

India can be divided into six major physiographic divisions:

                                    INDIA
                                      │
        ┌────────────────┬────────────┴────────────┬────────────────┐
        │                │                         │                │
   Himalayas      Northern Plains              Peninsular           Coastal
                  (Indo-Gangetic)               Plateau              Plains
        │                                          │                │
        ├─────── Indian Desert ──────────────────┤                Islands
        │      (Thar, western Rajasthan)         │                (Andaman,
        │                                        │                Lakshadweep)
        └────────────────────────────────────────┘

(Actually: Himalayas, Northern Plains, Peninsular Plateau, Indian Desert, Coastal Plains, Islands — six divisions.)

We'll examine each.

3. The Himalayas

The world's highest mountain range. Stretches across the northern frontier of India.

Three parallel ranges

The Himalayas have three nearly parallel ranges (from north to south):

1. Himadri / Greater Himalayas — northernmost, highest. Average altitude 6,000+ m. Permanent snow.
2. Himachal / Middle Himalayas — middle range. Average altitude 3,700-4,500 m. Famous hill stations (Shimla, Mussoorie, Nainital, Darjeeling).
3. Shivaliks — southernmost, lowest. Average altitude 900-1,100 m. Made of soft sediment, prone to landslides.

Regional divisions (west to east)

The Himalayas are divided into five regions by the rivers cutting through them:

1. Punjab Himalayas — between Indus and Sutlej rivers.
2. Kumaon Himalayas — between Sutlej and Kali rivers.
3. Nepal Himalayas — between Kali and Tista rivers. Tallest peaks (Everest, K2 in Karakoram).
4. Assam Himalayas — between Tista and Dihang rivers. Steepest, wettest.
5. Purvanchal — eastern hill ranges that continue south, forming India's borders with Myanmar.

Important Himalayan peaks

K2 is in the Karakoram Range, a sub-range of the Himalayas in Indian-administered Kashmir.

4. The Northern Plains (Indo-Gangetic Plains)

India's most fertile region — formed by sediment deposition from the Himalayan rivers.

Formation

Over millions of years, the Indus, Ganga, and Brahmaputra rivers have eroded the Himalayas and deposited the eroded material (alluvium) in the lowlands south of the mountains. This created vast plains:

• Indus Plain (mostly in Pakistan) — extends into Indian Punjab and Haryana.
• Ganga Plain — from Haryana to West Bengal.
• Brahmaputra Plain — Assam.

Subdivisions of the Northern Plains

Based on relief variations:

1. Bhabar — narrow belt at the foothills. Composed of pebbles brought down by rivers. Rivers disappear into this belt and re-emerge below.
2. Tarai — south of Bhabar. Wet, marshy, fertile land. Originally densely forested; now mostly converted to agriculture.
3. Bhangar — older alluvium, slightly above flood level. Less fertile than Khadar.
4. Khadar — newer alluvium, flooded every year. Most fertile.

Economic importance

The Northern Plains are home to:

• ~ 40% of India's population.
• Most of India's wheat and rice production.
• Mughal-era cities (Delhi, Lucknow, Kolkata).
• The Ganga River — sacred to Hindus.

5. The Peninsular Plateau

The oldest land in India. A massive triangular plateau covering most of central and southern India.

Geological history

Originally part of Gondwanaland, the Peninsular Plateau is composed of ancient (Precambrian) rocks — much older than the Himalayas (which are only 50 million years old).

Two main parts

(a) Central Highlands

• North of the Narmada River.
• Includes the Aravali Mountains (one of the oldest in the world), Vindhya Range, Satpura Range.
• Western parts: Malwa Plateau.
• Eastern parts: Bundelkhand, Baghelkhand.
• Drained by Chambal, Betwa, Ken rivers (north into the Yamuna and Ganga).

(b) Deccan Plateau

• South of the Narmada.
• A triangular plateau bounded by the Western Ghats (west), Eastern Ghats (east), and Vindhyas/Satpuras (north).
• Major rivers (Godavari, Krishna, Kaveri) flow east across the plateau.

Famous features

• Western Ghats — also called Sahyadri. Continuous mountain range parallel to the western coast. Heavily forested, rainy.
• Eastern Ghats — less continuous, lower than Western Ghats. Heavily eroded.
• Nilgiri Hills — meeting of Western and Eastern Ghats. Famous for tea plantations and Western Ghats wildlife.
• Anai Mudi — highest peak in South India, 2,695 m (Western Ghats, Kerala).

Economic importance

• Major mineral reserves: iron ore (Karnataka, Odisha), bauxite (Jharkhand), manganese (MP), coal (Jharkhand, MP, WB).
• Black soil (regur) in Deccan — ideal for cotton.
• Major rivers for hydroelectricity and irrigation.

6. The Indian Desert (Thar)

The 9th largest desert in the world. Located in western Rajasthan.

Features

• Area: ~ 200,000 sq km.
• Annual rainfall: less than 150 mm in many places.
• Temperatures: up to 50°C in summer, near 0°C in winter nights.
• Sand dunes (Barchans), rocky areas, salt lakes.

Climate

• Hot desert — extreme temperatures.
• Dry — even monsoon brings little rain.
• Sandstorms common (April-July).

Inhabitants

• Population density very low.
• Pastoral nomads (Bishnoi, Bhil, Raika).
• Some settled agriculture using groundwater.
• Modern: solar and wind power development (one of India's largest renewable energy regions).

Why a desert?

The Thar Desert is at 27-29° N latitude — the band where global subtropical high-pressure systems push dry air downward. Plus, the desert is in the rain shadow of:

• The Aravali Mountains (to the south).
• The Himalayas (to the north).

The Aravalis block monsoon winds blowing northward from the Indian Ocean.

7. The Coastal Plains

India has ~ 7,500 km of coastline. The coastal plains are narrow strips of low-lying land bordering the coast.

Western Coastal Plains

Stretches from Gujarat to Kerala. Three subdivisions:

1. Konkan (Maharashtra, Goa) — narrow plain.
2. Karnataka coast — narrow plain.
3. Malabar Coast (Kerala) — slightly wider; has backwaters (lagoons connected to the sea).

The Western Ghats run parallel to the coast just inland. Major ports: Mumbai (Maharashtra), Mormugao (Goa), Mangalore (Karnataka), Kochi (Kerala).

Eastern Coastal Plains

Stretches from West Bengal to Tamil Nadu. Wider than the Western Coastal Plains. Subdivisions:

1. Coromandel Coast (Tamil Nadu, southern Andhra) — south.
2. Northern Circars (northern Andhra, Odisha) — north.

The Mahanadi, Godavari, Krishna, and Kaveri rivers form large deltas where they meet the Bay of Bengal.

Major ports: Chennai (Tamil Nadu), Visakhapatnam (Andhra Pradesh), Paradip (Odisha), Kolkata (West Bengal).

8. The Islands

India has two major island groups:

Andaman and Nicobar Islands (Bay of Bengal)

• ~ 572 islands (only ~ 38 inhabited).
• Located in the Bay of Bengal.
• Tropical rainforests, coral reefs.
• Home to indigenous tribes (Sentinelese, Onge, Jarawa, Shompen).
• Strategic location: controls approach to the Strait of Malacca.

Lakshadweep Islands (Arabian Sea)

• 36 coral islands (only 10 inhabited).
• Located off the Kerala coast.
• Smaller than the Andamans.
• Coral atolls and lagoons.
• Tourism, fishing economy.

9. Summary table — six divisions

10. Closing thought

Every part of India tells a different geological story:

• The Himalayas — youngest, still rising, world's highest.
• The Northern Plains — sediment from the Himalayas, world's most fertile.
• The Peninsular Plateau — ancient Gondwanaland, mineral-rich.
• The Thar Desert — hot, dry, ancient.
• The Coastal Plains — river deltas, where land meets sea.
• The Islands — outposts of India in distant seas.

This physical diversity is the foundation of India's:

• Climatic diversity (covered in Chapter 4 — Climate).
• Agricultural diversity (different crops for different regions).
• Cultural diversity (different communities adapted to different terrains).
• Biological diversity (different ecosystems for different species).

In the rest of Class 9 Geography (Drainage, Climate, Vegetation, Population), you'll see how these physical features shape water, weather, plants, and people. This chapter is the foundation.