CBSE Class 9 Social Science Physical Features of India Notes Set 03

Plate Tectonics and the Making of India's Relief

India has mountains, plains, plateaus, deserts and islands. Geological formations together with weathering, erosion and deposition have shaped them.
The earth's crust has seven major plates. They may move towards each other (convergent), away from each other (divergent) or slide past each other (transform). The Indo-Australian plate drifted north after Gondwanaland broke up and collided with the Eurasian plate, so the sediments of the Tethys sea were folded into the Himalayas. The depression in front of the mountains was filled by river deposits to form the Northern Plains.

The Himalayas

They are young fold mountains about 2,400 km long, running from the Indus to the Brahmaputra. The Himadri (average 6,000 m) is snow-bound; the Himachal (3,700 to 4,500 m, with Pir Panjal, Dhaula Dhar and Mahabharat) has valleys and hill stations; the Shiwaliks (900 to 1,100 m) are made of loose sediments, and the valleys between them and the Himachal are called Duns. The Purvanchal forms the eastern hills.
By region from west to east: Punjab Himalaya (Indus to Satluj), Nepal Himalaya (Kali to Tista), Assam Himalaya (Tista to Dihang).

The Northern Plains

Formed by the Indus, Ganga and Brahmaputra systems, they are about 2,400 km long and 240 to 320 km wide. They are divided into the Punjab, Ganga and Brahmaputra plains, and by relief into Bhabar, Terai, Bhangar (old alluvium with kankar) and Khadar (new, fertile alluvium).

Plateau, Desert, Coasts and Islands

The Peninsular Plateau, a part of Gondwanaland, is made of old crystalline rocks and includes the Central Highlands, the Deccan Plateau, the Northeastern Plateau and the Aravalis. The Western Ghats are higher, continuous and the source of large rivers; the Eastern Ghats are lower and broken by rivers.
The Indian Desert (Marusthali) receives less than 150 mm of rain, with barchans and the Luni river. The western coast is narrow and submerged with no deltas, while the eastern coast is broad, emergent and has deltas of the Mahanadi, Godavari, Krishna and Kaveri.
The Andaman and Nicobar group in the Bay of Bengal and the coral Lakshadweep islands in the Arabian Sea are the two island groups. Each physical division complements the others: mountains give water and forests, plains give grain, the plateau gives minerals, and coasts give ports and fishing.