On the basis of the stratigraphic and tectonic history, relief characteristics and erosional processes India may be divided into four major physiographic regions, viz., 1. The Northern Mountains, 2. The Great Plains, 3. The Peninsular Uplands and 4. The Indian Coasts and Islands. These may be further subdivided into a number of meson and micro regions.
The Northern Mountains
The region extends all along the northern frontiers of the country, from the eastern boundary of Pakistan to the borders of Myanmar, for about
Physiographic Divisions 2500 km. with a varying width of 240 to 320 km. and a total area of about 5, 00,000 km2. The main axis of the Himalayas lays in west-east direction in an actuate shape between the Indus river and the Brahmaputra river encompassing the parts of the states like Jammu and Kashmir, Himachal Pradesh, Uttaranchal,
Nepal, Sikkim, West Bengal, Bhutan and Arunachal Pradesh. Its offshoots run in north-south direction along the India-My anmar boundary traversing through Nagaland, Manipur and Mizoram. Himalayas, the abode of snow, represent the youngest and the highest folded mountains of the earth, rising to over 8000m. above sea level and consisting of three parallel ranges: (a) Himadri (Greater Himalaya), (b) Himanchal (Lesser Himalaya), and (c) the Siwaliks (Outer Himalayas). Antecedent rivers like Indus, Satluj, Kali, Kosi and Brahmaputra have carved out deep gorges across these ranges to enter the Great Plains. The troughs intervening the ranges are occupied by the longitudinal valleys of the streams in their upper reaches.