THE HIMALAYAN MOUNTAINS The Himalayas are a geologically young range of mountains that are folded structurally. They are the world's tallest and most rugged mountains, and they are formed by them. They stretch all the way across India's northern borders. They form an arc that spans approximately 2400 kilometres in length. The width of these rivers varies from 400 kilometres in Kashmir to 150 kilometres in Arunachal Pradesh. From the Indus to the Brahmaputra rivers, these mountain ranges run in a west-east direction from the Himalayas. At the Himalayas, the altitudinal variations (differences in height) are greater in the eastern half of the mountain range than they are in its western half. In terms of their longitudinal extent, the Himalayas are composed of three parallel ranges. The Himadri, Himachal, and Shiwalik ranges are the ones in question.