The fold of Great Himalayas are asymmetrical in nature. the core of this part of Himalayas is composed of granite . It is perennially snow bound and a number of glaciers descend from this range.
The range lying to the south of the Himadri forms the most rugged mountain system and is known as Himachal or lesser Himalaya. The ranges are mainly composed of highly compressed and altered rocks. The altitude varies between 3700 and 4500 metres and the average width is of 50 km . While the pir Panjal range forms the longest and the most important range , the Dhaula dhar and the Mahabharat ranges are also prominent ones. This ranges consists of the famous valley of Kashmir , the Kangra and Kullu valley in Himachal Pradesh . This region is well known for its hill stations.
The outer most range of Himalayas is called the Shiwaliks. They extend over a width of 10 – 50 km and have an altitude varying between 900 and 1100 metres.
These ranges are composed of unconsolidated sediments brought down by rivers from the main Himalayan ranges located farther north . These valleys are covered with thick gravel and alluvium. The Longitudinal valley lying between Lesser Himalaya and the shiwaliks are Known as Duns. Dehra Dun, Kotli Dun and Patli Dun are some of the Well-known Duns.
Besides the longitudinal divisions, the Himalayas have been divided on the basis of regions from west to east. These division have been demarcated by river valleys.
The Brahmaputra marks the eastern most boundary of the Himalayas.