Sivalik

The Sivalik Hills is a mountain range of the outer Himalayas. It is about 2,400 km (1,500 mi) long enclosing an area that starts almost from the Indus and ends close to the Brahmaputra, with a gap of about 90 kilometres (56 mi) between the Teesta and Raidak rivers in Assam. The width of the Sivalik Hills varies from 10 to 50 km (6.2 to 31.1 mi), their average elevation is 1,500 to 2,000 m (4,900 to 6,600 ft).

In some Sanskrit texts, the region is called Manak Parbat. Shivalik literally means 'tresses of Shiva’. Other spelling variations used include Shivalik and Siwalik, originating from the Hindi and Nepali word shiwālik parvat. Other names include Churia hills, Chure hills, and Margalla Hills.

Geologically, the Sivalik Hills belong to the Tertiary deposits of the outer Himalayas. They are chiefly composed of sandstone and conglomerate rock formations, which are the solidified detritus of the great mountain range to their north, but often poorly consolidated. The remnant magnetization of siltstones and sandstones suggests a depositional age of 16-5.2 million years with the Karnali River exposing the oldest part of the Sivalik Hills in Nepal.

They are the southernmost and geologically youngest east-west mountain chain of the Himalayas. They have many sub-ranges and extend west from Arunachal Pradesh through Bhutan to West Bengal, and further westward through Nepal and Uttarakhand, continuing into Himachal Pradesh and Kashmir. The hills are cut through at wide intervals by numerous large rivers flowing south from the Himalayas.

...
Wikipedia