1911 Encyclopædia Britannica/Siwalik Hills
SIWALIK HILLS, a name given to the foot-hills of the Himalayas in Dehra Dun district of the United Provinces of India, and in Nahan state and Hoshiarpur district of the Punjab. The range runs parallel with the Himalayan system from Hardwar on the Ganges to the banks of the Beas, with a length of 200 m. and an average width of 10 m. The elevation varies from 2000 to 3500 ft.
Geologically, the Siwaliks belong to the tertiary deposits of the outer Himalayas, and are chiefly composed of low sandstone and conglomerate hills, the solidified and upheaved detritus of the great range in their rear The intermediate valley lying between the outer hills and the Mussoorie mountains is known as the Dehra Dun (or Dehra valley) and contains a considerable Eurasian colony and some British teaplanters. The principal pass is that of Mohan by which the main road from Saharanpur to Dehra and Mussoorie traverses the range.
The Siwalik formation (distinguished for its extraordinary wealth of palaeontological remains) is found on the North-West Frontier occupying much the same position relatively to the Suliman range as it does to the Himalayas: it faces the plains and becomes the outermost wall of the hills.