(C) The Sivalik Hills, also known as Churia Hills, are mountain ranges of the outer Himalayas that stretches from the Indus River about 2,400 km eastwards close to the Brahmaputra River. It is 10–50 km wide with an average altitude of 1,500–2,000 m.Between the Teest a and Raidak Rivers in Assam is a gap of about 90 km. They are chiefly composed of sand stone and conglomerate rock formations, which are the solidified detritus of the Himalayas.