The IHR physiographically, starting from the foothills of south (Shivaliks), this mountain range extends up to Tibetan plateau on the north (Trans-Himalaya). Three major geographical entities, the Himadri (greater Himalaya), Himanchal (lesser Himalaya) and the Shiwaliks (outer Himalaya) extending almost uninterrupted throughout its length, are separated by major geological fault lines. Mighty but older streams like the Indus, Sutlej, Kali, Kosi and Brahmaputra have cut through steep gorges to escape into the Great Plains and have established their antecedence.