Sivalik Hills
The Sivalik Hills (also known as the Shivalik Hills and Churia Hills) are a mountain range of the outer Himalayas that stretches from the Indus River about eastwards close to the Brahmaputra River, spanning across the northern parts of the Indian subcontinent. It is wide with an average elevation of . Between the Teesta and Raidāk Rivers in Assam is a gap of about . "Sivalik" literally means 'tresses of Shiva'. Sivalik region is home to the Soanian archaeological culture. Geology. 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 Himalayas to their north; they are poorly consolidated. The remnant magnetisation of siltstones and sandstones indicates that they were deposited 16–5.2 million years ago. In Nepal, the Karnali River exposes the oldest part of the Shivalik Hills. They are bounded on the south by a fault system called the Main Frontal Thrust, with steeper slopes on that side. Below this, the coarse alluvial Bhabar zone makes the transition to the nearly level plains. Rainfall, especially during the summer monsoon, percolates into the Bhabar, then is forced to the surface  by finer alluvial layers below it in a zone of springs and marshes along the northern edge of the Terai or plains. Prehistory. Remains of the Lower Paleolithic (around 500,000 to 125,000 BP) Soanian culture were found in the Sivalik region. Contemporary to the Acheulean, the Soanian culture is named after the Soan Valley in the Sivalik Hills of Pakistan. The Soanian archaeological culture is found across Sivalik region in present-day India, Nepal and Pakistan. "Sivapithecus" (a kind of ape, formerly known as "Ramapithecus") is among many fossil finds in the Sivalik region. The Sivalik Hills are also among  the richest fossil sites for large animals anywhere in Asia; the hills had revealed that all kinds of animals lived there. They were early ancestors to the sloth bear; "Sivatherium", an ancient giraffe; and "Megalochelys atlas", a giant tortoise named the Sivaliks giant tortoise; amongst other creatures. A number of fossil ratites were reported from the Sivalik Hills, including the extinct Asian ostrich, "Dromaius sivalensis" and "Hypselornis". However, the latter two species were named only from toe bones that have since been identified as belonging to an ungulate mammal and a crocodilian, respectively. Demographics. The low human population density in  the Sivalik Hills and along the steep southern slopes of the Lower Himalayan Range created a cultural, linguistic, and political buffer zone between populations in the plains to the south and the hills beyond the Mahabharat escarpment, enabling different evolutionary paths with respect to language and culture. In culture. The Indian Navy's "Shivalik"-class frigate is named after these ranges.