Shiwalik

The Shiwalik (also spelled Shivalik or Sivalik) is the southernmost major mountain belt of the Himalayas, forming the outer foothills at the edge between the Lesser Himalaya and the plains. It extends from the Indus River in the west to the Brahmaputra in the east, passing through parts of northern India and Nepal. The range is a low, often discontinuous chain of ridges and valleys, typically 10 to 50 kilometers wide, with elevations commonly ranging from about 600 to 1,500 meters above sea level, higher in the eastern portions.

Geology and structure: The Shiwalik is primarily composed of relatively young sedimentary rocks—sandstone, mudstone, siltstone, and conglomerates—that were deposited during the Miocene to Pliocene epochs and are collectively referred to as the Sivalik Group. These rocks are largely unconsolidated and prone to erosion and landslides. The belt sits atop the Indian plate and is heavily faulted and folded by ongoing Himalayan tectonics, marking the active southern margin of the orogenic system.

Geography and hydrology: The foothills are deeply dissected by numerous rivers and streams that rise in the higher Himalaya, creating numerous valleys, gorges, and drainage patterns. The Shiwalik forms a natural boundary that reflects the transition from the rugged highlands to the more fertile plains and, in some areas, blends into the Terai forest zones.

Ecology and human activity: Lower elevations support mixed forests with deciduous species and, in some eastern sections, pine. The foothills are home to densely populated agricultural communities, and several hill towns are located along the ridges and valleys. Landslides and soil erosion are common hazards during the monsoon.