Siwalik Hills

The Siwalik Hills are the youngest and southernmost Himalayan foothills, formed mainly from sediments eroded from the rising Himalaya and deposited along its outer edge.

Siwalik Group: A thick sequence of Neogene and Quaternary sedimentary rocks forming much of the Siwalik Hills. This rock sequence makes up the hills and preserves their depositional history.
Conglomerate: A sedimentary rock made of rounded gravel-sized clasts cemented together. Coarse conglomerates in the Siwalik Group indicate energetic rivers carrying Himalayan debris.
Indian Plate: A tectonic plate carrying the Indian subcontinent and adjacent oceanic crust. Its ongoing collision with Eurasia drives the uplift that feeds sediment into the foothills.
Siwalik Hills landslides: Slope failures in the Siwalik Hills, often involving weak sedimentary rocks and intense rainfall. Erodible slopes and monsoon rain make landslides a recurring local hazard.
Greater Himalaya: The high, central Himalayan range containing many of the region’s tallest peaks. It is far higher and lies north of the younger, sediment-built foothills.
Himalayan foreland basin: A sediment-filled depression formed as the Indian Plate flexed beneath the advancing Himalaya. It received sediment eroded from the growing Himalaya before that sediment was uplifted into the hills.
Sandstone: A sedimentary rock composed mainly of sand-sized mineral or rock grains. Siwalik sandstones preserve deposits from ancient channels and floodplains.
Eurasian Plate: A tectonic plate comprising much of Europe and Asia north of the Indian Plate. Its collision with India built the Himalaya from which Siwalik sediments were eroded.
Soil erosion: The removal and transport of soil by water, wind, or other forces. Rapid erosion of hillslopes affects streams, farmland, and downstream sediment loads.
Sub-Himalaya: The southernmost Himalayan tectonic belt, commonly identified with the Siwalik Hills and their associated rocks. This geological name emphasizes the hills’ place as the outer Himalayan belt.

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