Building the landscape of Nepal, the formation of the Himalayas

Fig. 1 Satellite Image of Himalayas and Tibetan Plateau

Fig. 2\ Movement of the Indian plate

Nepal is home to 800 Kilometers (497 miles) of the Himalayan mountain range, from the Mahakali River in the west to the Tista River in the east. Their formation started about 55 million years ago, when the Indian plate collided with the Eurasian plate. "When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways." (USGS 2012) Over millions of years the colliding continents formed the Himalayan mountains and the Tibetan Plateau.

The Himalayas are the tallest mountains in the world, and are home to Mount Everest. They follow the leading edge of the Indian plate’s collision with the Eurasian plate, visible when you compare them from Fig. 1 to the leading face shown in Fig. 2.

Sunset view of towering, snow-capped Mt. Everest, from the village of Lobuche (Solu-khumbu), Nepal. (Photograph by Gimmy Park Li.)

Nepal is comprised of the Terai Plain, the Siwalki Hills and the Himalays. The Terai plain is a low elevation plain, comprised of alluvial sediment from the Himalayas. The Siwalik hills are comprised of sandstone and mudstone, and have been folded from the pressures of the collision of the Indian continent and the Eurasian continent. The Himalayas are made up of the Higher Himalayas and the Lower Himalayas, separated by a thrust fault. Both are comprised of metamorphic rock, but the Higher Himalayas have undergone greater metamorphism. On the northern slope of the Himalaya lies a layer of oceanic sediment from the Tethys ocean as the Indian continent approached the Eurasian continent. Between the Tibetan Plateau and the Himalayas a Batholith was formed. The Batholith was uplifted during the creation of the Himalayas and the Tibetan Plateau, the magma that formed it is believed to be from the subduction and partial melting of the Neo-Tethyan slab beneath the Eurasian plate.

Sources:

http://www.geo.arizona.edu/geo5xx/geo527/Himalayas/geology.html

http://www.ranjan.net.np/ranjan/index.php/geology-of-nepal

http://pubs.usgs.gov/gip/dynamic/himalaya.html

http://pubs.usgs.gov/gip/dynamic/understanding.html