The geology of the Himalayas is a record of the most dramatic and visible creations of the immense mountain range formed by plate tectonic forces and sculpted by weathering and erosion. The Himalayas, which stretch over 2400 km between the Namcha Barwa syntaxis in Tibet and the Nanga Parbat syntaxis in Kashmir, are the result of an ongoing orogeny — the collision of the continental crust of two tectonic plates namely the Indian Plate thrusting into the Eurasian Plate. The Himalaya-Tibet region supplies fresh water for more than one-fifth of the world population, and accounts for a quarter of the global sedimentary budget. Topographically, the belt has many superlatives: the highest rate of uplift (nearly 10 mm/year at Nanga Parbat), the highest relief (8848 m at Mt. Everest Chomolangma), among the highest erosion rates at 2–12 mm/yr, the source of some of the greatest rivers and the highest concentration of glaciers outside of the polar regions. This last feature earned the Himalaya its name, originating from the Sanskrit for "the abode of the snow".

From south to north the Himalaya (Himalaya orogen) is divided into 4 parallel tectonostratigraphic zones and 5 thrust faults which extend across the length of Himalaya orogen. Each zone, flanked by the thrust faults on its north and south, has stratigraphy (type of rocks and their layering) different from the adjacent zones. From south to north, the zones and the major faults separating them are the Main Frontal Thrust (MFT), Subhimalaya Zone (also called Sivalik), Main Boundary Thrust (MBT), Lesser Himalaya (further subdivided into the "Lesser Himalayan Sedimentary Zone (LHSZ) and the Lesser Himalayan Crystalline Nappes (LHCN)), Main Central thrust (MCT), Higher (or Greater) Himalayan crystallines (HHC), South Tibetan detachment system (STD), Tethys Himalaya (TH), and the Indus‐Tsangpo Suture Zone (ISZ). North of this lies the transhimalaya in Tibet which is outside the Himalayas. Himalaya has Indo-Gangetic Plain in south, Pamir Mountains in west in Central Asia, and Hengduan Mountains in east on China–Myanmar border.

From east to west the Himalayas are divided into 3 regions, Eastern Himalaya, Central Himalaya, and Western Himalaya, which collectively house several nations and states.

 

Note:   The above text is excerpted from the Wikipedia article Geology of the Himalaya, which has been released under the GNU Free Documentation License.