orogenesis

In its original, literal sense, orogenesis means ‘mountain building’, but today it more specifically refers to the tectonics of mountain building (as opposed to mountain building by erosion).

Orogenesis is brought about by the movements of the rigid plates making up the Earth's crust and uppermost mantle (described by plate tectonics). Where two plates collide at a destructive margin rocks become folded and lifted to form chains of mountains (such as the Himalayas). Processes associated with orogeny are faulting and thrusting (see fault), folding, metamorphism, and plutonism (see plutonic rock). However, many topographical features of mountains – cirques, U-shaped valleys – are the result of non-orogenic processes, such as weathering, erosion, and glaciation. Isostasy (uplift due to the buoyancy of the Earth's crust) can also influence mountain physiography.