Orogeny facts for kids
Orogeny is the process of mountain-building. It takes place when two tectonic plates come together. Orogens develop while a continental plate is crumpled and thickened to form mountain ranges, and involve a great range of geological processes collectively called orogenesis. Examples:
- Where a continent rides over an oceanic plate (non-collisional):
- Where two continental plates converge (collide):
There is a third process, called delamination. Here an unstable portion of cold root of the lithosphere drips down into the mantle, decreasing the density of the lithosphere and causing buoyant uplift. Example:
- The Sierra Nevada in California.
Areas that are rifting apart, such as mid-ocean ridges and the East African Rift have mountains due to thermal buoyancy caused by the hot mantle underneath them, which pushes them up. This thermal buoyancy is known as dynamic topography. Examples:
Images for kids
Two processes that can contribute to the formation of orogens. Top: delamination of orogenic roots into the asthenosphere; Bottom: Subduction of lithospheric plate to mantle depths. The two processes lead to differently located metamorphic rocks (bubbles in diagram), providing evidence as to which process actually occurred at convergent plate margins.
Continental collision of two continental plates to form a collisional orogen. Typically, continental crust is subducted to lithospheric depths for blueschist to eclogite facies metamorphism, and then exhumed along the same subduction channel. (example: the Alps)
Sierra Nevada Mountains (a result of delamination) as seen from the International Space Station.
Mount Rundle, Banff, Alberta.
Orogeny Facts for Kids. Kiddle Encyclopedia.