Orogeny typically produces
orogenic belts, which are elongated regions of deformation bordering continental
cratons. Young orogenic belts, in which
subduction is still taking place, are characterized by frequent
volcanic activity and
earthquakes. Older orogenic belts are typically deeply
eroded to expose displaced and deformed
strata. These are often highly
metamorphosed and include vast bodies of
intrusive igneous rock called
batholiths. File:Active Margin.svg|
Subduction of an
oceanic plate beneath a
continental plate to form an accretionary orogen. (example: the
Andes) File:Continental-continental convergence Fig21contcont.gif|
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
Himalayas) Orogenic belts are associated with subduction zones, which consume
crust, thicken
lithosphere, produce earthquake and volcanoes, and often build
island arcs. These island arcs may be added to a continental margin during an accretionary orogeny. The orogeny may culminate with continental crust from the opposite side of the subducting oceanic plate arriving at the subduction zone. This ends subduction and transforms the accretional orogeny into a collisional orogeny. The collisional orogeny may produce extremely high mountains, as has been taking place in the
Himalayas for the last 65 million years. == Notes ==