Orogenic belt

Overview

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.

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.

Prominent orogenic belts on the Earth are the circum-Pacific orogenic belt (the Pacific Ring of Fire) and the Alpine-Himalayan orogenic belt. Since these orogenic belts are young, they form large mountain ranges; crustal activity is active and accompanied by volcanic belts and seismic belts.