orogeny,mountain-building event, generally one that occurs ingeosynclinal areas. In contrast toepeirogeny, an orogeny tends to occur during a relatively short time in linear belts and results in intensive deformation. Orogeny is usually accompanied byfolding andfaulting of strata, development of angular unconformities (interruptions in the normaldeposition of sedimentary rock), and thedeposition of clastic wedges ofsediments in areasadjacent to the orogenic belt. Regionalmetamorphism andmagmatic activity are often associated with an orogenic event as well. Orogenies may result fromsubduction, terrane accretion (landmass expansion due to its collision with other landmasses), the underthrusting of continents by oceanic plates, continental collisions, the overriding of oceanic ridges by continents, and other causes.Seeplate tectonics.