<Table> <Tr> <Td> </Td> <Td> This section needs expansion . You can help by adding to it . (June 2010) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section needs expansion . You can help by adding to it . (June 2010) </Td> </Tr> <P> Orogeny is the process of mountain building . Subducting plates can lead to orogeny by bringing oceanic islands, oceanic plateaus, and sediments to convergent margins . The material often does not subduct with the rest of the plate but instead is accreted (scraped off) to the continent resulting in exotic terranes . The collision of this oceanic material causes crustal thickening and mountain - building . The accreted material is often referred to as an accretionary wedge, or prism . These accretionary wedges can be identified by ophiolites (uplifted ocean crust consisting of sediments, pillow basalts, sheeted dykes, gabbro, and peridotite). This accretion process is thought by many geologists to be the reason for the crustal growth of western North America and of the uplift that produced the Rocky Mountains . </P> <P> Subduction may also cause orogeny without bringing in oceanic material that collides with the overriding continent . When the subducting plate subducts at a shallow angle underneath a continent (something called "flat - slab subduction"), the subducting plate may have enough traction on the bottom of the continental plate to cause the upper plate to contract leading to folding, faulting, crustal thickening and mountain building . This flat - slab subduction process is thought to be one of the main causes of mountain building and deformation in South America . </P>

A seafloor plate slides under a continental plate during subduction