Off the coast of Peru, the Nazca Plate subducts beneath the South American Plate at a rate of . This subduction process, along with the subduction of the Antarctic Plate also underneath the South American Plate, is responsible for the volcanism in the Andes and the uplift of the mountain chain. In the Cordillera Occidental (Western Cordillera) uplift commenced about 50million years ago in the Eocene, paused until 25 millionyears ago in the Oligocene, and increased substantially after about 10million years ago in the Miocene. Andean uplift in the area of Coropuna is ongoing.