What created the Andes?

The Andes are the result of the subduction of the Nazca Plate beneath the South American Plate. As the Nazca Plate moves eastward, it is forced beneath the South American Plate. This process, known as subduction, causes the rocks of the Nazca Plate to melt and rise to the surface. The molten rock then forms volcanoes, which can be seen along the entire length of the Andes Mountains.