The South American Plate is in motion. "Parts of the plate boundaries consisting of alternations of relatively short transform fault and spreading ridge segments are represented by a boundary following the general trend."[2] Moving westward away from the Mid-Atlantic Ridge. The eastward-moving and more dense Nazca Plate is subducting under the western edge of the South American Plate along the Pacific coast of the continent at a rate of 77 mm per year.[3] This collision of plates is responsible for lifting the massive Andes Mountains and causing the volcanoes which are strewn throughout them.
^Meijer, P.T.; Wortel, M.J.R. (July 30, 1992). "The Dynamics of Motion of the South American Plate". Journal of Geophysical Research97.|access-date= requires |url= (help)