The easterly side is a divergent boundary with the African Plate forming the southern part of the Mid-Atlantic Ridge. The southerly side is a complex boundary with the Antarctic Plate and the Scotia Plate. The westerly side is a convergent boundary with the subducting Nazca Plate. The northerly side is a boundary with the Caribbean Plate.

The remains of the Farallon Plate, split into the current Cocos Plate and Nazca Plate are still subducting under the western edge of the South American Plate. This subduction is responsible for lifting the massive Andes Mountains and causing the volcanos which are strewn throughout them. There is some speculation that in addition to subducting the Cocos and Nazca Plates, the westward motion of the South American Plate may have forced the Caribbean and Scotia Plates at its northern and southern ends respectively to squeeze around it. Both share a similar shape and are being subducted along their eastern boundary. They are thought to be ancient volcanic regions formed on the Farallon Plate, with their crust too thick to be subducted under the South American Plate.

There is evidence that South American plate continues to move northwards at a very slow rate.http://www.geophysics.rice.edu/department/research/alan1/SECAR/Plate_Tectonic_Evolution_.htm

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