The South American plate encompasses the continent of South America and an extensive sector of the adjacent Atlantic seafloor, extending eastward to its divergent contact with the African plate and forming the southern segment of the Mid‑Atlantic Ridge. At its eastern margin this spreading boundary records continuous seafloor formation as the South American plate moves away from Africa; many parts of the plate boundary comprise short transform faults alternating with spreading‑ridge segments, yielding a sinuous boundary geometry that parallels the plate’s overall trend and reflects an ongoing westward migration of the plate away from the ridge.
Tectonic interactions along the plate margins are diverse. Along the Pacific coast the plate boundary is convergent: the denser Nazca plate is subducting eastward beneath South America at roughly 77 mm yr−1, a process that has produced the Andean orogeny and the chain of Andean volcanoes, including both stratovolcanoes and shield volcanoes. Near the Taitao–Tres Montes Peninsula the Chile Rise is presently being consumed at the Chile triple junction, producing a localized ridge–trench collision and attendant complexity in deformation and seismicity. To the south the plate meets the Antarctic, Scotia and Sandwich plates in a multi‑segment boundary that combines transform, compressional and extensional regimes. At the northern margin the South American plate interacts with the Caribbean plate and adjacent oceanic crust associated with the North American plate, producing a mix of transform and otherwise complex plate interactions in northern South America and offshore regions.