South American Plate

The South American Plate is one of the major tectonic plates of the Earth's crust. It underlies the entire continent of South America and about half of the Atlantic Ocean floor to the southwest. For this reason, the plate comprises both types of crust: continental crust (thick, low density) and oceanic crust (thin but dense).

The plate moves progressively westward, moving away from the African Plate. This movement creates different types of boundaries: a divergent boundary to the east, a convergent boundary to the west, and transform boundaries elsewhere.

Plate Boundaries

To the east, the boundary is the Mid-Atlantic Ridge, where new crust is generated. There the South American Plate and African Plate move apart, and the Atlantic Ocean widens. To the west, the Nazca Plate—an oceanic plate—subducts beneath the continental plate. To the north lies a major boundary with the Caribbean Plate, while to the south and southeast are the Scotia Plate and Antarctic Plate.

The Andes and Earthquakes

The collision of the Nazca Plate with the South American Plate is the primary cause of the uplift of the Andes mountain range, which runs along the western coast of the continent. The same process has created the Peru–Chile Trench and the chain of Andean volcanoes. When plates collide and then continue to push against each other, very powerful earthquakes occur; the coasts of Chile and Peru are among the regions with the highest earthquake activity in the world.

Interior Structure

The center and east of the continent are underlain by ancient, highly stable cratons (for example, the Amazon Craton and the Brazilian Craton to the east). In these areas tectonic activity is minimal, and there are broad sedimentary basins such as the Amazon Basin. The contrast between the active west and the stable east is the most significant feature of the plate's geography.