Where it is and what it carries
The Scotia Plate fills the space between South America and Antarctica. It is mostly oceanic, lying under the Scotia Sea and part of the Drake Passage. Its only land is the southern part of Tierra del Fuego, south of the Magallanes-Fagnano Fault, which takes in about 3% of Chile and a sliver of Argentina.
Its northern and southern edges are long, mostly underwater ridges, the North Scotia Ridge and the South Scotia Ridge. Together with the South Sandwich Islands in the east, they form the Scotia Arc, a loop that links the Andes to the mountains of the Antarctic Peninsula.
What happens at its edges
The northern boundary with the South American Plate runs about 3,400 km, mostly strike-slip faults along the North Scotia Ridge and through Tierra del Fuego. Relative motion is slow, about 0.5 cm/yr. On land, the Magallanes-Fagnano Fault carries this boundary across Tierra del Fuego and along Lake Fagnano.
The southern boundary with the Antarctic Plate follows the South Scotia Ridge and the Shackleton Fracture Zone. It is a mix of strike-slip, spreading and convergent segments, with relative motion of about 1.2 cm/yr. In the southwest, a short convergent boundary meets the tiny Shetland Plate at about 0.9 cm/yr.
The fastest edge is in the east. The East Scotia Ridge is a back-arc spreading center that separates the Scotia Plate from the Sandwich Plate at about 7.3 cm/yr, reaching 8.1 cm/yr in places. It opens because South American seafloor sinks at the South Sandwich Trench and the trench retreats eastward, stretching the crust behind it.
How it formed
The Scotia Sea opened as South America and Antarctica drifted apart during the Cenozoic. Spreading centers in the western Scotia Sea, now inactive, built much of the plate’s floor. The new gap between the continents created the Drake Passage. Geologists agree this gap mattered for global climate but still debate its exact timing. Today the Antarctic Circumpolar Current, the largest ocean current on Earth by volume, flows through the Drake Passage above the plate.
The eastern part of the plate has a different history. As the South Sandwich Trench retreated east, back-arc spreading at the East Scotia Ridge added young seafloor, and that process continues today on the plate’s eastern edge.
Earthquakes and volcanoes
The plate has had 15 earthquakes of magnitude 6.5 or larger since 1900, none reaching magnitude 8. The largest, a M7.42 in 1908, struck in the Falkland Islands region on the plate’s northern edge. A M7.4 hit the South Georgia Island region in 2016, and another M7.4 struck the Drake Passage in 2025. Most of these quakes come from strike-slip motion on the plate’s northern and southern edges.
Only one volcano in the dataset sits on the plate: Fueguino, a field of lava domes in the Chilean part of southern Tierra del Fuego.