Scotia Plate - Tectonic Setting

Tectonic Setting

Bounded by subducting, spreading and transform ridges, the Scotia plate lies in a particular setting. Surrounded by 2 major and 3 minor plates, its tectonic location is generally reflective of the relative motion between the Antarctic plate and the South American plate.

The Southern edge of the plate is bordered by the Antarctic plate forming the South Scotia Ridge. The South Scotia ridge is a left lateral transform boundary sliding at a rate of roughly 11 mm/yr. Though the South Scotia ridge is overall a transform fault, small sections of the ridge are spreading to make up for the somewhat jagged shape of the boundary.

The Western edge of the plate is bounded by the Antarctic plate, forming the Shackleton Fracture zone and the Southern Chile trench. The Southern Chile trench is a southern extension of the subduction of the Antarctic and Nazca plate below South America. Heading south along the ridge, the subduction rate decreases until its remaining oblique motion evolves into the Shackleton Fracture Zone transform boundary. The Shackleton Fracture zone is a left lateral transform boundary that occupies the southern half of the Antarctic-Scotia plate boundary. The relative motion between the Scotia plate and the Antarctic plate on the western boundary is roughly 13 mm/yr.

The Northern edge of the Scotia plate is bounded by the South American plate forming the North Scotia ridge. The North Scotia ridge is a left lateral transform boundary with a transform rate of roughly 7.1 mm/yr.

The eastern edge of the Scotia plate is a spreading ridge bounded by the South Sandwich microplate forming the East Scotia ridge. The East Scotia ridge is a back-arc spreading ridge that formed due to subduction of the South American plate below the South Sandwich plate along the South Sandwich Island arc. Exact spreading rates in the literature are still being disputed, but it has been agreed rates are between 65-90 mm/yr.

The south-western edge of the plate is bounded by the Shetland microplate separating the Shackleton Fracture Zone and the South Scotia ridge.