South American–Antarctic Ridge

Near the Bouvet triple junction the spreading half rate is 9 mm/a (0.35 in/year), which is slow, and the SAAR has the rough topography characteristic of slow-spreading ridges.

Since 15 Ma, the oceanic crust of the Antarctic plate is being slowly subducted (20–24 mm/a (0.79–0.94 in/year)) under South America along this trench which is currently extending northward.

During the past 40 Ma (or since the opening of the Drake Passage) the South Sandwich Trench has been migrating eastward due to the evolution of a back-arc basin, effectively consuming the SAAR.

It can be inferred, based on fracture zone topography and magnetic anomalies in the Weddell Sea, that this change in direction occurred during the Cretaceous and Cenozoic.

[5] The break-up of Gondwana began in the Mid- to Late Jurassic in what is today the Mozambique Basin east of Africa, whereas the South American and African plates started to break apart during the Early Cretaceous.