The initiation of the South Sandwich subduction zone, a convergent plate margin,began around 66 Ma in response to regional convergence of the Antarctic and South American tectonic plates. Gradual extension of the Scotia Sea and subduction roll back of South American oceanic lithosphere created the ancestral Scotia Plate. The South Sandwich Microplate separated from the Scotia Plate around 15 Ma as a back arc basin formed with development of the East Scotia Rise. There is continued debate over the reason for the separation of the South Sandwich Plate from the Scotia plate. Two primary mechanisms have been proposed, subducting slab roll back and absolute motion of the scotia plate away from the trench. A combination of these two mechanisms could also contribute to current plate boundary configurations.[2]