Remote, rugged and swept by icy gales, the South Sandwich Islands lie on their own microplate, in the extreme South Atlantic. Over the past 3 million years, this small tectonic plate has been rifting from the Scotia Plate, a rectangular, oceanic plate that stretches eastward from the tip of South America.
The rifting between the Scotia and Sandwich Plates is forcing the latter to the east and, as a result, it has been overriding the southern edge of the South American Plate. The subduction of the South American Plate (an ongoing process) has produced a volcanic island arc (the South Sandwich Islands) atop the Sandwich Plate. Geologists have noted the similarity of this island chain to the Lesser Antilles of the eastern Caribbean; both island arcs are at the eastern end of long, narrow tectonic plates (the Caribbean and Scotia Plates) that were likely squeezed between South America and its adjacent continental plates (North America and Antarctica) as the Atlantic opened and the American Plates moved westward.
Unlike the Lesser Antilles, the South Sandwich Islands, discovered by James Cook in 1775, do not provide idyllic settings for human habitation. Rather, they are home to huge populations of sea birds, penguins and marine mammals that feed in the rich, cold waters of the South Atlantic. Indeed, this isolated archipelago harbors one of the largest congregations of marine life on the planet, nourished by krill-laden currents from the coast of Antarctica.