The formation of the Scotia Arc was initiated by an acceleration in South America's westward migration in the mid-Cretaceous which led to the uplift of the Fuegan Andes and the then adjacent and embryonic North Scotia Ridge. The uplift of the ridge initiated the eastward migration of the South Georgia microcontinent from Tierra del Fuego towards its current location. In the Late Cretaceous South America started to move west relative to Antarctica. Little changed in the region between the Late Cretaceous and Oligoceneexcept for the subduction of the Phoenix Plate on the Pacific margin of the land bridge that still connected South America and Antarctica — what would become the Drake Passage was at this time a cusp on the Pacific side of the land bridge. The Late Paleocene to the Early Eocene saw rift basin formation in the Fuegan Andes which led to crustal extension: the first sign of separation between the two continents and the formation of the South Scotia Sea and South Scotia Ridge. Spreading in the West Scotia Sea led to the further lengthening of the North Scotia Ridge and South Georgia moving further east. Spreading in the West Scotia Sea finally led to the rifting of the South Orkney microcontinent from the tip of the Antarctic Peninsula. This event initiated the South Scotia Ridge. The banks of the South Scotia Ridge are made of continental crust that rifted off the land bridge 40-30 Ma. The banks on the northern Central Scotia Sea, on the other hand, are volcanic constructs overlaying an oceanic basement parts of which is the spreading centre of the separation between South America and Antarctica. Seafloor spreading in the West Scotia Sea continued until 6.6-5.9 Ma. The oldest volcanic activity in Central and Eastern Scotia Sea, i.e. the first signs of a volcanic arc, has been dated to 28.5 Ma. The SouthSandwich Islands fore-arc originated in the Central Scotia Sea and was translated eastward by the back-arc spreading centre in the East Scotia Sea, i.e. the East Scotia Ridge. South Georgia's eastward migration ended about 9 Ma when the microcontinent collided with the Northeast Georgia Riselarge igneous province on the South American Plate north-east of South Georgia. A submerged equivalent to the current South Sandwich Arc was relocated westward by the same spreading centre. After, and probably because of, the collision, the East Scotia Sea spreading centre split the ancestral South Sandwich Arc leaving a remnant arc under the Central Scotia Sea. The collision also produced the rugged Allardyce Range on South Georgia, making the -high range three times higher than the conjugate rocks on Navarino Island in Tierra del Fuego. The driving mechanism behind the formation of the arc, as proposed by, is a mantle return-flow from the Pacific to the Atlantic.
