Scotia Plate - Paleo-tectonics

Paleo-tectonics

The timing of the formation of the Scotia plate and opening of the Drake Passage has long been the subject of much debate due to its important implications for changes in ocean currents and shifts in paleo-climate. The thermal isolation of Antarctica and formation of the Antarctic ice sheet has largely been attributed to the opening of the Drake Passage.

During the early Eocene (50 Ma), the Drake passage between the southern tip of South America at Cape Horn, Chile and the South Shetland Islands of Antarctica was a small opening with limited circulation. A change in motion between the South American plate and the Antarctic plate would have severe effects, causing seafloor spreading and the formation of the Scotia plate. Marine geophysical data indicates that motion between the South American plate and the Antarctic plate shifted from N-S to WNW-ESE accompanied by an eightfold increase in the separation rate. This shift in spreading initiated crustal thinning and by 30-34 Ma, the Mid-Scotia spreading ridge formed. Spreading began to generate two new oceanic plates between South American and Antarctica, the so-called Magellan and Central Scotia plates. Thinner and denser than the continental Antarctic and South American plates, the growing Magellan and Central Scotia plates formed a deep and increasingly wide passage, the Drake Passage between South America and Antarctica. The eventual death of the Mid-Scotia ridge led the Magellan and Central Scotia plates to join forming the Scotia plate as seen today.