South Sandwich Islands, southern Atlantic Ocean

The South Sandwich Islands consist of a chain of eleven main islands that bend in an arc 240 miles (~400 km) long. The water surrounding the volcanoes has an average depth of about 8,500 feet (2,600 m). About 80% of each island is covered by glaciers. These volcanic islands are west of the South Sandwich trench. The map is based on Barker and Hill (1981).

The islands were first sighted in 1775, but the first landing didn't occur until 1818 when seal hunters visited. The islands are administered by the United Kingdom and claimed by Argentina. The South Sandwich Islands are uninhabited and far away from commercial shipping and air routes. Because high latitude of the islands and the frequent cloudy days photographs by the Space Shuttle astronauts are rare.

The South Sandwich Islands are a volcanic island arc caused by the subduction of the South American Plate beneath the South Sandwich Plate. The South Sandwich plate is one of the smallest geologic plates and is created at the South Sandwich spreading center. This small plate is less than 8 million years old and moves to the east at about 7 cm per year. The volcanic arc is younger than 5 million years. Arrows on the map show direction of movement. The map is based on Barker and Hill (1981).

Basalt makes up at least 70% of the islands. On average, about 60% of each island is made of lava and about 40% by tephra.

If you have any photos of these volcanoes we would like to borrow them to scan and add to the VolcanoWorld collection. Thanks!

The islands/volcanoes from south to north:

Sources of Information--South Sandwich Islands section:

Baker, P.E., 1968, Comparative volcanology and petrology of the Atlantic island arcs: Bulletin of Volcanology, v. 32, p. 189-206.

Baker, P.E., 1978, The South Sandwich Islands: III, Petrology of volcanic rocks. British Antarctic Survey Science Report No. 93.

Baker, P.E., 1990, The South Sandwich Islands in LeMasurier, W.E., and Thomson, J.W., editors, Volcanoes of the Antarctica Plate and southern oceans: Washington, DC, American Geophysical Union, p. 361-395.

Barker, P.F., and Hill, I.A., Back-arc extension in the Scotia Sea: Phil. Trans. R. Soc. London, Series A, v. 300, p. 249-262.

Berninghausen, W.H., and Neumann van Padang, M., 1960, Antarctica: Catalogue of the active volcanoes of the world, Rome, IAVCEI, 10, 32 p.

Coombs, D.S., and Landis, C.A., 1966, Pumice from the South Sandwich eruption of 1962 reaches New Zealand: Nature, v. 209, p. 289-290.

Gass, I.G., Harris, P.G., and Holdgate, M.W., 1963, Pumice eruption in the area of the south Sandwich Islands: Geol. Mag., v. 100, p. 321-330.

LeMasurier, W.E., and Thomson, J.W., editors, 1990, Volcanoes of the Antarctica Plate and southern oceans: Washington, DC, American Geophysical Union, p.487

Leat, P., et al., 2000. Journal of Petrology Volume 41 Number 6 Pages 845-866

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