Scotia Arc

The Scotia Arc was formed

Islands of the Scotia Arc

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.

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Tectonics of the Scotia Arc

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.

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Volcanic Island Arc

Form at convergent boundaries where oceanic crust subducts underneath oceanic crust. Plate friction causes the crust to heat up making magma which rises to the surface and builds a volcanic island arc.


South Sandwich Island Cloud Wakes (Image from: NASA Earth Observatory)

Unique images of cloud wakes produced by island peaks in the Scotia arc illustrate a strong relationship between landmasses and climate in this region