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May 5, 2014
(9 Jan. 2011) --- Onekotan Island, part of the Russian Federation in the western Pacific Ocean, is featured in this image photographed by an Expedition 26 crew member on the International Space Station. Snow cover highlights calderas and volcanic cones that form the northern and southern ends of the island. Calderas are depressions formed when a volcano empties its magma chamber in an explosive eruption, followed by collapse of the overlaying material into the newly evacuated space. The northern end of the island is dominated by the Nemo Peak volcano that began forming within an older caldera approximately 9,500 years ago, according to scientists. The last recorded eruptive activity at Nemo Peak occurred in the early 18th century. The southern end of the island is formed by the 7.5 kilometer wide Tao-Rusyr Caldera. The caldera is filled by Kal'tsevoe Lake and Krenitzyn Peak, a volcano that has only erupted once in recorded history during 1952. Extending between northeastern Japan and the Kamchatka Peninsula of Russia, the Kuril Islands are an island arc located along the Pacific "Ring of Fire". Island arcs form along an active boundary between two tectonic plates where one plate is being driven beneath the other (subduction). Magma generated by the subduction process feeds volcanoes which eventually form volcanic islands over the subduction boundary.

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