Wikipedia:Today's featured article/October 23, 2011

Calabozos is a Holocene caldera in the Maule Region in central Chile. Part of the Chilean Andes' volcanic segment, it is considered a member of the Southern Volcanic Zone. This most active section of the Andes runs through central and western Chile, and includes more than 70 of Chile's stratovolcanoes and volcanic fields. Calabozos and the majority of the Andean volcanoes formed from the subduction of the oceanic Nazca Plate under the continental South American continental lithosphere. The caldera is in a transitional region between thick and thin lithosphere, and is probably supplied by a pool of andesitic and rhyolitic magma. It sits on a historic bed of volcanic and plutonic sedimentary rock that in turn sits on top of a layer of merged sedimentary and metamorphic rock. Calabozos is responsible for the huge Loma Seca Tuff, a body of material 200 to 500 cubic kilometres (48 to 120 cu mi) in volume. It accumulated over at least three eruptive periods, beginning 800,000 years ago and lasting until 150,000 years ago. The caldera's dimensions are 26 by 14 kilometres (16 by 9 mi), and it has an elevation of 3,508 metres (11,509 ft). (more...)

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