Volcanoes near Usulutan, El Salvador are featured in this image photographed by an Expedition 23 crew member on the International Space Station. The Pacific coastline of much of Central America is marked by a line of active and quiescent volcanoes known to geologists as the Central American Volcanic Arc, or CAVA. The volcanoes result from the upward movement of magma generated along the subduction zone between the Cocos and Caribbean tectonic plates; frequent earthquakes also occur along the plate boundary. This photograph includes four stratovolcanoes — a type of volcano associated with active subduction zones — located near the midpoint of the CAVA in El Salvador. Scientists believe while all of the volcanoes shown here have been active during the Holocene Epoch (approximately 10,000 years ago to present), only the 2,130-meter-high San Miguel (also known as Chaparrastique) has been active during historical times. The most recent activity of San Miguel was a minor gas and ash emission in 2002. The steep conical profile and well-developed summit crater are evident at left, along with dark lava flows produced by San Miguel. Immediately to the northwest the truncated summit of Chinameca volcano (also known as El Pacayal) is marked by a two-kilometer-wide caldera, formed when the volcano’s magma chamber was emptied by a powerful eruption followed by collapse of the chamber’s roof. Like its neighbor San Miguel, Chinameca’s slopes host coffee plantations. Moving to the southwest the eroded cone of El Tigre volcano is visible. According to scientists, El Tigre volcano formed during the Pleistocene Epoch (1.8 million to approximately 10,000 years ago) and is likely the oldest of the stratovolcanoes depicted in the image. Usulutan volcano is located directed to the southwest of El Tigre. While the flanks of Usulutan have been dissected by stream flow it still retains a summit crater that is breached on the eastern side. Several urban areas – recognizable as light gray to white regions contrasting with green vegetation and tan fallow agricultural fields – are located in the vicinity of these volcanoes, including Usulutan (upper right) and Santiago de Mara (lower right).
Image/caption credit: NASA
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