El Misti volcano in Peru is featured in this image photographed by an Expedition 21 crew member on the International Space Station. The symmetric conical shape of El Misti is typical of a stratovolcano -- a type of volcano characterized by interlayered lavas and products of explosive eruptions, such as ash and pyroclastic flow deposits.
Stratovolcanoes are usually located on the continental crust above a subducting tectonic plate. Magma feeding the stratovolcanoes of the Andes Mountains -- including 5,822 meter-high El Misti -- is associated with ongoing subduction of the Nazca Plate beneath the South American Plate. El Misti's most recent -- and relatively minor -- eruption occurred in 1985. The city center of Arequipa, Peru lies only 17 kilometers away from the summit of El Misti; the gray urban area is bordered by green agricultural fields (right).
With almost one million residents in 2009, it is the second city of Peru in terms of population. Much of the building stone for Arequipa, known locally as sillar, is quarried from nearby pyroclastic flow deposits that are white in color.
Arequipa is known as "the White City" because of the prevalence of this building material. The Chili River extends northeastwards from the city center, and flows through a canyon (left) between El Misti volcano and Nevado Chachani to the north. high res (0.6 M) low res (65 K)