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Volcano at the end of the world

Volcán Villarrica

Volcán Villarrica, an active volcano near the southern tip of South America.

Near the southern tip of South America, a trio of volcanoes lines up perpendicular to the Andes Mountains. The most active is the westernmost, Volcán Villarrica, pictured in this photo-like image from the Advanced Land Imager on NASA’s Earth Observing-1 (EO-1) satellite on May 15, 2010.

The 2,582-metre-high (9,357-foot) stratovolcano is mantled by a 30-square-kilometre (10-square-mile) glacier field, most of it amassed south and east of the summit in a basin made by a caldera depression. To the east and northeast, the glacier is covered by ash and other volcanic debris, giving it a rumpled, brown look.

The western slopes are streaked with innumerable grey-brown gullies, the paths of lava and mudflows (lahars). Beyond the reach of ash and debris deposits, the volcano is surrounded by forests; the area is a national park.

See the full-size image here (4MB, new window).

The biggest recent eruption was in the early 1970s; lava flows melted glaciers and generated lahars that spread at speeds of 30–40 kilometres per hour (20-30 mph) toward Lago Villarrica (visible to the northwest in large image) and southwest toward Lago Calafquéen (lower left).

NASA Earth Observatory image by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Rebecca Lindsey.

World’s highest volcano

Satellite image of Llullaillaco Volcano.

South America’s Llullaillaco Volcano is the world's highest historically active volcano.

The summit of South America’s Llullaillaco Volcano has an elevation of 6,739 metres (22,110 feet) above sea level, making it the highest historically active volcano in the world.

The current stratovolcano—a cone-shaped volcano built from successive layers of thick lava flows and eruption products like ash and rock fragments—is built on top of an older stratovolcano.

The last explosive eruption of the volcano, based on historical records, occurred in 1877.

This detailed astronaut photograph of Llullaillaco illustrates an interesting volcanic feature known as a coulée (image top right). Coulées are formed from highly viscous, thick lavas that flow onto a steep surface.

As they flow slowly downwards, the top of the flow cools and forms a series of parallel ridges orientated at 90 degrees to the direction of flow (somewhat similar in appearance to the pleats of an accordion).

The sides of the flow can also cool faster than the centre, leading to the formation of wall-like structures known as flow levees (image centre).

Llullaillaco is also a well-known archaeological site—the mummified remains of three Inca children, ritually sacrificed 500 years ago, were discovered on the summit in 1999.

Image provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by William L. Stefanov.