Llullaillaco Volcano
April 5, 2010
The summit of South America’s Llullaillaco Volcano has an elevation of
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 photograph of Llullaillaco,
taken from aboard the International Space Station, illustrates an
interesting volcanic feature known as a coulée. 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 oriented 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 center, leading to the
formation of wall-like structures known as flow levees. 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 Credit: NASA
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