Astronaut photograph ISS021-E-23475 was acquired on November 11, 2009, with a Nikon D2Xs digital camera fitted with a 400 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 21 crew. The image in this article has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by William L. Stefanov, NASA-JSC.
The Central American country of El Salvador occupies a land area nearly the same size as the U.S. State of Massachusetts, and it includes numerous historically active volcanoes. This detailed astronaut photograph highlights the Ilopango Caldera that is located approximately 16 kilometers to the east of the capital city, San Salvador. Calderas are the geologic record of powerful volcanic eruptions that empty out a volcano’s magma chamber; following the eruption, the overlying volcanic structure collapses into the newly formed void, leaving a large crater-like feature (the caldera).
The last caldera-forming eruption at Ilopango occurred during the fifth century AD; it was a powerful event that produced pyroclastic flows that destroyed early Mayan cities in the region. Later volcanic activity included the formation of several lava domes within the lake-filled caldera and near the shoreline. The only historical eruption at Ilopango took place in 1879-80. This activity resulted in the formation of a lava dome in the center of Lake Ilopango. The summit of the dome forms small islets known as Islas Quemadas (visible as small white dots in the larger image). The city of Ilopango borders the lake to the west (image left), while green, vegetated hills ring the rest of the shoreline. White, patchy cumulus clouds are also visible in the image (center and upper left).
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This image originally appeared on the Earth Observatory. Click here to view the full, original record.