Earth Observations taken by the Expedition 21 Crew

ISS021-E-023475 (11 Nov. 2009) --- Lake Ilopango, El Salvador is featured in this image photographed by an Expedition 21 crew member on the International Space Station. The Central American country of El Salvador occupies a land area nearly the same as the US State of Massachusetts, and includes numerous historically active volcanoes. This detailed photograph highlights the Ilopango Caldera that is located approximately 16 kilometers to the east of the capital city of 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 5th 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 which forms small islets today known as Islas Quemadas. The city of Ilopango borders the lake to the west (left) while green vegetated hillslopes ring the rest of the shoreline. White patchy cumulus clouds are also visible in the image (center and upper left).