page_title: Lake Ilopango
section_title: Eruptive history
hierarchical_section_title: Lake Ilopango / Eruptive history
caption_attribution_description: U.S. Soldiers with the 7th Special Forces Group and Salvadoran service members maneuver after jumping from the ramp of a U.S. Army CH-47 Chinook helicopter during a joint airborne operations training exercise over Lake Ilopango, El Salvador, Jan. 21, 2014. The training allowed service members from both nations to maintain currency while strengthening the relationship between the forces. (DoD photo by Capt. Zach Anderson, U.S. Air Force/Released)
context_page_description: Lake Ilopango is a crater lake which fills an 8 by 11 km volcanic caldera in central El Salvador, on the borders of the San Salvador, La Paz, and Cuscatlán departments. The caldera, which contains the second largest lake in the country and is immediately east of the capital city, San Salvador, has a scalloped 100 m to 500 m high rim. Any surplus drains via the Jiboa River to the Pacific Ocean. An eruption of the Ilopango volcano is considered a possible source for the extreme weather events of 535–536. The local military airbase, Ilopango International Airport, has annual airshows where international pilots from all over the world fly over San Salvador City and Ilopango lake.
context_section_description: Four major dacitic–rhyolitic eruptions occurred during the late Pleistocene and Holocene, producing pyroclastic flows and tephra that blanketed much of the country.
  The caldera collapsed most recently sometime between 410 and 535 AD (based on radiocarbon dating of plant life directly related to the eruption), which produced widespread pyroclastic flows and devastated Mayan cities. The eruption produced about 84 km³ (20 cu mi) of tephra (several times as much as the 1980 eruption of Mount St. Helens), thus rating a 6 on the (VEI) Volcanic Explosivity Index. The "ash-cloud fallout ... blanketed an area of at least 10,000 square kilometers waist-deep in pumice and ash", which would have stopped all agricultural endeavor in the area for decades. It is also theorized that the eruption and subsequent weather events and agricultural failures directly led to the abandonment of Teotihuacan by the original inhabitants. Other researchers estimated that in its sixth-century eruption, Ilopango expelled the equivalent of 10.5 cubic miles of dense rock, making it one of the biggest volcanic events on Earth in the last 7,000 years. There is an opinion that this eruption caused the extreme weather events of 535–536 in Europe and Asia. 
  Later eruptions formed several lava domes within the lake and near its shore. The only historical eruption, which occurred from December 31, 1879, up to March 26, 1880, produced a lava dome and had a VEI of 3. The lava dome reached the surface of the lake, forming the islets known as Islas Quemadas.
caption: U.S. soldiers with the 7th Special Forces Group and Salvadoran service members maneuver after jumping from the ramp of a U.S. Army CH-47 Chinook helicopter during a joint training exercise over Lake Ilopango, El Salvador, January 21, 2014.
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