|Elevation||450 m (1,480 ft)|
|Last eruption||1879 to 1880|
|Location||Central El Salvador|
|Basin countries||El Salvador|
|Max. length||11 km (6.8 mi)|
|Max. width||8 km (5.0 mi)|
|Surface area||72 km2 (28 sq mi)|
|Max. depth||230 m (750 ft)|
|Surface elevation||440 m (1,440 ft)|
Lake Ilopango is a crater lake which fills an 8 by 11 km (72 km2 or 28 sq mi) 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 (330 ft) to 500 m (1,600 ft) 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.
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.
- "Lake Ilopango". Encyclopædia Britannica. Retrieved 13 July 2012.
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- Dull, Robert A.; Southon, John R.; Sheets, Payson (2001). "Volcanism, Ecology and Culture: A Reassessment of the Volcan Ilopango Tbj eruption in the Southern Maya Realm". Latin American Antiquity. Latin American Antiquity, Vol. 12, No. 1. 12 (1): 25–44. doi:10.2307/971755. JSTOR 971755., esp. p.27.
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- Clive Oppenheimer (2011). Eruptions that shook the world. Cambridge University Press. ISBN 978-0-521-64112-8.
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- "Historia y cultura de Ilopango". Elsalvadorenelmundo.com. Archived from the original on 2014-02-04. Retrieved 2014-02-02.