Lake Ilopango

Lake Ilopango
Lake Ilopango seen from the east, San Salvador city and San Salvador Volcano can be seen just behind the lake looming in the haze
Highest point
Elevation	450 m (1,480 ft)
Coordinates	13°40′N 89°03′W / 13.67°N 89.05°W / 13.67; -89.05
Geography
Location	El Salvador
Geology
Mountain type	Caldera
Last eruption	1879 to 1880

Lake Ilopango is a crater lake which fills a scenic 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. The lake is known for being a possible source for the extreme weather events of 535–536. The military airbase, Ilopango International Airport, has annual airshows where international pilots from all over the world fly over San Salvador City and Ilopango lake.

Four major dacitic - rhyolitic eruptions occurred during the late 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 25 km³ (6.0 cu mi) of tephra (20 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 kilometres waist-deep in pumice and ash", which would have stopped all agricultural endeavor in the area for decades.