Lake Ilopango

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 to 500 m high rim. Any surplus drains via the Jiboa River to the Pacific Ocean. 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.

Eruptive history
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 CE (based on radiocarbon dating of plant life directly related to the eruption), which produced widespread pyroclastic flows and devastated Mayan cities; however, a team of scientists concluded that the volcanic eruption might have happened in, based on volcanic shards taken from ice cores in Greenland, levels of sulphur recorded in ice cores from Antarctica, and radiocarbon dating of a charred tree found in volcanic ash deposits. The eruption is estimated to have produced around 37-82 km3 of ejecta (DRE—several times more than the 1980 eruption of Mount St. Helens), which puts it at a rating of 6 on the Volcanic Explosivity Index (VEI) and makes it one of the biggest volcanic events on Earth in the last 7,000 years. Fallout from the eruption column blanketed an area of at least 10000 km2 with pumice and ash to a depth of at least 50 cm, and an area of nearly 2000000 km2 to a depth of at least 0.5 cm, which would have stopped all agricultural production in the most-severely affected 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.

It was hypothesized that this eruption caused the extreme weather events of 535–536 in Europe and Asia, but this is unlikely given the research published in 2020 that dates the eruption to 431 CE.

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.

Events
On July 5, 2004 the illusionist, Francis Fanci was tagged and submerged inside a trunk from which he emerged after thirty seconds. On the other hand, in 2004 Matthew Hatfield Knight, eldest son of the owner of the international consortium of Nike sports shoes, died of a heart attack while diving with his colleagues.