When people think of the most dangerous and destructive volcanoes on the planet, a number of
volcanoes come to mind. Vesuvius. Krakatoa. Pelee. Pinatubo. However, there is another volcano which
produced an eruption larger than the combined power of the four aforementioned volcanoes. This
volcano is located in El Salvador, and is known as Ilopango. It last erupted in 1880, and will
certainly erupt again. This video will discuss this active volcano, its massive eruption in 431
AD, and mention what its future hazards are. The Ilopango volcano can be found in the
central portion of El Salvador, where it is located 16 kilometers
east of the nation's capital, San Salvador. This volcano is quite fascinating, as it is
one of the oldest volcanoes on the planet which is still active today. Its origins can be traced
back 1.8 million years ago to a time when magmas related to the subduction of the Cocos tectonic
plate underneath the Caribbean plate to the south of El Salvador reached the surface in the region.
Initially, the magma which erupted onto the surface formed a number of small volcanic features
known as lava domes. These lava domes contained a highly siliceous magma known as dacite. Dacite
is typically only found at the most explosive volcanoes on the planet, and this volcano was
no exception. At depth, a large magma chamber was slowly expanding, causing pressure and gasses to
built while these small eruptions were ongoing. Then, 1.78 million years ago, this pressure was
released via a massive eruption. This eruption was of an unimaginable scale. As a quick comparison,
the largest recent eruption in Central America was the 1902 eruption of Santa Maria in Guatemala.
This eruption produced 10 cubic kilometers of tephra, which is still quite significant.
However, this ancient eruption more than a million years ago was far larger. It erupted 300 cubic
kilometers of tephra, which was subsequently spread across all of what is now El Salvador.
After the ash from this eruption had cleared, what remained was a 16 kilometer wide caldera.
For a 220,000 year period after this eruption, very little, if any volcanic activity occurred.
Although it is quite possible that some sustained activity took place, any evidence
of such was likely lost in the geologic record in subsequent supermassive eruptions.
Then, 1.56 million years ago, a second major eruption occurred. Although this eruption was far
smaller than the first caldera forming eruption, its effects were still catastrophic. This eruption
ejected 11 cubic kilometers of lava, and expanded the existing caldera in a southwards direction.
Afterwards, this volcano became quiet once again for another 220,000 years.
Then, 1.34 million years ago, the third massive eruption took place. This eruption was similar
in size to the last major eruption, and expanded the caldera to the west. In the aftermath of this
eruption, a much smaller version of Lake Ilopango formed in the center of the overlapping calderas.
Then, for the next 1.3 million years, the area lied dormant. We do not know why the
volcano was dormant for this long, but one possible explanation is that magma from
plate subduction was redirected over the long term to a different section of the country.
However, by the end of the last ice age, something had changed. Magma once again started to fill
the magma chamber beneath the volcano. This magma caused more and more pressure to build,
until finally, the volcano erupted in 431 AD. As a plume of ash was carried more than 30 kilometers
into the atmosphere, a vast pyroclastic flow erupted from the center of the caldera.
This pyroclastic flow quickly swept over the surrounding landscape, destroying
the land in a 100 kilometer radius. Some of the pyroclastic flows even reached the Pacific Ocean.
The long term effects of this eruption were extreme. A long term cooling period and
short term volcanic winter subsequently occurred, leading to many Mayan settlements being abandoned.
In total, 102 cubic kilometers of tephra was ejected, meaning that this eruption was one of the
largest on the planet of the last 10,000 years. However, Ilopango has not yet become dormant
once again. At the center of the caldera, another eruption occurred from 1879 to 1880.
This eruption, instead of being destructive, created a series of overlapping lava domes.
Today, the remnants of these lava domes can be found as a tiny group
of islets in the center of Lake Ilopango. Although Ilopango has not erupted since, it
will erupt again. The next eruption from Ilopango will likely build another series of lava domes,
most likely in a similar location or just to the east or west of the 1880 eruption. Overall,
Ilopango represents an incredibly dangerous volcano which catastrophically erupts followed
by long periods of little activity. I hope that you enjoyed this video.
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