The word "supervolcano" is used to describe volcanoes which have produced the world's
largest explosive eruptions, which at a minimum eject hundreds of cubic kilometers of volcanic
rock in a single eruption.
As an example, the most recent supervolcano to erupt on the planet originated from the
Aira caldera in Japan, which ejected more than 400 cubic kilometers of volcanic rock
22,000 years ago.
This eruption formed the massive caldera which is now a bay adjacent to the city of Kagoshima
that today contains the erupting Sakurajima volcano.
Looking around South America, you can find a number of large calderas from similarly
sized massive eruptions.
One of these calderas is from a supervolcano which is still geologically active, as beneath
its edifice is a massive magma reservoir with 22,000 cubic kilometers of molten rock.
This dormant supervolcano is located in Argentina, and is known as Cerro Galan.
It is the only supervolcano within South America which could erupt again.
The Cerro Galan supervolcano is located in northwest Argentina where it is 200 kilometers
southwest of the city of Salta.
From satellite, its massive caldera rim is easy to distinguish alongside a central peak
referred to as a resurgent dome.
This caldera measures 40 kilometers long and 25 kilometers wide, which formed in a single
supermassive eruption.
Around 15 million years ago, volcanic activity started in this region of Argentina, producing
clusters of gray stratovolcanoes and lava dome complexes.
Over time, these volcanic centers slowly shifted eastwards until they reached the eventual
site of Cerro Galan.
Three stratovolcanoes were subsequently constructed, forming distinct peaks on the western edge
of Galan's caldera.
A significant change occurred around 6.6 million years ago, as not only did several distinct
magma chambers merge, but they also became more silica rich.
This allowed for very large explosive eruptions to occur, similar in magnitude to the largest
known eruptions from Mount Hudson in Chile, rating on the volcanic explosivity index as
a 6.
7 such highly explosive eruptions occurred between 6.5 and 3.8 million years ago, each
depositing a distinct layer of highly welded pyroclastic rock known as ignimbrite.
Several of these eruptions may have even formed distinct small calderas, but these were later
obliterated if they ever even existed.
Then, for the next 1.7 million years, only small volume eruptions occurred at Cerro Galan.
During this timespan, a massive amount of pressure continued to build underlying its
edifice, along with hundreds of cubic kilometers worth of magma.
Finally, 2.08 million years ago, something caused this pressure to be released, triggering
a catastrophic eruption.
Several vents simultaneously erupted along a northward facing fissure, ejecting a column
of ash more than 45 kilometers into the atmosphere.
As the day seemingly turned to night due to the density of falling ash, energetic kilometer
high pyroclastic flows seemingly defied topography as they travelled up mountains and advanced
across the terrain in every direction.
These flows buried everything in a 40 kilometer radius with hundreds of meters thick of rock,
while also depositing smaller superheated layers of pyroclastic rock up to 80 kilometers
distant.
Then, as a portion of the underlying magma chamber was now empty, a large section of
overlying ground collapsed downwards to fill this empty space, forming a massive caldera.
In total, this caldera forming eruption ejected 1030 cubic kilometers of molten rock and had
a volcanic explosivity index of 8, marking it as a true supereruption.
Since some shallow magma remained, rhyodacite composition lava then erupted onto the edge
of the caldera in two locations, forming large lava domes which are marked on screen.
Over the subsequent two million years, magma has since refilled much of the area which
subsided during the supereruption, which has pushed the center of Cerro Galan's caldera
upwards forming what is termed as a "resurgent dome".
This massive dome was uplifted by more than 1400 meters or 4600 feet, and continues to
be slowly uplifted today!
Although Cerro Galan is not presently showing signs of activity, it could erupt again in
the future.
Active hot springs and fumaroles around its complex are merely further evidence that its
magma chamber is still present.
Thus, the area should be actively monitored just in case this massive complex decides
to produce another caldera forming eruption.
I hope that you enjoyed this video.
If you would like to request a specific topic, please leave a comment below!
Additionally, I would like to thank my new patron Cameron Walker for supporting this
channel!