Within the United States, there are 3 known supervolcanoes which are all considered to
be active and have each produced catastrophic eruptions.
These include Yellowstone in Wyoming, Long Valley in California, and the Valles Caldera
in New Mexico.
However, recent evidence is pointing towards the nation having a fourth potentially active
supervolcano, which is located in the Aleutian island chain.
Although the existence of this supervolcano has yet to be proven, evidence is definitively
pointing towards the existence of a massive caldera; a feature formed when a large swath
of ground collapses downwards to fill a partially empty magma chamber.
This possible supervolcano just happens to contain one of Alaska's most active volcanoes,
Mount Cleveland.
The proposed supervolcano is located within the central portion of the Aleutian island
chain, where it consists of the so called "Islands of Four Mountains".
This island chain despite its name in fact contains 6 active volcanoes, which have all
produced eruptions since the end of the last ice age.
So, what evidence is there to support the hypothesis of a large supervolcano in the
region?
The most significant piece of evidence is bathymetry taken largely during the 1950s,
which indicates the relative depth of the ocean floor.
In the dataset shown here, there are several areas which look like calderas seen at other
supervolcanoes as there is a higher area representing a rim with a circular shape and a lower area
representing a caldera floor.
Additionally, there is a very special type of volcanic rock found on the Tana volcano
known as ignimbrite which would not exist there without a recent large volume explosive
eruption.
For context, when an explosive eruption occurs, a dense mixture of pumice, ash, and gas is
frequently released in what is termed a pyroclastic flow.
These pyroclastic flows often leave behind a rock type known as tuff where they traveled.
In contrast, ignimbrite is a special type of highly welded tuff only generated by the
world's most explosive volcanic eruptions.
As an example, the catastrophic 1980 eruption of Mount Saint Helens, which was the largest
eruption to occur in the lower 48 states since 1800 did not produce any ignimbrite.
Meanwhile, the 1912 eruption of Novarupta in Alaska, which was 30 times larger did deposit
this type of rock, forming what is known as the valley of 10,000 smokes.
Therefore, the presence of this rock indicates that a very large explosive eruption did occur
at some point in the past, rating on the volcanic explosivity index as at least a 6.
These large eruptions almost always produce calderas, meaning that one should be close
by.
Additionally, a gravitational abnormality was detected near the suspected center of
the caldera, and it looks like the echo seen at other large calderas such as Los Humeros
in Mexico.
Mount Cleveland is also more active than would be expected if it truly existed as not part
of a caldera.
Around the planet, stratovolcanoes which almost continuously produce eruptions are frequently
constructed within large calderas such as Sakurajima in the Aira Caldera.
In the context of Sakurajima, Cleveland's unusually high level of activity would make
the most geologic sense if it was merely a single vent of a large caldera.
Another piece of evidence is that gasses emitted from various fumaroles around the 6 volcanoes
have compositions consistent with a very large underlying magma chamber.
While the exact location of the caldera if it even exists is up for debate, researchers
suggested that its approximately outline looked like this image, and that it measures 25 kilometers
long and 20 kilometers wide.
With this being said, there might be more than 1 caldera in this complex, as supervolcanoes
such as Yellowstone produced more than 1 caldera forming eruption, resulting in so called "nested"
calderas.
In summary, there is likely a supervolcano located around six volcanoes in the Aleutian
Island chain.
Although it is more likely than not to exist, its presence has not yet fully been proven.
Thus, we do not know when this supervolcano produced its large eruptions or what future
hazards it might pose as further studies are needed.
If more data becomes available which proves or disproves the existence of this supervolcano,
I will let my audience know.
I hope that you enjoyed this video!
If you would like to request a specific topic, please leave a comment below!
Additionally, if you would like to support this channel, consider becoming a patron on
patreon.