Since August 5th, 2021, the Aleutian islands have been unusually active as three volcanoes
are simultaneously erupting.
Of these three volcanoes, the most notable eruption so far has originated from the "Great
Sitkin" volcano, which thus far has constructed a 1 kilometer wide lava dome.
Then, on December 10th, a series of earthquakes with a potential magmatic signature were detected
at a fourth volcano, causing its alert level to be raised to yellow.
Normally, adding another volcano to the watch list due to a potential imminent eruption
is not big news, as Alaska contains 86 active volcanoes.
However, what made this announcement so unusual is that it occurred at a volcano which was
thought to be extinct, as it had not erupted in more than 10,000 years.
Known as Davidof, this volcano is sometimes nicknamed "the Alaskan Krakatoa" as its edifice
contains a group of 5 once interconnected islands which mark the edges of a large caldera.
So, will this volcano erupt?
How rare is it for a volcano thought to be extinct to produce an eruption?
This video will answer these two questions and discuss what might happen next.
The Davidof volcano is located far away from the Alaskan mainland in the remote western
reaches of the Aleutian island chain.
As part of the "Rat Islands", there are no nearby settlements, and this volcano is inbetween
two other active volcanoes, Segula to the west and Little Sitkin to the east.
The Davidof volcano began forming an estimated 3 million years ago, when magma related to
the subduction of the Pacific Plate underneath the North American plate migrated upwards
before erupting onto the ocean floor on a plateau at a depth of 300 feet.
Over time, a large submarine volcanic cone was built, which towered towards the surface.
After finally breaking the surface in an explosive eruption, an ash rich plateau was built, forming
the base of the volcano.
Volcanic eruptions during the subsequent phase of activity produced large lava domes, as
the viscous lava flows were unable to travel very far, resulting in the creation of overlapping
domes of material.
This lava was unusually silica rich, resulting in the emplacement of both dacite and rhyolite
volcanic rock.
For context, when these two rock types are observed in a volcano, it is indicative of
the average eruption being highly explosive, as the viscous lava makes it very difficult
for underlying combustible gasses to escape.
Then, around 2.6 million years ago, a large plug built on top of the Davidof volcano.
Over time, a large amount of magma and gas grew underneath this plug, causing an immense
amount of pressure to build.
Finally, the pressure was released, causing a large section of the volcano to collapse
into the ocean.
As a tsunami was generated, pyroclastic flows raced across the surrounding landscape, potentially
even reaching other nearby islands.
After the eruption ended, what remained was a 2.5 kilometer or 1.6 mile wide caldera which
left a prominent circular scarp in the remaining islands.
During the last ice age, smaller volume explosive eruptions constructed additional land on the
remaining islands.
Although one paper suggested that this activity has continued into the last 10,000 years,
the Alaskan scientists I asked deemed this claim to be unlikely.
The reason for the raised alert level at Davidof relates to a series of still ongoing small
to moderate magnitude earthquakes which are occurring beneath its edifice.
Some of these earthquakes are as shallow as 100 meters, suggesting the presence of an
intrusion of magma at that depth.
Despite this apparent activity, the lack of nearby sensors makes it incredibly difficult
to make a firm conclusion on exactly what is occurring.
I would place the odds of a new eruption at around 20%, which if one was to occur would
construct a new lava dome and perhaps disrupt nearby air traffic.
Assuming an eruption does occur, it wouldn't be the first occasion in the last century
of a volcano long thought to be dormant or extinct producing an eruption.
In 2006, the Fourpeaked volcano southwest of Homer in Alaska produced its first eruption
in more than 10,000 years, surprising nearby residents.
Even more impressive is the distant Australian McDonald Island, which erupted in 1992 after
75,000 years of dormancy.
I hope that you enjoyed this video.
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