From a volcanologist's perspective, the Katmai National Park and Preserve within Alaska is
one of the most fascinating areas on the planet.
In this incredibly volcanically active area which is slightly larger than the state of
Connecticut, there are 13 active volcanoes which have or are suspected to have erupted
at some point in the last 11,650 years.
The last of these to produce an eruption was the Fourpeaked volcano, which produced an
unexpected phreatic eruption in 2006.
As a result of the sheer number of volcanoes and the threats this can pose to regional
aircraft if an eruption was to occur, the area is heavily monitored.
After producing a series of 14 closely spaced eruptions between 1949 and 1974, the Trident
volcano which is the single most recently active volcano in the national park has not
really shown any signs of life.
For 48 years, not much was detected at this volcano.
This all changed beginning on August 24th of 2022, when a swarm of earthquakes began
striking underneath the volcano.
While only 9 volcanic earthquakes occurred on August 25th, by August 26th, this figure
had increased to 42 earthquakes.
Over the next week, earthquake intensity remained elevated as the quakes continued to get shallower
and shallower.
While they largely occurred at a depth of 38 kilometers on the 24th, by the 28th they
were occurring at 14 kilometers in depth.
On the 29th, the depth of the earthquakes dramatically got shallower, occurring at about
5 kilometers in depth.
The number of earthquakes would subsequently continue to decline, albeit with another spike
on September 3rd, before eventually reaching approximately the same abundance of quakes
in the last week as seen before the earthquake swarm began.
As a result of all of this activity, the Alaskan Volcano Observatory just posted an information
statement about the earthquake swarm, but kept the alert level of the volcano at green
due to the swarm's declining intensity.
So, what exactly occurred?
Is a new volcanic eruption of this highly active volcano likely?
This video will answer these two questions and discuss the ongoing seismic unrest.
The Trident volcano is located on the scenic Aleutian Peninsula where it is 64 miles southeast
of the city of King Salmon.
This volcano is also just southeast of the famed Novarupta volcano which produced the
largest volcanic eruption of the 20th century in 1912, creating the valley of 10,000 smokes
which forms the distinctive beige coloration from that eruption's pyroclastic flow deposits.
Like the other 12 volcanoes in Katmai National Park, Trident exists due to the offshore collision
of two tectonic plates.
There, the Pacific Plate is subducting underneath the North American Plate.
The melted material from this collision then migrates upwards, until it erupts onto the
surface, forming a chain of volcanoes.
The Trident volcano is a group of four partially overlapping volcanic cones which have altogether
been erupting for 150,000 years.
The tallest cone of this complex is quite eroded, and it does not appear to have produced
an eruption in the last 10,000 years.
Instead, all recent eruptions have originated from the Southwest Trident cone.
Its eruptions have been mildly to moderately explosive, although pyroclastic flow deposits
from this volcano are surprisingly uncommon.
The latest eruptive sequence produced a series of blocky andesite lava flows which travelled
up to 4.5 kilometers away, while the eruptions themselves consisted of vulcanian and possibly
one sub-plinian eruption.
Most of Trident's eruptions rate on the volcanic explosivity index as a 2 or a 3.
If Trident was to erupt again, another group of phreatic to vulcanian explosions would
be expected, potentially leading to the creation of another lengthy andesite lava flow.
In terms of the latest unrest at Trident, it is still unclear exactly what occurred
but I am quite suspicious that some sort of magmatic intrusion or movement of magmatic
fluids did occur.
The earthquakes seemingly started at about the depth of the crust mantle boundary, then
progressively got shallower over time.
Such continual decreases in depth cannot typically be associated with a fault line.
While the current earthquake sequence seems to be ending, more earthquake swarms and potential
magmatic intrusions could occur in the next several months but this isn't a certainty.
However, for the time being it appears unlikely that Trident will erupt anytime soon.
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