A Group of volcanoes on the Aleutian Chain may actually be one undiscovered giant volcano

Hypothesis of a caldera in Alaska does not add any level of danger to the state
 Cleveland Volcano on a clear day (From Alaska Volcano Observatory)
Cleveland Volcano on a clear day (From Alaska Volcano Observatory) (KTUU)
Published: Dec. 6, 2020 at 9:15 AM AKST
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ANCHORAGE, Alaska (KTUU) -New research has led scientists to suspect a group of volcanoes on the Aleutian Chain is actually part of one undiscovered giant volcano.

According to a release from the American Geophysical Union, volcanologists have a new hypothesis that a tight cluster of volcanoes in the Four Mountains region may be part of a caldera, however, more research is needed to make the final determination.

The area consists of six volcanoes currently classified as stratovolcanoes, which are what people typically think of when picturing a volcano.

The six are Carlisle, Cleveland, Herbert, Kagamil, Tana and Uliaga. They are on the Four Mountains area of the Aleutian Chain between Unalaska and Atka.

According to a release from the AGU, “Unlike stratovolcanoes, which tend to tap small- to modestly-sized reservoirs of magma, a caldera is created by tapping a huge reservoir in the Earth’s crust. When the reservoir’s pressure exceeds the strength of the crust, gigantic amounts of lava and ash are released in a catastrophic episode of eruption.”

Carnegie Institution Volcanologist Diana Roman said she and her team initially went to the Four Mountains area thinking the volcanoes were separate islands and volcanic systems.

Roman said they are somewhat in a ring-like shape suggesting maybe the outline of a larger system.

Roman and her mentor Geophysicist John Power, who is with the USGS Alaska Volcano Observatory, and their team have been working in the Four Mountains area for five or six years.

If the area is a caldera, Power said it does not heighten any level of danger for Alaska.

“This is a system that has probably been there for thousands and thousands of years,” Power said.

There is no immediate cause for alarm and no change of hazard based on this particular discovery in the short term, Power said.

“We are of course, always concerned about Mount Cleveland. It erupts very frequently. The last eruption was on June 2, 2020, just this year,” Power said.

Mount Cleveland is one of the most active volcano in North America.

The team initially went to the area to study Cleveland Volcano’s activity.

“We started noticing various aspects of our observations that seems to suggest potentially a larger system,” Roman said. “Those include things like where the microearthquakes are distributed, the nature of some of the rock deposits that were observed on the different islands. And we started looking at some additional data once we started thinking that there might be a bigger system there.”

Identifying whether the area is a caldera could help the scientists understand why Mount Cleveland is very active, Power said. “It also helps us understand what we might expect going forward into the future in terms of eruptive activity in this part of the Aleutian Arc.”

Roman and Power came up with the initial hypothesis of the potential caldera while standing on the bow of their research vessel.

“We were sailing up towards the islands of the Four Mountains, and we were looking at them,” Roman said. “John looked at me, and he said, ‘I’ve always wondered why there’s this tight cluster of small islands here.’”

If the area is a caldera, it would fall under the same category as the Yellowstone Caldera, according to the release from AGU.

Roman said it would not be entirely accurate to compare the possible caldera on the Aleutian Chain to Yellowstone or to call it a supervolcano, as Yellowstone has been.

“We, as volcanologists, don’t really like to use the term supervolcano because it implies that any eruption by that volcano or that system is going to be large, and that’s actually not the case,” Roman said.

While Yellowstone has had large eruptions, Roman said most recent eruptions have been very small.

“This or Yellowstone, in fact, should not be considered a supervolcano, but volcanoes that have in their past had super-eruptions,” she said.

Roman said another reason to not compare the possible caldera on the Aleutian chain to Yellowstone is that Yellowstone is one of the largest caldera systems on Earth.

Based on the limited evidence the scientists have collected, they think if the area of Four Mountains is a caldera, “it’s not nearly on the scale of the world’s biggest calderas like Yellowstone and Mount Toba in Indonesia. It’s a relatively modest size caldera.”

Scientists have started looking elsewhere in the Aleutian Islands “for similar kinds of relationships that might suggest larger systems,” Power said. “There certainly are some other candidates.”

Power said more research would need to be done to definitively decide if or where other calderas could be.

He also said right now, the Alaska Volcano Observatory does not have any volcanoes in the state at an elevated alert level. He said this is the first time since July 2011.

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