An Alaskan Caldera System?

Like a string of pearls, the Aleutian Islands connect Alaska to Siberia. But these are dangerous pearls, because they are part of the so-called Ring of Fire that encircles the Pacific Ocean. Therefore, numerous volcanoes can be found on these barren islands.

[Volcanoes from bottom to top: Tana, Herbert, Cleveland, Carlisle]

The Islands of the Four Mountains in the central Aleutians harbour six stratovolcanoes named Carlisle, Cleveland, Herbert, Kagamil, Tana and Uliaga. New evidence suggests that this cluster may be an interconnected giant volcano.

Researchers have been studying Mount Cleveland, the most active volcano of the group, trying to understand the nature of the Islands of the Four Mountains. They have gathered multiple pieces of evidence showing that the islands could belong to one interconnected caldera[1].

The researchers mapped the sea floor of the region and discovered several curved structures on the sea floor. A depression more than 400 feet deep was seen that may be part of the caldera.

[A massive caldera]

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.

If the researchers’ suspicions are correct, the newfound volcanic caldera would belong to the same category of volcanoes as the Yellowstone Caldera and other volcanoes that have had super-eruptions with severe global consequences.

Caldera-forming eruptions are the most explosive volcanic eruptions on Earth and they often have had global effects. The huge amounts of ash and gas they put into the atmosphere can severely affect Earth’s climate and trigger social upheaval. For example, the eruption of nearby Okmok volcano in the year BCE 43 has been recently implicated in the disruption of the Roman Republic[2].

Diana Roman, co-author of the study, and her team have collected a range of evidence, including gravity anomalies from satellite data and bathymetric surveys that were conducted in the area shortly after World War II.

If their suspicions are confirmed, the team believes that the potential underwater basin may have resulted from a volcanic explosion that was just shy of earning the label 'super eruption.'

[Update] At first, I called this system a 'supervolcano', but Diana Roman kindly contacted me to explain that the term is overused, misrepresentative, and misapplied. Instead, she suggests, I should call it 'caldera system'. See here. Which I agree with and which also explains the altered title of this post.

[1] Power et al: Multi-Disciplinary Evidence for a Large, Previously Unrecognized Caldera in the Islands of Four Mountains, Central Aleutian Arc, Alaska in AGU Fall Meeting – 2020
[2] McConnell et al: Extreme climate after massive eruption of Alaska’s Okmok volcano in 43 BCE and effects on the late Roman Republic and Ptolemaic Kingdom in PNAS - 2020