Group of Alaskan islands may belong to a single, massive volcano

Group of Alaskan islands may belong to a single, massive volcano. A cluster of volcanic islands in Central Alaska may be part of one interconnected giant volcano, according to the American Geophysical Union. If this theory is correct, the massive volcanic caldera would belong to the category of supervolcanoes that have produced the largest eruptions in Earth’s history.

The Islands of the Four Mountains in the central Aleutians is a group of six stratovolcanoes named Carlisle, Cleveland, Herbert, Kagamil, Tana, and Uliaga. With their steep conical mountains, stratovolcanoes can have enormous eruptions, like that of Mount St. Helens in 1980. 

While studying Mount Cleveland, the most active volcano of the group, researchers from multiple institutions have found evidence to suggest that the islands belong to one interconnected caldera.

Caldera-forming eruptions are the most explosive and dangerous volcanic eruptions. The volume of ash and gas released by these events can have global impacts on the climate, and can also trigger abrupt social change. For example, the fall of the Roman Republic was recently linked to an eruption of the nearby Okmok volcano in the year BCE 43.

The proposed caldera in Alaska would be even larger than Okmok. Study co-author Diana Roman said that if the caldera is confirmed, it would become the first in the Aleutians that is hidden underwater. She described the difficulty of studying such a remote place.”We’ve been scraping under the couch cushions for data,” said Roman. “But everything we look at lines up with a caldera in this region.”

Study lead author John Power is a a researcher with the U.S. Geological Survey at the Alaska Volcano Observatory. He and Roman emphasized that the existence of the caldera is not yet proven. To investigate further and confirm the caldera, the team must return to the islands and gather more direct evidence to fully test their theory.

“Our hope is to return to the Islands of Four Mountains and look more closely at the seafloor, study the volcanic rocks in greater detail, collect more seismic and gravity data, and sample many more of the geothermal areas,” said Roman. She noted that the caldera hypothesis may also help explain the frequent explosive activity seen at Mount Cleveland.

For the last 20 years or longer, Mount Cleveland has likely been the most active volcano in North America. It is known to produce ash clouds as high as 15,000 and 30,000 feet above sea level, which poses serious hazards to aircraft.

“It does potentially help us understand what makes Cleveland so active,” said Power. “It can also help us understand what type of eruptions to expect in the future and better prepare for their hazards.”

The research will be presented on December 7, 2020 at the AGU Fall Meeting 2020.

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By Chrissy Sexton, Earth.com Staff Writer