A Massive Supervolcano May Lurk Beneath Alaska’s Aleutian Islands

Multiple lines of evidence led scientists to the idea that a group of six volcanoes in the islands are actually part of a 12-mile-wide caldera

Alaska's Islands of Four Mountains
An aerial oblique photo of the volcanoes of the Islands of Four Mountains in Alaska's Aleutian Island chain. In the center is the summit of Mount Tana. Behind Tana are (left to right) Herbert, Cleveland and Carlisle Volcanoes. John Lyons / USGS

On a map, Alaska’s Aleutian Islands form an increasingly faint wisp of land arching across the North Pacific toward the Russian coast. As if it weren’t enough that these rugged, remote islands get battered by some of the harshest storms on the planet, they are also studded with 44 volcanoes.

But now, researchers think the island chain may also be home to a supervolcano, reports Maya Wei-Haas for National Geographic.

The proposed supervolcano, presented yesterday by researchers at the American Geophysical Union’s (AGU) 2020 Fall Meeting, would unite six of the known volcanoes in the Aleutians into the rim of one massive caldera similar to Yellowstone’s imposing supervolcano.

Somewhat confusingly, the six Aleutian volcanoes are located in a group of islands called the Islands of Four Mountains. Named Carlisle, Cleveland, Herbert, Kagamil, Tana and Uliaga, all six are what scientists call stratovolcanoes—the steep-sided, conical shapes most people associate with the word “volcano,” according to a statement from AGU.

Stratovolcano eruptions are nothing to sneeze at—Mount St. Helens is a stratovolcano—but huge calderas like the one in Yellowstone are in a different category. That’s because calderas tend to sit atop massive reservoirs of magma that lurk beneath Earth’s crust, and can launch so much ash and gas into the sky that they can alter the climate of the entire planet.

John Power, a geophysicist at the U.S. Geological Survey’s Alaska Volcano Observatory and one of the researchers behind the findings, tells Beth Geiger of Science News that this proposed Aleutian caldera is so big that if it erupted during the last few thousand years it could have thrown civilizations around the world into disarray.

The researchers arrived at their hypothesis by looking at the region’s seismic activity, gas emissions, geochemistry and even measurements of gravity, reports Mindy Weisberger for Live Science.

“There’s no one smoking gun,” Diana Roman, a volcanologist at Carnegie Institution for Science and co-author of the research, tells Science News. The six volcanoes of the Four Mountains look distinct enough from one another, but multiple lines of evidence converged on the notion that they are merely vents of a single 12-mile-wide supervolcano.

According to Science News, the peaks are arranged in a semicircle that becomes a ring when taken together with maps of the seafloor created in the 1950s that show ridges completing the circle along with a 426-foot depression in the proposed center of the caldera.

"Everything we look at lines up with a caldera in this region," Roman says in the statement.

Fortunately, even if the newly proposed caldera is confirmed, it doesn’t suggest the Aleutians are any more likely to catastrophically blow their top, National Geographic.

“This new research result doesn’t change the hazards,” Power tells National Geographic. “We’re not forecasting something dangerous here.”