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3D image reveals why Great Sitkin volcano has been erupting

Great Sitkin volcano’s alert level has been in ORANGE/WATCH since its first explosive eruption of ash, followed by lava, on July 23, 2021.
Matt Loewen
Alaska Volcano Observatory
Photo was taken on Aug. 2023. Great Sitkin volcano’s alert level has been in ORANGE/WATCH since its first explosive eruption of ash, followed by lava, on July 23, 2021.

The Great Sitkin volcano, located on a remote island 23 miles northeast of Adak, has been erupting since July 2021. Scientists have now discovered the reason behind the years-long eruption, which is helping them assess the volcano's potential hazards more accurately.

According to Matthew Haney, chief scientist at the Alaska Volcano Observatory, the Great Sitkin volcano showed signs of unrest for four years before it finally erupted an ash cloud followed by thick lava in 2021.

“It does seem it is unique in that its period of elevated earthquakes leading into the eruption,” he said.

Haney was part of a national research team that developed a 3D model of the Great Sitkin volcano, which showed its magma plumbing system. The model shows the volcano is erupting because of two magma reservoirs below it. It also depicts the pathway to the magma eruptions.

This information helps scientists understand the potential hazards the eruptions could pose to nearby communities, such as Adak and Atka, and air travel. As many international planes fly over the Aleutian Islands, volcanic ash emissions can significantly impact those flights.

“Having this picture looking inside the volcano is important for volcanologists involved in monitoring to have sort of a concept of, you know, what makes this volcano tick,” said Haney.

The study was conducted by scientists from Purdue University in Indiana, the Carnegie Institution for Science in Washington D.C., and the Alaska Volcano Observatory in Anchorage. The team paired data from earthquakes and ambient sounds from Great Sitkin Island, where the volcano is located. They used data that showed the speed of sounds collected from ocean waves hitting the island and from storms passing over it. Haney said the process was like doing a CAT scan of the Earth.

“It is not a useless kind of noise,” he said. “It's a type of noise that can be exploited to find out what is the velocity of those seismic waves that are being generated by the ocean.”

The Great Sitkin volcano is currently oozing lava and forming a lava dome, which is common for Alaska volcanoes, Haney said. Scientists are not sure how long it’ll continue to erupt, but the Alaska Volcano Observatory is closely monitoring the eruption using various approaches, including local seismic and infrasound sensors, satellite data, and other technologies.

Sofia was born and raised in the Rocky Mountains of Colorado. She’s reported around the U.S. for local public radio stations, NPR and National Native News. Sofia has a Master of Arts in Environmental Science and Natural Resource Journalism from the University of Montana, a graduate certificate in Documentary Studies from the Salt Institute and a Bachelor of Arts in Studio Arts from the University of Colorado Boulder. In between her studies, Sofia was a ski bum in Telluride, Colorado for a few years.
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