Magma under a long dormant volcano has been observed moving upwards

Research reveals magmatic activity beneath Mount Edgecumbe.

According to a recent study by the Alaska Volcano Observatory, magma beneath the long-dormant Mount Edgecumbe volcano in southeast Alaska has moved upward through the Earth’s crust. .

The observatory’s innovative method could allow early identification of volcanic activity in Alaska. According to computer modeling based on satellite data, Mount Edgecumbe’s magma rises from a depth of about 12 miles to about 6 miles, causing substantial surface deformation and earthquakes.

“This is the fastest rate of volcanic deformation we currently have in Alaska,” said the research paper’s lead author, Ronni Grapenthin, associate professor of geodesy at the University of Alaska Fairbanks. “And while it’s not uncommon for volcanoes to deform, the activity at Edgecumbe is unusual because the reactivation of dormant volcanic systems is rarely seen,” he said.

According to Grapenthin, an eruption is not imminent. Researchers from the UAF Geophysical Institute and the US Geological Survey recently published their findings in the journal Geophysical Research Letters.

The Alaska Volcano Observatory cooperated with another unit of the Geophysical Institute, the Alaska Satellite Facility, to analyze the data in the cloud – a first for the volcano team. Instead of having to download and organize data, which can take weeks or months, researchers can use cloud computing, which uses remote servers to store data and provide computing services.

When a series of earthquakes were detected near Mount Edgecumbe on April 11, 2022, the search team got to work. The researchers analyzed ground deformation detected in satellite radar data over the past 7.5 years.

Four days later, on April 15, the team had a preliminary result: an intrusion of new magma was causing the earthquakes. A small number of earthquakes started under Edgecumbe in 2020, but the cause was ambiguous until the deformation results were produced.

Further data processing confirmed the preliminary conclusion. The Alaska Volcano Observatory notified the public on April 22, less than two weeks after the latest batch of Edgecumbe earthquakes were reported.

“We’ve done this kind of analysis before, but new streamlined cloud-based workflows have reduced weeks or months of analysis to just days,” said David Fee, Observatory Coordinating Scientist. Alaska Volcanoes at the Geophysical Institute.

Mount Edgecumbe, at 3,200 feet, is on Kruzof Island on the western side of Sitka Sound. It is part of the Mount Edgecumbe volcanic field, which includes the domes and the adjacent Crater Ridge crater. Most striking to researchers was an area of ​​ground uplift south of Kruzof Island 10.5 miles in diameter and centered 1.5 miles east of the volcano. Upward deformation began abruptly in August 2018 and continued at a rate of 3.4 inches per year, for a total of 10.6 inches through early 2022.

Later computer modeling indicated the cause was the intrusion of new magma. The new deformation-based analysis will enable earlier detection of volcanic unrest because ground deformation is one of its earliest indicators. Deformation can occur without accompanying seismic activity, making ground heaving a key symptom to watch for.

The Volcano Observatory is applying the new approach to other Alaskan volcanoes, including Trident Volcano, about 30 miles north of Katmai Bay. The volcano shows signs of high unrest. Mount Edgecumbe shows no signs of an imminent eruption, Grapenthin said.

“This magma intrusion has been going on for over three years now,” he said. “Before an eruption, we expect more signs of unrest: more seismicity, more deformation and, importantly, changes in seismicity and deformation patterns.”

The researchers say the magma likely reaches an upper chamber through a nearly vertical conduit. But they also believe that the magma is prevented from moving higher by thick magma already in the upper chamber.

The new magma instead forces the entire surface upwards. Mount Edgecumbe is 15 miles west of Sitka, which has a population of approximately 8,500. The volcano last erupted 800–900 years ago, as cited in the Lingít oral history transmitted by Herman Kitka. A group of Tlingits in four canoes had camped on the coast about 15 or 20 miles south of some large plumes of smoke, according to the account. A reconnaissance team in a canoe was sent to investigate the smoke and reported: “a mountain flashing, spitting fire and smoke”.

Reference: “Return from Dormancy: Rapid Inflation and Seismic Unrest Driven by Transcrustal Magma Transfer at Mt. Edgecumbe Volcano (L’ux Shaa), Alaska” by Ronni Grapenthin, Yitian Cheng, Mario Angarita, Darren Tan, Franz J. Meyer, David Fee and Aaron Wech, October 10 Geophysical Research Letters.
DOI: 10.1029/2022GL099464

The Alaska Volcano Observatory is a joint program of the Geophysical Institute, the U.S. Geological Survey, and the Alaska Geological and Geophysical Surveys Division.