Research shows magma activity beneath Mount Edgecumbe.
According to a recent study by the Alaska Volcano Observatory, magma has been moving up through the Earth’s crust beneath the long-dormant Mount Edgecumbe volcano in Southeast Alaska.
The observatory’s innovative method could allow early identification of volcanic activity in Alaska. Magma at Mount Edgecumbe rises from a depth of about 12 miles to about 6 miles, causing significant surface deformation and earthquakes, according to computer models based on satellite data.
“This is the fastest volcanic deformation rate we’ve seen in Alaska right now,” 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, activity at Edgecumbe is unusual because 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 worked with another Geophysical Institute unit, the Alaska Satellite Facility, to analyze data in the cloud — a first for the volcano team. Instead of downloading and organizing 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 research team got to work. The researchers analyzed ground deformations detected in satellite radar data over the past 7 1/2 years.
Four days later, on April 15, the team had a preliminary result: an intrusion of new magma caused the earthquakes. A small number of earthquakes began under Edgecumbe in 2020, but the cause was not clear until the deformation results were compiled.
Additional data processing confirmed the preliminary finding. The Alaska Volcano Observatory briefed the public on April 22, less than two weeks after the last string of Edgecumbe earthquakes was reported.
“We’ve done this type of analysis before, but new streamlined cloud-based workflows are cutting weeks or months of analysis down to just days,” said David Fee, coordinating scientist for the Alaska Volcano Observatory at the Geophysical Institute.
Mount Edgecumbe sits at 3,200 feet on Kruzof Island on the west side of Sitka Sound. It is part of the Mount Edgecumbe volcanic field, which includes the domes and crater of the adjacent Crater Ridge. Most striking to researchers was an area of uplift on southern 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 an annual rate of 3.4 inches through early 2022, for a total of 10.6 inches.
Subsequent computer models showed that the cause was the intrusion of new magma. The new deformation-based analysis will allow for earlier detection of volcanic unrest, as ground deformation is one of its earliest indicators. Deformations can occur without accompanying seismic activity, making ground uplift an important symptom to monitor.
The Volcano Observatory is applying the new approach to other Alaskan volcanoes, including Trident Volcano, about 30 miles north of Katmai Bay. The volcano is showing signs of increased unrest. Mount Edgecumbe is showing no signs of an impending 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 the patterns of seismicity and deformation.”
The researchers say the magma likely reaches an upper chamber through a near-vertical conduit. But they also believe that thick magma already in the upper chamber is preventing the magma from moving further up.
Instead, the new magma pushes the entire surface up. Mount Edgecumbe is 15 miles west of Sitka, which has a population of approximately 8,500. The volcano last erupted 800 to 900 years ago, as quoted in the Lingít Oral History handed down by Herman Kitka. According to the report, a group of Tlingits in four canoes had camped about 15 or 20 miles south of some large coastal smoke plumes. A scouting party in a canoe was sent to examine the smoke and reported: “A mountain blinks, spewing fire and smoke.”
Reference: “Returning from Dormant: Rapid Inflation and Seismic Unrest by Transcrustal Magma Transfer at Mt. Edgecumbe Volcano (L’úx Shaa), Alaska” by Ronni Grapenthin, Yitian Cheng, Mario Angarita, Darren Tan, Franz J. Meyer, David Fee and Aaron Wech, October 10, 2022, Geophysical Research Letters.
The Alaska Volcano Observatory is a joint program of the Geophysical Institute, the US Geological Survey, and the Alaska Division of Geological and Geophysical Surveys.