Researchers discover activity at dormant Mt. Edgecumbe

15 miles west of Sitka, a dormant volcano has recently seismic activity.
Published: Oct. 25, 2022 at 9:20 AM AKDT
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FAIRBANKS, Alaska (KTVF) - 15 miles west of Sitka, Alaska, dormant volcano, Mt. Edgecumbe has had a resurgence of activity after centuries of being considered inactive.

In April, 2022, Mt. Edgecumbe experienced a swarm of small earthquakes, attracting scientists to investigate the activity. Researchers utilized a new method of data analysis to quickly arrive at an understanding of the seismic event. Using cloud computing, they were able to analyze decades of data in less than two weeks, saving time on an important discovery that could have taken months if traditional analysis methods were used. What they discovered was unexpected.

Deformities were discovered at the surface level showing an upward change of 10.6 inches. The deformities are the result of magma rising from about 12 miles below the surface to six miles below the surface. Data indicates that the magma rise abruptly began in a surface uplift in 2018, holding a constant rate of 3.4 inches per year.

This particular event has scientists intrigued because it is rare for an inactive volcano to see activity return. Adding to the unusual circumstance, Mt. Edgecumbe and the surrounding area sits on a “transform fault,” according to Dr. Ronni Grapenthin, an associate professor of Geodesy at the University of Alaska Fairbanks (UAF). A transform fault is a place where tectonic plates, are sliding past each other. This is the same type of fault as the San Andreas fault in California. Due to the movement of the plates, volcanoes are unlikely to be active. In comparison, the volcanoes in the Aleutians sit on a subduction which means that one tectonic plate is being pushed down while another is being pushed up, commonly resulting in the formation of volcanoes.

The last eruption at Mt. Edgecumbe is theorized to have taken place about 800 or 900 years ago. According to local accounts passed down through Alaska Natives over the generations, the last eruption had visible smoke and inhabitants were able to canoe closer to the volcano to investigate the smoke. Grapenthin believes that the account suggests that the eruption was very localized. He added there is a lack of data surrounding that eruption and current data suggests the volcano would be capable of erupting in different ways. One point of evidence supporting this claim, according to Grapenthin, is the existence of Basalt, a type of igneous rock. Basalt is associated with highly viscous magma, or lava that doesn’t flow far from the point of eruption, “much like volcanoes in Hawaii,” said Grapenthin.

There a lot of variables that still need to be researched, but Grapenthin does not perceive any current danger of an eruption. “We just don’t know enough, in enough detail, what the actual properties in the ground surface are to make very accurate predictions about what the life time of the magma reservoir at that depth is and whether or not magma might propagate further upward,” said Grapenthin.

If an eruption were to develop, “we would have plenty of signals,” said the UAF associate professor of Geodesy. We do know the discovery of activity at Mt. Edgecumbe will lead to more research from different fields and approaches.