Scientists traced a cluster of small earthquakes around Sitka, Alaska in 2020 to magma activity beneath Mount Edgecumbe, about 400 kilometers northwest of Prince Rupert, B.C. Through computer modeling with satellite radar, scientists at the Alaska Volcano Observatory were able to determine in April that the many small earthquakes were caused by rising magma levels below the 976-meter summit on the southern tip of remote Kruzof Island. Despite the activity, scientists say an eruption is highly unlikely and no emergency protocols need to be put in place.
Magma that causes the ground to rise
According to the observatory findings released last monthvolcanic activity has been brewing since 2018 but has gone unnoticed for several years due to minimal monitoring in the area. Magma levels have risen by about 10 kilometers from a depth of 20 kilometers since about late 2014, said Ronni Grapenthin, an associate professor of geosciences at the University of Alaska and lead author of the study. The study says the rising magma reservoirs have also caused deformations in the ground around the volcano – the most dramatic of which is just east of the mountain, where an area about 17km in diameter has risen almost 27cm in less than four years. Grapenthin likened the rising magma to an inflating balloon. “If you have magma moving at a shallower depth, moving through a space and adding pressure, then the surface above it will move up slightly,” he said.
No imminent explosion
Mount Edgecumbe last erupted explosively about 4,000-5,000 years ago, according to Grapenthin. Oral histories from the Klingit Nation in Alaska also report less explosive activity about 900 years ago. Grapenthin says Edgecumbe isn’t going to explode anytime soon. “The magma will continue to pool where it is and sit there happily. We see that happening a lot around volcanoes. Magma more often just moves to a shallower depth and then doesn’t erupt,” he said. Max Enders of the US Geological Survey and Max Kaufman of the UAF Institute of Geophysics at a temporary seismic station on Crater Ridge, near Mount Edgecumbe. Enders and Kaufman are also with the Alaska Volcano Observatory. (Max Kaufman Volcano Observatory/Alaska (Submitted by Ronni Grapenthin)) The city of Prince Rupert said its emergency personnel have been made aware of the regional volcanic activity and have reviewed their emergency plans. “At this point, no local alert or hazard watch has been issued for our area,” he said in a statement to CBC News. Melanie Kelman, a volcanologist at the Geological Survey of Canada who monitors volcanic hazards, also says an eruption is unlikely. “It’s in an area where there’s air traffic overhead, so obviously, it’s a concern for the aviation community if it explodes,” Kelman said. “Right now, it’s really a sign that it shows the speed of magmatic turbulence. Often this kind of turbulence is not followed by an eruption.”
Constant observation
However, Grapenthin says the risk of an eruption could increase if too much magma moves into the area where it pools, increasing the pressure and causing the rock to break. He also says a major earthquake would increase the likelihood. “That would literally shake up the magma like you would shake a soda, and that would quickly build up those pressures,” he said. Grapenthin says the observatory is still trying to determine what caused the resurgence of volcanic activity. Researchers have installed instruments in the ground to monitor seismic activity in the area. As well as monitoring earthquakes in the region, scientists at the observatory are looking at whether deformation patterns are changing and whether there are gases being brought to the surface.
