Scientists at the Alaska Volcano Observatory are warning that it's possible there could be an eruption at Tanaga Volcano after earthquakes were recorded beneath the volcano's summit.
Earthquake activity began to increase "slowly" under the volcano, which is located on an uninhabited island, at around 1:30 p.m. local time on March 8, according to a post on the observatory's Facebook account. By 8:45 p.m. that evening, the activity had escalated. Two or three earthquakes were occurring each minute, the observatory said.
"We started seeing a whole lot of earthquakes occurring, one after the other, several per minute," John Power, a research geophysicist with the U.S. Geological Survey, or USGS, stationed in Anchorage at the observatory, told the Associated Press.
The earthquakes have all been relatively small, with magnitudes between 2 and 3, the observatory said. Their location beneath the volcano's summit poses a threat.
"That indicates that we're seeing significant unrest at the volcano," Power told the Associated Press.
As a result, the volcano's alert level was raised from "NORMAL" to "ADVISORY." This is the second of four levels used by the USGS, which is part of the U.S. Department of the Interior. An advisory alert means that a volcano is "exhibiting signs of elevated unrest above known background level," according to the USGS.
Power told the Associated Press that despite the raised threat level and the increased earthquakes, it's still too early to say if there could be an eruption.
"But we are concerned about it enough that we have gone and elevated the warning level," he said.
The volcano, which is monitored with local seismic and infrasound networks, regional infrasound and lightning detection networks, and satellite data, is the tallest of three volcanic edifices on Tanaga Island. The island, located in the Andreanof Islands, is about 50 miles west of Adak and 1,260 miles southwest of Anchorage.
The last reported eruption of Tanaga was in 1914, the observatory said on Facebook. Before that, eruptions were reported in 1763, 1770, 1791 and 1829. Those eruptions seem to have resulted in blocky lava flows and occasional ash clouds, the observatory said, based on deposits on the volcano.
Power told the Associated Press that instead of the red rivers of lava many people associate with a volcano eruption, there would likely be more viscous, slow-moving lava similar to the kind seen at Mount St. Helens when it erupted in 1980. The biggest threat, he said, would be to aircraft, because the islands are beneath the routes that jets use to fly between North America and Asia.
