Earthquakes at Alaskan Volcano Trigger Worries of Eruption

A file photo shows the Tanaga Volcano in Alaska's Aleutian Range. (MW Loewen/US Alaska Volcano Observatory/USGS).

A series of earthquakes have been recorded at the Tanaga Volcano in Alaska, sparking worries that the long-dormant volcano might be prepping up for an eruption.

On Tuesday, the Alaska Volcano Observatory (AVO) raised the alert level for Tanaga to “Yellow” after the earthquakes intensified. “Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase,” the observatory said in an advisory.

There have been hundreds of small earthquakes with a magnitude of less than 2.75 concentrated below the volcano’s summit, John Power, a research geophysicist with the U.S. Geological Survey (USGS) stationed at AVO told the Associated Press.

“We started seeing a whole lot of earthquakes occurring, one after the other, several per minute … That indicates that we’re seeing significant unrest at the volcano,” Power said,

“Whether or not this will lead to an eruption is something we can’t say at this point in time … But we are concerned about it enough that we have gone and elevated the warning level.”

Power pointed out that even though the intense earthquake activity is a cause for concern, such activity could also ease down without an eruption.

Eruption Consequence

Tanaga is part of a complex of three volcanoes on an uninhabited island in the Aleutian Islands. It is located around 1,250 miles southwest of Anchorage, Alaska. It is the tallest of the three. All three volcanoes have a history of eruption in the last 1,000 years.

The last time there was a confirmed eruption at the Tanaga volcano was in 1914, with the previous eruption roughly a century earlier in 1829.

According to a 2007 report (pdf) by USGS, the “primary hazard” from a Tanaga volcanic eruption would be airborne ash that can affect aircraft. Though the wind is expected to carry the ash mainly to the east, the ash can travel in any direction.

A file photo shows the Tanaga Volcano in Alaska's Aleutian Range. (MW Loewen/US Alaska Volcano Observatory/USGS).

“Airborne ash is hazardous to aircraft because of the detrimental effect on jet engines. Because heavily traveled air routes between North America and Asia overlie the volcano, ash clouds probably are the most hazardous phenomena associated with eruptions of the Tanaga volcanic cluster,” the report states.

“Heavy ash fall can collapse buildings, harm mechanical equipment, damage vegetation, clog streams, and effect wildlife … Ash in the atmosphere can interfere with radio communications and damage power lines. Ash fall downwind of Tanaga may affect airport and fishing port operations.”

Volcanic Earthquakes

Earthquakes occurring near volcanoes may indicate a change in the behavior of these volcanoes and can occur in high frequency, according to a post by the Alaska Earthquake Center (ACE) at the University of Alaska Fairbanks.

“These changes may be due to the movement of magma or gas, may result from moving ice or debris, or may simply reflect the adjustment of stresses in the surrounding region,” according to the AEC.

“Each of these sources produces seismograms with unique signatures that can often be used to assess the cause of the earthquake. At times, the presence of certain types of earthquakes or numerous earthquakes, accompanied by other indicators, can be indicative of forthcoming eruptions.”

On Jan. 10, a swarm of earthquakes were recorded off Alaska’s Aleutian Islands, which included a quake with a magnitude of 6.8 that was preceded by foreshocks.

An hour after the 6.8 quake, another quake of magnitude 6.6 was triggered in the same region, followed by several aftershocks measuring 4.0 or higher. The Aleutian Islands saw quite a lot of seismic activity in 2022.