The likelihood that a volcano 78 miles southwest of Anchorage will imminently erupt has decreased from March, though scientists say it’s still possible.
Since October, scientists have been monitoring heightened signs of unrest on Mount Spurr, including earthquakes beneath the volcano, gas emissions, ground deformation from magma beneath the surface, and the melting of snow and ice at the summit. Last month, the combined signs of unrest prompted the Alaska Volcano Observatory to warn Southcentral Alaska residents of a likely Mount Spurr eruption within “weeks to months.”
Since then, the number of shallow earthquakes under Spurr have decreased slightly, though activity still remains elevated, scientists said in a statement Thursday. “Ground deformation has also slowed over the past three weeks,” the statement said.
But while the likelihood of an eruption has decreased with recent monitoring data, the uncertainty of the prognosis has increased due to an incomplete data set, said Alaska Volcano Observatory scientist-in-charge Matt Haney.
Poor weather conditions have inhibited scientists from measuring Spurr’s gas emissions — whether by helicopter or by satellite capturing — for several weeks, Haney said.
“We don’t have the full suite of of data sets that, in an ideal case, we would be drawing upon to make our interpretation,” Haney said. He said his team expects a good weather window this weekend to fly over the volcano and measure gas emissions.
“So, overall, the likelihood of interruption has decreased, but it’s not zero,” Haney said.
[How to prepare for what scientists say is the likely eruption of Mount Spurr]
Seismic activity is still measuring above-average at about 70 earthquakes below Mount Spurr per week, he said, down from roughly 300 per week in January. Inflation of the mountain’s surface also suggests magma intrusions into the volcano’s crust, Haney said.
If an eruption were to occur, the scientists say, the most likely scenario would be similar to previous eruptions in 1953 and 1992, when about a quarter-inch of ashfall rained down across Southcentral communities for several hours, temporarily shutting down airports, offices and schools.
As of April 17, Mount Spurr is back at a yellow advisory level, indicating elevated volcanic activity. If the volcano were to erupt again, scientists say they expect to have weeks to months of lead time to warn the public.
“This type of volcano, Mount Spurr, I would call it well-behaved. If it progresses, first we’ll see that strong volcanic tremor,” Haney said.
Volcanic tremors started three weeks before the June 1992 Spurr eruption, and two months before Redoubt erupted in 2009. “It shows lots of unrest signals before it can develop into an into an eruption,” Haney said.
AVO has posted a new livestream of Mount Spurr from a vantage point at Glen Alps.
The state Division of Homeland Security and Emergency Management said in a statement Thursday that agencies have “observed numerous false or misleading social media about the Mount Spurr Volcano” in recent weeks.
Currently, travel, tourism and recreation in Alaska have not been affected by the volcano, the emergency management division said.
[Correction: An earlier version of this story incorrectly reported that Mount Spurr’s advisory level changed in March from yellow to orange. It has remained at yellow.]
