Alaskan Volcano Likely to Erupt in the Next Weeks or Months, Experts Warn

Accurately predicting when a volcano will erupt is nearly impossible, but Alaska’s Mount Spurr is sending clear warning signs to volcanologists.

Experts at the Alaska Volcano Observatory (AVO) warn that Mount Spurr—a snow-covered volcano 75 miles (120 kilometers) west of Anchorage—is likely to experience an explosive eruption in the coming weeks or months, according to an AVO statement posted Wednesday to the U.S. Geological Survey’s website. Though volcanologists expect to see increased gas, seismic, and heat activity leading up to the potential event, the volcano could also explode without further warning.

Scientists first noticed volcanic unrest at Mount Spurr in April last year, when they detected an unexpected number of earthquakes beneath the volcano, according to an earlier AVO statement. Between April and early October, the volcano averaged 30 earthquakes per week. From early October to early February, that number jumped to 125 per week, though in the past month the weekly rate has declined slightly to 100 earthquakes each week.

In April, AVO scientists also noted some ground deformation along the volcano’s flanks. Though the deformation has shifted the ground by only 2.6 inches (6.5 centimeters) so far, it may indicate the accumulation of magma, fluids, or gases beneath the surface, according to the statement. Furthermore, a lake appeared at the top of Mount Spurr’s icy summit over the summer, implying increased heat within its crater.

This month, scientists measured higher emissions of sulfur dioxide (SO2) from the summit and carbon dioxide (CO2) from both the summit and Crater Peak—a volcanic vent 2 miles (3.5 km) from Mount Spurr’s summit, which now features active gas vents.

“The current unrest at Mount Spurr indicates that new magma has intruded into the Earth’s crust beneath the volcano and that the probability of an eruption has increased,” the Wednesday AVO statement noted. “It is likely that magma has been accumulating beneath Mount Spurr’s summit for some months. The recent gas data suggest that a new pathway towards the Crater Peak vent has opened, and that fresh magma may rise and erupt there.”

The statement goes on to explain that the most likely event will be an explosive eruption, or eruptions, from Crater Peak vent, similar to those that took place in 1953 and 1992. Mount Spurr last erupted from its summit thousands of years ago.

“We use a lot of our knowledge from past eruptions to kind of see what we think might happen in the future,” David Fee, a coordinating scientist from the University of Alaska Fairbanks’s Geophysical Institute, told CNN.

If a future eruption mirrors those of 1953 and 1992, “one or more explosive events, each lasting as long as a few hours, would produce ash clouds carried downwind for hundreds of miles and minor ashfall (up to about 0.25 inches) over south central Alaska. The flanks of Mount Spurr likely would be swept by pyroclastic flows (hot avalanches) and impacted by ballistic showers [flying rocks].” Mudflows, known as lahars, “could inundate the upper Chakachatna River valley,” the statement reads.

For now, scientists don’t expect the eruption to take place imminently. “If we were to see strong, sustained volcanic tremors, that would be kind of a telltale sign that we think an eruption is much closer,” Fee told Alaska Beacon. “We have not seen that yet, and we’re looking very closely for any signs of it. There could be other signs as well.”

“At the current level of unrest, we plan to conduct routine overflights to measure gas emissions, evaluate surface changes, and measure ground surface temperatures,” the AVO statement concludes.