Why Alaska’s Largest Volcano has 50-50 Eruption Risk?

Mount Spurr, Alaska’s biggest volcano, is exhibiting the possibility of eruption with heightened underground activity. The stratovolcano, 124 kilometers west of Anchorage over Cook Inlet, has witnessed a rise in earthquake activity since April 2024, and this has alarmed scientists at the Alaska Volcano Observatory (AVO). The AVO suspects that the quakes are due to magma movement under the surface.

Increased Earthquake Activity

In the last month, earthquake activity has increased in frequency, with shaking migrating to a lower zone approximately 2 miles (3 kilometers) down the slope. The center of this activity is close to Crater Peak, a side vent that produced eruptions in 1992 and 1953, both of which emitted huge ash clouds that rose to 65,000 feet (20,000 meters).

Matt Haney, the head scientist at the AVO with the US Geological Survey, said that the chance of a similar eruption is 50-50. He added, “It’s had an above-normal rate of earthquakes for several months. But in the last month, that increased itself, and also the place where the earthquakes are occurring changed.”

Although the activity increase may decrease without resulting in an eruption, there have been past events when earthquake activity increased in 2004 and 2005 before calming down by 2006. Nevertheless, an eruption from the summit crater of the volcano is extremely improbable since no such eruption has ever happened in the last 5,000 years. Scientists say that any eruption would be more likely to occur from Crater Peak, where the present-day seismic activity is focused.

What if the Volcano Actually Erupts?

In case Mount Spurr faces an eruption, it might cause violent ash and pyroclastic flows meaning rapid avalanches of gas, ash, and rock moving at velocities of more than 200 mph (320 km/h). The eruption heat will also soften the snow and ice, creating mudflows, or lahars.

There are no communities in the direct path of these flows, but ashfall is a serious issue. The 1992 eruption was widely disruptive, closing Anchorage’s airport and covering the city in dust. Today, with more air traffic, a similar eruption would result in major travel disruptions, such as delays or cancellations of flights between North America and Asia that fly over Alaska.

Haney stressed that extended-duration tremors would be one of the primary warning signs. “If we observed this more long-duration volcano shaking in our seismic data, that would be a more unequivocal sign that the unrest is moving toward a more definite eruption,” he stated.