Volcanic Unrest at Mount Spurr, Alaska (February 2025)

Summary:

Mount Spurr, a stratovolcano located approximately 75 miles west of Anchorage, Alaska, is exhibiting signs of increased volcanic activity, prompting close monitoring by the Alaska Volcano Observatory (AVO). The primary indicators are an increase in seismic activity, changes to the summit crater, and observations of fumaroles. While an eruption is not certain, volcanologists estimate a roughly 50-50 chance of an eruption at Crater Peak and are closely watching for additional signals that would indicate an increased likelihood. Past eruptions, particularly those in 1953 and 1992, demonstrate the potential for significant disruption to air travel due to ashfall.

Key Themes and Details:

• Increased Seismic Activity: A significant increase in earthquakes has been recorded since April, escalating from approximately 30 per week to 125 per week. Over 2,700 earthquakes have been recorded in total, with the largest being a magnitude 2.9 quake on January 2. As noted by one article, "thousands of earthquakes and notable shifts in the terrain have been observed over recent weeks, indicating that the volcano may be on the verge of an eruption."
• Location of Potential Eruption: If an eruption occurs, scientists believe it is most likely to occur at Crater Peak, a vent located about two miles below the Spurr summit. Crater Peak erupted in 1953 and 1992.
• Potential Hazards: An eruption at Crater Peak could release "streams of hot gas, rock and ash traveling at speeds of more than 200 miles per hour." This could also lead to lahars (mudflows) due to melting snow and ice. While the immediate area around Mount Spurr is sparsely populated, the primary concern is ashfall affecting Anchorage and disrupting air travel.
• Impact on Air Travel: The 1992 eruption caused significant travel disruptions by blanketing Anchorage in ash and shutting down the airport. The USGS reports that "planes are highly susceptible to volcanic materials, which can damage the fuselage, blades and significantly hinder engine performance." The increased volume of air traffic in 2025 compared to 1992 suggests that a similar eruption could be even more disruptive today.
• Monitoring Efforts: The AVO is closely monitoring Mount Spurr using 11 seismic stations and conducting overflights to take gas measurements and maintain instruments. They are looking for specific warning signs that would indicate an imminent eruption, including increased seismic activity, gas emissions, surface heating, and changes in surface deformation. As Matt Haney stated, "We’re watching it very closely... We’re saying that there’s unrest above background [levels], but it’s uncertain if this is actually building to an eruption."
• Uncertainty of Eruption: While there is a 50-50 chance of an eruption, it is also possible that the volcanic unrest will subside without an eruption. Past episodes of increased activity have not always resulted in eruptions. According to one of the articles, "Sometimes there can be a build-up of magma beneath the volcano, but it doesn’t have enough magma to ultimately proceed all the way and produce a volcanic eruption."
• Advanced Warning: The AVO expects to see additional warning signs before an eruption, potentially providing "days to a few weeks" of advanced notice, although this is not guaranteed. The AVO stated that, "it is very likely that if an eruption were to occur it would be preceded by additional signals that would allow advance warning."