Volcanic unrest persists at Mount Spurr with elevated seismicity and surface deformation, Alaska

Seismic monitoring recorded 68 earthquakes near Mount Spurr during the past week. Although this number is lower than in previous weeks, the Alaska Volcano Observatory (AVO) reported fluctuating earthquake rates as part of the ongoing unrest.

Gas emission measurements collected during a March 21 overflight were consistent with earlier readings from March 7 and 11. Satellite data also showed repeated detections of gas emissions from the summit, while visible steam was intermittently observed during clear weather conditions, with increased steaming on March 26 attributed to atmospheric factors rather than volcanic changes.

“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,” AVO volcanologists said on March 12.

“It is likely that magma has been accumulating beneath Mount Spurr summit for some months.”

Current data indicate a possible magma pathway towards Crater Peak, the vent responsible for all known historical eruptions.

The volcano’s Alert Level remains at Advisory, and the Aviation Color Code at Yellow.

Based on all available monitoring data, AVO considers the most likely scenario to be explosive eruption(s) like those in 1953 and 1992. 

In this scenario, one or more explosive events, each lasting several hours, would produce ash clouds transported downwind for several hundred kilometers and minor ashfall of up to approximately 6 mm (0.24 inches) over south-central Alaska. The flanks of Mount Spurr would likely be affected by pyroclastic flows and ballistic projectiles, while mudflows (lahars) could inundate the upper Chakachatna River valley.

Mount Spurr is located approximately 120 km (75 miles) west of Anchorage. It is a snow- and ice-covered stratovolcano, with historical eruptions documented in 1953 and 1992 from the Crater Peak vent, located 3.5 km (2 miles) south of the summit. These past eruptions were explosive, generating ash columns up to 20 km (65 000 feet) high and producing ash fall across south-central Alaska, including Anchorage.

According to AVO, any future eruption is expected to be preceded by increased earthquake activity, deformation, and other signs detectable through their monitoring systems. Hazards associated with an eruption include widespread ash clouds, localized ash fall, pyroclastic flows, and lahars, particularly affecting the south and east flanks of the volcano.

References:

¹ Weekly update for Mount Spurr – AVO – March 28, 2025

² Information statement for Mount Spur – AVO – March 12, 2025