Alaska Volcano Observatory

On October 16, 2024, AVO raised the color code and alert level to YELLOW/ADVISORY, stating: "AVO has observed a gradual increase in volcanic unrest over a period of several months at Mount Spurr, located about 120 km (75 miles) west of Anchorage (https://avo.alaska.edu/image/view/196123). GNSS receivers have detected sustained upward and outward ground deformation since March 2024. An increase in seismic activity has also been noted since April (https://avo.alaska.edu/image/view/196122). Other indications of elevated activity include the development of a small lake in the summit crater in early summer of 2024.
"The largest magnitude earthquake detected in this current period of unrest is a M2.3 earthquake on October 6th. This increase in activity was described in detail in an Information Statement (https://avo.alaska.edu/news/hans/DOI-USGS-AVO-2024-10-09T19:43:26+00:00) that AVO released on October 9th. Analysis of seismic data indicates a subtle increase in the rate and size of earthquakes over the past few weeks. Because this is a notable departure from the normal background seismicity of the volcano, AVO is raising the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. However, there are no indications that an eruption is imminent. Often this type of seismicity and ground deformation will decline without producing an eruption.
"AVO continues to closely monitor activity at Mount Spurr for signals that would indicate that the volcano is moving closer to an eruption. Based on previous eruptions, changes from current activity in the earthquakes, ground deformation, summit lake, and fumaroles would be expected if magma began to move closer to the surface. Therefore, it is very likely that if an eruption were to occur it would be preceded by additional signals that would allow advance warning. "
Over the following two weeks, there were more than 180 small earthquakes at Mount Spurr. Over the week of November 1st, there were also a few episodes of possible volcanic tremor, which might indicate deep fluid movement. No unusual activity or surface changes were observed in satellite data or webcam views. AVO staff visited on October 24th to conduct pre-winter maintenance on Spurr’s monitoring network and noted that the fumaroles (steam/gas vents) in Spurr summit’s crater were steaming.
Over the following weeks, earthquakes continued at varying rates, as is typical during periods of unrest. Steam was occasionally visible rising from Spurr’s summit during clear weather. On December 10, there was a M2.8 earthquake beneath the summit, and a few more episodes of tremor were recorded that week.
On Wednesday, December 18, AVO staff conducted a gas flight at Mount Spurr. Measurements of H2O, SO2, H2S, and CO2 were collected. Results were similar to the previous gas flight conducted on June 23, 2024. Personnel also took images and video during the flight that allowed accurate measurements of the crater lake that formed this year, showing that it has grown considerably since June despite the transition into winter. No activity was observed at Crater Peak.
As the new year turned, there were some notable periods of increased earthquake activity within the context of the larger unrest episode. The week of January 3, 2025, over 260 earthquakes were located, the largest being an M2.9 on January 2. Meanwhile, GPS data continued to show slow, steady inflation of the ground surface. Satellite radar data the week of January 10 showed that the crevasses in the summit crater were widening, demonstrating continued heat input to the area.
During January 20-22, the monitoring network at Mount Spurr experienced some issues transmitting data back to AVO due to poor weather, not unusual for this time of year.