Mount Spurr activity Information Statement July 3, 2024

Summary of Current Activity

New observations of a small lake in the summit crater of Mount Spurr support recent seismic and deformation data that indicate a possible minor intrusion of magma has occurred beneath the volcano over the last several months. While the formation of the lake is new, gas emissions remain low and seismic activity is declining, suggesting the probability of an eruption in the near future has not significantly increased. No surface changes have been observed at Crater Peak, the vent 2 miles (3 km) south of the summit associated with all historical eruptions.

The lake first appeared between May 15 and June 15, and was well documented during a June 23 overflight (see photo below) when it had an area of about 1 acre (3800 square meters). The last time a crater lake formed at the summit of Mount Spurr was during seismic unrest in 2004 that did not lead to an eruption.

Crater lake visible at the summit of Mount Spurr, along with degassing fumaroles on the lake shore.

The June 23 overflight also monitored gas emissions from the volcano and detected low levels of sulfur dioxide and carbon dioxide. The measured compositions are similar to background levels measured in previous years. Deep intrusion of magma is sometimes associated with anomalously high volcanic carbon dioxide emissions, but no such anomaly was detected during the overflight.

Seismic activity beneath Mount Spurr has been above normal levels since spring 2024, but starting on May 20, the degree of seismic unrest has declined and remains slightly elevated (see figure below). The occurrence of deeper (>12.4 miles or 20 km) low frequency earthquakes has been above background levels since spring 2024. A small amount of deformation, consistent with a shallow (less than 3 miles or 5 km depth) source of inflation, has been observed in GNSS data. Similar to the earthquake activity, the rate of deformation appears to be decreasing.

Earthquakes located under Mount Spurr, Alaska from January 1, 2023 to July 2, 2024. The top panel shows earthquake depths through time and the bottom panel shows earthquakes per day. The size of the circles in the top panel reflects the magnitude of the earthquakes as shown in the legend. An increase in the amount and occurrence of deep low frequency earthquakes began in April 2024, the overall rate of earthquakes has decreased the past few weeks. A seismic network outage in early 2024 limited AVO's ability to locate earthquakes. The increase in earthquakes in summer 2023 is related to nearby glaciers and not associated with volcanic activity.

Monitoring Status

Mount Spurr is monitored by a local seismic network, GPS and infrasound sensors, and a webcam. Remote sensing data including satellite imagery, regional infrasound sensors, and lightning data are also used to detect potential eruptions at the volcano.


Mount Spurr volcano is an ice- and snow-covered stratovolcano located on the west side of Cook Inlet approximately 75 miles (120 km) west of Anchorage. The only known historical eruptions occurred in 1953 and 1992 from the Crater Peak flank vent located 2 miles (3.5 km) south of the summit of Mount Spurr. These eruptions were brief, explosive, and produced columns of ash that rose up to 65,000 feet (20 km)above sea level and deposited minor ashfall in south-central Alaska (up to ΒΌ inch or 6 mm). The last known eruption from the summit of Mount Spurr was more than 5,000 years ago. In 2004, Mount Spurr experienced an episode of increased seismicity, surface uplift, and heating that melted a large hole in the summit ice cap and generated debris flows. Primary hazards during future eruptions include far-traveled ash clouds, ash fall, pyroclastic flows, and lahars or mudflows that could inundate drainages all sides of the volcano, but primarily on the south and east flanks.