USGS Volcano Notice - DOI-USGS-AVO-2025-05-08T17:56:17+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, May 9, 2025, 11:11 AM AKDT (Friday, May 9, 2025, 19:11 UTC)

SPURR (VNUM #313040)
61°17'56" N 152°15'14" W, Summit Elevation 11070 ft (3374 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Unrest continues at Mount Spurr. The level of unrest is still above background, but lower than observed in early 2025. The likelihood of an eruption has declined since March, but explosive eruptions like those in 1953 and 1992 are still possible. Should unrest escalate, we expect seismicity at higher levels than present, lasting weeks or months, more robust gas emissions, and higher deformation rates. 

Earthquakes detected at the volcano are smaller than those caused by tectonic activity and cannot be felt. During the past week, 66 earthquakes were located with most of the quakes smaller than Magnitude 1. Smaller quakes that cannot be located also occur several times per hour. Ground deformation at Mount Spurr has slowed over the past month, like the pause that occurred for several weeks in November and December 2024.

Views of the summit from local web cameras showed a vapor plume when viewing conditions were clear. No significant surface changes were observed at Crater Peak. Sulfur dioxide emissions were detected several times in satellite data this week when clouds did not obscure the volcano summit. A recently established livestream of Mount Spurr, as viewed from Glen Alps in Anchorage, is available here: Mount Spurr Live Stream (ANCG).

AVO continues to closely monitor activity at Mount Spurr for signals indicating the volcano is moving closer to an eruption using local seismic, infrasound, and GNSS (GPS) stations, web cameras, airborne and satellite gas measurements, regional infrasound, lightning networks, and satellite images. Based on previous eruptions, additional changes in earthquakes, ground deformation, the summit lake, and fumaroles would be expected if magma moves closer to the surface. Therefore, if an eruption occurred, it would be preceded by additional signals allowing advance warning. 
 

Mount Spurr is an ice- and snow-covered stratovolcano located on the west side of Cook Inlet approximately 80 miles (129 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 about 65,000 feet (20 km) above sea level and deposited minor ashfall in southcentral Alaska (up to ¼ 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.

GREAT SITKIN (VNUM #311120)
52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Activity at Great Sitkin Volcano continued over the past week. The unrest was characterized by the slow eruption of lava in the summit crater and occasional small earthquakes. Satellite and web camera observations were obscured by clouds over the past week.

Since the May 2021 explosion, there have been no other explosions at Great Sitkin Volcano. The lava eruption that began in July 2021 is ongoing. It has filled most of the summit crater and advanced into valleys below. The volcano is monitored using local seismic and infrasound sensors, satellite data and web cameras, and regional infrasound and lightning networks.

Great Sitkin Volcano is a basaltic andesite volcano that occupies most of the northern half of Great Sitkin Island, a member of the Andreanof Islands group in the central Aleutian Islands. It is located 26 miles (42 km) east of the community of Adak. The volcano is a composite structure consisting of an older dissected volcano and a younger parasitic cone with a ~1 mile (1.6 km)-diameter summit crater. A steep-sided lava dome, emplaced in the crater during an eruption in 1974, has been mostly buried by the ongoing eruption. The 1974 eruption produced at least one ash cloud that likely exceeded an altitude of 25,000 ft (7.6 km) above sea level. A poorly documented eruption also occurred in 1945, producing a lava dome that was partially destroyed in the 1974 eruption. Within the past 280 years a large explosive eruption produced pyroclastic flows that partially filled the Glacier Creek valley on the southwest flank. 

CONTACT INFORMATION:

Matt Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497
David Fee, Coordinating Scientist, UAFGI dfee1@alaska.edu (907) 378-5460

 

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.