USGS Volcano Notice - DOI-USGS-AVO-2025-04-18T16:36:39+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, April 18, 2025, 10:44 AM AKDT (Friday, April 18, 2025, 18:44 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

AVO released an updated Information Statement on April 17 that summarized and updated observations, interpretations, and possible outcomes. Based on the recent modest changes in monitoring data and the inability to measure gas for the last month, the outcome of the current unrest is less certain. The likelihood of an eruption has decreased from March, but the volcano remains at an elevated level of unrest and an explosive eruption (or eruptions) like those that occurred in 1953 and 1992 is still possible.

The current unrest at Mount Spurr volcano is characterized by ongoing earthquake activity. Seismicity remains elevated above background with 52 located earthquakes over the last week. Earthquake rates have shown variability during this current period of unrest. Ground deformation at Mount Spurr has slowed over the past three weeks, like the pause in deformation observed for several weeks in November and December, 2024.

No sulfur dioxide emissions were detected in satellite data over the past week and an overflight of the volcano to measure gas emissions is planned for the next good weather day. Steaming from the summit continues to be observed in web camera images during periods of clear viewing conditions. High resolution satellite data from this past week show continued collapse of ice from the summit crater wall into the summit crater lake. The Mount Spurr monitoring network is functioning well.  New snowfall this week has covered up the CKT web camera, but other web cameras (like SPCR) are snow free and functioning well. A new 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 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 that would allow advance warning. 

Mount Spurr volcano 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, characterized by the slow eruption of lava in the summit crater. Satellite radar data (which can see through clouds) from April 17 shows lava flow inflation and subtle advance of the lava flow front to the east and south-east compared to previous data from April 6. Intermittent, small volcanic earthquakes continue to occur. Other satellite and web camera observations were mostly 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

Contact AVO: https://avo.alaska.edu/contact

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.