USGS Volcano Notice - DOI-USGS-AVO-2025-05-02T17:16:21+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, May 2, 2025, 11:23 AM AKDT (Friday, May 2, 2025, 19:23 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, though at a lower level than observed in early 2025. While the likelihood of an eruption has decreased since March, 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. We would expect to see weeks or longer of more elevated unrest that would provide advance warning of an eruption.

Seismicity remains above background rates, with 73 located earthquakes over the last week. These earthquakes are much smaller than those caused by tectonic activity and cannot be felt. All from the past week are smaller than Magnitude 1. Earthquake rates have shown variability during this current period of unrest. In addition to located events, much smaller quakes are occurring 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.

AVO last conducted an overflight of the volcano on April 24, when field crews measured surface temperatures at the summit and Crater Peak using an infrared camera, measured gas emissions, and dug out and augmented the power system at station SPCG. Views of the summit at that time showed steaming from fumaroles on the upper flanks and along the shoreline of the crater lake. The lake remains mostly covered in floating ice. No significant surface changes were observed at Crater Peak. Gas data from the flight show emission rates close to those measured in March.

Sulfur dioxide emissions were not detected in satellite data over the last week, largely because of poor viewing conditions related to cloudy weather. Snow is currently covering up the CKT web camera, but other web cameras (like SPCR) are snow free and functioning well, although the rainy weather has prevented views of the volcano over the last week. 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 that would allow 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, characterized by the slow eruption of lava in the summit crater. Satellite data from May 1 shows continued growth of the lava dome. A video taken April 9, recently shared with AVO, shows the steaming lava dome. 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.

ATKA VOLCANIC COMPLEX (VNUM #311160)
52°19'51" N 174°8'20" W, Summit Elevation 5030 ft (1533 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

AVO has detected no activity at the Atka volcanic complex since a small explosion occurred at the summit of Korovin Volcano on the morning of April 25. Korovin is one of the volcanoes that makes up the Atka volcanic complex. Satellite and webcam views were cloudy over the past week, and seismicity remains low.

The Atka volcanic complex is monitored by local seismic and infrasound sensors and webcam, satellite data, and regional lightning detection instruments.

The Atka volcanic complex forms the northern part of Atka Island, located about 16 km north of the community of Atka and 1,761 km southwest of Anchorage. The Atka volcanic complex includes a possible older caldera and several younger vents, including Korovin Volcano, Mount Kliuchef, and Sarichef Volcano. Korovin Volcano, a 1553-m-high (5030 ft) stratovolcano, has been the site of most historical volcanic activity, and has a small, roiling crater lake that occasionally produces energetic steam emissions. Korovin has erupted several times in the past 200 years, including 1973, 1987, and 1998, and has likely had small ash emissions as recently as 2005. Typical recent Korovin eruptions produce minor amounts of ash and occasional but small lava flows. Reports of the height of the ash plume produced by the 1998 eruption ranged as high as 10,600 m (35,000 feet) above sea level. Mount Kliuchef is composed of a series of five vents aligned northeast–southwest. The two main summit vents of Kliuchef appear relatively young and the easternmost was probably the source of an 1812 eruption that is sometimes attributed to Sarichef.

CONTACT INFORMATION:

Matt Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497

Pavel Izbekov, Acting Coordinating Scientist, UAFGI peizbekov@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.