USGS Volcano Notice - DOI-USGS-AVO-2025-06-20T19:31:47+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, June 20, 2025, 1:05 PM AKDT (Friday, June 20, 2025, 21:05 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 activity is still above background, but lower than observed in early 2025. This decrease in activity suggests that the magma intrusion beneath Mount Spurr has stalled. The likelihood of an eruption has declined since March, but fluctuations in unrest are not uncommon, and explosive eruptions are still possible. Should unrest escalate towards an eruption, we expect increases in seismic activity, gas emissions, surface deformation, and surface heating.

During the past week, 42 earthquakes were located, all smaller than magnitude 1. The number of located earthquakes this week is about the same as the last two weeks, and lower than weekly counts from earlier in 2025. However, they are within the variability observed from week to week during this entire period of unrest. Ground deformation, as measured by GNSS (GPS) stations, remains paused as it has for the last two months.

Minor sulfur dioxide emissions were observed in satellite data one day this week. The last gas flight occurred June 11 and found that gas compositions and emission rates were broadly unchanged from those measured during the previous gas flight on May 23. Yesterday, June 19, AVO installed a new continuous gas sensor on the rim of Crater Peak. Initial readings from the station show high carbon dioxide emissions from the vent, and no sulfur dioxide, consistent with past gas flights. The new station will allow for continuous measurements of Crater Peak gas emissions when wind conditions allow, includes seismic and infrasound instrumentation, and is a significant improvement to our monitoring capabilities.

No significant surface changes were observed at Mount Spurr over the past week. Earlier this week, AVO installed a new livestream camera at station SPCL: Mount Spurr Live Stream (SPCL). A livestream of Mount Spurr, as viewed from Glen Alps in Anchorage, is also 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.

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

Slow eruption of lava in the summit crater of Great Sitkin continues. Satellite and web camera views of the volcano show slight inflation of the summit lava dome above the vent area, and small rockfalls from the steep southern and southeastern sides of the upper lava dome. Occasional small earthquakes, including some likely caused by rockfalls from the dome, occurred throughout the 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.