USGS Volcano Notice - DOI-USGS-AVO-2025-02-14T20:27:46+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, February 14, 2025, 12:46 PM AKST (Friday, February 14, 2025, 21:46 UTC)

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 has remained unchanged over the past week, with lava continuing to erupt slowly in the summit crater. Satellite radar data from February 10 shows continued slow growth of lava toward the north-northeast. Intermittent, small volcanic earthquakes persist. A few clear views of the volcano in satellite and webcam images showed no unusual activity.

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.

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

Volcanic unrest continues at Mount Spurr. More than 80 earthquakes were located under Mount Spurr during the past week which is a decrease from the previous week when over 200 earthquakes were located. These small (mostly less than magnitude 1) events were located both under the north side of the Spurr Summit as well as Crater Peak, the flank vent south of the summit that was the site of the 1953 and 1992 eruptions. Data from GNSS stations show that outward inflation continues at about the same rate as has been occurring since spring of 2024. An AVO field crew did an overflight of the volcano on February 7. Thus far we see no obvious changes at the Crater Peak vent. The ice-filled crater lake at the Spurr summit is still present but is reduced slightly in water depth and surface area and a high-temperature fumarole field is visible on the north shore of the crater lake. Infrared images of the fumarole field show temperatures as high as 320 degrees F (160 degrees C). Although conditions were not ideal for measuring gas during the February 7 overflight, data that were collected show no significant changes in gas output from the volcano. Sulfur dioxide and carbon dioxide gas are similar to background levels measured in previous years. Clear views of the volcano by satellite and web cameras much of this week showed steaming from summit crater which was notably more robust on February 13. This steaming was also reported and photographed by a lodge operator located about 30 mi (48 km) northeast of the volcano.

The Spurr monitoring network is functioning well after AVO engineers visited the volcano to make repairs this and last week, and to dig out stations that were covered in snow and ice. Photographs from the AVO field crew show before and after views of geophysical monitoring station SSN located on Mount Susitna on February 7.

AVO continues to closely monitor activity at Mount Spurr for signals that would indicate that the volcano is moving closer to an eruption using local seismic, infrasound, web camera, and GNSS stations along with regional infrasound, lightning networks and satellite data. Based on previous eruptions, additional changes in earthquakes, ground deformation, the summit lake, and fumaroles would be expected if magma begins to move closer to the surface. Therefore, it is very likely that if an eruption were to occur 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 120 km (75 mi) west of Anchorage. The only known historical eruptions occurred in 1953 and 1992 from the Crater Peak flank vent located 3.5 km (2 mi) south of the summit of Mount Spurr. These eruptions were brief, explosive, and produced columns of ash that rose up to 20 km (65,000 ft) above sea level and deposited several mm of ash in south-central Alaska, including approximately 6 mm of ash in Anchorage in 1953. The last known eruption from the summit of Mount Spurr was more than 5,000 years ago. 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.

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.