ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, March 14, 2025, 12:29 PM AKDT (Friday, March 14, 2025, 20:29 UTC)
Volcanic unrest continues at Mount Spurr volcano and is characterized by ongoing earthquake activity, surface deformation, and volcanic gas emissions. Seismicity remains elevated and increased slightly compared to last week. Over the past week, 145 earthquakes were located, most in the summit region and fewer near Crater Peak. No unusual activity was observed in satellite or webcam data, although minor steam emissions from the summit of the volcano were sometimes seen from nearby communities during periods of clear weather. Overflights on March 7 and 11 to measure volcanic gases found elevated levels of SO2 and CO2 being emitted from the summit of Mount Spurr and CO2 being emitted from Crater Peak. Reactivated gas vents were also observed within the crater at Crater Peak. AVO released an Information Statement earlier this week that discusses these observations and more. The Mount Spurr monitoring network is functioning well, although the web camera at station CKT remains obscured by snow and ice.
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, 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 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 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 possibly 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.
Activity at Great Sitkin Volcano continued over the past week, characterized by the slow eruption of lava in the summit crater. Satellite radar data through March 6 shows ongoing slow growth of the lava flow. Intermittent, small volcanic earthquakes continue to occur. The volcano has been obscured by clouds in satellite and web camera views all 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.
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.