USGS Volcano Notice - DOI-USGS-AVO-2025-04-04T18:20:00+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, April 4, 2025, 12:31 PM AKDT (Friday, April 4, 2025, 20:31 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

Volcanic unrest continues at Mount Spurr volcano and is characterized by ongoing earthquake activity, surface deformation, and volcanic gas emissions. Seismicity remains elevated with about 52 located earthquakes last week. While this is lower than previous weeks, earthquake rates have gone up and down during this current period of unrest. Gas emissions from the summit were detected in satellite data on March 28. High resolution satellite data from March 28 showed some collapsing of ice on the crater wall, adding ice to the summit crater lake. Minor steam emissions could be seen from the summit earlier in the week. Ground deformation at Mount Spurr has slowed down over the last week, similar to the pause in deformation observed for several weeks this past November and December. The Mount Spurr monitoring network is functioning well.

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.

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. Intermittent, small volcanic earthquakes continue to occur. Weakly elevated surface temperatures were observed in overnight satellite data consistent with slow lava effusion. Steaming from the summit was also observed earlier in the week in web camera imagery.

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.

KATMAI (VNUM #312170)
58°16'44" N 154°57'12" W, Summit Elevation 6716 ft (2047 m)
Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN

On March 31, strong northwesterly winds near Katmai and the Valley of Ten Thousand Smokes picked up loose volcanic ash from the 1912 Novarupta-Katmai eruption and carried it southeast. The National Weather Service issued a SIGMET for this low-level event and suggested that the maximum cloud height was 4,000 ft (1.2 km) above sea level.

This phenomenon is not the result of recent volcanic activity and occurs during times of high winds and dry snow-free conditions in the Katmai area and other young volcanic areas of Alaska. No eruption is in progress. All volcanoes of the Katmai area (Trident, Snowy, Griggs, Katmai, Novarupta, Mageik, Martin) remain at color code GREEN. Resuspended volcanic ash should be considered hazardous and could be damaging to aircraft and health.

Resuspended volcanic ash should be considered hazardous and could be damaging to aircraft and health. For more information on volcanic ash and human health, visit the following website: http://volcanoes.usgs.gov/ash/. Official warnings about these ash resuspension events are issued by the National Weather Service: http://www.weather.gov/afc. Forecasts of airborne ash hazard to aircraft: http://www.weather.gov/aawu . Volcanic Ash Advisories: http://vaac.arh.noaa.gov/ . Forecasts of ash fall: http://www.weather.gov/afc. Air quality hazards and guidance from Alaska Department of Environmental Conservation, Division of Air Quality: http://dec.alaska.gov/Applications/Air/airtoolsweb/Advisories/Index

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.