USGS Volcano Notice - DOI-USGS-AVO-2026-08-28T16:59:04+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, August 28, 2026, 10:37 AM AKDT (Friday, August 28, 2026, 18:37 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

Summary: Slow eruption of lava continues within the summit crater associated with low-level seismicity.

Lava continues to erupt slowly within the summit crater. Satellite data indicate gradual eastward expansion of the lava dome. Although clouds limited most satellite and web camera views last week, field teams observed steam emissions from the summit (https://avo.alaska.edu/image/view/197476). Seismic activity remains low, with only occasional minor volcanic earthquakes and signals from small rockfalls.

The current lava eruption began in July 2021 and has filled most of the summit crater and advanced into the valleys below. There have been no explosions at Great Sitkin Volcano since an event in May 2021. The volcano is monitored using local seismic, geodetic, 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.

SHISHALDIN (VNUM #311360)
54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Summary: Unrest continues with small earthquakes, tremor, infrasound signals and gas emissions detected.

Volcanic activity remains elevated, with frequent small earthquakes, ongoing tremor, and occasional infrasound signals from minor explosions in the conduit. Steam plumes are visible in web camera images during clear weather. Satellite data detected sulfur dioxide gas emissions on 4 days this past week.

Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. In addition to the local monitoring network, the Alaska Volcano Observatory uses nearby geophysical networks, regional infrasound and lightning data, and satellite data to monitor the volcano.

Shishaldin Volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a conical stratovolcano with a base diameter of approximately 10 miles (16 km). It is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest, including over 28 confirmed eruptions since 1824. Most eruptions are relatively small, although activity during the 1999 and 2023 eruptions generated ash columns that reached up to 46,000 ft (16 km) above sea level.

KUPREANOF (VNUM #312060)
56°45" N 159°47'28" W, Summit Elevation 6217 ft (1895 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Summary: Low-level unrest continues at Mount Kupreanof this week.

Mount Kupreanof continues to exhibit low-level unrest, with occasional local earthquakes and steam emissions observed in web camera images. Seismic activity remained low throughout the week, and no sulfur dioxide emissions have been detected since August 21.

A new temporary monitoring station was installed near Mount Kupreanof in July 2026 and is intermittently providing seismic data, infrasound data, gas measurements, and web camera images. Intermittent data transmission is by design to conserve battery power, but the frequency of data acquisition can be increased if activity warrants. The closest functioning seismometers that provide continuous data are approximately 10 miles (16 km) to the northeast of the volcano as part of the Mount Veniaminof network. Mount Kupreanof is also monitored by satellite data, remote infrasound and lightning networks, and visual observations from pilots and mariners passing by the volcano.

Mount Kupreanof is a heavily glaciated stratovolcano on the Alaska Peninsula with no known historical eruptions. Very little is known about its eruptive history. A single debris flow or block-and-ash flow deposit with a suspected Holocene age has been mapped in a valley south of the volcano. Eruptions will likely produce lahars and pyroclastic flows on the volcano's flanks and into the surrounding uninhabited valleys. Ash plumes could affect communities and airplanes downwind of the volcano. A vigorous fumarole field just west of the summit produces persistent steam plumes.

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.