Alaska Volcano Observatory

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, May 29, 2026, 12:19 PM AKDT (Friday, May 29, 2026, 20:19 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 with associated low-level seismicity.

A satellite radar image from May 29 confirms that lava is slowly advancing east in the summit crater at Great Sitkin Volcano. Cloud cover obscured other satellite and webcam images. Seismic activity remains low, with occasional small volcanic earthquakes and minor rockfalls within the crater.

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 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.

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: Seismic activity and volcanic gas emissions continue at Mount Kupreanof.

Earthquakes continue near Kupreanof Volcano, though most are minor and difficult to locate with regional seismometers. Cloud cover obscured satellite observations of the surface, but sulfur dioxide gas emissions were detected several times during the week.

There is no real-time geophysical monitoring network at Mount Kupreanof. The closest functioning seismometer is approximately 17 miles (27 km) to the east of the volcano as part of the Mount Veniaminof network. Mount Kupreanof is also monitored by satellite data, regional 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.

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.

Seismic and infrasound activity remain elevated, with numerous small earthquakes, frequent infrasound signals, and volcanic tremor recorded this week. Cloud cover obscured most satellite and webcam images, though occasional clear views showed minor steaming at the summit. Satellite data indicated elevated sulfur dioxide emissions on most days.

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.

CONTACT INFORMATION:

Matt Loewen, Acting Scientist-in-Charge, USGS mloewen@usgs.gov (907) 786-7036

David Fee, Coordinating Scientist, dfee1@alaska.edu UAFGI (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.