USGS Volcano Notice - DOI-USGS-AVO-2025-02-21T19:36:30+00:00

AVO/USGS Volcanic Activity Notice

Volcano: Atka volcanic complex (VNUM #311160)

Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: WATCH

Current Aviation Color Code: YELLOW
Previous Aviation Color Code: ORANGE


Issued: Friday, February 21, 2025, 11:14 AM AKST
Source: Alaska Volcano Observatory
Notice Number: 2025/A110
Location: N 52 deg 19 min W 174 deg 8 min
Elevation: 5030 ft (1533 m)
Area: Aleutians

Volcanic Activity Summary:

There has been no further activity detected at the Aka volcanic complex since the small explosive event from 4:26 UTC on February 21 (7:26 pm on 2/20/25 AKST), and seismicity remains low. Thus, the Aviation Color Code and Alert Level are being reduced to YELLOW/ADVISORY. 

Further analysis of geophysical data confirms the source of the explosion as the summit lake region of Korovin Volcano and satellite data from last evening show no evidence of hot material at the surface. Our interpretation is that this was a steam-driven explosion, caused by overpressure of the subsurface cap beneath the lake. This type of singular explosion is common at Korovin Volcano. Minor amounts of ash were likely erupted in the immediate vicinity of the vent but have not been confirmed. Additional explosions are possible in the near future, but unlikely.  

Local seismic and infrasound sensors, and web cameras are used to monitor the Atka volcanic complex. The local sensor network is supplemented with regional infrasound and lightning networks, and satellite data. 

Recent Observations:
[Volcanic cloud height] n/a
[Other volcanic cloud information] n/a
[Ballistics] n/a
[Lava flow/dome] n/a
[Lava flow] n/a

Hazard Analysis:
[General hazards] n/a
[Ash cloud] n/a
[Ashfall] n/a
[Lava flow/dome] n/a
[Mud flow] n/a
[Volcanic gas] n/a
[Other hazards] n/a
[Lava flow] n/a

Remarks:

The Atka volcanic complex forms the northern part of Atka Island, located about 16 km north of the community of Atka and 1,761 km southwest of Anchorage. The Atka volcanic complex includes a possible older caldera and several younger vents, including Korovin Volcano, Mount Kliuchef, and Sarichef Volcano. Korovin Volcano, a 1553-m-high (5030 ft) stratovolcano, has been the site of most historical volcanic activity, and has a small, roiling crater lake that occasionally produces energetic steam emissions. Korovin has erupted several times in the past 200 years, including 1973, 1987, and 1998, and has likely had small ash emissions as recently as 2005. Typical recent Korovin eruptions produce minor amounts of ash and occasional but small lava flows. Reports of the height of the ash plume produced by the 1998 eruption ranged as high as 10,600 m (35,000 feet) above sea level. Mount Kliuchef is composed of a series of five vents aligned northeast–southwest. The two main summit vents of Kliuchef appear relatively young and the easternmost was probably the source of an 1812 eruption that is sometimes attributed to Sarichef.

Contacts:

Matt Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497

Ronni Grapenthin, Acting Coordinating Scientist, UAFGI, rgrapenthin@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.