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USGS Volcano Notice - DOI-USGS-AVO-2026-10-01T15:57:08+00:00
Volcano: Gareloi (VNUM #311070)
Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: NORMAL
Current Aviation Color Code: YELLOW
Previous Aviation Color Code: GREEN
Issued: Thursday, October 1, 2026, 8:42 AM AKDT
Source: Alaska Volcano Observatory
Notice Number: 2026/A749
Location: N 51 deg 47 min W 178 deg 47 min
Elevation: 5161 ft (1573 m)
Area: Aleutians
Summary: A single brief explosion was detected in geophysical data at 07:27 AM AKDT (15:27 UTC). Aviation Color Code/ Volcano Alert Level was changed to YELLOW/ADVISORY. It is unknown if an ash cloud was produced due to cloud cover at the volcano.
Volcanic Activity:
A single brief explosion was detected in geophysical data at 07:27 AM AKDT (15:27 UTC). As a result, AVO is raising the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. It is unknown if a volcanic ash cloud was produced as cloud cover up to about 20,000 feet above sea level is obscuring the volcano. If an ash cloud were produced, the amount of ash would be minor due to the short duration (less than 1 min) of the explosion. Infrasound data indicates the explosion likely occurred from the south crater of Mount Gareloi.
Mount Gareloi is monitored by a local seismic and infrasound network, satellite data, and regional infrasound and lightning-detection networks.
Remarks:
Mount Gareloi, which makes up all of Gareloi Island, is a stratovolcano located in the Delarof Islands group of the Aleutian Islands, about 2,000 km (1,242 mi) west-southwest of Anchorage and about 150 km (93 mi) west of Adak, the westernmost community in Alaska. This small volcano is 10 × 8 km (6.2 × 5.0 mi) in diameter at its base with two summits, separated by a narrow saddle. The northern, slightly higher peak contains crater about 300 m (1,000 ft) across. The southern summit has a crater open to the south and a persistent degassing vent (fumarole) on its western rim. Gareloi has been one of the most active in the Aleutians since the 1740s, with 16 reports of eruptive activity at Gareloi since 1760. In 1929, its largest historical eruption produced sixteen small south- to southeast-trending craters that extend from the southern summit to the coast, as well as lava flows and pyroclastic deposits on the southeastern flank of the volcano. Eruptions of Gareloi commonly produce ash clouds and lava flows, and the primary hazard is airborne clouds of ash that could affect aircraft. Since seismic instruments were installed in 2003, they have detected small but consistent seismic signals from beneath Mount Gareloi’s edifice.
Contacts:
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.
VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
WMAK01 PAVO 011642
VONA
DTG: 20261001/1642Z
VOLCANO: GARELOI 311070
PSN: N5147 W17848
AREA: ALASKA
SOURCE ELEV: 5161FT AMSL
NOTICE NR: 2026/01
CURRENT COLOUR CODE: YELLOW
PREVIOUS COLOUR CODE: GREEN
SVO: ALASKA VOLCANO OBSERVATORY
ACT STS: ERUPTION OCCURRED
ONSET: 20261001/1527Z
DUR: 1 MIN
VA CLD HGT: UNKNOWN
HGT SOURCE: SATELLITE
MOV: UNKNOWN
CTC: AVO DUTY SCIENTIST 907-786-7497
RMK: A SINGLE BRIEF EXPLOSION DETECTED IN GEOPHYSICAL DATA. UNKNOWN IF VA CLOUD WAS
PRODUCTED, BUT IF SO, EMMISSIONS WOULD BE MINOR DUE TO THE SHORT DURATION OF THE
EXPLOSION. NOTHING SEEN IN SATELLITE DATA WITH MET CLOUD TOPS AT 20,000 AMSL
NXT NOTICE: A NEW VONA WILL BE ISSUED IF COND CHANGE SIGNIFICANTLY OR IF THE COLOR CODE CHANGES
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