USGS Volcano Notice - DOI-USGS-AVO-2024-02-12T21:48:20+00:00

AVO/USGS Volcanic Activity Notice

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: Monday, February 12, 2024, 1:10 PM AKST
Source: Alaska Volcano Observatory
Notice Number: 2024/A158
Location: N 51 deg 47 min W 178 deg 47 min
Elevation: 5161 ft (1573 m)
Area: Aleutians

Volcanic Activity Summary:

Over the past several hours, AVO has detected an increase in seismicity at Mount Gareloi (Gareloi volcano) beginning at 09:15 AKST (18:15 UTC). The current activity marks a change in character above background rates, and AVO is raising the Aviation Color Code to YELLOW and Volcano Alert Level to ADVISORY.

There have been no other notable changes at the volcano in satellite data or webcam views. Mount Gareloi persistently emits magmatic gases from a fumarole field on the south crater and commonly exhibits low-level seismic activity. These observations suggest the presence of shallow magma and potential interaction with a hydrothermal system. The current increase in seismicity likely reflects a change to the magmatic-hydrothermal system, but it is not clear that the likelihood of a volcanic eruption has increased. AVO will continue to monitor activity to determine if the recent changes are related to influx of new magma or other changes to the magma system.

Mount Gareloi is monitored by a local seismic and infrasound network, satellite data, and regional infrasound and lightning-detection networks.

Recent Observations:
[Volcanic cloud height] None
[Other volcanic cloud information] n/a

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

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.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20240212/2210Z)
(3) Volcano:	Gareloi (VNUM #311070)
(4) Current Color Code:	YELLOW
(5) Previous Color Code:	GREEN
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2024/A158
(8) Volcano Location:	N 51 deg 47 min W 178 deg 47 min
(9) Area:	Aleutians
(10) Summit Elevation:	5161 ft (1573 m)
(11) Volcanic Activity Summary:	Over the past several hours, AVO has detected an increase in seismicity at Mount Gareloi (Gareloi volcano) beginning at 09:15 AKST (18:15 UTC). The current activity marks a change in character above background rates, and AVO is raising the Aviation Color Code to YELLOW and Volcano Alert Level to ADVISORY. There have been no other notable changes at the volcano in satellite data or webcam views. Mount Gareloi persistently emits magmatic gases from a fumarole field on the south crater and commonly exhibits low-level seismic activity. These observations suggest the presence of shallow magma and potential interaction with a hydrothermal system. The current increase in seismicity likely reflects a change to the magmatic-hydrothermal system, but it is not clear that the likelihood of a volcanic eruption has increased. AVO will continue to monitor activity to determine if the recent changes are related to influx of new magma or other changes to the magma system. Mount Gareloi is monitored by a local seismic and infrasound network, satellite data, and regional infrasound and lightning-detection networks.
(12) Volcanic cloud height:	None
(13) Other volcanic cloud information:	n/a
(14) 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.
(15) 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
(16) Next Notice: