USGS Volcano Notice - DOI-USGS-AVO-2025-08-22T22:51:56+00:00

AVO/USGS Volcanic Activity Notice

Volcano: Shishaldin (VNUM #311360)

Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: NORMAL

Current Aviation Color Code: YELLOW
Previous Aviation Color Code: GREEN

Issued: Monday, August 25, 2025, 11:48 AM AKDT
Source: Alaska Volcano Observatory
Notice Number: 2025/A516
Location: N 54 deg 45 min W 163 deg 58 min
Elevation: 9373 ft (2857 m)
Area: Aleutians

Volcanic Activity Summary:

Over the past month, signs of volcanic unrest at Shishaldin Volcano have been gradually increasing. Sulfur dioxide emissions have increased, a more vigorous vapor plume from the summit crater has been observed, and seismic and infrasound data have shown moderate increases in both the number of events and their amplitude. 

These observations represent a departure from background behavior and the Aviation Color Code and Volcano Alert Level are thus being increased to YELLOW/ADVISORY.

An eruption is not certain, and this unrest could eventually decline over time. In the lead up to prior eruptions of Shishaldin, heat emissions were observed in satellite data as magma approached the floor of the summit crater. We have not detected elevated surface temperatures in the summit crater or observed anything else of significance, including during helicopter overflights by an AVO field crew on August 17 and 22, to indicate that magma is rising in the conduit.  

Eruptions at Shishaldin are sometimes preceeded by days to weeks of seismic tremor (continuous shaking of the ground) that would provide warning of a possible explosive eruption. 

Gas emissions from the summit crater have at times been mistaken by observers for ash emissions under certain viewing conditions (location of the sun relative to the observer), but there is no evidence for ash deposits on the snow around the summit crater in high resolution satellite data.  The absense of ash deposits was confirmed by the close overflight observations of the summit crater made last week by an AVO field crew. 

Local seismic and infrasound sensors, web cameras, and a geodetic network are used to monitor Shishaldin Volcano. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lightning data, and satellite data to detect eruptions.

To view information about Shishaldin Volcano: https://www.avo.alaska.edu/activity/Shishaldin.php

Recent Observations:
[Volcanic cloud height] typically less than 1000 ft above the summit
[Other volcanic cloud information] No ash emissions. Plume is steam and sulfur dioxide gas.

Hazard Analysis:
[General hazards] none

Remarks:

Shishaldin Volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 10 miles (16 km). A 660 ft. (200 m) wide funnel-shaped summit crater typically emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 26 confirmed eruptions since 1824. Most eruptions are relatively small, although activity during July–November, 2023 generated ash columns that reached between 30,000 ft (9 km) and 42,000 ft (13 km) above sea level.

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.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20250825/1948Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	YELLOW
(5) Previous Color Code:	GREEN
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2025/A516
(8) Volcano Location:	N 54 deg 45 min W 163 deg 58 min
(9) Area:	Aleutians
(10) Summit Elevation:	9373 ft (2857 m)
(11) Volcanic Activity Summary:	Over the past month, signs of volcanic unrest at Shishaldin Volcano have been gradually increasing. Sulfur dioxide emissions have increased, a more vigorous vapor plume from the summit crater has been observed, and seismic and infrasound data have shown moderate increases in both the number of events and their amplitude.  These observations represent a departure from background behavior and the Aviation Color Code and Volcano Alert Level are thus being increased to YELLOW/ADVISORY. An eruption is not certain, and this unrest could eventually decline over time. In the lead up to prior eruptions of Shishaldin, heat emissions were observed in satellite data as magma approached the floor of the summit crater. We have not detected elevated surface temperatures in the summit crater or observed anything else of significance, including during helicopter overflights by an AVO field crew on August 17 and 22, to indicate that magma is rising in the conduit.   Eruptions at Shishaldin are sometimes preceeded by days to weeks of seismic tremor (continuous shaking of the ground) that would provide warning of a possible explosive eruption.  Gas emissions from the summit crater have at times been mistaken by observers for ash emissions under certain viewing conditions (location of the sun relative to the observer), but there is no evidence for ash deposits on the snow around the summit crater in high resolution satellite data.  The absense of ash deposits was confirmed by the close overflight observations of the summit crater made last week by an AVO field crew.  Local seismic and infrasound sensors, web cameras, and a geodetic network are used to monitor Shishaldin Volcano. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lightning data, and satellite data to detect eruptions. To view information about Shishaldin Volcano: https://www.avo.alaska.edu/activity/Shishaldin.php
(12) Volcanic cloud height:	typically less than 1000 ft above the summit
(13) Other volcanic cloud information:	No ash emissions. Plume is steam and sulfur dioxide gas.
(14) Remarks:	Shishaldin Volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 10 miles (16 km). A 660 ft. (200 m) wide funnel-shaped summit crater typically emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 26 confirmed eruptions since 1824. Most eruptions are relatively small, although activity during July–November, 2023 generated ash columns that reached between 30,000 ft (9 km) and 42,000 ft (13 km) above sea level.
(15) Contacts:	Matt Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497 David Fee, Coordinating Scientist, UAFGI dfee1@alaska.edu (907) 378-5460
(16) Next Notice: