Alert level raised as unrest increases at Shishaldin volcano, Alaska
The Alaska Volcano Observatory (AVO) raised the Volcano Alert Level for Shishaldin volcano, Alaska, to Advisory and the Aviation Color Code to Yellow on August 25, 2025, following increased seismicity, gas emissions, and vapor activity.
The Alaska Volcano Observatory (AVO) reported a gradual increase in unrest at Shishaldin volcano, located in the eastern Aleutian Islands, prompting an alert level change from Normal to Advisory and an Aviation Color Code change from Green to Yellow at 11:48 AKDT (19:48 UTC) on August 25, 2025.
According to AVO, sulfur dioxide emissions have increased, a more vigorous vapor plume from the summit crater has been observed, and seismic and infrasound monitoring has detected moderate increases in both the number and amplitude of events. These represent a departure from background activity, though no evidence currently indicates magma ascent toward the surface.
Field observations conducted by AVO crews during helicopter overflights on August 17 and 22 confirmed no elevated surface temperatures and no signs of new ash deposits around the summit. While satellite imagery occasionally shows plumes that may resemble ash under certain lighting conditions, high-resolution data and direct observation confirm these consist of gas and steam.
AVO noted that past eruptions at Shishaldin were sometimes preceded by days to weeks of seismic tremor. The current activity, however, does not yet indicate imminent eruptive behavior.
Shishaldin is one of the most active volcanoes in Alaska, with frequent historical eruptions since the 18th century, typically characterized by Strombolian explosions and occasional lava flows. The glacier-covered stratovolcano rises 2 857 m (9 373 feet) and is part of the Aleutian Islands UNESCO Biosphere Reserve.
Monitoring of the volcano continues through seismic and infrasound stations, web cameras, geodetic sensors, satellite data, and regional geophysical networks.
Featured image: Shishaldin volcano summit close-up on August 17, 2025. Credit: AVO/USGS, Matt Loewen
Teo Blašković founded The Watchers in 2011 and edited it until 2026, covering seismic and volcanic activity, extreme weather, space weather and near-Earth objects. Articles on this page are his archive.
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