USGS Volcano Notice - DOI-USGS-AVO-2026-02-23T18:17:36+00:00

Lava continues to erupt slowly within the summit crater of Great Sitkin Volcano. Seismic activity continues at a very low level. Satellite and webcam images were cloudy. 

The current lava eruption began in July 2021 and, since then, has filled most of the summit crater and advanced into valleys below. There have been no explosions at Great Sitkin Volcano since an event in May 2021. The volcano is monitored using local seismic and infrasound sensors, satellite data, webcams, and regional infrasound and lightning networks.

Unrest continues at Shishaldin Volcano. Seismic activity remains elevated, with numerous small earthquakes and periods of volcanic tremor being observed. Weakly elevated surface temperatures were observed at the summit in satellite imagery, and a weak gas plume was seen in webcam images.   

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 images to detect eruptions. 

A small explosion occurred yesterday evening at Semisopochnoi volcano and was detected by seismic and infrasound sensors on Semisopochnoi Island. Weather conditions have been cloudy, and no eruption cloud or deposits were detected in satellite or webcam data. No subsequent infrasound has been detected, and seismicity has returned to background levels. This unheralded event posed little hazard, as it was localized to Mount Young, which last erupted in 2023. The north cone of Mount Young—the likely source of the explosion—hosts a crater lake and has vigorous fumaroles that produce a small gas plume. The alert level at the volcano was not changed following this event and remains at GREEN and NORMAL.

Semisopochnoi volcano is monitored by local seismic and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data.