USGS Volcano Notice - DOI-USGS-AVO-2023-10-04T13:20:25-08:00

Following the significant explosive event yesterday at Shishaldin, ash clouds below 12,000 ft. (3.7 km) above sea level continued until 2 pm AKDT (22:30 UTC). These ash clouds were primarily generated off the sides of the volcano where hot rock avalanches continued down drainages to the southwest and northeast from the crater rim. Two explosion craters were observed at the base of the northeast deposits and web camera images showed these were a source of persistent ash. The National Weather Service issued a SIGMET for this ash cloud, and a Special Weather Statement was issued for islands west of Shishaldin for possible trace ashfall.

Overnight and this morning ash clouds were no longer apparent downwind of the volcano in satellite images, however, continued small local ash plumes are visible in web camera images from occasional collapse events. These will likely continue due to instability of the summit crater and interaction of hot deposits on ice that covers the side of the volcano.

Seismic activity including frequent small earthquakes remains elevated at Shishaldin, but is gradually decreasing. No significant explosions have been detected.

Twelve significant explosive events have occurred at Shishaldin since July 12, 2023. These events have been preceded by increases in seismicity in the hours to days before they occur. It is unknown how long this period of ongoing activity will last. However, previous eruptions of Shishaldin Volcano have lasted weeks to months with repeated cycles of eruptive activity like those seen since July.

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

Slow eruption of lava in the summit crater continues. Seismicity remains low with a few earthquakes detected over the past day. Clouds obscured satellite and web camera images, but a satellite radar image last night confirmed continued slow advance of the lava flow in the summit crater.

The current lava flow at Great Sitkin Volcano began erupting in July 2021. No explosive events have occurred since a single event in May 2021.

Local seismic and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data are used to monitor the volcano.

Seismic activity near Trident Volcano was low with a few local earthquakes detected over the past day. No volcanic activity was noted in clear satellite or web camera images, although resuspended ash from the 1912 eruption of Katmai is visible in the region.

The current period of seismic unrest began on August 24, 2022. Increases in seismic activity have been detected previously at Trident Volcano and other similar volcanoes and did not result in eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and ground movement, to precede any future eruption if one were to occur.   

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