Hazard Notification System (HANS) for Volcanoes


U.S. Geological Survey
Saturday, September 23, 2023, 11:02 AM AKDT (Saturday, September 23, 2023, 19:02 UTC)

54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Activity continues at Shishaldin Volcano. There has been an increase in seismic tremor over the past day and the level of seismicity remains high, although it is no longer climbing. Based on previous episodes of activity, if seismicity begins to increase again, eruptive activity in the form of lava fountaining and ash emissions will be likely within hours. No temperatures indicative of lava at the surface or ash emissions have accompanied the elevated seismicity at this time. If geophysical or remote sensing signals intensify, the Alaska Volcano Observatory will issue further notices of volcanic activity.

There have been ten periods of elevated eruptive activity resulting in significant ash emissions and mass flows of volcanic debris on the volcano's flanks since the onset of the current eruption. These periods of elevated eruptive activity have been preceded by increases in seismicity in the hours before they occur. Collapse of accumulated lava near the summit crater can occur without warning and generate hot mass flows on the upper flanks and small volcanic ash clouds. The ongoing eruptive period started on July 12, and it is unknown how long this eruptive episode will last. However, previous eruptions of Shishaldin Volcano have lasted weeks to months with repeated cycles of activity like those seen over the last month.

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.

52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Slow eruption of lava in the summit crater continues. Seismicity was quiet over the past day. Elevated surface temperatures were observed in the vent region of the lava flow in partly cloudy satellite imagery. Web camera views of the volcano were mostly obscured by clouds.

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.

58°14'3" N 155°6'9" W, Summit Elevation 3599 ft (1097 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Seismic activity near Trident Volcano remained elevated over the past day with some earthquakes detected. No activity observed in partly cloudy satellite and web camera views of the volcano over the past day.

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.   AVO issued an Information Statement on July 25 providing a more detailed update on the volcanic unrest at Trident Volcano and the broader Katmai volcanic cluster (https://www.avo.alaska.edu/news.php?id=1595).

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


Matt Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497

David Fee, Coordinating Scientist, UAFGI dfee1@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.