Hazard Notification System (HANS) for Volcanoes


U.S. Geological Survey
Wednesday, September 27, 2023, 1:25 PM AKDT (Wednesday, September 27, 2023, 21:25 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

Low-level eruption activity continues at Shishaldin Volcano. Seismicity remains elevated with tremor and frequent small earthquakes occurring over the past day along with ongoing gas emissions. Satellite data from September 26 show hot, steaming pyroclastic flow and lahar (mud flow) deposits from the September 25 eruption on all flanks of the volcano including more extensive flows on the ENE and WSW sectors below the two new collapse scarps from September 25. Web camera views this morning showed small ash clouds most likely generated from collapses of the summit cone and/or small explosions at the summit. These small collapses of the summit cone have been observed multiple times during this course of this eruption and occur with no warning and produce small ash clouds that dissipate quickly. 

There have been eleven periods of elevated eruptive activity that resulted in significant ash emissions, edifice collapses events of the summit cone, 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 to days before they occur. Additional collapse of accumulated lava near the summit crater can occur without warning and generates hot mass flows on the upper flanks and small volcanic ash clouds. The ongoing eruption started on July 12, and it is unknown how long this episode will last. However, previous eruptions of Shishaldin Volcano have lasted weeks to months with repeated cycles of 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.

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 likely continues. Seismicity remains low with a few earthquakes detected over the past day. Clouds obscured views of the volcano by satellite and web camera today.

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 signifcant activity was observed in satellite views and web camera images were partially obscured by resuspended volcanic ash in this 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.   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.