ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Saturday, September 2, 2023, 11:12 AM AKDT (Saturday, September 2, 2023, 19:12 UTC)
Low-level explosive activity is likely occurring within the summit crater of Shishaldin Volcano. Seismic and infrasound data show signals of small repetitive explosions. This type of activity has been observed previously between episodes of larger and more significant ash emission events. Web camera observations during periods of clear weather show variable steam emissions from the summit crater but no evidence of ash was seen. A moderate resolution satellite image from yesterday afternoon showed steam filling the summit crater and obscuring views of the hot vent region. Hot deposits from the previous explosive event on August 25-26 were seen on the northeast flank near the summit.
Shishaldin has now had eight periods of elevated eruptive activity resulting in significant ash emissions and mass flows of volcanic debris on the volcano's flanks. 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.
Slow eruption of lava in the summit crater continues. An AVO geology team conducted field work on the volcano yesterday and sampled the lava flow, did airborne photography and thermal imaging surveys, and measured gas emissions. Satellite and web camera observations were mostly obscured by clouds over the past day High winds masked seismic observations and no events were seen in the noisy data.
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 remained slightly elevated over the past day. Satellite and web camera images were obscured by clouds.
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 firstname.lastname@example.org (907) 786-7497
David Fee, Coordinating Scientist, UAFGI email@example.com (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.
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