ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Wednesday, July 26, 2023, 2:12 PM AKDT (Wednesday, July 26, 2023, 22:12 UTC)
The eruption of Shishaldin Volcano has gradually declined after increasing overnight. Seismicity has decreased and significant explosions are no longer being detected in infrasound data. Meteorological clouds up to 20,000–25,000 ft (6.1–7.6 km) above sea level began obscuring views of the volcano starting around 11:30 am AKDT (17:30 UTC). It is likely that lingering low-level ash emissions are continuing in the vicinity of the volcano.
Seismic activity and satellite data indicated that eruptive activity began increasing around 10:00 pm AKDT on July 25 (July 26 06:00 UTC). A sustained 15,000 ft (6 km) ash cloud was detected around 5:00 am AKDT (13:00 UTC) and drifted ENE from the volcano. Ash emissions, while diffuse, were visible in satellite data extending about 78 mi (125 km) from the volcano until clouds obscured views starting around 11:30 AKDT (17:30 UTC). The National Weather Service issued a SIGMET for this cloud. The Aviation Color Code and Volcano Alert Level remain at ORANGE/WATCH for this level of activity. AVO issued three Volcanic Activity Notices warning of the lead up to explosive activity at 2:11 am AKDT (10:11 UTC); for the onset of confirmed ash eruption at 3:51 am AKDT (11:51 UTC); and for the decline in eruptive activity at 1:27 pm AKDT (21:27 UTC). AVO will continue to monitor the volcano closely.
Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. The local monitoring network has been partially impaired over the last few weeks due to telecommunications issues but seismic stations and web cameras south of the volcano were brought back online on July 19. 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 continues at Great Sitkin Volcano, where it is producing a thick lava flow within the summit crater. Earthquake activity remains slightly elevated. No significant activity was observed in cloudy web camera and satellite images over the past day.
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.
The volcano is monitored by local seismic and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data.
Seismicity was quiet at Cleveland volcano over the last day. Cloudy conditions obscured views of the volcano in satellite and web camera images.
Episodes of lava effusion and explosions can occur without advance warning. Explosions from Mount Cleveland are normally short-duration and only present a hazard to aviation in the immediate vicinity of the volcano. Larger explosions that present a more widespread hazard to aviation are possible but are less likely and occur less frequently.
Cleveland volcano is currently monitored with a five-station real-time seismic network and three nearby web cameras. Based on past events, explosive eruptions of Cleveland may occur with little or no warning. Rapid detection of an ash-producing eruption may be possible using a combination of seismic, infrasound, web camera, lightning, and satellite data.
Seismic activity near Trident Volcano remained elevated over the past day including a magnitude 2.5 earthquake. No volcanic activity or unrest was observed in clear satellite and web camera images.
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.
Seismicity was low at Aniakchak volcano with a few local earthquakes detected over the past day. No volcanic activity was observed in partly cloudy satellite and clear web camera views.
The current period of seismic unrest began in October 2022. Increases in seismic activity have been detected previously at other similar volcanoes, with no subsequent eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and additional surface deformation to precede any future eruption, if one were to occur.
Aniakchak volcano is monitored by local seismic and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data.
Seismicity was quiet at Semisopochnoi Island over the last day. No activity was observed in partly cloudy satellite and cloudy web camera images.
Small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Young and ash clouds usually under 10,000 ft. (3 km) above sea level have characterized recent periods of eruption since 2018. The last evidence of ash emission from the volcano was on May 5, 2023, and consisted of a minor dusting of ash on the northwest flank of the north crater of Mount Young. Additional ash-producing events could occur again with little or no warning.
Semisopochnoi volcano is monitored by local seismic and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data.
Matt Loewen, Acting 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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