ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Thursday, July 20, 2023, 3:23 PM AKDT (Thursday, July 20, 2023, 23:23 UTC)
Cloudy weather over the past day has obscured direct observations of Shishaldin Volcano. No ash emissions have been detected in satellite or web camera images. Earthquake tremor levels have been relatively low and infrasound sensors have not detected any explosions. A low-level eruption, however, may continue within the summit crater, and the eruption could increase again without warning.
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 a web camera south of the volcano were brought back online yesterday. 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. Around 10 local earthquakes were detected over the past day. A clear Landsat satellite and webcam image showed light steaming from the active lava flows and minimal change the overall lava flow extent, consistent with other recent observations.
An eruption of lava began at Great Sitkin Volcano in July 2021 and has continued to slowly erupt since, but no explosive events have occurred. An explosive event occurred in May 2021, before the current eruption of lava. The volcano is monitored by local seismic and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data.
Around 18 small local earthquakes were detected at Cleveland volcano over the last day, although many of these are too small to locate. Steaming and gas emissions from the summit of Mount Cleveland were visible in clear web camera images. A clear satellite image into the crater showed no significant surface changes.
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 24 hours. No volcanic activity or unrest was observed in clear satellite and web camera images 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, with no subsequent eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and surface deformation, 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.
Seismicity was low at Aniakchak volcano over the past day with 5 local earthquakes detected. No activity was observed in partly cloudy satellite and web camera images over the past 24 hours.
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.
Only minor seismic activity was detected over the last day at Semisopochnoi Island. Clouds obscured all satellite and 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. Additional ash-producing events could occur again with little warning.
Semisopochnoi volcano is monitored by local seismic and infrasound sensors, web cameras, regional infrasound and lightning networks, and satellite data.
Kristi Wallace, 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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