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AVO VOLCANO ACTIVITY NOTIFICATION

ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Thursday, March 25, 2021, 1:00 PM AKDT (Thursday, March 25, 2021, 21:00 UTC)


VENIAMINOF VOLCANO (VNUM #312070)
56°11'52" N 159°23'35" W, Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Low-level eruptive activity continues at Veniaminof. Satellite observations from the past day show fresh ash deposits extending for ~10 km (6.2 miles) to the SE on snow in the summit caldera. Highly elevated surface temperatures were observed at the summit cone and the at nearby flank vent from which lava is likely being erupted under the glacial ice. No evidence of more distant ash clouds since the morning of March 24. Seismicity remains elevated with periods of repeating seismic events and tremor (continuous shaking). Explosive activity has decreased over the past day with fewer ground-coupled airwaves (pressure waves) observed on seismic data, and no evidence of activity on distant infrasound networks. The FAA web camera in Perryville is back online but low clouds have obscured observations of the summit over the past day.

Eruptive activity at Veniaminof usually consists of minor ash emissions, lava fountaining and lava flows from the small cone in the summit caldera. Ash emissions are typically confined to the summit crater, but larger events can result in ash fall in nearby communities and drifting airborne ash.

The partial restoration of local seismic data will help the Alaska Volcano Observatory to detect changes in unrest that may lead to a more significant explosive eruption. AVO combines seismic, infrasound, lightning, web camera, and satellite data for rapid detection of such events.


SEMISOPOCHNOI VOLCANO (VNUM #311060)
51°55'44" N 179°35'52" E, Summit Elevation 2625 ft (800 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Unrest continues. Three explosions were detected in regional infrasound sensors over the past day at 10:42, 12:20, and 15:45 UTC (01:42, 3:30 and 6:45 HADT). Broken mid-level meteorological clouds (~6,000 to 8,000 ft asl) were in the region during the time of these explosions and no definitive ash cloud was observed rising above them in satellite data. High-resolution satellite data from yesterday (3/24) prior to the explosions show probable minor ash deposits on the island. These deposits may be due to explosive activity earlier in the week, or from smaller events that were not detected in the regional infrasound data.

Semisopochnoi is monitored by satellite data, regional infrasound, and lightning detection instruments. An infrasound array on Adak Island may detect explosive emissions from Semisopochnoi with a slight delay (approximately 13 minutes) if atmospheric conditions permit.


CLEVELAND VOLCANO (VNUM #311240)
52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

No activity has been observed in seismic or infrasound data in the past 24 hours. No activity observed in partly cloudy satellite data.

Episodes of lava effusion and explosions can occur without advance warning. Explosions from 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 monitored by only two seismic stations, which restricts AVO's ability to detect precursory unrest that may lead to an explosive eruption. Rapid detection of an ash-producing eruption may be possible using a combination of seismic, infrasound, lightning, and satellite data.


OTHER ALASKA VOLCANOES

Information on all Alaska volcanoes is available at : http://www.avo.alaska.edu.

For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://www.avo.alaska.edu/color_codes.php

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CONTACT INFORMATION:

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

David Fee, Coordinating Scientist, UAFGI
dfee1@alaska.edu (907) 322-4085

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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