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U.S. Geological Survey
Saturday, March 27, 2021, 11:35 AM AKDT (Saturday, March 27, 2021, 19:35 UTC)

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

Unrest continues at Veniaminof, but the eruption may have paused. Seismicity remains elevated with periods of repeating seismic events and tremor (continuous shaking), but at lower amplitude than earlier in the week. Satellite and web camera observations have been mostly obscured by clouds for the past day, but pilot reports yesterday afternoon indicated no new ash emissions. Satellite data show no evidence of sulfur dioxide emissions. No explosive activity was detected on local seismic stations or on distant infrasound networks. Pauses in eruptive activity are common at Veniaminof (and at most volcanoes) and ash emissions and explosive activity could resume without warning.

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.

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. Two explosions were detected on regional infrasound sensors over the past day at 06:30 and 09:30 UTC (21:30 on March 26 and 00:30 on March 27 HADT). High meteorological clouds (> 30,000 ft asl) were in the region during the time of these explosions and no ash cloud was observed rising above them in satellite data. Satellite observations of the volcano were obscured by clouds over the past day. No evidence of sulfur dioxide emissions was observed in satellite data yesterday afternoon. These small explosions are typical for the recent eruptive behavior at Semisopochnoi.

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.

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

Yesterday morning, a magnitude 4.3 earthquake occurred in the vicinity of Cleveland. This may be associated with volcanic unrest and represents a significant departure from background earthquake activity. Smaller earthquakes have continued to occur near Cleveland (as is expected for earthquakes of this size) but their rate has declined over the past day. The unrest could result in a future eruption, however that is not a certainty. There have been no signs of activity observed in infrasound or satellite data over the past day, and no evidence of sulfur dioxide gas emissions or elevated surface temperatures were 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 precisely locate earthquakes and 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.


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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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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Page modified: December 2, 2016 10:12
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