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AVO VOLCANO ACTIVITY NOTIFICATION

ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Thursday, May 27, 2021, 2:02 PM AKDT (Thursday, May 27, 2021, 22:02 UTC)


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

Seismic data from Semisopochnoi was restored by AVO field engineers yesterday after being offline since November 2020 due to failure of the satellite data uplink on Amchitka Island. Periods of seismic tremor were observed in the data, and was energetic at times. Seismic tremor (continuous shaking) has been observed frequently at Semisopochnoi in during this current period of unrest that began in 2018. Satellite observations have been obscured by clouds over the past day. No activity observed.

Small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Cerberus and ash clouds under 10,000 ft above sea level are typical of recent activity at Semisopochnoi. Small explosions may occur undetected by regional infrasound sensors and cloudy weather conditions.

Semisopochnoi is monitored by a local seismic network, 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.


GREAT SITKIN VOLCANO (VNUM #311120)
52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

The Aviation Color Code and Volcano Alert Level was reduced to YELLOW/ADVISORY earlier today due to decreased activity. Seismicity was at very low levels over the past day. Satellite observations were mostly obscured by clouds over the past day, but very minor steaming and slightly elevated surface temperatures were observed during breaks in the cloud cover yesterday afternoon. No ash emissions have been observed since the explosive event on May 25 (local time).

The prognosis for renewed eruptive activity is uncertain. Additional explosive events, the eruption of lava, or a return to non-eruptive behaviors are all possible. AVO will report on significant changes and observations in monitoring data should they occur.

Great Sitkin volcano is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.


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 was observed in seismic or infrasound data over the past day. Satellite observations have been obscured by clouds.

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.

When operational, 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.


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:

Michelle Coombs, Scientist-in-Charge, USGS
mcoombs@usgs.gov (907) 786-7497

David Fee, Coordinating Scientist, UAF
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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