ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Tuesday, June 1, 2021, 1:19 PM AKDT (Tuesday, June 1, 2021, 21:19 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

Volcanic activity at the north crater of Mount Cerberus appears to have subsided and only low-level seismic activity and minor gas emissions are occurring. Nothing significant has been noted in seismic data or in satellite views of the volcano over the past day. Possible sulfur dioxide emissions were detected in satellite data late yesterday afternoon which is consistent with the low-level degassing behavior of the volcano observed over the past several days. AVO field teams on Semisopochnoi Island report only low level steaming at north crater. Overall the volcano is restless but activity has remained low.

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 without warning and could be 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.

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 indicated elevated surface temperatures in the summit crater of the volcano. Elevated temperatures are likely associated with hot gasses escaping the vent.

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.

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

Seismicity has remained at low levels since the last update. Satellite observations over the past day show moderately elevated surface temperatures in the summit crater. The elevated temperatures are likely the result of cooling pyroclastic debris around the vent, emission of hot gasses, or both. No additional ash emissions have been observed since the explosive event on May 25 (local time).

The prognosis for renewed eruptive activity is uncertain, although the ongoing quiescence is suggestive of a gradual return to normal background conditions. It remains possible for the level of unrest at the volcano to change quickly, and if so, additional explosive events could occur in the coming days, weeks or months. AVO is monitoring the volcano closely and 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.

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

SUBSCRIBE TO VOLCANO ALERT MESSAGES by email: http://volcanoes.usgs.gov/vns/

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CONTACT INFORMATION:

Kristi Wallace, Acting Scientist-in-Charge, USGS
kwallace@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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