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ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Wednesday, September 8, 2021, 12:01 PM AKDT (Wednesday, September 8, 2021, 20:01 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

Eruptive activity continues at the north crater of Mount Cerberus on Semisopochnoi Island. Seismicity remains elevated and variable, with periods of continuous tremor, and occasional short-lived explosions of several minutes duration being detected in infrasound data. These explosive events are generating small ash clouds that typically rise from 10,000 to 15,000 ft asl and dissipate within an hour or two (as observed in satellite). Periods of lower-altitude ash emissions, interspersed with robust steaming, were observed in web camera images over the past day. These ash clouds were blown horizontally by the wind with little vertical uplift at altitudes below 5,000 ft asl. Sulfur dioxide emissions continue to be observed in satellite data (once per day).

Small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Cerberus and ash clouds usually under 10,000 feet above sea level have characterized the recent activity, which shows no signs of abating. Small explosions may continue to occur and could be difficult to detect, especially during poor weather conditions.

Semisopochnoi Island is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.


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

The lava dome likely continues to grow, but satellite and web camera observations were obscured by clouds over the past day. Small earthquakes were detected over the past day at Great Sitkin Volcano, consistent with continued growth of a lava dome. No explosions or ash emissions were detected in seismic, infrasound, or satellite data.

There is no indication of how long lava effusion will continue during the current eruption, and it is possible that explosive activity could occur with little or no warning. Great Sitkin Volcano is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.


PAVLOF VOLCANO (VNUM #312030)
55°25'2" N 161°53'37" W, Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Unrest continues at Pavlof Volcano, but no ash emissions were detected in seismic or infrasound data over the past day. Seismicity continues but at low levels. Satellite and web camera images were mostly obscured by clouds, but there were no observations of ash emissions during brief periods of clear weather. Additional small explosions accompanied by low-level ash emissions could happen at any time.

The level of unrest at Pavlof can change quickly and the progression to more significant eruptive activity can occur with little or no warning. Pavlof 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

Unrest continues at Cleveland volcano. Satellite observations were mostly obscured by clouds over the past day. Seismic data is currently not available, but no explosive activity was detected in regional infrasound or 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.

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

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

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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.