ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Thursday, August 12, 2021, 1:06 PM AKDT (Thursday, August 12, 2021, 21:06 UTC)

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

Over 10 small explosions were detected in seismic and infrasound sensors from Pavlof Volcano over the past day. Small ash emissions were observed this morning for one of these events in clear web camera images. Ash appeared to quickly dissipate and deposits were limited to areas near the vent.

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.

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

Elevated surface temperatures and small earthquakes were detected over the past day at Great Sitkin Volcano consistent with continued growth of a lava dome. A steam and gas plume could be seen drifting downwind from the summit. No explosions or ash emissions were detected.

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.

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

Over 20 small explosions were detected from North Cerberus crater at Semisopochnoi over the past day. None of these were noted in satellite images, and a steady, low-level steam plume, possibly containing ash, was observed in clear web camera images this morning. Ash emissions from these explosions are likily similar to recent days, but not always detected due to low altitudes and cloud cover.

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

Semisopochnoi 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

A typical steam plume was observed in a high-resolution satellite image from Semisopochnoi yesterday, and was visible in a clear web camera image this morning. Seismicity has been at low levels over the past day and no evidence of explosive activity was detected in seismic, 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.

ATKA VOLCANIC COMPLEX VOLCANO (VNUM #311160)
52°19'51" N 174°8'20" W, Summit Elevation 5030 ft (1533 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Small earthquakes continue to be detected but at a reduced rate relative to the previous day. The Alaska Volcano Observatory continues to carefully monitor the volcano for signs of increasing unrest that could lead to an eruption. The area is monitored by local seismic and infrasound sensors, satellite data, and regional lightning detection instruments.

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.

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