ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Thursday, August 19, 2021, 1:08 PM AKDT (Thursday, August 19, 2021, 21:08 UTC)

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. Satellite imagery from yesterday shows the lava dome has a diameter of ~850 m (~2800 ft). 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.

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

Low-level eruptive activity continues at Pavlof volcano. Elevated seismicity and occasional small explosions were detected in geophysical data over the past day. Satellite and web camera views of the volcano were mostly obscured by clouds, but minor, low-level ash emissions likely continue. Weakly elevated surface temperatures were observed at the active vent in overnight satellite data.

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.

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

Activity at the north crater of Mount Cerberus on Semisopochnoi Island continues. Over the past day, several explosions and seismic tremor have characterized the seismicity. Low-level ash emissions were observed in satellite data overnight. Ash fall is likely occurring on parts of Semisopochnoi Island following these explosions.

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

Unrest continues at Cleveland volcano. Weakly elevated surface temperatures and steaming were detected in partly cloudy satellite data over the past day. Seismicity has been at low levels 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 (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 and seismic tremor continue to be detected. No significant activity was detected in satellite images.

The Alaska Volcano Observatory continues to carefully monitor for signs of increasing unrest that could lead to an eruption. The Atka volcanic complex 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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