ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Tuesday, October 5, 2021, 11:56 AM AKDT (Tuesday, October 5, 2021, 19:56 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

Seismicity has remained elevated with intermittent bursts of activity and at least two explosions were detected in infrasound data over the past day. No new ash clouds were observed in satellite data but local ash fallout on Semisopochnoi Island reached local web camera sites within 5-6 km of the active vent at north crater.

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.

Tremor and occasional relatively large low frequency events continue.

At times the tremor is continuous for tens of minutes.

The local infrasound stations show there to be ground-coupled airwaves at ~10:33 UTC and ~15:29 UTC.

The former produced a volcano alarm.

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 significant seismic or infrasound activity was detected over the past day. Weakly elevated surface temperatures were observed in 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.

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

Seismicity remains slightly elevated with small earthquakes consistent with lava effusion continuing. No explosive activity or ash emissions have been detected in seismic, infrasound, or satellite data. Elevated surface temperatures were observed in clear satellite images over the past day and a small vapor plume extending from the summit was evident in a few clear web camera views from yesterday morning.

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

Seismicity has remained elevated and at least two minor explosions occurred over the past day that were detected in regional infrasound data. Mostly cloudy conditions have obscured views of the volcano in satellite and web camera data, although minor volcanic emissions (most likely water vapor and sulfur gases) were evident in a few web camera images from this morning.

Small explosions accompanied by low-level ash emissions could happen at any time, and are typically a hazard in the immediate vicinity of the summit. 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.




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/

FOLLOW AVO ON FACEBOOK: https://facebook.com/alaska.avo

FOLLOW AVO ON TWITTER: https://twitter.com/alaska_avo

CONTACT INFORMATION:

Matt Haney, Acting Scientist-in-Charge, USGS
mhaney@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.

---