ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Monday, September 17, 2018, 3:41 PM AKDT (Monday, September 17, 2018, 23:41 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

Unrest continues at Semisopochnoi volcano. The onset of continuous seismicity yesterday prompted AVO to raise the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY. Retrospective analysis of satellite data from September 10 shows evidence of a small ash deposit on the flanks of the north cone of Mount Cerberus, which may have resulted from two minor seismic tremor bursts recorded on September 8. This satellite imagery, combined with a further increase in seismic tremor amplitudes today, prompted AVO to raise the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH. While the recent ash deposit suggests the potential for ash emissions coincident with elevated seismicity, there have been no ash emissions observed in cloudy satellite images around the time of today's tremor increase. Furthermore, there has been no eruptive activity recorded on regional pressure sensors in Adak, although current atmospheric conditions limit signal propagation between Semisopochnoi and Adak.

Semisopochnoi is monitored with an on-island seismic network, and remotely by satellite and lightning sensors. An infrasound array on Adak Island may detect explosive emissions from Semisopochnoi with a 13 minute delay if atmospheric conditions permit.


VENIAMINOF VOLCANO (VNUM #312070)
56°11'52" N 159°23'35" W, Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Eruption of a lava flow from Veniaminof volcano's summit cone likely continues, as suggested by continued observations of elevated seismic activity, nighttime incandescence in webcam images, and elevated surface temperatures in thermal satellite data. No significant ash emissions have been observed.

Veniaminof Volcano is monitored with a local real-time seismic network, which will typically allow AVO to detect changes in unrest that may lead to an explosive eruption. Rapid detection of an ash-producing eruption would be accomplished 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

Low-level unrest continues at Great Sitkin Volcano. Earthquake activity remains elevated. No significant activity was observed in partly cloudy satellite images over the past day.

Great Sitkin Volcano is monitored with a local real-time seismic network, which will typically allow AVO to detect changes in unrest that may lead to an explosive eruption. Rapid detection of an ash-producing eruption would be accomplished using a combination of seismic, infrasound, lightning, and satellite data.

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

Low-level unrest continues at Cleveland Volcano. Elevated surface temperatures were observed in satellite images over the past day. However, no significant activity has been detected in seismic or pressure sensor (infrasound) data.

Cleveland volcano is monitored by only two seismic stations, which restricts AVO's ability to 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, UAFGI
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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