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ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Wednesday, November 21, 2018, 2:40 PM AKST (Wednesday, November 21, 2018, 23:40 UTC)


SEMISOPOCHNOI VOLCANO (VNUM #311060)
51°55'44" N 179°35'52" E, Summit Elevation 2625 ft (800 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

No eruptive activity was observed in cloudy satellite imagery or regional infrasound over the past day. Due to the lack of observed activity over the last 2 weeks, the alert level was lowered to Yellow/Advisory this morning. Seismic unrest maybe ongoing and undetected as the satellite link that transmits seismic data from Semisopochnoi failed on November 1. An infrasound array on Adak Island should still detect significant explosive emissions from Semisopochnoi (with a 13-minute delay) if atmospheric conditions permit. Additional explosions are possible and will likely occur without warning.

Semisopochnoi is monitored with an on-island seismic network, though this is currently off-line, and remotely by satellite and lightning sensors. As noted above, 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: WARNING
Current Aviation Color Code: RED

Seismic activity has remained elevated in the past 24 hours, and ramped up around 08:00 UTC before falling slightly throughout the day today. By 11:43 UTC an ash plume was observed in satellite data extending 80 miles to the SE, with maximum height estimated at 13,000 ft asl. This plume continued to develop throughout the night extending to over 150 miles. In response, the national weather service issued a SIGMET. Clear webcam views in the morning indicated continued ash emission to the SE, and a second plume developed extending over 120 miles to the SE. A pilot report from the morning indicated that the ash cloud was below 10,000 ft.

In response to this increase of activity, the color code and alert level was raised to Red/Warning. Ash3d forecasts suggest a possible shift to northerly winds overnight tonight that may result in ash impacts on the community of Perryville, and the National Weather Service has issued an advisory for trace to minor ash fall.

No satellite observations of thermal anomalies associated with the continued lava flow were observed in the last 24 hours, but such signatures could be obscured by increased ash emissions and/or cloud cover.

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 a more significant explosive eruption. Rapid detection of such an event 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. Nothing significant has been detected in seismic or regional infrasound data over the past day. Nothing seen in partly cloudy satellite images.

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. The web camera, one seismic station, and the local infrasound array are offline due to a equipment failure on September 23rd. This hampers efforts to rapidly detect explosive activity; however, Cleveland remains monitored with a single seismic station and regional instruments.


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. Numerous small earthquakes associated with the ongoing unrest continue to be recorded on the local seismic network. No activity was observed in partly cloudy satellite images. No explosive activity was detected on a regional infrasound array on Adak Island.

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.


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.
VOLCANO ALERT LEVELS
NORMAL
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
ADVISORY
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
WATCH
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.
WARNING
Hazardous eruption is imminent, underway, or suspected.
AVIATION COLOR CODES
GREEN
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
YELLOW
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
ORANGE
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].
RED
Eruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].
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Page modified: February 17, 2017 10:11
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