ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Thursday, July 18, 2019, 1:47 PM AKDT (Thursday, July 18, 2019, 21:47 UTC)

SHISHALDIN VOLCANO (VNUM #311360)
54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Elevated surface temperatures were observed in multiple satellite images over the past 24 hours accompanied by periods of weak seismic tremor. No eruptive activity was detected in infrasound data and cloudy conditions obscured web camera views of the volcano.

Shishaldin is monitored by local seismic and infrasound sensors, satellite data, a web camera, a telemetered geodetic network, and distant 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

Seismic activity levels have continued to increase at Semisopochnoi, prompting a change in the color code/activity level to ORANGE/WATCH. An strong burst of tremor overnight at 07:39 UTC / 23:39 AKDT generated an airwave detected on the Adak array 260 km (161 miles) to the east. A low-level plume has been observed intermittently in mostly cloudy satellite images over the past 24 hours. It extended west-southwest from the area of the Cerberus vent up to 80 km (50 miles); however, no ash signatures have been detected. The meteorological cloud deck has been around 10,000' asl (3000 m) over Semisopochnoi, and thus far no volcanic plumes have been observed above the weather clouds. No lightning from the eruption has been detected.

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

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

Elevated surface temperatures were observed at the summit of the volcano in mostly cloudy satellite views over the last 24 hours. No activity was detected in regional seismic or infrasound data.

Additional episodes of lava effusion and explosions are likely and will 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.

Local seismic and infrasound data at Cleveland have been unavailable since January 26, 2019. This restricts AVO's ability to rapidly detect an explosive eruption. AVO is able to monitor the volcano for signs of eruptive activity with satellite, lightning, and regional seismic and infrasound 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/

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

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

CONTACT INFORMATION:

Michelle Coombs, Scientist-in-Charge, USGS
mcoombs@usgs.gov (907) 786-7497

Jessica Larsen, Acting Coordinating Scientist, UAFGI
jflarsen@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.

---