ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Tuesday, August 22, 2017, 1:09 PM AKDT (Tuesday, August 22, 2017, 21:09 UTC)

BOGOSLOF VOLCANO (VNUM #311300)
53°55'38" N 168°2'4" W, Summit Elevation 492 ft (150 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Unrest continues at Bogoslof Volcano. Some minor explosions were detected in infrasound (air pressure) data this morning at about 4:10 AKDT (12:10 UTC), but no significant activity resulted. Satellite data obtained today indicates that the lava dome within the intra-island lake just west of the 1992 lava, has grown to about 525 feet (160 m diameter) since August 20. The presence of a growing mound of lava has heralded the end of several past eruptions of Bogoslof. However, during some eruptive periods, lava effusion has been followed by additional explosions and dome destruction. If future explosions do occur, it is possible that the resulting volcanic cloud could be more ash-rich than those that have occurred thus far during the 2016-17 Bogoslof eruption.

The Aviation Color Code remains at ORANGE and the Alert Level remains at WATCH.

Bogoslof volcano remains at a heightened state of unrest and in an unpredictable condition. Activity can escalate quickly with explosions producing high-altitude (>15,000 ft) volcanic clouds with little to no detectable precursory activity. Some previous explosions have been preceded by an increase in earthquake activity that allowed for short-term forecasts of imminent significant explosive activity. Although we are able to detect energetic explosive activity in real-time, there can be a lag of tens of minutes until we can characterize the magnitude of the event and the altitude of the volcanic cloud. With existing data sources, AVO may not detect low-level unrest, including explosive activity. Such low-level periods of unrest and possible explosions could pose hazards near the volcano. A Temporary Flight Restriction (TFR) remains in effect over the volcano. Please see http://tfr.faa.gov/tfr2/list.html for the status of the TFR.

AVO has no ground-based volcano monitoring equipment on Bogoslof volcano. We continue to monitor volcanic activity with satellite images, seismic and infrasound instruments on nearby islands, and lightning data from the Worldwide Lightning Location Network.

CLEVELAND VOLCANO (VNUM #311240)
52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Unrest continues at Cleveland Volcano. A roughly one-minute long explosion occurred this morning at 10:43 AKDT (18:43 UTC) that likely removed all or part of the lava flow observed on the floor of the summit crater in satellite data yesterday. The explosion signal was detected in seismic and infrasound data. Elevated surface temperatures at the summit also were observed in satellite data today, prior to the mid-morning explosion. Nothing of note was observed in web camera images throughout the afternoon and early evening yesterday.

Cleveland volcano is monitored with a limited real-time seismic network, which inhibits 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.

PAVLOF VOLCANO (VNUM #312030)
55°25'2" N 161°53'37" W, Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

No activity observed in mostly to partly cloudy satellite and web camera images. No significant activity has been detected in seismic and infrasound data over the past day.

The level of unrest at Pavlof can change quickly and the progression to eruptive activity can occur with little or no warning. We continue to monitor Pavlof closely and will provide any new information about the status of the volcano when or if it becomes available.

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:

John Paskievitch, Acting Scientist-in-Charge, USGS
jpaskie@usgs.gov (907) 786-7497

Jeff Freymueller, Coordinating Scientist, UAFGI jfreymueller@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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