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U.S. Geological Survey
Tuesday, January 31, 2017, 2:10 PM AKST (Tuesday, January 31, 2017, 23:10 UTC)

53°55'38" N 168°2'4" W, Summit Elevation 492 ft (150 m)
Current Volcano Alert Level: WARNING
Current Aviation Color Code: RED

Elevated unrest continues at Bogoslof volcano. Volcanic emissions have ceased following the eruption that began at 5:20 UTC, January 31 (20:20 AKST, January 30). The eruption was first detected by a series of discrete tremor bursts detected on nearby seismic stations. The onset of these bursts was accompanied by an infrasound signal and a small weak eruption cloud that was seen in satellite data. An escalation of explosive activity at the volcano was detected by high amplitude infrasound signals and increased seismic tremor between 8:40 and 9:30 UTC consistent with continuous emissions at the volcano. At 09:00 UTC, a continuous volcanic plume was seen to extend for a distance of 125 km toward the southeast over Unalaska Island at an altitude of up to 25,000 feet above sea level. Numerous lightning strokes related to eruptive activity were detected during this eruptive phase. Trace amounts of ash fall and a sulfur smell were reported in Dutch Harbor through this morning but have now ended. The higher level ash cloud, up to 25,000 feet, is currently southeast of Unalaska Island and dissipating.

Satellite images from earlier today show significant changes at Bogoslof Island. Whereas previous explosive events in this sequence had issued from a vent in shallow seawater, freshly erupted volcanic rock and ash have formed a barrier that separates the vent from the sea for the first time since the eruptive sequence began. As a result, we infer that this change has resulted in the more ash-rich emissions that occurred during the evening of January 30 to 31 (AKST).

For an overview of the eruptive activity at Bogoslof since December 2016 through the current events, please see the Information Statement released earlier today ( />
Bogoslof volcano remains at a heightened state of unrest and in an unpredictable condition. Additional explosions producing high-altitude volcanic clouds could occur at any time. 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 is typically a lag of tens of minutes until we can characterize the magnitude of the event and the altitude of the volcanic cloud. Low-level explosive activity that is below our ability to detect in our data sources may be occurring. These low-level explosions could pose a hazard in the immediate vicinity of the volcano. When such low-level activity occurs, it is considered to be consistent with Aviation Color Code ORANGE and Volcano Alert Level WATCH.

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

51°52'1" N 178°1'37" W, Summit Elevation 4754 ft (1449 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

The energetic earthquake swarm on Tanaga Island that began on January 23, 2017 is ongoing but continues to decrease in rate and intensity. No activity has been detected in partly cloudy satellite views over the past day.

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 significant activity has been detected in seismic or pressure sensor data during the past day. No activity has been observed in partly cloudy satellite images. Ice/snow in the web camera housing is obscuring views of the volcano.

The degree of unrest at Pavlof can change quickly. A return to eruptive activity can occur with with little or no warning.

52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Moderately elevated surface temperatures were seen in satellite views overnight. No significant activity observed in seismic or pressure sensor data during the past day.


Information on all Alaska volcanoes is available at :

AVO scientists conduct daily checks of earthquake activity at all seismically-monitored volcanoes, examine web camera and satellite images for evidence of airborne ash and elevated surface temperatures, and consult other monitoring data as needed.

For definitions of Aviation Color Codes and Volcano Alert Levels, see:





Michelle Coombs, Scientist-in-Charge, USGS (907) 786-7497

Jeff Freymueller, Coordinating Scientist, UAFGI (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.