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U.S. Geological Survey
Thursday, December 22, 2016, 2:14 PM AKST (Thursday, December 22, 2016, 23:14 UTC)

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

Following about 25 hours of relative quiescence, another short-lived eruption occurred at Bogoslof yesterday late afternoon producing a large eruption cloud that rose to 35,000 ft asl, quickly detached, and moved northeastward over the Bering Sea. The cloud-forming eruption started at around 16:10 AKST 21 Dec 2016 (01:10 UTC, 22 Dec 2016) with seismicity visible on stations located on nearby islands that lasted ~30 minutes. The eruption was also detected on several nearby infrasound arrays. Observers in Dutch Harbor reported seeing the cloud as it developed. AVO elevated the Aviation Color Code to RED and the Volcano Alert Level to WARNING at 16:32 AKST 21 Dec (02:32 UTC 22 Dec). After the eruption, seismicity abruptly declined to low levels and remained so through the evening. At 23:18 AKST (08:18 UTC 22 Dec) AVO lowered the Color Code/Alert Level to ORANGE/WATCH.

Recent satellite imagery shows that this eruption dramatically changed Bogoslof Island, and that a new, small island has formed just offshore of the northeast end of the main island. The former shore and much of the northeast side of Bogoslof Island adjacent to this island has been largely removed, and deposition of material has occurred on the west side of the island. The excavated area of the former northeast shore is likely the vent for this recent eruption, which appears to be just below sea level.

Seismicity was relatively low into the early morning hours of 22 December until 01:20 AKST (10:20 UTC) with the sudden onset of strong tremor that continued until 07:40 AKST (16:40 UTC). Although this likely was eruptive activity, no evidence of ash emission was observed in satellite images. Seismicity was low until an abrupt increase in moderate tremor began at about 11:04 AKST (21:04 UTC). This activity began to decline within the past hour. No ash emissions or elevated surface temperatures are evident in satellite images.

AVO has no ground-based volcano monitoring equipment on Bogoslof volcano. We are monitoring eruptive activity using satellite images and data from distant seismic and infrasound instruments.

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

Unrest continues at Pavlof Volcano. No significant activity was observed in mostly clear satellite images today. Web camera images were obscured by low clouds. Nothing significant was detected in seismic or pressure sensor data during the past day.

The degree of unrest at Pavlof can change quickly. A return to eruptive activity can occur with with little or no warning. AVO is closely monitoring the volcano.

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. No significant activity observed in mostly clear satellite images today. No significant activity was detected in seismic or pressure sensor data during the past 24 hours.


Other Alaska volcanoes show no signs of significant unrest: http://www.avo.alaska.edu/activity/

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: http://www.avo.alaska.edu/color_codes.php


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

Janet Schaefer, Acting Coordinating Scientist, DGGS
janet.schaefer@alaska.gov (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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URL: avo.alaska.edu/activity/report.php
Page modified: December 2, 2016 10:12
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