|(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)|
|(3) Volcano:||Semisopochnoi (VNUM #311060)|
|(4) Current Color Code:||ORANGE|
|(5) Previous Color Code:||YELLOW|
|(6) Source:||Alaska Volcano Observatory|
|(7) Notice Number:||2021/A490|
|(8) Volcano Location:||N 51 deg 55 min E 179 deg 35 min|
|(10) Summit Elevation:||2625 ft (800 m)|
|(11) Volcanic Activity Summary:||Continuous volcanic tremor (constant shaking) began to be observed at ~2000 UTC (12 pm AKDT) and continues through the present time. Ash emissions were visible in satellite data beginning around 2100 UTC (1 pm AKDT) to an altitude of less than 5,000 feet asl (based on wind direction). Satellite observations from yesterday afternoon showed a robust steam plume and sulfur dioxide gas emissions. These observations indicate an increase in unrest and the Aviation Color Code is being increased to ORANGE, and the Volcano Alert Level is being increased to WATCH. Additional ash emissions are probable, but not certain.
When occurring, small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Cerberus and ash clouds under 10,000 ft above sea level are typical of activity at Semisopochnoi.
|(12) Volcanic cloud height:||Less than 5,000 ft asl.|
|(13) Other volcanic cloud information:||Observed in GOES-17 satellite|
|(14) Remarks:||Semisopochnoi is monitored by a local seismic and infrasound network, regional lightning and infrasound sensors, and satellite data.|
|(15) Contacts:||Michelle Coombs, Scientist-in-Charge, USGS email@example.com (907) 786-7497
David Fee, Coordinating Scientist, UAF firstname.lastname@example.org (907) 322-4085
|(16) Next Notice:||A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at http://www.avo.alaska.edu|
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