(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20210616/2159Z)
(3) Volcano:	Semisopochnoi (VNUM #311060)
(4) Current Color Code:	YELLOW
(5) Previous Color Code:	ORANGE
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2021/A374
(8) Volcano Location:	N 51 deg 55 min E 179 deg 35 min
(9) Area:	Aleutians
(10) Summit Elevation:	2625 ft (800 m)
(11) Volcanic Activity Summary:	No ash emissions or explosions from Semisopochnoi have been detected in satellite or infrasound data since May 30, and the level of seismic activity has been relatively low. Satellite views over the past few weeks have detected elevated surface temperatures, and sulfur dioxide emissions were observed on several occasions, indicating continued volcanic unrest, but no recent ash deposits have been observed. Because of the low level of seismicity and lack of significant explosive activity, AVO is lowering the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY. 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:	Unknown
(13) Other volcanic cloud information:	Unknown
(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 mcoombs@usgs.gov (907) 786-7497 David Fee, Coordinating Scientist, UAF dfee1@alaska.edu (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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AVO/USGS Volcanic Activity Notice

Volcano: Semisopochnoi (VNUM #311060)

Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: WATCH

Current Aviation Color Code: YELLOW
Previous Aviation Color Code: ORANGE

Issued: Wednesday, June 16, 2021, 1:59 PM AKDT
Source: Alaska Volcano Observatory
Notice Number: 2021/A374
Location: N 51 deg 55 min E 179 deg 35 min
Elevation: 2625 ft (800 m)
Area: Aleutians

Volcanic Activity Summary: No ash emissions or explosions from Semisopochnoi have been detected in satellite or infrasound data since May 30, and the level of seismic activity has been relatively low. Satellite views over the past few weeks have detected elevated surface temperatures, and sulfur dioxide emissions were observed on several occasions, indicating continued volcanic unrest, but no recent ash deposits have been observed. Because of the low level of seismicity and lack of significant explosive activity, AVO is lowering the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY.

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.

Recent Observations:
[Volcanic cloud height] Unknown
[Other volcanic cloud information] Unknown

Hazard Analysis:
[Ash cloud] Explosions detected in infrasound data and confirmed in satellite imagery.

Remarks: Semisopochnoi is monitored by a local seismic and infrasound network, regional lightning and infrasound sensors, and satellite data.

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

David Fee, Coordinating Scientist, UAF dfee1@alaska.edu (907) 322-4085

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

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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