(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20211020/2309Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	UNASSIGNED
(5) Previous Color Code:	GREEN
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2021/A949
(8) Volcano Location:	N 54 deg 45 min W 163 deg 58 min
(9) Area:	Aleutians
(10) Summit Elevation:	9373 ft (2857 m)
(11) Volcanic Activity Summary:	The Shishaldin Volcano monitoring network has several outages affecting local GPS, seismic, and infrasound stations that are likely to persist through the winter months. Due to the impaired local monitoring stations, the Alaska Volcano Observatory is changing the Aviation Color Code and the Volcano Alert Level to UNASSIGNED/UNASSIGNED. The Alaska Volcano Observatory continues to monitor Shishaldin with seismic, GPS, and infrasound instruments on nearby networks, as well as with Cold Bay web camera imagery and satellite data.
(12) Volcanic cloud height:	not applicable
(13) Other volcanic cloud information:	not applicable
(14) Remarks:	Shishaldin Volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 16 km (10 mi). A 200-m-wide (660 ft) funnel-shaped summit crater typically emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 24 confirmed eruptions since 1775. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft above sea level.
(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:

---

AVO/USGS Volcanic Activity Notice

Volcano: Shishaldin (VNUM #311360)

Current Volcano Alert Level: UNASSIGNED
Previous Volcano Alert Level: NORMAL

Current Aviation Color Code: UNASSIGNED
Previous Aviation Color Code: GREEN

Issued: Wednesday, October 20, 2021, 3:09 PM AKDT
Source: Alaska Volcano Observatory
Notice Number: 2021/A949
Location: N 54 deg 45 min W 163 deg 58 min
Elevation: 9373 ft (2857 m)
Area: Aleutians

Volcanic Activity Summary: The Shishaldin Volcano monitoring network has several outages affecting local GPS, seismic, and infrasound stations that are likely to persist through the winter months. Due to the impaired local monitoring stations, the Alaska Volcano Observatory is changing the Aviation Color Code and the Volcano Alert Level to UNASSIGNED/UNASSIGNED.

The Alaska Volcano Observatory continues to monitor Shishaldin with seismic, GPS, and infrasound instruments on nearby networks, as well as with Cold Bay web camera imagery and satellite data.

Recent Observations:
[Volcanic cloud height] not applicable
[Other volcanic cloud information] not applicable

Remarks: Shishaldin Volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 16 km (10 mi). A 200-m-wide (660 ft) funnel-shaped summit crater typically emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 24 confirmed eruptions since 1775. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft above sea level.

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

David Fee, Coordinating Scientist, UAF, dfee1@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.

---