Alaska Volcano Observatory - AVO Volcano Activity Notification

AVO VOLCANO ACTIVITY NOTIFICATION

AVO/USGS Volcanic Activity Notice

Volcano: Shishaldin (VNUM #311360)

Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
Previous Aviation Color Code: RED

Issued: Sunday, July 16, 2023, 7:34 AM AKDT
Source: Alaska Volcano Observatory
Notice Number: 2023/A1067
Location: N 54 deg 45 min W 163 deg 58 min
Elevation: 9373 ft (2857 m)
Area: Aleutians

Volcanic Activity Summary:

Explosive eruptive activity at Shishaldin Volcano has declined. Seismicity has significantly declined and no explosion signals are being detected in infrasound (pressure sensor) data. The drifting ash cloud from last night's activity is still visible in satellite imagery about 350 nautical miles ESE from the volcano. The NWS has a SIGMET for this cloud and estimate it to be under 16,000 ft (4.9 km) above sea level. In response to this decline in explosive activity, the Aviation Color Code is being reduced to ORANGE and the Volcano Alert Level is being raised to WATCH.

Explosive eruptive activity can resume quickly and with little warning. Eruptions from Shishaldin have produced minor and on occasion significant ash clouds in the past. Shishaldin is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. The local monitoring network is partially impaired, therefore AVO is also using nearby geophysical networks, satellite data and regional infrasound and lighting data to detect activity. AVO will continue to closely monitor unrest at Shishaldin Volcano.

Recent Observations:
[Volcanic cloud height] none detected at the volcano, drifting ash cloud under 16,000 ft above sea level
[Other volcanic cloud information] ESE Drifting ash cloud still seen in satellite imagery, see current NWS SIGMET

Hazard Analysis:
[Ash cloud] ESE drifting ash cloud still observed in satellite data, see current NWS SIGMET
[Ashfall] trace ashfall possible downwind of the volcano.
[Mud flow] on all flanks of the volcano

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 26 confirmed eruptions since 1824. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft above sea level.

Contacts:

Kristi Wallace, Acting Scientist-in-Charge, USGS kwallace@usgs.gov (907) 786-7497

Pavel Izbekov, Acting Coordinating Scientist, UAFGI peizbekov@alaska.edu (907) 378-5460

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.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20230716/1534Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	ORANGE
(5) Previous Color Code:	RED
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2023/A1067
(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:	Explosive eruptive activity at Shishaldin Volcano has declined. Seismicity has significantly declined and no explosion signals are being detected in infrasound (pressure sensor) data. The drifting ash cloud from last night's activity is still visible in satellite imagery about 350 nautical miles ESE from the volcano. The NWS has a SIGMET for this cloud and estimate it to be under 16,000 ft (4.9 km) above sea level. In response to this decline in explosive activity, the Aviation Color Code is being reduced to ORANGE and the Volcano Alert Level is being raised to WATCH. Explosive eruptive activity can resume quickly and with little warning. Eruptions from Shishaldin have produced minor and on occasion significant ash clouds in the past. Shishaldin is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. The local monitoring network is partially impaired, therefore AVO is also using nearby geophysical networks, satellite data and regional infrasound and lighting data to detect activity. AVO will continue to closely monitor unrest at Shishaldin Volcano.
(12) Volcanic cloud height:	none detected at the volcano, drifting ash cloud under 16,000 ft above sea level
(13) Other volcanic cloud information:	ESE Drifting ash cloud still seen in satellite imagery, see current NWS SIGMET
(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 26 confirmed eruptions since 1824. 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:	Kristi Wallace, Acting Scientist-in-Charge, USGS kwallace@usgs.gov (907) 786-7497 Pavel Izbekov, Acting Coordinating Scientist, UAFGI peizbekov@alaska.edu (907) 378-5460
(16) Next Notice: