USGS Volcano Notice for Aviation - DOI-USGS-AVO-2023-08-04T17:22:44-08:00

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20230805/0355Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	ORANGE
(5) Previous Color Code:	RED
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2023/A1216
(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:	Volcanic activity has significantly declined at Shishaldin Volcano and any remaining ash emissions are likely low level. Seismic tremor began declining from a peak at 2:00 pm AKDT (22:00 UTC) and is and is currently at low levels. The eruption produced a sustained ash plume ash plume during the period of high seismicity which drifted to the northeast. Currently, meteorological clouds at 30,000 ft (9 km) above sea level have obscured the volcano and any potential ash clouds. It is possible that low level ash production could be continuing during this period of waning seismicity. Due to this decrease in intensity of the eruption, the Aviation Color Code is being lowered to ORANGE and the Alert Level is being lowered to WATCH. Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lighting data, and satellite images to detect eruptions.
(12) Volcanic cloud height:	Unknown
(13) Other volcanic cloud information:	Unknown
(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 10 miles (16 km). A 660 ft. (200 m) wide 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. (14 km) above sea level.
(15) Contacts:	Matt Loewen, Acting Scientist-in-Charge, USGS, mloewen@usgs.gov, (907) 786-7497 Ronni Grapenthin, Acting Coordinating Scientist, UAFGI, rgrapenthin@alaska.edu, (907) 378-5460
(16) Next Notice:	Should volcanic activity change significantly, a new notice will be issued.