USGS Volcano Notice for Aviation - DOI-USGS-AVO-2023-09-15T23:52:02-08:00

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20230916/0844Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	ORANGE
(5) Previous Color Code:	RED
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2023/A1393
(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:	Activity at Shishaldin Volcano has declined. Seismicity decreased rapidly around 6:30 pm AKDT Sept. 15 (4:30 UTC, Sept. 16) yet remained elevated until 9:00 p.m. AKDT. During this period of waning seismicity, volcanic lightning continued to be detected, indicating continued ash production. The last detection of volcanic lighting was at 8:48 p.m. AKDT and seismicity has returned to pre-eruptive levels, indicating that significant ash emissions have ended. Thus, the Aviation Color Code and Volcano Alert Level are being decreased to ORANGE/WATCH. Trace ash fall was reported in the community of False Pass between 18:00 and 20:30 AKDT (0200 to 0430 UTC). The National Weather Service has issued a SIGMET for the drifting ash cloud, and a Special Weather Statement has been issued for trace ash on False Pass. 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 Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497 David Fee, Coordinating Scientist, UAFGI dfee1@alaska.edu (907) 378-5460
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