USGS Volcano Notice for Aviation - DOI-USGS-AVO-2023-07-26T01:05:14-08:00

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20230726/1011Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	ORANGE
(5) Previous Color Code:	ORANGE
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2023/A1144
(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 level of unrest has increased at Shishaldin Volcano. A steady increase in seismic tremor over the past 4 hours and an increase in temperatures at the volcano observed in satellite data over the past 2 hours suggests that explosive activity is imminent. Despite cloud cover obscuring the volcano, elevated surface temperatures consistent with lava erupting at the summit are evident in the latest satellite data. Based on previous eruption cycles, minor ash emissions are likely to occur and may increase over the next few hours. The last four significant ash events during the current eruption resulted in ash clouds with heights up to 40,000 ft. (12 km) above sea level, similar to other historical eruptions. These events can occur with little warning. Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. The local monitoring network has been partially impaired over the last few weeks due to telecommunications issues but seismic stations and web cameras south of the volcano were brought back online on July 19. 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 but explosive eruption is imminent.
(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:	Chris Waythomas, Acting Scientist-in-Charge, USGS, cwaythomas@usgs.gov, (907) 786-7497 David Fee, Coordinating Scientist, UAFGI, dfee1@alaska.edu, (907) 378-5460
(16) Next Notice: