USGS Volcano Notice for Aviation - DOI-USGS-AVO-2023-09-25T04:38:24-08:00

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20230925/1325Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	ORANGE
(5) Previous Color Code:	ORANGE
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2023/A1428
(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 activity at Shishaldin remains high, with increasing seismicity and evidence for lava eruption and volcanic flows. Elevated surface temperatures consistent with lava fountaining over the crater rim have been observed during clear conditions overnight. Low-level ash emissions less than 15,000 ft. (4.5 km) above sea level were observed starting at 6 pm AKDT yesterday (02:00 UTC September 25), but these dissipated quickly. Beginning at 12 am AKDT today (08:00 UTC), a series of seismic signals consistent with volcanic flows were recorded on the north side of the volcano. Meteorologic clouds up to 20,000 ft. (6 km) above sea level have obscured view of the volcano since this time, and no ash emissions above this level have been observed. The current period of heightened seismicity at Shishaldin, which started yesterday morning, has lasted longer than previous events during the 2023 eruption. It remains possible that higher ash emissions will occur along with this increased activity. Previous recent significant ash events resulted in ash clouds with heights up to 40,000 ft (12 km) above sea level. These events can occur with little warning. It is also possible that ash emissions may occur at a lower level and be sustained for many hours. AVO is monitoring the volcano closely and will issue additional Volcanic Activity Notices about significant changes in activity as they occur. 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:	Not observed currently
(13) Other volcanic cloud information:	Any ash emissions remain below 20,000 ft. asl
(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
(16) Next Notice: