(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20160310/2230Z)
(3) Volcano:	Shishaldin (VNUM #311360)
(4) Current Color Code:	GREEN
(5) Previous Color Code:	YELLOW
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2016/A1
(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:	There has been a steady decrease in detected thermal activity at Shishaldin over the past several months. No anomalous activity has been observed in several clear satellite images of Shishaldin since moderately elevated surface temperatures were detected on Jan. 13. Airwaves associated with low-level explosive degassing have not been detected in infrasound data since Feb. 7. Low-amplitude seismic tremor consistent with an open, degassing system continues to be seen in seismic data and is considered to be within the bounds of background activity for Shishaldin. AVO is therefore downgrading the status of Shishaldin Volcano from aviation color code YELLOW to GREEN and from volcano alert level ADVISORY to NORMAL. AVO will continue to monitor satellite, seismic and infrasound data from Shishaldin as part of routine monitoring operations.
(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 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 24 confirmed eruptions since 1775. 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:	John Power, Scientist-in-Charge, USGS jpower@usgs.gov (907) 786-7497 Pavel Izbekov, Acting Coordinating Scientist, UAFGI pavel@gi.alaska.edu (907) 322-4085
(16) Next Notice:	A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at http://www.avo.alaska.edu

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AVO/USGS Volcanic Activity Notice

Volcano: Shishaldin (VNUM #311360)

Current Volcano Alert Level: NORMAL
Previous Volcano Alert Level: ADVISORY

Current Aviation Color Code: GREEN
Previous Aviation Color Code: YELLOW

Issued: Thursday, March 10, 2016, 1:30 PM AKST
Source: Alaska Volcano Observatory
Notice Number: 2016/A1
Location: N 54 deg 45 min W 163 deg 58 min
Elevation: 9373 ft (2857 m)
Area: Aleutians

Volcanic Activity Summary: There has been a steady decrease in detected thermal activity at Shishaldin over the past several months. No anomalous activity has been observed in several clear satellite images of Shishaldin since moderately elevated surface temperatures were detected on Jan. 13. Airwaves associated with low-level explosive degassing have not been detected in infrasound data since Feb. 7. Low-amplitude seismic tremor consistent with an open, degassing system continues to be seen in seismic data and is considered to be within the bounds of background activity for Shishaldin. AVO is therefore downgrading the status of Shishaldin Volcano from aviation color code YELLOW to GREEN and from volcano alert level ADVISORY to NORMAL. AVO will continue to monitor satellite, seismic and infrasound data from Shishaldin as part of routine monitoring operations.

Recent Observations:
[Volcanic cloud height] Unknown
[Other volcanic cloud information] Unknown

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 24 confirmed eruptions since 1775. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft above sea level.

Contacts: John Power, Scientist-in-Charge, USGS
jpower@usgs.gov (907) 786-7497

Pavel Izbekov, Acting Coordinating Scientist, UAFGI
pavel@gi.alaska.edu (907) 322-4085

Next Notice: A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at
http://www.avo.alaska.edu

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