AVO/USGS Volcanic Activity Notice
Volcano: Shishaldin (CAVW #1101-36-)
Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: NORMAL
Current Aviation Color Code: YELLOW
Previous Aviation Color Code: GREEN
Issued: Tuesday, January 6, 2009, 3:28 PM AKST (20090106/0028Z)
Source: Alaska Volcano Observatory
Notice Number: 2009/A2
Location: N 54 deg 45 min W 163 deg 58 min
Elevation: 9373 ft (2857 m)
Area: Aleutians Alaska
Volcanic Activity Summary: AVO has detected a significant thermal anomaly and a slight increase in earthquake activity at
Shishaldin Volcano on Unimak Island in the eastern Aleutians. Together, these observations indicate a departure from background
conditions at Shishaldin. AVO is raising the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. There is no
indication that an eruption is imminent or certain, although the potential for an eruption has increased. AVO will continue to
monitor the volcano closely.
[Other observations] Over the past 24 hours, several satellite passes over the volcano have recorded strong thermal signatures
over the summit of the volcano. Such intense thermal anomalies are fairly rare for Shishaldin. Over the past 36 hours, AVO
seismic networks have recorded a small but significant number of earthquakes below the volcano. AVO has received no reports
of unusual steaming or activity at the volcano from airline pilots or residents of the lower Alaska Peninsula or False Pass,
the nearest community. Steaming from the summit crater is quite common, however.
[General hazards] Higher thermal output and small earthquakes could increase the possibility of rock and snow avalanches on the
steep cone. Sudden steam explosions could also produce minor amounts of ash and blocky ejecta on the slopes of the volcano.
In the event this unrest leads to an explosive eruption, primary hazards would be ash clouds, minor ash fall in nearby
communities, and lahars that could reach the sea.
A complete description of these hazards during future eruptions of Shishaldin Volcano can be found online at:
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 small summit crater typically emits a
noticeable steam plume with occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian
volcanic arc, erupting atleast 28 times since 1775. Most of Shishaldin's eruptions have consisted of small ash and steam plumes,
although the most recent eruption in April-May 1999 produced an ash column that reached a height of 45,000 ft above sea level.
Contacts: Peter Cervelli, Acting Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Jon Dehn, Acting Coordinating Scientist, UAFGI
email@example.com (907) 474-6499
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
The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks
Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.