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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE

U.S. Geological Survey

Friday, December 11, 2015, 3:11 PM AKST (Saturday, December 12, 2015, 00:11 UTC)







SHISHALDIN VOLCANO

(VNUM #311360)


54°45'19" N 163°58'16" W,
Summit Elevation 9373 ft (2857 m)


Current Volcano Alert Level: ADVISORY

Current Aviation Color Code: YELLOW




Low-amplitude seismic tremor continued throughout the week at Shishaldin. No anomalous activity has been seen in satellite data since weakly elevated surface temperatures were detected on October 16. Web camera views on one day over the past week showed minor steaming from the summit vent.




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.





CLEVELAND VOLCANO

(VNUM #311240)


52°49'20" N 169°56'42" W,
Summit Elevation 5676 ft (1730 m)


Current Volcano Alert Level: ADVISORY

Current Aviation Color Code: YELLOW




Elevated surface temperatures were detected in satellite images once over the past week at Cleveland. On a few occasions, steam plumes were observed in webcam views. Nothing significant was reported in seismic or infrasound (pressure sensor) data.




Cleveland volcano forms the western portion of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. The volcano is located about 75 km (45 mi) west of the community of Nikolski, and 1500 km (940 mi) southwest of Anchorage. The most recent significant period of eruption began in February, 2001 and produced 3 explosive events that generated ash clouds as high as 39,000 ft above sea level. The 2001 eruption also produced a lava flow and hot avalanche that reached the sea. Since then, Cleveland has been intermittently active producing small lava flows, often followed by explosions that generate small ash clouds generally below 20,000 ft above sea level. These explosions also launch debris onto the slopes of the cone producing hot pyroclastic avalanches and lahars that sometimes reach the coastline.





VENIAMINOF VOLCANO

(VNUM #312070)


56°11'52" N 159°23'35" W,
Summit Elevation 8225 ft (2507 m)


Current Volcano Alert Level: NORMAL

Current Aviation Color Code: GREEN




AVO downgraded the status of Veniaminof from aviation color code YELLOW to GREEN and from volcano alert level ADVISORY to NORMAL today. Seismic activity, indicative of unrest, at Veniaminof had decreased to background levels during the past two weeks. Minor steaming from the intracaldera cone has not been observed since November 16.




Mount Veniaminof volcano is an andesitic stratovolcano with an ice-filled 10-km diameter summit caldera located on the Alaska Peninsula, 775 km (480 mi) southwest of Anchorage and 35 km (22 mi) north of Perryville. Veniaminof is one of the largest (~300 cubic km; 77 cubic mi) and most active volcanic centers in the Aleutian Arc and has erupted at least 13 times in the past 200 years. Recent significant eruptions of the volcano occurred in 1993-95, 2005, and 2013. These were Strombolian eruptions that produced lava fountains and minor emissions of ash and gas from the main intracaldera cone. During the 1993-95 activity, a small lava flow was extruded, and in 2013, five small lava flows effused from the intracaldera cone over about five months. Minor ash-producing explosions occurred nearly annually between 2002 and 2010. Previous historical eruptions have produced ash plumes that reached 20,000 ft above sea level (1939 and 1956) and ash fallout that blanketed areas within about 40 km (25 mi) of the volcano (1939).






OTHER ALASKA VOLCANOES



Other Alaska volcanoes show no signs of significant unrest: http://www.avo.alaska.edu/activity/



AVO scientists conduct daily checks of earthquake activity at all seismically-monitored volcanoes, examine web camera and satellite images for evidence of airborne ash and elevated surface temperatures, and consult other monitoring data as needed.



For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://www.avo.alaska.edu/color_codes.php



FOR MORE INFORMATION ON ALASKA VOLCANOES: http://www.avo.alaska.edu



SUBSCRIBE TO VOLCANO ALERT MESSAGES by email: http://volcanoes.usgs.gov/vns/



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CONTACT INFORMATION:


John Power, Scientist-in-Charge, USGS

jpower@usgs.gov (907) 786-7497



Jeff Freymueller, Coordinating Scientist, UAFGI

jeff.freymueller@gi.alaska.edu (907) 322-4085



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.