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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
Friday, November 16, 2012 11:00 AM AKST (Friday, November 16, 2012 20:00 UTC)


CLEVELAND VOLCANO (CAVW #1101-24-)
52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

On Saturday, November 10, a small explosion at Cleveland was detected by infrasound instruments on neighboring islands, and produced an ash cloud that was visible in satellite imagery. Clouds have mostly prevented views of the volcano since then but no further activity has been detected.

Further sudden explosions of blocks and ash remain possible with little or no warning. Ash clouds, if produced, could exceed 20,000 feet above sea level. If a large ash-producing event occurs, nearby seismic, infrasound, or volcanic lightning networks should alert AVO staff quickly. However, for some events, a delay of several hours is possible. There is no real-time seismic monitoring network on Mount Cleveland and AVO is unable to track activity in real time.

Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 and it produced 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. The 2001 eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The current eruptive episode began in July 2011 and has included the growth of several small lava domes at the volcano's summit as well as over twenty short-lived explosions that have sent ash as high as 20,000 feet above sea level.

ILIAMNA VOLCANO (CAVW #1103-02-)
60°1'55" N 153°5'30" W, Summit Elevation 10016 ft (3053 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Seismicity remained elevated at Iliamna throughout the past week. Nothing unusual was observed in partly cloudy satellite and web camera views. AVO has received no reports of activity at the volcano.

Iliamna volcano is located on the western side of lower Cook Inlet in the Lake Clark National Park. Iliamna is a snow-covered stratovolcano which rises 10,020 feet above sea level. Although steam plumes occur on its eastern flanks, there has been no historic volcanic activity at Iliamna. Iliamna is located 225 km (140 miles) southwest of Anchorage and 113 km (70 miles) northwest of Homer.

LITTLE SITKIN VOLCANO (CAVW #1101-05-)
51°57'11" N 178°32'8" E, Summit Elevation 3898 ft (1188 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Throughout most of the past week, seismic activity was slightly above background. Beginning at 13:09 AKST yesterday, November 15, a swarm of volcano tectonic earthquakes was detected at the volcano. The swarm has since quieted but AVO continues to monitor the situation carefully. Yesterday's activity was similar to that recorded in August, at the beginning of the current unrest. Nothing unusual has been observed in mostly cloudy satellite images and AVO has received no reports of unusual activity at Little Sitkin over the past week.

Little Sitkin volcano occupies Little Sitkin Island in the western Aleutian Islands, and is within the Aleutian Island National Wildlife Refuge. The active stratovolcano rises 1188 m (3898 ft) in the center-northeastern part of the island. The island is 330 km (200 mi) northwest of the community of Adak, 377 km (234 mi) southeast of Attu, and 2173 km (1350 mi) southwest of Anchorage, Alaska. Little Sitkin has no confirmed historical eruptions, although eruptive activity near the turn of the last century seems probable based on vegetation cover of the youngest-looking lava flows. Three long-lived fumarolic and hot springs areas are known including a cluster of boiling, acidic pools on the west flank of the volcano.

OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 29 volcanoes in Alaska. Satellite images of all Alaskan volcanoes are analyzed daily for evidence of ash plumes and elevated surface temperatures. Some volcanoes may currently display anomalous behavior but are not considered to be at a dangerous level of unrest. Akutan, Aniakchak, Augustine, Dutton, Fisher, Fourpeaked, Gareloi, Great Sitkin, Griggs, Isanotski, Kanaga, Katmai, Mageik, Makushin, Martin, Novarupta, Okmok, Pavlof, Redoubt, Shishaldin, Snowy, Spurr, Tanaga, Trident, Ugashik-Peulik, Ukinrek Maars, Veniaminof, and Westdahl volcanoes are in color code GREEN and volcano alert level Normal. All are at or near normal levels of background seismicity. AVO did not detect ash plumes or significant elevated surface temperatures in the vicinity of any of these volcanoes.

Please see http://www.avo.alaska.edu/color_codes.php for complete definitions of Aviation color codes and Volcano alert levels.

VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu
RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478

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) 378-7556

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.