ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, May 15, 2009, 3:19 PM AKDT (Friday, May 15, 2009, 23:19 UTC)

REDOUBT VOLCANO (VNUM #313030)
60°29'7" N 152°44'38" W, Summit Elevation 10197 ft (3108 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

The 2009 eruption of Redoubt continues and is characterized by slow growth of the lava dome in the summit crater, continued high gas output, and elevated seismicity. Seismic activity over the past week has declined from the levels seen from May 2-7, but remains above background levels. Small rock avalanches, discrete earthquakes and minor volcanic tremor have been evident in seismic data throughout the week. The lava dome continues to grow as new magma reaches the surface. Incandescence at the dome has been observed in nighttime images from the hut web camera, and thermal anomalies have been persistent in mostly clear satellite views of the summit most of the week. The lava dome is now about 30 to 60 million cubic meters (about 40 to 80 million cubic yards) in volume, and is extending slightly down the upper Drift glacier canyon. The dome has been visible in web camera images throughout the week, and typically shows a robust steam plume rising from the southern part of the dome base. Rock avalanches also have been observed in web camera images. The avalanches typically generate small diffuse ash plumes that linger in the vicinity of the summit crater, but otherwise are not detected in radar or satellite data. Growing lava domes associated with steep terrain may become gravitationally unstable and can collapse with little or no precursory seismicity. If the lava dome in the summit crater does collapse, or is removed by a sudden explosive event, significant ash emissions, possibly to more than 30,000 feet above sea level, and trace to minor ash fall on communities in south-central Alaska are likely. Pyroclastic flows associated with dome collapse or removal also may develop, and if they sweep across snow and ice on and around Drift glacier, they could initiate lahars and floods in the Drift River valley.

Although the level of unrest has not changed significantly over the past week, the apparent lull in activity does not indicate that the eruption is ending. Gas emissions remain very high, and effusion of lava and slow growth of the lava dome continue. Explosive activity could resume before the level of unrest declines and the eruption ends.

AVO is monitoring Redoubt volcano closely and the observatory is staffed 24/7. AVO will provide frequent updates of the volcano's status and the earliest possible warning of significant explosive activity and other hazardous phenomena.

VENIAMINOF VOLCANO (VNUM #312070)
56°11'52" N 159°23'35" W, Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Seismicity at Veniaminof has been above background levels throughout the week. Short periods of low amplitude volcanic tremor and some discrete earthquakes are continuing. No unusual activity has been observed in satellite data this week, and AVO has received no reports of unusual activity from from pilots or observers in the area.





OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 31 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, Iliamna, Isanotski, Kanaga, Katmai, Korovin, Mageik, Makushin, Martin, Novarupta, Okmok, Pavlof, Shishaldin, Snowy, Spurr, Tanaga, Trident, Ugashik-Peulik, Ukinrek Maars, Westdahl, and Wrangell 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 volcano.

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:

Tom Murray, Scientist-in-Charge, USGS
tlmurray@usgs.gov (907) 786-7497

Steve McNutt, Coordinating Scientist, UAF
steve@giseis.alaska.edu (907) 474-7131

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.

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