ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, April 3, 2009, 4:04 PM AKDT (Saturday, April 4, 2009, 00:04 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 Volcano continues. Over the past several days, the intensity of ash-production has decreased while a lava dome is growing in the summit crater. Therefore, Alaska Volcano Observatory (AVO)lowered the alert level to WATCH and aviation color code to ORANGE this morning. AVO continues to monitor the situation closely and the observatory is staffed 24/7.

Following last Friday's update, Redoubt had seven more powerful ash explosions through Saturday evening, with the resulting plumes reaching between 25,000 to 50,000 feet above sea level. In total, AVO has observed 18 major explosive events since the start of the eruption. The last major explosive event occurred at 19:23 AKDT on March 28 (03:23 UTC, March 29). Over the last few days, a diffuse cloud of volcanic gas, ash, and steam is rising to variable altitudes over the volcano, but mostly less than 15,000 feet above sea level. At times of more vigorous ash production, the cloud has risen as high as 25,000 feet. Lightning has been detected several times in conjunction with ash emission this week. Trace amounts of ash fall (less than 0.8 mm or less than 1/32 inch) have been reported at Kenai and at Valdez. The area in the immediate vicinity of the volcano is blanketed by a thin layer of ash visible in the AVO web cameras. The larger explosions produced lahars in the Drift River Valley and minor ash fall in areas across south-central Alaska including Anchorage. A broad layer of volcanic haze extended east of the volcano over the Kenai Peninsula, the Anchorage Bowl, and the Matanuska-Susitna Valley on March 31.

AVO overflights and photography have confirmed that a lava dome is actively growing in the summit crater. Occasional avalanches of hot blocks tumbling from the dome are traveling a short distance down the north flank of the volcano.

Seismicity at the volcano had been declining over the course of the week until around 8:00 AM AKDT Thursday morning. Since then small repetitive volcanic earthquakes have been visible on stations closest to the summit crater. These earthquakes have continued up to the time of this report.

Based on its past activity, the current Redoubt eruption is expected to continue for weeks to months. During this time, a cycle of relatively quiet periods of lava dome growth followed by explosive episodes of dome destruction will likely take place. Future explosions pose an ongoing threat of lahars in the Drift River Valley, trace to minor ash fall throughout south-central Alaska, and ash-related impacts to aviation.


Heavily ice-mantled Redoubt volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano which rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, and 1989-90. The 1989-90 eruption produced mudflows, or lahars, that traveled down the Drift River and partially flooded the Drift River Oil Terminal facility. The ash plumes produced by the 1989-90 eruption affected air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other nearby communities.

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

AVO has received no new reports of activity at Cleveland over the last week. Satellite views of the volcano have been obscured by clouds.

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, Veniaminof, 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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