Volcano Update from Archive

Monday, March 23, 2009 12:18 PM AKDT (Monday, March 23, 2009 2018 UTC)

Redoubt Volcano
60°29'7" N 152°44'38" W, Summit Elevation 10197 ft (3108 m)
Current Volcano Alert Level: WARNING
Current Aviation Color Code: RED

Beginning last night (Sunday March 22, 2009) at approximately 22:38 AKDT, Redoubt Volcano produced a series of five explosive eruptions that each lasted from four to thirty minutes. The last one ended at 5:00 AM AKDT this morning (March 23). National Weather Service radar, pilot reports, and AVO analysis of satellite imagery suggest that these events produced ash clouds that reached 60,000 ft above sea level (asl), with the bulk of the ash volume between 25 - 30,000 ft asl. Traces of ash fall have been reported in Skwentna, Talkeetna, Wasilla, and Trapper Creek.

AVO remains at Avation Color Code RED and Alert Level WARNING. Seismic unrest continues at Redoubt in the form of elevated volcanic tremor. NEXRAD radar data show that the last significant ash emission was concurrent with the final explosive event at 5:00 AM AKDT. Since that time, no ash has been visible in radar, suggesting that if ash emission is occurring, it is below approximately 13,000 ft asl and/or too fine to be detected. Poor weather at the volcano currently hinders visual observations.

Last night's explosive eruptions caused melting of the Drift glacier and greatly increased discharge down the Drift River. AVO plans a helicopter overflight to the area today to assess conditions at the volcano and along the Drift River. The explosions also destroyed one seismic station near the volcano's summit (RSO), and disrupted telemetry from AVO's obsveration hut. This telemetry outage affects the web camera, a continuous GPS station, and two broadband seismic stations. Repairs to this data link will be undertaken as conditions permit. Seven telemetered seismic stations surrounding Redoubt remain in operation.

The eruptions were preceded by approximately 60 hours of elevated seismicity in the form of discrete earthquakes under the volcano. AVO raised the Aviation Color Code/Alert Level from YELLOW/ADVISORY to ORANGE/WATCH on Saturday, March 21 at 22:09 AKDT. This increase in seismicity likely reflected the upward movement of magma towards the surface. Prior to this weekend, Redoubt had exhibited signs of volcanic unrest beginning in the Fall of 2008 which then escalated in late January, 2009. Last night's explosions were the first significant ash-producing eruptions of the unrest.

Further explosive activity could occur with little or no warning, and could occur intermittently for weeks or months. AVO remains staffed 24 hours per day will issue further information as it becomes available.

For up-to-date Ashfall Advisories and wind trajectories, please refer to the National Weather Service website: http://pafc.arh.noaa.gov/volcano.php.

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 international air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other nearby communities.

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.