ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, April 17, 2009, 2:45 PM AKDT (Friday, April 17, 2009, 22:45 UTC)
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 week, a lava dome has continued to grow in size within the summit crater. Based on photography and thermal images obtained yesterday, the current dome is estimated to be about 500 m (1640 ft) by 700 m (2297 ft) and at least 50 m (160 ft) thick. Dome growth during the past week has been accompanied by intermittent emissions of volcanic gases and minor amounts of ash. The aviation color code remains ORANGE and the alert level WATCH. AVO continues to monitor the situation closely and the observatory is staffed 24/7.
The last explosive event during the current eruption occurred on the morning of April 4 (05:55 AKDT). Since then, seismicity has remained elevated above background reflecting the ongoing process of dome growth and occasional rock falls. The nearly constant vapor and gas cloud rising above the volcano has remained mostly below 15,000 feet above sea level. Satellite images show thermal anomalies at the summit as well as the low -level plumes and sulfur dioxide clouds drifting away from the volcano. Over the week, pilots have noted occasional sulfur smell down wind.
On Thursday, April 16, AVO field crews repaired a summit seismic station (RSO) that had been destroyed in the March 23 explosion. In addition, they installed a new camera at the AVO hut that has remote zooming capabilities. AVO geologists sampled material from the last explosive event and investigated the site of a smaller ash and water vapor plume seen intermittently down slope from the summit earlier over the past two weeks. Based on their observations, it appears that this secondary plume was the result of hot pyroclastic debris falling into a crevasse in glacial ice. Also on Thursday, April 16, AVO completed a gas measurement flight.
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 aviation and resulted in minor or trace amounts of ash in the city of Anchorage and other nearby communities.
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 received no reports of activity at Cleveland during the past week. Satellite views of the volcano showed no evidence of recent activity at the volcano.
Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about 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 had 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. This eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in January 2009.
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
Tom Murray, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Steve McNutt, Coordinating Scientist, UAF
email@example.com (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.