2012年2月22日星期三

Another Alaska volcano awakens - Alaska Dispatch

Alaska Dispatch | Feb 19, 2012

First it was Alaska's Mount Cleveland that awoke and threatened to erupt. Now Kanaga, another Alaska volcano is growing restless.

This weekend, the?Alaska Volcano Observatory?raised the threat level to yellow on Kanaga, located on Kanaga Island, one of the most southerly of the central Aleutian Islands chain. ?

"Somewhat elevated seismicity continues at Kanaga Volcano," the observatory reported, adding that on Saturday a weak ash cloud may have been detected after a volcanic tremor.

Kanaga Volcano last erupted in 1994-1995. At least two significant ash plumes were recorded over the course of this eruption. The Aleutian community of Adak received a light dusting of ash and air traffic was disrupted due to continuing low-level activity and cloudy conditions, which prevented visual approaches to the Adak air field.

Meantime, scientists continue to monitor Mount Cleveland, which is located on Chuginadak Island, a remote and uninhabited island in the east central Aleutians.

Cleveland's current threat level is orange, with the observatory reporting a new 200-foot-diameter lava dome.

"There have been no observations of ash emissions or explosive activity during this current lava eruption," according to Alaska Volcano Observatory. Photos: Mount Cleveland, AlaskaAerial photograph of the Mt. Cleveland lava and summit crater on August 8, 2011. Mt. Cleveland is on Chuginadak Island in Alaska's Aleutian chain. Photos: Mount Cleveland, AlaskaAnnotated NOAA satellite image from 5:02 AM AST on 29 December 2011 showing a drifting ash cloud from a small eruption of Cleveland Volcano. Photos: Mount Cleveland, AlaskaSatellite radar image from the TerraSAR-X sensor, showing the summit of Cleveland Volcano on February 10, 2012. It shows the presence of a small lava dome within the summit crater. Photos: Mount Cleveland, AlaskaThis GeoEye IKONOS image shows a faint plume issuing from Cleveland Volcano at 2:31 PM on September 14, 2010. Red in this image highlights areas of vegetation detected by the near-infrared channel.Photo courtesy Alaska Volcano Observatory/GeoEye Photos: Mount Cleveland, AlaskaA small volcanic plume rose above remote Mount Cleveland on June 1, 2010. This false-color image was acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard NASA’s Terra satellite.Image by NASA Earth Observatory Photos: Mount Cleveland, AlaskaAerial photograph of the Mt. Cleveland lava and summit crater on August 8, 2011. Mt. Cleveland is on Chuginadak Island in Alaska's Aleutian chain. Photos: Mount Cleveland, AlaskaAerial photograph of the Mt. Cleveland lava and summit crater on August 8, 2011. Mt. Cleveland is on Chuginadak Island in Alaska's Aleutian chain. Photos: Mount Cleveland, AlaskaWorldview satellite image collected on August 9, 2011 of the summit crater of Cleveland Volcano. The irregularly shaped dark object in the center of the image is the newly erupted lava dome. It is surrounded by brightly colored mineral deposits produced...Image courtesy of AVO/USGS, copyright 2011 DigitalGlobe Photos: Mount Cleveland, AlaskaAshfall on the Lady Gudny on July 21, 2008.Photo courtesy Anne Hillman, KIAL/Unalaska Community Broadcasting Photos: Mount Cleveland, Alaska2008 aerial photograph of the Island of Four Mountains region, including Mount Cleveland.Photo by Cyrus Read/ AVO, U.S. Geological Survey Photos: Mount Cleveland, AlaskaThe eruption of Cleveland Volcano on May 23, 2006, is featured in this image photographed by an Expedition 13 crewmember on the International Space Station.Photo courtesy Image Analysis Laboratory, NASA Johnson Space Center Photos: Mount Cleveland, AlaskaThe island with a prominent caldera in left (west) of image is Herbert, just northeast of it is Carlisle, and Mount Cleveland lies almost directly east. The western flanks of Tana are visible in the lower right of the image. Photographed on January 1,...Photo courtesy Image Analysis Laboratory, NASA Johnson Space Center Photos: Mount Cleveland, AlaskaMount Cleveland is a 1,730-m (5,676 ft)-high stratovolcano in Alaska's Aleutian chain. Photographed on July 24, 1994.Photo by M. Harbin/AVO, University of Alaska Fairbanks

Seismic activity has occurred on and off for nearly 90 years at Cleveland, according to the observatory, though events have become more frequent over the last 20 years. Cleveland's become rather active over the last eight months, building lava domes and producing what volcanologists call "geothermal activity." That activity climaxed on Christmas Day 2011 and a few days later, when the volcano spit ash 15,000 feet into the air, threatening international travel.?


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