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Magnitude of Anatahan eruption fluctuates
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Posted on Mar 24 2005
Anatahan’s volcano continues to erupt with Strombolian explosions and fluctuating seismicity.
In a joint report, the Emergency Management Office and the U.S. Geological Survey also disclosed yesterday that lava has been flowing from the volcano’s crater.
The agencies said a plume of volcanic smog has now spread to about 260 nautical miles west of the volcano, citing monitoring being conducted by the Air Force Weather Agency.
They said that seismicity on Anatahan has been fluctuating, but described it yesterday as “moderately high.”
The volcano has been erupting for the third time this year since Friday, spewing clouds of ash into the air, days after a scientific mission visited the island to collect rock samples and measure emissions of sulfur dioxide, a major air pollutant.
The volcano erupted for the first time this year in early January, with pyroclastic rocks with diameters of about a meter and over being thrown from the crater to hundreds of feet into the air.
That eruption, which was considered as Anatahan’s third historical eruption, peaked on Jan. 26 and Feb. 2, during which time the volcano sent ash as high as 15,000 to 20,000 feet locally and as far as 100 miles downwind, and volcanic smog nearly 600 miles downwind.
Fresh lava covered the entire crater floor by up to about one kilometer in diameter some two weeks later, according to the USGS and the EMO.
Anatahan’s volcano first erupted after centuries of dormancy on May 10, 2003, with ash plume rising to an altitude of over 30,000 feet that covered over 1-million-square kilometers of airspace above the Pacific Ocean. That eruption, which ceased by mid-June that year, deposited about 10-million cubic meters of material over Anatahan Island and the sea. The second batch of volcanic eruptions happened from April to June 2004.
