Anatahan volcano update (Mariana Islands)
jeudi mai 19, 2005 12:28 | AUTEUR : TOM PFEIFFER
During the past 48 hours, volcanic tremor beneath Anatahan increased to eight times the pre-May 18th background level. Discrete earthquakes are largely absent from the seismic record and acoustic records show no apparent explosive events. Satellite imagery indicates ash propagation at 10,000 feet beginning to shift from the southeast to the northwest. Vog and steam is apparent from visual imagery in two regions, the first between 50 and 55 nautical miles northeast of Anatahan, and a wider swath extending from 45 to 130 nautical miles southeast of Anatahan.
While effecting repairs on May 14, Andy Lockhart (USGS) and personnel from EMO reported hearing a continuous roaring sound from 2-3 km west of the active vent. They observed ash and steam rising by pure convection, not explosively, to 10,000 feet. The Mugabe (ANAM) station located 1 km west of the active vent was found to be buried under a meter of ash from the February and April eruptions.
The eruption of 6 April 2005 was the largest historical eruption of Anatahan and expelled roughly 50 million cubic meters of ash. The eruption column and the amplitude of harmonic tremor both grew slowly over about 5 hours and both peaked about 0300 on 6 April local time, 1700 April 5 UT, when the eruption column topped at about 50,000 feet. The peak of the eruption lasted about one hour and then the activity declined rapidly over the following hour.
Restricted Access: The Emergency Management Office, Office of the Governor, CNMI, has placed Anatahan Island off limits until further notice and concludes that, although the volcano is not currently dangerous to most aircraft within the CNMI airspace, conditions may change rapidly, and aircraft should pass upwind of Anatahan or beyond 10 nautical miles downwind from the island and exercise due caution within 10 nautical miles of Anatahan.
SOURCE: adapted from USGS Anataha eruption update
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