Report on Anatahan (United States) — 3 August-9 August 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 August-9 August 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Anatahan (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 3 August-9 August 2005. Smithsonian Institution and US Geological Survey.
16.35°N, 145.67°E; summit elev. 790 m
All times are local (unless otherwise noted)
During 3-9 August, eruptive activity continued at Anatahan with plumes rising several thousands of meters above the volcano. From 3 to 9 August the National Weather Service at Tiyan, Guam issued multiple volcanic ash advisories for the surrounding islands. According to a news article on the night of 3 August, an aircraft suffered engine trouble in mid-air shortly after taking off from the Saipan International Airport, prompting it to return for an emergency landing. The article noted that the Ports Police said no one was injured in the incident.
Geologic Background. The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of a large stratovolcano with a 2.3 x 5 km compound summit caldera. The larger western portion of the caldera is 2.3 x 3 km wide, and its western rim forms the island's high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern portion of the caldera contained a steep-walled inner crater whose floor prior to the 2003 eruption was only 68 m above sea level. A submarine cone, named NE Anatahan, rises to within 460 m of the sea surface on the NE flank, and numerous other submarine vents are found on the NE-to-SE flanks. Sparseness of vegetation on the most recent lava flows had indicated that they were of Holocene age, but the first historical eruption did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera.
Sources: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program, Washington Volcanic Ash Advisory Center (VAAC), Saipan Tribune