Report on Anatahan (United States) — 4 June-10 June 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 June-10 June 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Anatahan (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 4 June-10 June 2003. Smithsonian Institution and US Geological Survey.
16.35°N, 145.67°E; summit elev. 790 m
All times are local (unless otherwise noted)
Emissions of ash and gas at Anatahan, which began on 10 May, continued during 4-10 June. The highest reported ash plume rose to ~7.6 km a.s.l. on 3 June at 2013 according to observations from an aircraft. US Geological Survey and Commonwealth of the Northern Mariana Islands Emergency Management Office (EMO) personnel visited Anatahan on 6 June and repaired the seismic station in the east crater. EMO recommended that the state of emergency for Anatahan be extended due to continued volcanism, and that Anatahan residents be permanently relocated.
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.