Report on Anatahan (United States) — June 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 6 (June 1992)
Managing Editor: Lindsay McClelland.
Anatahan (United States) Thermal activity but deformation unchanged
Please cite this report as:
Global Volcanism Program, 1992. Report on Anatahan (United States) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 17:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199206-284200.
16.35°N, 145.67°E; summit elev. 790 m
All times are local (unless otherwise noted)
A six-member team of USGS volcanologists visited the Commonwealth of the Northern Mariana Islands 11-27 May 1992 at the request of the CNMI Office of Civil Defense. The team observed all of the islands in the chain N of Saipan, installed a new seismic station at the base of frequently active Pagan, remeasured existing EDM networks, mapped the geology of Alamagan, sampled fumaroles and hot springs, and collected rocks and charcoal for radiocarbon dating. No volcanoes in the chain erupted during the observation period.
Remeasurement of the EDM network on 22 May showed no significant changes, consistent with the lack of shallow seismicity since September 1990. Boiling hot springs on the eastern crater floor and solfataras at the base of the nearby crater wall had maximum temperatures of 98°C.
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.
Information Contacts: R. Moore, USGS; R. Koyanagi, M. Sako, and F. Trusdell, HVO.