Bad weather obscured both visual and satellite observation of Chiginagak throughout most of December 1997 and January 1998. Residents of Pilot Point (60 km NW) reported a robust steam plume on 2 December and some less intense puffing on 3 December. No further activity was reported, generally because of the poor weather, until Pilot Point residents again saw a plume on 9 January 1998.

AVO had received several reports of increased steaming, snow-melt, and sulfur smells at the volcano beginning in late October. Prior to that, residents of the area, including those in Pilot Point, had noticed increased steam emissions as early as mid-summer 1997. Chiginagak is not monitored by scientific instrumentation; however, satellite imagery and observers in Pilot Point provide information. In addition, the volcano is located in a National Wildlife Refuge; the U.S. Fish and Wildlife Service frequently overflies the area, especially when activity persists or intensifies.

Geological Summary. The symmetrical, calc-alkaline Chiginagak stratovolcano located about 15 km NW of Chiginagak Bay contains a small summit crater, which is breached to the south, and one or more summit lava domes. Satellitic lava domes occur high on the NW and SE flanks of the glacier-mantled volcano. An unglaciated lava flow and an overlying pyroclastic-flow deposit extending east from the summit are the most recent products of Chiginagak. They most likely originated from a lava dome at 1687 m on the SE flank, 1 km from the summit of the volcano, which has variably been estimated to be from 2075 to 2221 m high. Brief ash eruptions were reported in July 1971 and August 1998. Fumarolic activity occurs at 1600 m elevation on the NE flank of the volcano, and two areas of hot-spring travertine deposition are located at the NW base of the volcano near Volcano Creek.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.