When scientists from the Alaska Volcano Observatory (AVO) conducted an overflight to Chiginagak on 11 March, the summit was visible but a thin cloud layer at about 1,700-1,900 m altitude obscured the fumarolic areas. Above the fumaroles, however, bulbous gray clouds penetrated through the thin cloud layer and extended to about 2,100 m altitude.

A strong sulfur smell was noticed 16-49 km downwind of the volcano. The gray clouds and sulfur smell supported observations from Pilot Point (60 km NW) that indicated continued vigorous fumarolic activity. Increased fumarolic activity has been reported at the volcano beginning as early as mid-1997 (BGVN 22:11 and 23:01). According to AVO, the increased activity did not imply an imminent eruption.

Geological Summary. The symmetrical, glaciated Chiginagak stratovolcano locatedon the Alaska Peninsula ~15 km NW of Chiginagak Bay contains a small summit crater, which is breached to the south, and one or more summit lava domes. Lava domes occur high on the NW and SE flanks of the calc-alkaline volcano. An unglaciated lava flow and an overlying pyroclastic-flow deposit extending E from the summit are the most recent eruption products, which most likely originated from a lava dome on the SE flank, 1 km from the summit. Brief ash eruptions were reported in July 1971 and August 1998. Fumarolic activity has bene reported on the NE flank, and two areas of hot-spring travertine deposition are located at the NW base 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.