Eruptive activity continued through early November. On the night of 23-24 October, Perryville residents observed lava fountains at the summit, and on 30 October they observed lava flowing down the SW flank of the intra-caldera cone. On 31 October and 1 November, an ash cloud rose 1 km above the vent.

Bad weather prevented overflights by USGS personnel during late October. During a 4 November overflight, a very light-colored vapor plume containing a little ash rose approximately 100 m and was blown S. Lava flowed down the SW side of the intra-caldera cone, extending the lava delta to the S. They did not observe any water in the large ice pits previously melted into the caldera ice by the lava flows, but their view was obscured by the eruption cloud.

Seismic records available through 8 October showed low-amplitude continuous volcanic tremor beginning 1 October at 1200. On 2 October the amplitude increased to slightly less than half that during the June eruption (8:5, 8). The tremor remained continuous and of about this amplitude through 8 October. Some slightly larger bursts of tremor were recorded 4-8 October. The eruptive activity reported on 3 October by Perryville residents was not distinguishable on the seismic record.

Geological Summary. Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Information Contacts: M.E. Yount, USGS, Anchorage; S. McNutt, LDGO.