Report on Veniaminof (United States) — September 1983
Scientific Event Alert Network Bulletin, vol. 8, no. 9 (September 1983)
Managing Editor: Lindsay McClelland
Veniaminof (United States) Eruption resumes; Strombolian activity; lava flows
Please cite this report as:
Global Volcanism Program, 1983. Report on Veniaminof (United States). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 8:9. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198309-312070.
56.17°N, 159.38°W; summit elev. 2507 m
All times are local (unless otherwise noted)
After declining in August and September, eruptive activity resumed on 3 October, when Perryville residents reported ashfall on the town and saw incandescence at the volcano.
During an overflight on 5 October, USGS personnel observed Strombolian bursts of lava from the previously active vent within the summit crater of the intra-caldera cone. An ash cloud rose 300-1,200 m above the vent and extended E. On 7 October, ash and bombs were ejected 60-90 m above the vent. Lava flowed SW from the vent on top of flows erupted June-July, adding a new lobe to the lava delta at the base of the intra-caldera cone. Steam rose from the active flow fronts. The meltwater lake formed during previous activity remained frozen and had apparently not increased in size.
During the next overflight, from 1345 to 1425 on 13 October, a thin wispy ash cloud rose about 60 m above the cone and drifted N, depositing ash on the caldera floor ice N and NE of the intra-caldera cone. Bursts of ash and incandescent bombs were ejected from the summit of the cinder cone at rhythmic intervals of a few seconds early in the overflight, but became more continuous later. Lava flowed from SW flank vents slightly below the summit of the cinder cone down the steep flank of the intra-caldera cone. They extended the lava delta to the SE, remelting the SE portion of the meltwater lake.
Geologic Background. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3700 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 reaches an elevation of 2156 m and 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: T. Miller and M.E. Yount, USGS, Anchorage.