Report on Veniaminof (United States) — 25 September-1 October 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 September-1 October 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Veniaminof (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 25 September-1 October 2002. Smithsonian Institution and US Geological Survey.
56.17°N, 159.38°W; summit elev. 2507 m
All times are local (unless otherwise noted)
AVO reported that seismic unrest that began at Veniaminof on 10 September continued through the 27th. The intensity of tremor and small earthquakes under the volcano had decreased since the 10th, but remained above the background level established during the summer of 2002. Visual observations of Veniaminof were hampered by poor weather. On 24 September, residents of Perryville, 35 km S of the volcano, reported and photographed small bursts of steam, possibly containing minor amounts of ash, rising just above the historically active intracaldera cinder cone. Without additional observations, AVO could not determine if this indicated very low-level eruptive activity or vigorous steaming from the cone. On several occasions of relatively clear weather conditions, AVO observed no signs of elevated temperature or ash emission on satellite imagery. Due to the continuing seismicity and reports of unusual steaming, the Concern Color Code remained at Yellow.
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.