Report on Veniaminof (United States) — 20 October-26 October 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 October-26 October 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Veniaminof (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 20 October-26 October 2004. Smithsonian Institution and US Geological Survey.
56.17°N, 159.38°W; summit elev. 2507 m
All times are local (unless otherwise noted)
AVO lowered the Concern Color Codeat Veniaminof on 26 October from Yellow to Green. Seismicity, which had been associated with ash emissions that occurred during the summer of 2004, decreased to levels that indicated ash, ash-and-steam, or steam emissions were no longer occurring on a regular basis. Since early September, no ash emissions were seen on the web camera and no evidence of ash was visible on satellite imagery. Also, AVO had received no recent reports of ash from pilots or ground observers. AVO considered the intermittent, low-level seismic tremor that continued to be recorded at the volcano to be part of the background activity. They reported that steaming from the intracaldera cone may still occur.
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.