Report on Veniaminof (United States) — 5 September-11 September 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 5 September-11 September 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Veniaminof (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 5 September-11 September 2018. Smithsonian Institution and US Geological Survey.
56.17°N, 159.38°W; summit elev. 2507 m
All times are local (unless otherwise noted)
On 4 September low-level ash emissions (less than 3 km or 10,000 ft a.s.l.) from Veniaminof were evident in webcam images and confirmed by observers in Perryville (35 km S), prompting AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch. Seismicity was elevated. During 4-6 September pulsating, low-altitude ash plumes were visible from a Perryville webcam and reported by a pilot, and a small thermal anomaly was visible in satellite data. On 7 September the thermal signal increased, suggesting lava fountaining at the summit. Webcam images the next day showed minor ash or steam near the summit cone. Ash deposits on the snowfield formed a “V” shape from the summit, extending to the SSW and SE. On 9 September a lava flow, about 800 m long, was identified on the S flank in satellite data. Witnesses aboard a ferry passing Veniaminof early the next morning noted lava fountaining and an active lava flow. Lava flows continued on 11 September, though were confined to the summit caldera.
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 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.