Report on Avachinsky (Russia) — 16 November-22 November 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 November-22 November 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Avachinsky (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 16 November-22 November 2005. Smithsonian Institution and US Geological Survey.
53.256°N, 158.836°E; summit elev. 2717 m
All times are local (unless otherwise noted)
Seismic activity at Avachinsky began to increase significantly on 21 November, with very shallow earthquakes and several hybrid earthquakes recorded at the volcano during 0800-2400. A weak thermal anomaly near the volcano's summit was visible on satellite imagery during 20-21 November. KVERT reported that based on these changes, the possibility of sudden ash explosions had increased. The Concern Color Code remained at Yellow as it has since 8 November.
Geologic Background. Avachinsky, one of Kamchatka's most active volcanoes, rises above Petropavlovsk, Kamchatka's largest city. It began to form during the middle or late Pleistocene, and is flanked to the SE by the parasitic volcano Kozelsky, which has a large crater breached to the NE. A large horseshoe-shaped caldera, breached to the SW, was created when a major debris avalanche about 30,000-40,000 years ago buried an area of about 500 km2 to the south underlying the city of Petropavlovsk. Reconstruction of the volcano took place in two stages, the first of which began about 18,000 years before present (BP), and the second 7000 years BP. Most eruptive products have been explosive, with pyroclastic flows and hot lahars being directed primarily to the SW by the breached caldera, although relatively short lava flows have been emitted. The frequent historical eruptions have been similar in style and magnitude to previous Holocene eruptions.