Report on Avachinsky (Russia) — 3 October-9 October 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 October-9 October 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Avachinsky (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 3 October-9 October 2001. Smithsonian Institution and US Geological Survey.
53.256°N, 158.836°E; summit elev. 2717 m
All times are local (unless otherwise noted)
During 25 August until at least 5 October several earthquakes, with magnitudes between 1.2 and 2.5, were detected near Avachinsky. On 5 October at 0759 an earthquake inside the volcano's edifice was accompanied by a small gas-and-steam explosion with small amounts of ash that rose less than 1 km above the crater. A thin layer of ash covered the SE sector of the volcano's edifice. The same day at 1000 larger gas-and-steam plumes were observed rising above the volcano. Mudflows traveled 50-100 m down Avachinsky's SE slope. KVERT personnel believe the mudflows were caused by intensive activity at a single fumarole on the SE side of the summit. On 5 October the Concern Color Code at Avachinsky was raised from Green to Yellow.
Geologic Background. Avachinsky, one of Kamchatka's most active volcanoes, rises above Petropavlovsk, Kamchatka's largest city. Avachinsky 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. It has a large horseshoe-shaped caldera, breached to the SW, that was formed when a major debris avalanche about 30,000-40,000 years ago buried an area of about 500 sq km 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.