Report on Bezymianny (Russia) — May 1983
Scientific Event Alert Network Bulletin, vol. 8, no. 5 (May 1983)
Managing Editor: Lindsay McClelland.
Bezymianny (Russia) Explosions destroy part of lava dome; ash ejection; pyroclastic flow; lava extrusion from dome's summit
Please cite this report as:
Global Volcanism Program, 1983. Report on Bezymianny (Russia). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 8:5. Smithsonian Institution. https://dx.doi.org/10.5479/si.GVP.SEAN198305-300250.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
Bezymianny began to erupt 22 May, without premonitory seismicity. Ash was ejected to 5-6 km height and covered the E foot of the volcano. The total area of the ash deposit was about 1,500 km2. Strong explosions destroyed part of the Novy (new) lava dome (see below) and a 4-5 km-long pyroclastic flow was noted at its E base. Andesitic lava was extruded from the dome's summit. Since the beginning of the eruption, the volcano has remained cloud-covered, making observations difficult.
Imagery returned 1 June by the NOAA 7 polar orbiting satellite showed a dark band extending about 250 km ESE from the vicinity of Bezymianny, above a layer of heavy weather clouds. Because of the clouds, it was not possible to locate the dark band's origin more closely than about 56°N, 160°E, or determine if the volcano was feeding the dark band at that time. Continued poor weather has prevented additional satellite observations of eruption plumes.
No eruptions of Bezymianny were known for more than 250 years after the Russian discovery of Kamchatka in 1697. Ash eruptions that began in late 1955, followed by lava dome extrusion and intrusive activity, culminated in a paroxysmal directed explosion on 30 March 1956 that destroyed the summit and formed a large crater, elongate to the E. Lava extrusion then resumed, accompanied by numerous explosive episodes, and has continued through the present, building the Novy dome (Bogoyavlanskaya and Kirsanov, 1981).
Geologic Background. Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.
Information Contacts: G. Bogoyavlenskaya, IVP; M. Matson, NOAA/NESS.