Report on Bezymianny (Russia) — October 1984
Scientific Event Alert Network Bulletin, vol. 9, no. 10 (October 1984)
Managing Editor: Lindsay McClelland.
Bezymianny (Russia) Ash cloud; pyroclastic flows; part of dome destroyed
Please cite this report as:
Global Volcanism Program, 1984. Report on Bezymianny (Russia). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 9:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198410-300250.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
"Activity increased from late September through mid-October. On 4 September, small surface earthquakes began to be recorded at a seismic station 13 km from the volcano. By 8 October, the number of recorded events was 300 per day. On 9 October, ash ejections became frequent and rockslides occurred from the dome. On 13-14 October the eruption entered its main phase. Volcanic tremor began and an eruption column rose to 5 km height. Several explosions destroyed the E portion of the summit dome. Pyroclastic flows descended along two routes, the larger more than 8 km long. Ashfall occurred to the ENE. The ash layer 16 km NE of the volcano was 2 kg/m2. Weaker activity followed and by 19 October the eruption was over."
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 and P. Tokarev, IVP.