Report on Bezymianny (Russia) — September 1995
Bulletin of the Global Volcanism Network, vol. 20, no. 9 (September 1995)
Managing Editor: Richard Wunderman.
Bezymianny (Russia) Explosive eruption causes 2-3 mm of ashfall 50 km away
Please cite this report as:
Global Volcanism Program, 1995. Report on Bezymianny (Russia). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 20:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199509-300250.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
At 0500 on 6 October, regional seismic stations began to record volcanic tremor with a maximum amplitude of 5-6 µm. An ash plume was detected by the Alaska Volcano Observatory (AVO) on a satellite image taken at 0824. The Institute of Volcanology (IV) reported that an eruptive column first appeared over Bezymianny around that time, and by 0900 it was ~8 km high. Weather satellite imagery at 0948 showed that the plume had reached the coastline nearly due E, with a top estimated to be 10 km above sea level.
At 0930, volcanic ash started to fall in Kliuchi, ~50 km NNE. Tremor and ash emission increased up to 1200, followed by 3 hours of intense ashfall; during a period of 140 minutes 700 g/m2 of ash fell in Kliuchi. Because the air in Kliuchi was strongly polluted with volcanic gas, a warning was issued for the residents to take precautions. From Kliuchi, E. Zhdanova, a volcanologist from the Institute of Volcanic Geology and Geochemistry (IVGG), reported that ashfall had stopped at about 1700 on 6 October after 2-3 mm of deposition. AVO satellite imagery at 1813 showed the disconnected ash plume ~150 km E. The plume was moving ENE and was over 400 km from the source. By about 0930 on 7 October, the ash plume had undergone significant diffusion and was no longer detectable on satellite images.
As of the morning of 7 October the volcano was obscured, but there was no more tremor. Zhdanova suggested that the explosive phase of the eruption had ended and a lava dome was forming again. This interpretation was confirmed by a large hot spot seen at the vent on AVHRR imagery after the ash cloud had disconnected from the volcano.
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: Alaska Volcano Observatory; E. Zhdanova and V. Kirianov, Institute of Volcanic Geology & Geochemistry, Piip Avenue 9, Petropavlovsk-Kamchatsky, 683006, Russia; N.A. Zharinov and S.A. Fedotov, Institute of Volcanology, Petropavlovsk-Kamchatsky, 683006, Russia.