Report on Bezymianny (Russia) — 16 June-22 June 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 June-22 June 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Bezymianny (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 16 June-22 June 2004. Smithsonian Institution and US Geological Survey.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
According to KVERT, an eruption at Bezymianny on 19 June led them to raise the Concern Color Code to Red, the highest level. Activity first began to increase during 11-14 June, when seismicity was above background levels with 2-3 shallow earthquakes daily. On 16 June KVERT raised the Concern Color Code from Yellow to Orange. Then, on 19 June, seismic data were interpreted to indicate that explosive activity during 0840-0930 may have produced an ash plume to 8-10 km a.s.l. Video observations later confirmed the plume height. Satellite imagery showed that the plume extended about 200 km by 1319. Later that day, seismicity decreased and the Concern Color Code was reduced to Orange.
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.