Assessing the Volumes of Material Discharged by Bezymyannyi Volcano during the 1955–2009 Period

摘要

We present data on the volumes of material discharged during the main phases of the volcano’s recent activity from its start in October 1955 until December 2009. The amount of ash discharged onto the ground surface during the preculmination period (October 1955 to March 1956) is estimated as 400 million tons; the paroxysmal eruption of March 30, 1956 discharged more than 400 million tons, the volume of pyro-clastic flows was estimated as 1416 million tons. The following estimates were obtained for the material dis-charged onto the ground surface for the period from 1956 to 2009. The weight of the lava cone that grew in the newly formed crater is 941 million tons, the deposits of pyroclastic flows weighed 491 million tons, and the ash weight was 117 million tons. Effusive activity was insignificant; the weight of the lava flows was ～9.2 million tons. The amount of material erupted during the third phase is estimated as 1560 million tons. The mean annual discharge between April 1956 and December 2009 was 29 million tons. This figure is half that for the giant Klyuchevskoi volcano and six times larger than the mean discharge found for the 5000– 5500 years of the existence of Bezymyannyi Volcano.