The 2019–2021 Eruptions of Klyuchevskoi Volcano, Kamchatka

This paper provides information on the volumes of ejecta discharged by lateral and summit eruptions during the period from 1932 to 1989. We show that the volumes of ejecta from lateral eruptions were larger than those of the summit eruptions for the period. We examine subsequent variations in the character of eruptions. Lateral and summit eruptions had been occurring on the volcano from 1932 to 1989, and summit eruptions alone from 1990 to 2016. Changes occurred in 2016 with the resumption of lateral eruptions on the volcano’s slopes. We note one characteristic feature, namely, all summit eruptions terminated in collapse events in the central crater. The collapse structures are characterized. The formation of the collapse structures is related to changes in the density and volume of magma as it was ascending to the ground surface. Data are provided relating to the summit eruptions of 2019–2021 and on the 2021 lateral eruption named after G.S. Gorshkov. New data are presented showing changes in the morphology of the summit crater during eruptions and collapses in the crater after the eruptions.