The devestating explosive eruptions at Khangar (about 7000 14C BP), Khodutkinskiy "maar" (about 2800 14C BP), and Baraniy Amphitheater (about 1500 14C BP) are classified into a special type, subcaldera eruptions. They were analogues of caldera-forming eruptions by their dynamics, erupted volume (1.5-15 km^3), aspect, facies family, and the composition {from dacites to rhyolites) of the pyroclastics, but were not followed by the development of collapse calderas whose cavity volumes would fit the volume of discharge pyroclastics when converted to solid rock (magma). The discrepancy between a "caldera-like" aspect of the pyroclastics and the type of erupting vent can probably be explained by the greal depths of reservoirs of silicic magma which were "galvanized" when hot basaltic magma was injected into them. A subcaldera eruption usually began with a violent discharge of tephra, much greater in volume than the other volcanic products, to be followed by the formation of pyroclastic flows associated with pyrociastic surges. This sequence of events repeated itself several times during the eruption. No major explosion breccias were formed. Intensive ashfall involved areas of n * 10^4 ... n * 10^5 km^2, so that dated tephra beds have been excellent regional marker horizons. Subcaldera eruptions are hypothesized to have influenced the Earth's climate and are reflected as synchronous acid peaks in the Greenland glacier shield.

A detailed reexamination of the deposits and comparison with the descriptions of the eruption revealed that on March 30, 1956, a collapse and a landslide 0.5 km3 in volume took place on the eastern slope of Bezymyannyi (Central Kamchatka). After a series of explosions, an old dome was slowly uplifted by rising magma, and a cryptodome intruded the eastern flank prior to a cataclysmic explosion. A rockslide changed to a cold (< 100°C) debris avalanche which rushed down at a speed of more than 60 m/s and covered a distance of 10 km from the volcano. The avalanche split into three branches that flowed along the river valleys. The central flow covered the largest distance (22 km). The avalanche stripped and pushed the material at the volcano's foot (snow, soil, alluvium, and vegetation), which produced long mud flows. The landslide unroofed the cryptodome and triggering a devastating lateral blast followed by the eruption of pyroclastic flows.