The authors for the first time characterize the main stages of formation of the primary vegetation on the terminal moraines against the dynamics of the glaciers at Bolshoi Semyachik Volcano (Eastern Kamchatka). The vegetation was investigated and described from the terminal moraines dated back to the late 19th century to the modern boundary of the glacier.

A velocity structure of the lithosphere has been determined in the junction area of the Kuril-Kamchatka and Aleutian island arcs based on travel times of compressional (P) and shear (S) waves excited by regional and volcanotectonic earthquakes using the algorithm of successive anomaly subtraction. We describe deep-seated velocity heterogeneities at different depths in the lithosphere, their relation to tectonics and to seismicity. It is shown that the deep-seated source of magma supply for the Klyuchevskoi volcanic cluster is confined to a junction of deep-seated mantle faults (in map view this occurs at the location where the Kamchatka R. streambed turns eastward). The heterogeneity in question probably has asthenospheric roots. The crustal velocity structure beneath Klyuchevskoi Volcano together with data provided by other geological and geophysical methods (deep seismic sounding, electromagnetic methods, lineament analysis etc.) provides an idea of the model and of a general view of the tectonomagmatic processes going on there.

Results from detailed field work made it possible to describe the geologic structure of Late Pleistocene Old Shiveluch Volcano. Old Shiveluch activity consisted of two phase: extrusive-explosive activity of the initial phase was followed by numerous lava effusions from several eruptive centers. Location of the eruptive centers was reconstructed along the rim of the destroyed southern part of the volcano. Three main types of rocks were distinguished in the Old Shiveluch edifice: magnesian andesites (SiO2=57.3-63.8 wt.%, Mg#=52.5-57.0 mol. %), high-Mg basaltic andesites (SiO2=53.9-55.0 wt.%, Mg#=58.8-63.7 mol.%) and high-Al basaltic andesites (SiO2=53.5-55.7 wt.%, Mg#=52.1-56.1 mol.%). Relative sequence and the approximate volume ratios of the different types of rocks were revealed. New geologic data allowed suggesting what caused a sector collapse of Old Shiveluch edifice.