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.

The given work is devoted results of studying extremely interesting on the mechanism of activity of the Koryak Volcano eruption occurring since December, 2008 on the beginning of 2010. This eruption it is possible to characterize as weak explosive gas-ashed. Similar activity, considering that it is some to the previous eruption of a volcano in 1956-1957гг, it is possible to allocate in separate fumarolic or Koryak type of eruption.
Key words: a volcano, eruption, volcanic gases, volcanic ashes, fumarolla, infra-red survey

The authors studied deposits from pyroclastic flows associated with Karymsky Caldera, which is located in the central part of the Karymsky Volcanic Centre (KVC). The study distinguished 4 pyroclastic flows and revealed that deposits from each pyroclastic flow have stratification in composition distinctly observed in the initial phase of the eruption. The pumice debris and cores of plagioclase crystals in pumice give evidence for both upper rhyolite zone and lower dacite zone in the upper-crust magmatic chamber. The heterogeneous layers and non-equilibrium mineral association in pumice suggest that the initial phase of each eruption is caused by intrusion of basalt in the upper-crust magmatic chamber. The distribution of major and trace elements in pyroclastic rocks of Karymsky Caldera show that they have resulted from moderate calcareousalkali differentiates of magnesia-basalt of KVC. Mineralogical and geochemical data show that the fractional crystallization and crustal contamination play significant role in origin of the rocks.

Thick deposits of pyroclastic flow from Shiveluch Volcano (February 2005) have remained high temperature for 6 years after the eruption. Despite the increased temperature of the deposits, plants began its colonization in recent years. To identify features of succession certain characteristics of unusual ecotope have been studied, including distribution of temperature background.

The article provides data on historical events of the Kurile island arc’s most active Peak Sarychev Volcano, Matua Island, the Central Kuriles. During the study period the volcano was producing short terminal eruptions of explosive and explosive-effusive types discharging volcanites chiefly with pyroclastic flows and related formations.