The authors revealed trends of inter-phase distributions of rock-forming elements in the system melt–spinel–olivine based on experimental data obtained under a wide range of conditions. 78 equations allow us to evaluate phases equilibrium in multisystem melt–spinel–olivine, and consequently estimate equilibrium values of temperature, pressure and content of a variety of elements and their ratios in a melt.

The paper presents data that describe the Kuril Island Arc volcanic activity over the 2012-2015 period collected using satellite monitoring and visual observations, as well as the results of field studies at the active volcanoes. The authors analyzed eruptions of Ivan Grozny, Kudryavy (Iturup Island), Snow (Chirpoi Island), Chirinkotan (Chirinkotan Island), Sinarka (Shiashkotan Island), Chikurachki (Paramushir Island), and Alaid (Atlasov Island) volcanoes.

The article provides the analysis of the published data on anomalies of iridium and other platinum-group elements (PGE) at different Phanerozoic stratigraphical levels and gives evidences of heterogeneity of these anomalies and arguments of different authors about their relation with impact, volcanic, paleoclimatic and biotic events. Most of iridium anomalies coincide with large extinctions of sea organisms. The authors revealed in Cretaceous paleoceanic deposits of Eastern Kamchatka (Kamchatsky Mys peninsula) PGE anomalies at two levels corresponding to oceanic anoxic events OAE2 and MCE.

The paper proposes a formalized technique of probabilistic forecast by applying statistical estimation of seismicity level and a number of additional functions that characterize the predictive situation. The possibilities of this method are illustrated by the example of seismic activation before the eruptions of Bezymianny Volcano (Klyuchevskaya group, Kamchatka).
The initial data is the catalog of earthquakes of the Klyuchevskaya group of volcanoes during 1999-2014, compiled by the Kamchatka Branch of the Geophysical Survey, RAS. During this time there were 21 eruptions of Bezymianny Volcano. The precursor is defined as a threshold function associated with the current seismicity level and its characteristic form before the eruption.
The values of parameters characterizing the precursor are given including validity, reliability and efficiency, calculated by two methods. It is shown that the reliability of the precursor decreases with the increase in threshold values, and its validity increases.
The reliability of the method is 0.38–0.95, i.e., from 38 % to 95 % of eruptions had the precursor depending on the threshold level; and the validity is 0.3–0.6, i.e., from 30 % to 60 % of the identified precursors are realized also depending on the threshold level. Values of efficiency confirm the non-random nature of the precursor appearance.
The method includes determination of the probability of the forecast realization. The nomogram for probabilities depending on the duration of the forecast and the values of the prognostic parameter is designed.

Analysis of the spread of ash clouds and plumes from volcano eruptions is a complex interdisciplinary task, hence implementation of the necessary methods and technologies exclusively on a single platform is extremely difficult. A more efficient approach is associated with the organization of interaction between already existing information systems and services developed on the basis of particular scientific competence and specialized data archives formed and built in the corresponding supporting software and hardware infrastructure. Based on this approach, a software platform was implemented integrating three information systems: Signal, VOKKIA and VolSatView. The platform provides computer modeling of ash clouds and plumes from the volcanoes of Kamchatka, and joint analysis of modeling calculation results with remote sensing data. The paper describes the platform, and the architecture of interaction of specialized applications and information systems, tools and technologies used for computer modeling, exchange of scientific data and working with them. The article includes examples of user interfaces for setting computing tasks and conduct joint analysis of modeling results using the data obtained by remote sensing of the Earth from space.

The article presents new data on isotopic-geochemical composition of igneous rocks from Kumroch segment of Achayvayam-Valagin Late Mezosoic ― Early aleozoic volcanic arc. It is shown that three series of rocks may be distinguished in composition of island-arc basalt-andesite lava of volcanogenic-tuffaceous unit of Khapitskaya suite: low-potassium (tholeiitic), medium-potassium (calc-alkalic) and high-potassium (alkalic). These rock series differ in K2O content and proportion of femic components and SiO2. Compositions of the studied rocks were compared with composition of basalts from the Idzu-Bonin Island Arc. The obtained results suggest that the samples of medium-potassium and high-potassium groups were formed in back arc zone of the volcanic arc and low-potassium tholeiites were possibly formed in the inter-arc rift.