Kizimen Volcano began to erupt in December 2010. The eruption was preceded by a precursory period of seismicity that lasted for 20 months. This paper discusses the space-time features of the precursory seismicity. We provide a brief description of this explosive and effusive eruption between December 2010 and March 2013. The eruption started with some explosive activity followed by extrusion of a viscous lava flow. The extrusion of viscous andesitic magma and the motion of the lava flow down the slope were accompanied by unusual seismicity in the form of the quasiperiodic occurrence of microearthquakes, the so-called drumbeat phenomenon. It is shown that the occurrence of a drumbeat was first recorded during the extrusion process at the volcano's summit. Subsequently, the drumbeat mode of activity was caused by the front of the viscous lava flow as it was moving down the slope. The dynamic parameters of the microearthquakes varied in accordance with the dimensions of the lava flow front. The motion of the main tongue of the lava flow (March to September 2011) gave rise to drumbeat I with energy classes of microearthquakes K = 3-5.5, while the second tongue, which was smaller than the first, produced drumbeat II with microearthquakes of K < 3 during its motion down the slope. In January 2013 we saw a phenomenon similar to the drumbeat that was recorded at the start of the eruption. This was caused by an obelisk being extruded at the volcano's summit. В© 2014 Pleiades Publishing, Ltd.

This paper is concerned with the geological history and petrology of a major polygenic volcanic edifice dating back to Upper Pleistocene to Holocene time. This long-lived volcanic center is remarkable in that it combines basaltic and trachybasaltic magmas which are found in basaltic andesite and trachybasaltic– trachyandesite series. The inference is that the coexisting parent magmas are genetically independent and are generated at different sources at depth in an upper mantle volume. The associated volcanic rocks have diverse compositions, stemming from a multi-stage spatio–temporal crystallization differentiation of the magmas and mixing of these in intermediate chas.

High-precision electron microprobe analyses were obtained on olivine grains from Klyuchevskoy, Shiveluch and Gorely volcanoes in the Kamchatka Arc; Irazu, Platanar and Barva volcanoes of the Central American Arc; and mid-ocean ridge basalt (MORB) from the Siqueiros Transform. Calcium contents of these subduction zone olivines are lower than those for olivines from modern MORB, Archean komatiite and Hawaii. A role for magmatic H2O is likely for subduction zone olivines, and we have explored the suggestion of earlier workers that it has affected the partitioning of CaO between olivine and silicate melt. We provide a provisional calibration of DCaO Ol/L as a function of magmatic MgO and H2O, based on nominally anhydrous experiments and minimally degassed H2O contents of olivine-hosted melt inclusions. Application of our geohygrometer typically yields 3–4 wt % magmatic H2O at the Kamchatka and Central American arcs for olivines having 1000 ppm Ca, which agrees with H2O maxima from melt inclusion studies; Cerro Negro and Shiveluch volcanoes are exceptions, with about 6% H2O. High-precision electron microprobe analyses with 10–20 lm spatial resolution on some olivine grains from Klyuchevskoy and Shiveluch show a decrease in Ca content from the core centers to the rim contacts, and a sharp increase in Ca in olivine rims. We suggest that the zoning of Ca in olivine from subduction zone lavas may provide the first petrological record of temporal changes that occur during hydration of the mantle wedge and dehydration during ascent, and we predict olivine H2O contents that can be tested by secondary ionization mass spectrometry analysis.