A mathematical model and a method of computation are developed for the flow of magma with temperature-dependent viscosity in the conduit of a volcano. An example involves the following parameters: conduit radius is 10 m, depth to the magma chamber is 30 km, the overpressure, magma temperature and viscosity in the chamber are 20 bars, 1300° C, and 104, Ю5, 106Pa s, respectively. The initial phase of conduit operation lasting less than 10 years is considered. Conditions are determined under which the conduit freezes (stopping the extrusion), a quasistationary behavior sets in (steady flow), and the flow heats the conduit wall intensively.

This paper presents results of study of the 2012-2013 Tolbachik fissure eruption on the basis of remote sensing
techniques.
We have calculated values of vertical displacements, lava thickness and the volume of the erupted lava. Values of
vertical displacements were estimated using a series of
radar interferometric pairs for the Tolbachik eruption zone.
These pairs correspond to the concluding phase of the erupti
on, when vertical displacements were relatively small.
Vertical displacements were calculated for parts of lava fields with coherence value over 0,4. The obtained values of
vertical displacement are typical for subsidence caused by cooling lava flows. The maximum value of subsidence is
27 cm for 24 days. The calculation of lava thickness was based on comparison of multitemporal DEMs. Height profiles measured by geodetic GPS receivers during fieldwork in August 2013 were used to estimate the quality of DEMs, derived from satellite imagery: freely available SRTM, SRTM-X, ASTER GDEM and the DEMs calculated at RDC ScanEx from two stereopairs of SPOT6 images (of 18.07.2013 and 11.10.2013). The RMS error for heights of SRTM-X and
SPOT 6 in relation to GPS data is within ±5 m. This enables to estimate the total thickness of new lava fields on the
basis of height differences between SRTM-X and SPOT 6 DEMs. Both SPOT 6 DEMs were used together to eliminate errors caused by clouds and snow. The maximum lava thickness is over 80 m. The volume of the erupted lava is 0,521±0,25 km3.

The article provides an algorithm for recovery of parameters of ash emissions (total volume and its height distribution) during explosive eruptions. The solution for the corresponding inverse task uses a multiple regression approach with minimal a prior information on the eruption dynamics. As an example, we consider a strong explosive event at Bezymianny Volcano, Kamchatka, on 24.12.2006. The estimations showed that the mass distribution for ash emission with heights was partially controlled by the emission of ash material inside the clouds from pyroclastic flows. This peculiarity was revealed as a bimodal distribution of the emission mass with maximums at the mid tropospheric and low stratospheric heights.

Data of seismological, gravimetric and electromagnetic study are presented. Main peculiarities of deep-seated structure of the earth's crust and upper mantle to the depth of ~90 km have been revealed. Margins of the lithosphere blocks on ground and water area of the Avacha bay have been established. A complex geologic-geophysical model beneath Avachinsky volcano has been developed. It involves crustal magmatic chamber at depth 15 to 25 km, intrusion overlying it, peripheric chamber at depth ~0 to 2 km, and zone saturated with liquid fluids in Avachinsky graben. Major geodynamic processes, which have been operating in the earth's crust at present, are considered. An important role is given to the crustal permeable zone containing fluids. Recommendations are made for the deep well-drilling in the area of Avachinsky volcano with the aim of searching for geothermal deposits.

Results are presented from gravity, seismic and electromagnetic studies. Main features of the deep structure of the area have been identified. A multidisciplinary geologic-geophysical model has been developed for the crust beneath Avacha Volcano. The model involves a crustal magma chamber at a depth of about 15-25 km, an intrusion that overlies it, and a peripheral chamber under the volcanic cone at 0-2 km depth, as well as a fluid-saturated zone in the Avacha Graben. We discuss possible geodynamic processes that are going on in the crust at present. Importance is attached to the fluid-containing crustal permeable zone. Recommendations are provided for drilling a deep well in the Avacha Graben area to search for a geothermal field.

Рассмотрены методика и результаты магнитотеллурического зондирования в модификациях АМТЗ и МТЗ. Аудиомагнитотеллурическое зондирование (АМТЗ) было проведено впервые в районе современного извержения Толбачинского вулкана. Результаты анализа магнитотеллурических параметров свидетельствуют, что геоэлектрическую среду, в связи с региональным разломом, можно аппроксимировать в виде двумерно-неоднородной модели. В качестве основных для интерпретации приняты продольная и поперечная кривые зондирований. Совместный анализ этих кривых и псевдоразрезов фаз импеданса свидетельствуют о геоэлектрической неоднородности среды в районе прорыва магматических расплавов им. С.И. Набоко. По данным бимодальной инверсии кривых АМТЗ получен геоэлектрический разрез, содержащий проводящую неоднородность, связываемую с разломом, по которому флюиды поступают к дневной поверхности. Наряду с АМТЗ для изучения глубинной электропроводности использованы МТЗ в расширенном диапазоне, по которым выделяется коровая проводящая аномалия на глубинах 15–35 км. По данным АМТЗ, МТЗ и другой геолого-геофизической информации составлена концептуальная модель района, характеризующая возможную природу аномальных зон. Даны приближенные оценки пористости пород в разломной зоне, по которой магматические расплавы поступали в вышележащие толщи в районе прорыва им. С.И. Набоко.