Volcanism and geological structure of the Avachinsky volcanic group

Abstract

Magnetic, aeromagnetic and gravitional surveys carried out in the Avachinsky volcano area gave the following results. The body which is interpretated as the magmatic focal point breeding the Avachinsky volcano was distinguished by the geophysical data. The absence of any noticeable aeromagnetic anomaly over the Avachinsky volcano group can be explained by the anomalous temperature conditions within the break controlling the volcanic apparatus of the group. The dimensions of calderas, depressions and grabens connected with volcanic activity are defined by the sizes of the magmatic chambers of the volcanoes. The origin of the graben, in which the volcanoes of the Avachinsky group are disposed, can probably be explained by the subsidence of the earth's crust to the zone of magma generation. This zone is established by the decrease of seismic S-waves at a depth of 60–80 km under the Avachinsky volcanoes.