Complex investigations of the mineral composition and petromagnetic properties of the rock samples constituting the Minami-Khiosi submarine volcano which is located in the Mariana island arc were carried out for the first time. The Minami-Khiosi submarine volcano is part of the Khiosi volcanic complex in the alkaline province of the Izu-Bonin and Mariana island arcs. The rocks analyzed are enriched in К2О (1.34-3.30 %), Ва - 370-806 ppm, and Sr - 204-748 ppm. Basalts exhibit a porphyric structure. Impregnations are mostly olivine, its single crystals or their concretions. In some samples olivine is very large in size (about 2 cm), but at the same time the grain-size of the main bulk is fine-crystalline. The studied samples include no less than 3 Fe-bearing oxide minerals. Among them are dominant titanomagnetite, and ilmenite and Fe hydroxides are less abundant. It has been established that the studied samples are mainly magnetically isotropic, have high values of natural remanent magnetization and Königsberger factor. As in other Late Cenozoic island arc submarine volcanoes of the Western Pacific the studied samples are highly differentiated by the amount of natural remanent magnetization and magnetic susceptibility. The main carriers of magnetization are low coercive magnetic minerals (titanomagnetite and magnetite) pseudosingle-domain structure and high coercivity (hematite). High values of natural remanent magnetization are due to psevdosingle-domain structure of titanomagnetite grains and high values of magnetic susceptibility are explained by a high concentration of ferromagnetic grains.

This article represents a detail analysis of the spatial variations in volcanism from the Northern sector of the Kurile Island Arc. Investigations of the volcano time activity and comparison of the volume of erupted material made it possible to characterize features of the volcanism on the front and rear zones in dependence of the slab depth and location of faults. Data from volcanic location, as well as microscopic and geochemical analysis of its products allowed identifying geologic and petrologic peculiarities of volcanic formations in three main zones: the frontal, the intermediate, and rear zones.

Seismic activation of Avachinsky volcano was observed from late October to late December 2019, when 6 swarm sequences of volcanic earthquakes of various types occurred in its construction. In the swarm sequences, 15 plane-oriented clusters were identified and the characteristics of their seismogenic areas were determined. A comprehensive analysis of seismic events indicates that the activation of Avachinsky volcano at the end of 2019 arose because of the interaction of meteoric waters with magmatic bodies in the body of the cone, which arose during an effusive eruption in 1991.

The article presents a technique for formalized separation of volcano-tectonic earthquakes and low-frequency seismic events which occurred on volcanoes. The technique was used as a case study for four episodes of volcanic activity in Kamchatka based on data from seismic stations located near volcanoes: explosive eruption of Kizimen Volcano (2010-2011), activization of Gorely Volcano (2009-2011), activization of Koriaksky Volcano (2008-2009), long-term intense hydrothermal activity of Mutnovsky Volcano. For visualization of hidden correlation in waveform spectral characteristics we use the triangle diagram. We have targeted a trend in volcano investigation which supposes study of possible relation between types of volcano activity and distribution of spectral components in seismic records.