The article presents new petrogeochemical data on the Middle Miocene-Pliocene volcanic rocks from central part of Iturup Island (Great Kurile Chain). It is shown that volcanism of the Middle Miocene-Early Pliocene age in the central part of the Iturup Island took place in a suprasubduction setting. The distribution of high field strength elements (HFSE) and their ratio in the basaltoids indicate their formation upon partial melting of the depleted upper mantle, while the enrichment of rocks with large ionic lithophilic elements (LILE) indicates both a fluid mantle additive introduced into the melts during the evolution of primary magma and the participation of a low-temperature suprasubduction fluid. The established differences in the composition of the basaltoids of the frontal and rear zones due to the limited number of analyzed samples are considered preliminary. Thus, basaltoids in the rear zone are distinguished by higher concentrations of Th, Pb, HFSE (Nb, Zr, Y, Hf), relative enrichment in LREE, pronounced negative Zr and Hf anomalies, and positive Eu.

Based on the study of the waveforms and spectral composition of earthquakes recorded during the activation of Avachinsky volcano in 2019, three generally accepted types of volcanic earthquakes (VE) were identified: volcano-tectonic, hybrid and long-period, as well as the fourth – a “special” type of VE, characterized by differ of waveforms. 15 plane-oriented clusters have been identified and the characteristics of seismogenic areas
have been determined. Analysis of the seismic events recorded in autumn 2019 in the Young Cone of Avachinsky Volcano suggested a connection between the activation of the 1991 eruption in the body of the cone and their interaction with atmospheric precipitation with magmatic bodies. The most likely cause of the light flashes over the crater on December 8 is the interaction of a hydrogen-rich volcanic gas in contact with atmospheric oxygen.

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 current problems of hydrothermal processes and ore-forming systems are volcanic heat sources and mechanisms of heat
transfer. In Pauzhetsky, Semyachik and Mutnovsky geothermal areas in Kamchatka, active long-lived volcanic centers have been
studied, with which high-temperature hydrothermal systems are associated. In the Banno-Paratunsky geothermal area the Paleogene
and Neogene long-lived volcanic centers were identified, with which low-temperature hydrothermal systems are associated. The
geological history of the long-lived volcanic centers development is characterized by changes in their structure as a result of
hydrothermal-magmatic activity. These changes are manifested in the generation and evolution of magma chambers in the mantle
and in the Earth’s crust. Basalt melts of the mantle chambers transport the deep heat to the Earth’s surface through plane magmatic
channels without significant losses. The heat flow of these volcanic centers is short-lived and is characterized by a significant
capacity of ~8,000 kcal/km2s. The long-lived volcanic centers are characterized by the presence of magma chambers in the Earth's
crust. They shield the part of the mantle heat flow. Their thermal capacity on the Earth's surface is estimated from 1000 kcal/km2s
to 5000 kcal/km2s. It is assumed that a significant amount of thermal energy is retained in the long-lived volcanic centers. It is
spent on formation and activity of the chambers as well as the convective hydrothermal ore-forming systems. The evolution of such
centers is accompanied by the formation of complexes of metamorphic rocks which interaction with high-temperature mantle melts
is accompanied by redox reactions like combustion. As a result of these reactions, thermal energy is produced in such magma
chambers. A long-lived jet magmatic system is formed, and it provides the transfer of mantle heat. Heat transfer in the system is
accompanied by minimization of heat losses, accumulation of heat and its additional generation which is necessary for the heat
transfer in the structures with low thermal conductivity. The formation, evolution and extinction of magma chambers and reservoirs
in such heat-conducting structures are controlled by the thermophysical properties of the rocks, their geological structure and redox processes in them.

Bezymianny Volcano is one of the most active volcanoes in Kamchatka and in the world. This paper describes the preparation, behavior, products, dynamics, and the geological effect of the March 15, 2019 explosive eruption of the volcano, which was predicted 6.5 h before it began. The sequence of eruptive events was analyzed using data provided by video and satellite-based monitoring of the volcano; the quantitative characteristics for the distribution of pyroclastic deposits were obtained in the information system “Remote Monitoring of Activity of Volcanoes in Kamchatka and the Kurile Islands”. The explosions lifted ash to heights of 15 km above sea level (up to 12 km above the volcano), the eruptive cloud was moving northeastward and east from the volcano, the main ashfall area was 210 400 km2, including 15 000 km2 on land. Apart from tephra, the eruption produced pyroclastic flows and pyroclastic surges covering an area of 30 km2. The total volume of explosive products is estimated as 0.1–0.2 km3. The eruptive rocks are calc-alkaline moderate-K basaltic andesites (SiO2 = 54.84–56.29 wt %), they are the most mafic among all rocks of the current Bezymianny eruption cycle.