Based on the results of expeditionary studies (July 2021), geochemical features of thermal waters (natural manifestations and borehole waters) discharging near or directly on the Sea of Okhotsk and Pacific coasts of the central part of Iturup Island were considered: Reidovskie, Lososevye, Cape Konakov, Goryachie Klyuchi, Dachnye, water-recreational complex «Vannochki». The springs (with the exception of Lososevye) belong to subneutral Cl(Cl-HCO3)-Na waters with salinity less than 10 g/l. The Lososevye springs are of the weakly acidic HCO3-SO4-Ca-Na type with salinity of 3 g/l. The spontaneous gas is dominated by CO2 (Dachnye and Vannochki), N2 (Reidovskie and Cape Konakov) and CH4 (Goryachie Klyuchi). Against the background of a general extremely low content of microelements,  thermal waters are enriched with boron and lithium. The springs are characterized by small (0.1 l/s) to insignificant (0.02–0.05 l/s) flow rates, while wells drilled nearby uncover horizons of pressurized waters.

The large Tolbachik fissure eruption occurred in Kamchatka in 1975—1976. It was the largest basaltic eruption of the Kurile-Kamchatka volcanic belt and also one of the six largest fissure eruptions of the world over the historic period. The eruption had been predicted and studied in detail during its one-and-a-half-year activity and after its end. As a consequence of considerable investigations it became one of the best studied volcanic eruption. This monograph presents the main results of the seven-year investigations over the period 1975—1982: the detailed description of the eruption, its physical properties, the history of volcanism in the region of the eruption, petrology of its products, data on magmatic gases and postvolcanic processes, data of seismological, geodetic and other geophysical explorations, study and explanation of its mechanism.