Ichinsky volcano is the largest volcanic structure of the Sredinny Range of Kamchatka. The manifestation of fumarole activity on the northern slope of the volcano is known since 1956. 64 years after the discovery of the Ledovaya fumarole, it was inspected with a quadrocopter. It was found that the fumarole is located at an altitude of 2725 m and is a large funnel up to 60 m in size, covered with snow in the middle part. In the upper part of the funnel there is a hole in the ice mass 9.8 m in diameter, with vapor-gas clouds rising up to 5–10 m above its edge.. The walls of the ice well are covered with a grayish-yellow fouling of sublimations. The authors believe that the probable temperature of the vapor-gas mixture of fumaroles at the outlet of the volcano rocks is significantly higher than 100° C.

This report gives a brief description of field work on the Kuril Islands in summer 2021 carried out by staff of the Institute of Volcanology and Seismology of  FEB RAS within the framework of the Institute research theme and projects of the Russian Science Foundation (RSF) and Russian Fund for Basic Research (RFBR). To study chemical erosion of volcanic islands and to estimate hydrothermal export of magmatic volatiles, hydrological and hydrochemical works were carried out on the rivers draining the slopes and thermal fields of the Baransky volcano and the Bogdan Khmelnitsky volcanic massif (Iturup Island). Detailed hydrochemical studies with water sampling at different depths and a bathymetric survey of Lake Kipyashchey located in the caldera of Golovnin volcano (Kunashir Island) were performed. We also proceeded with studying the CO2 diffusion flux through thermal fields and volcanic lakes. In the course of ongoing regime observations on Ebeko volcano (Paramushir Island), aerial and infrared imaging of its near-crater part was carried out. For the first time since the eruption began in 2016, a quadcopter survey of the lake located in the Srednii (middle) crater of the volcano was conducted. For further analytical studies a large number of water and gas samples were taken, and the collection of sediments was replenished.

The chemical and isotopic composition of hot springs at the apical part of the active Ebeko volcano (Paramushir Island, Kuril Islands) is characterized based on the data obtained from fieldwork in 2020–2021. Thermal waters discharging from one of the sources of the Kuzminka River are ultra-acid (рН<2) Al-Ca-SO4-Cl type with mineralization up to 5 g/l and temperature up to 70°С. The anionic composition of waters is formed due to the dissolution in groundwater of acidic volcanic gases, partially «purified» in the main reservoir of the volcano's hydrothermal system. The cationic composition of waters, including rare-earth elements, is formed by isochemical dissolution of host rocks in the equivalent of 5 g per 1 liter of water. Differences in the isotopic composition and ratios of macrocomponents (SO4 /Cl, Al+Fe/Ca+Mg/Na+K) of waters of the near the summit  prings and the northwestern slope suggest the presence of different-level aquifers in the hydrothermal system confined to the edifice of the Ebeko volcano.

The paper presents the results of remote sensing interpretation of active faults of the Sredinny Range of Kamchatka. The use of remote sensing data allowed us to identify fault scarps and magma-conducting fractures, expressed in the topography by chains of eruption centers. Most of the detected faults are located on volcanic plateaus, what indicates the relation of faulting with thinning of the brittle crust under the volcanic belt, similar to the faults of the Eastern Volcanic Belt. The geometrical characteristics of the most preserved scarps provide an estimate of the magnitude of paleoearthquakes Mw = 5.8±0.2, which significantly exceeds the historical seismicity. The identified faults are located above the northern edge of the subducted portion of the Pacific plate and form a zone oblique to the axis of the Kuril-Kamchatka island-arc system. The strike and normal sense of the faults are consistent with the transverse extension in Kamchatka. These new data provide the northern and western boundaries of the above-subduction extensional setting in Kamchatka.

After a short period of quiescence, in February 2019, Karymsky volcano (Kamchatka Peninsula, Russia) became active. During the month, a large number of moderate explosions were recorded, some of which were preceded with some periodicity by long-period earthquakes with a high degree of similarity of waveforms. The duration of the multiplet events that preceded the explosions ranged from 4 to 70 minutes. The period between earthquakes decreased as the multiplets developed. The amplitude of earthquake records either increased or remained at the same level. The multiplets with higher amplitude of earthquake records preceded the strongest eruptions. The decreasing period between earthquakes is most likely related to the acceleration of magma ascent and an increase in gas pressure in the volcanic channel. If this is true, the absence of long-period earthquakes after the eruption marks a complete release of gas pressure in the volcanic edifice.

The paper reports the appearance of a new crater lake on the Ebeko volcano. There has been no thermal lake within the Northern Crater since mid-2006. The last eruption began on October 19, 2016 and ended on November 19, 2021. The pyroclastic cone of the new crater, which was named Korbut Crater, rose within the Northern Crater. There was strong fumarolic activity in the Korbut crater, which persists today. The lake in the still erupting Korbut crater was first recorded by the authors on a satellite image from September 17, 2021; already on a satellite image from September 25, the crater was dry again. After the end of the Ebeko eruption, due to the intensive flow of fluid with bottom fumaroles and due to a large amount of meteoric precipitation, a lake was formed in the Korbut crater (Sentinel 2 satellite data of December 11, 2021). In January 2022, the authors examined the Korbut crater: the diameters of the lake were 61 and 80 m (latitude and meridian, respectively), the mirror area was 4.5 thousand m2, and water temperature was 43°C. A brief literature review of the existence of thermal lakes on the northern flank of the Ebeko volcano is given.

This report presents a brief description of the expeditionary work performed by the staff of the Institute of Volcanology and Seismology, Far Eastern Branch of the Russian Academy of Sciences as part of the research topic and the Russian Science Foundation project on the Kuril Islands in the summer of 2022. In order to study the chemical erosion of volcanic islands and to assess the hydrothermal removal of magmatic volatiles, in addition to the works carried out in 2020 and 2021, hydrological and hydrochemical studies were comducted on the rivers draining the slopes of the volcanic ridges of the Paramushir, Onekotan and Shiashkotan islands. For the first time, with the help of a quadrocopter, sampling of the endorheic Lake Koltsevoe, which occupies the caldera of the Tao-Rusyr volcano (Onekotan Island), was carried out. A detailed hydrochemical testing on the thermal fields of the active volcanoes Sinarka and Kuntomintar (Shiashkotan Island) was performed, a number of regime observations of the Upper Yuryevsk springs (Paramushir Island) were replenished. In order to construct orthophotomaps and determine the boundaries of thermal anomalies, aerial and infrared surveys were carried out at the main study sites in parallel with geochemical sampling. A large number of water and gas samples were taken for further analytical studies during the expedition and the collection of sediments was replenished.

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.