Based on the data of field studies in different years, the macro- and microcomponent composition of the waters of the Zelenoe Lake in the crater of the Troitsky active volcano Maly Semyachik were considered. It is shown that the lake contains ultra-acidic (pH < 1) water of sulfate-chloride composition with mineralization from 8 to 42 g/L, depending on the state of the volcano. The anion composition of the lake is formed by the inflow and subsequent dissolution of acidic volcanic gases in the aquifer located directly under the lake. The cation composition of water is formed by the almost congruent dissolution of the host rocks. After a long period of dormancy, in 2008 a new stage of hydrothermal activation of the volcano began. The activity is ongoing. Against the background of a constantly increasing volume, there is an increase in the concentrations of the main macro components (SO4, Cl, Al, Fe) and in the salinity of water in general.

The paper presents the data on age, mineralogy, geochemistry, and isotope composition of rocks from the
Bolshoi Payalpan Volcano (Sredinny Range, Kamchatka). We compared these data with those on the Nosichan
and Belogolovsky volcanoes, located within the Belogolovsky volcanic center. The basalts of the neck and the
upper lava complex of Bolshoi Payalpan are compositionally similar to the intraplate-type trachybasalts of the
Belogolovsky Volcano, and the basaltic andesites of the lower lava and the cone complex are similar to the
island arc rocks of the Nosichan Volcano. Analysis of the data obtained evidences that spatial and temporal
manifestations of intraplate and island-arc volcanism at the Bolshoi Payalpan Volcano are not accidental, but may
be a consequence of a change in the degree and depth of melting of the same deep source with the involvement
of a mantle diapir. The Belogolovsky volcanic center formed in a setting of the Late Miocene-Early Pliocene
rifting. Its evolution, right up to its extinction, proceeded in the same geodynamic setting with an increase in
depth of the mantle source and a decrease in the degree of its melting. Rock compositions of the Lower-Middle
Pliocene Nosichan Volcano remain of the island-arc type under conditions of rifting, since they are associated
with the mantle reservoir located at a shallower depth, which has experienced a higher degree of melting. There
is good reason for considering large volcanic centers as spontaneously-developing geological entities. As the
endogenous activity dies down, the degree of melting decreases and the depth of melting increases with the
replacement of island-arc volcanism by intraplate volcanism. The volcanic center becomes extinct.

The article provides information about nival-volcanogenic, possibly glacial-volcanogenic, mudflows (lahars) on three streams on the south side of Atlasov Island (Kuril Islands, Russia). The island is an active stratovolcano Alaid, 2339 m asl high. The effusive-explosive eruption of the Alaid volcano began on September 10, 2022 and continues to the present day. Strombolian activity of the apical cone and lava outflow is observed. Lava filled the summit caldera by September 27. The lava flow then crossed the southern part of the caldera crest and began to descend down the erosional depression at the tops of the catchments of three unnamed streams. Photography and satellite images showed the presence of mudflow transformation of stream beds and slopes, and mudflows fan at the mouths of the streams. Analysis of meteorological and volcanological data showed that the formation of lahars was caused by rapid melting of snow/ice under the influence of lava flow and it occurred between September 29 and October 2.

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 article reports new data on the chemical and isotopic composition of volcanic gases and the SO2 flux and the soil CO2 flux from the active Ebeko volcano. Within the time interval of 2003–2021 the volcano erupted in 2009, 2010, 2011, October 2016–November 2021. Volcanic gas composition for 2003–2016, 2021 were obtained by direct sampling from fumaroles. The high-temperature gas (420–529°C) has a composition typical of magmatic gases with C/S atomic ratios <1, HCl content 5–7 mmol/mol; isotopic composition of the volcanic vapor δD ~ –24, δ18O = 2.6–4.9. Geochemical precursors of eruptions have been established: an increase in concentrations of CO2, H2, SO2, HCl; a drop in the C/S ratio up to values of <1, which is characteristic of magmatic gases of the Kuriles; an increase in temperature; heavier values of δD and δ18O in the gas condensates; increasing of the total gas output. А high soil CO2 flux was measured using the accumulation chamber method at two thermal fields (up to 10442 g/m2/day), exceeding the visible discharge (~50 t/day versus ~40 t/day). SO2 flux from the active crater was measured by DOAS instruments in 2020 and 2021: they were 99 ± 28 and 9 ± 2.7 t/day in gas plumes, and 747 ± 220 and 450 ± 130 t/day in ash plumes, respectively. A decrease of SO2 output is associated with the rise of degassed magma before the end of the eruption.

Работа посвящена методике восстановления оптических параметров вулканического H2SO4 по данным радиометра AHI спутника Himawari-8. Методика основана на использовании оптических моделей для различных смесей аэрозольных компонентов вулканического облака, представленных пеплом, кристаллами льда, каплями воды и каплями H2SO4. Использование многокомпонентных оптических моделей различного аэрозольного состава позволило оценить оптическую толщину и массовое содержание H2SO4 в сернокислом облаке, образованном после извержения вулкана Карымский 3 ноября 2021 г. Был проведен комплексный анализ спектральных характеристик сернокислого облака в коротковолновом и инфракрасном диапазоне длин волн, по результатам которого установлено, что сернокислое облако преимущественно представляет собой смесь капель H2SO4 и воды.

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.