Abstract A large dike intrusion and fissure eruption lasting 9 months began on November 27, 2013, beneath the south flank of Tolbachik Volcano, Kamchatka, Russia. The eruption was the most recent at Tolbachik since the Great Tolbachik Eruption from 1975 to 1976. The 2012 eruption was preceded by more than 6 months of seismicity that clustered beneath the east flank of the volcano along a NW–SE trend. Seismicity increased dramatically before the eruption, with propagation of the seismicity from the central volcano conduit in the final hours. We use interferometric synthetic aperture radar (InSAR) to compute relative displacement images (interferograms) for {SAR} data pairs spanning the eruption. We use satellite {SAR} data from the Canadian Space Agency's RADARSAT-2 and from the Italian Space Agency's COSMO-SkyMed missions. Data are modeled first through a Markov Chain Monte Carlo solution for a single tensile dislocation (dike). We then use a boundary element method that includes topography to model a distributed dike-opening model. We find the best-fitting dike dips 80° to the {WNW} with maximum opening of 6–8 m, localized in the near surface and more broadly distributed in distinct regions up to 3 km beneath the surface, which varies from 1 to 2 km elevation for the eruptive fissures. The distribution of dike opening and its correspondence with co-diking seismicity suggests that the dike propagated radially from Tolbachik's central conduit.

На примере двух мощных извержений конуса Квицапу вулкана Сьерро-Ассуль (Чили) рассматривается проблема эффузивных извержений магм с высокими предэруптивными содержаниями летучих. Предложен физико-химический механизм дегазации магм с потерей ими летучих до появления на поверхности. Модель основана на взаимодействии магм, находившихся в разных по глубине очагах, и различии между растворимостью воды в расплаве и ее равновесной концентрацией в протяженном по вертикали магматическом теле. При этом малоглубинный очаг может аккумулировать летучие, выделяющиеся из магмы, поступающей в него из глубинного очага. Дается объяснение резких различий в характере извержений 1846–1847 и 1932 г. при идентичном химико-петрографическом составе магм.

This paper presents the results of visual observations, particle-size analysis, seismological observations, and acoustic measurements carried out during a small-magnitude eruption of Bezymyannyi in June 1986. A mlodel is proposed for the mechanism of the eruption. A specific character of the eruption is explained by a deeper localization of a gas-rich aagia portion in the conduit,

The 1991 eruption of Avacha volcano resulted in a lava plug inside its crater, making high-temperature fumaroles available for sampling. At present, there are two high-temperature fumarolic fields: the Eastern (up to 665 ◦ C) and the Western (up to 840 ◦ C), both associated with a fissure in the lava plug caused by a weak 2001 explosion. The paper presents chemical and isotopic compositions (H-O-C-S) of the directly sampled fumaroles over the period 2013 – 2023, mainly from the Eastern field. We revealed seasonal variations of water isotopic composition and concentrations of some components of the gas. High-temperature gases from Avacha volcano are characterized by chemical and isotopic compositions typical for volcanoes in subduction zones, but with a slightly increased content of H2O, a reduced content of HCl. A relatively high concentration of methane is noted in the gases of low-temperature field. Methane in high-temperature gas with δ13C(CH4) = 16.8 ‰ has abiogenic origin. For high-temperature gases, their redox state (H2/H2O and CO/CO2) is controlled mainly by the sulfur gas buffer (H2S/SO2); methane is not chemically equilibrated. The molar ratio C/S ~ 1 is typical for volcanoes in the Kuril-Kamchatka Arc. The measured fumarolic temperatures at the Eastern field are descending over time from 626 ◦ C in 2013 to 410 ◦ C in 2023. The apparent equilibrium temperatures calculated for reactions that include CO, CO2, H2, H2O, H2S and SO2 are generally higher than the measured temperatures and do not show the descending trend. However, calculated equilibrium temperatures for the H2O-CO-CO2-CH4 system are very close to the measured temperatures. Two periods of the increased seismic activity which occurred from 2013 to 2023, in November 2014 – January 2015 and October – December 2019, correlated with changes in the morphology and gas flow rates at the Western fumarolic field.

The Sheveluch volcano is the northernmost active volcano in Kamchatka. In this work, we describe the activity of the new 300 Years of the RAS lava dome of volcano in 2024–2025. Explosive eruptions of the dome were observed on August 17–18, September 1–2, and November 7–10, 2024: eruptive columns rose up to 9, 8, and 11 km above sea level, respectively, and ash plumes were extended for 2400, 1100, and 3000 km to the east and northeast of the volcano. The results of detailed real-time monitoring of the volcanic eruption are presented using a video surveillance system and various satellite data from The Remote Monitoring of Volcanic Activity in Kamchatka and the Kurile Islands information system (VolSatView, http://kamchatka.volcanoes.smislab.ru).