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.

Geochemically fingerprinted widespread tephra layers serve as excellent marker horizons which can directly link and synchronize disparate sedimentary archives and be used for dating various deposits related to climate shifts, faulting events, tsunami, and human occupation. In addition, tephras represent records of explosive volcanic activity and permit assessment of regional ashfall hazard. In this paper we report a detailed Holocene tephrochronological model developed for the Kamchatsky Peninsula region of eastern Kamchatka (NW Pacific) based on ∼2800 new electron microprobe analyses of single glass shards from tephra samples collected in the area as well as on previously published data. Tephra ages are modeled based on a compilation of 223 14C dates, including published dates for Shiveluch proximal tephra sequence and regional marker tephras; new AMS 14C dates; and modeled calibrated ages from the Krutoberegovo key site. The main source volcanoes for tephra in the region are Shiveluch and Kliuchevskoi located 60–100 km to the west. In addition, local tephra sequences contain two tephras from the Plosky volcanic massif and three regional marker tephras from Ksudach and Avachinsky volcanoes located in the Eastern volcanic front of Kamchatka. This tephrochronological framework contributes to the combined history of environmental change, tectonic events, and volcanic impact in the study area and farther afield. This study is another step in the construction of the Kamchatka-wide Holocene tephrochronological framework under the same methodological umbrella. Our dataset provides a research reference for tephra and cryptotephra studies in the northwest Pacific, the Bering Sea, and North America.

On the basis of the chemical, isotopic and thermodynamic characteristics of fluids sampled between 1964 and 1989 a genetic model description is given for fumaroles of the Mutnovsky volcano. There are three individual groups of fumaroles in the Mutnovsky crater which show stable activity for a long period of time: “the Active Funnel” (temperatures exceed 600°C), the “Upper Field” (up to 320°C) and the “Bottom Field” (from 100 to 150°C). The three principal zones of emission have different gas composition, water isotopic composition, radioactivity and 3He/4He ratios. The abundance of magmatic components in the high-temperature fumaroles of the “Active Funnel” is much higher than those in gases from the other groups. Emission rate of SO2 from the “Active Funnel” is about 200 t/d, which requires complete degassing as a minimum of 1 km3 of magma every 20 years. Fluids of the “Upper Field” contain up to 80% of steam from the Mutnovsky geothermal system. Temperature variations of the “Bottom Field” fumaroles (from 97°C before 1982 to 151°C in 1989) result from changes in hydrological conditions in the crater. Evaporation of high-saline acid brine which is formed in the interior of the volcano is responsible for the composition of the “Bottom Field” gas-steam discharges.

This study revealed that the giant cirque of Bakening Volcano had been produced by its eruption ca. 8000-8500 carbon-14 year ago. The eruption is supposed to have been heralded by a large earthquake (M > 7) resulting in the collapse and slide of the SE sector of the cone. The landslide unroofed the hydrothermal system and triggered an explosion which was followed by an ash-and-block pyroclastic flow. A rockslide avalanche rolled down into the valley of the Srednyaya Avacha River and travelled as far as 10-11 km along it. The avalanche deposited its debris material over an area of 18-20 km2 measuring 0.4-0.5 km3 in volume. These deposits dammed the river, produced two lakes (Bezymyannoe and Verkhneavacha), and gave birth to a large lahar which traveled along the valley much farther.

The remote sub-arctic wilderness of Kamchatka contains a line of active volcanoes above the Pacific Ocean plate subduction zone. This guide is based on the itinerary of the 1999 GA excursion to sites around Petropavlovsk. Descriptions cover the Uzon caldera and its Valley of Geysers, and the volcanoes of Avacha, Karimsky, Gorely and Mutnovsky.

Abstract Prolonged basaltic effusive eruptions at high latitudes can have significant atmospheric and environmental impacts, but can be challenging to observe in winter conditions. Here, we use multi-sensor satellite data to assess sulfur dioxide (SO2) emissions from the 2012–2013 eruption of Plosky Tolbachik volcano (Kamchatka), which lasted ~ 9–10 months and erupted ~ 0.55 km3 DRE. Observations from the Ozone Monitoring Instrument (OMI), the Ozone Mapping and Profiler Suite (OMPS), the Atmospheric Infrared Sounder (AIRS), and the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to evaluate volcanic activity, SO2 emissions and heat flux associated with the effusion of lava flows. Gaps in the primary OMI SO2 time-series dataset occurred due to instrument limitations and adverse meteorological conditions. Four methods were tested to assess how efficiently they could fill these data gaps and improve estimates of total SO2 emissions. When available, using data from other {SO2} observing instruments was the most comprehensive way to address these data gaps. Satellite measurements yield a total SO2 loading of ~ 200 kt SO2 during the 10-month Plosky Tolbachik eruption, although actual SO2 emissions may have been greater. Based on the satellite SO2 measurements, the Fast Fourier Transform (FFT) multi-taper method (MTM) was used to analyze cyclical behavior in the complete data series and a 55-day cycle potentially attributable to the eruptive behavior of Plosky Tolbachik during the 2012 – 2013 eruption was identified.