Abstract—This paper is concerned with ground deformation and seismicity prior to the Tolbachik Fissure Eruption, which began in Kamchatka on November 27, 2012. Seismic and GPS data were analyzed to reveal synchronous precursory anomalies in crustal deformation and seismicity that lasted approximately 4 months (August to November 2012). The seismic anomaly was a statistically significant increase of seismicity with low energy (mostly KS = 4–6) beneath the Ploskii Tolbachik Volcano edifice at depths of less than 5 km. The rates of seismicity and seismic energy release were exceeded by factors of approximately 40 compared with the
2000–2011 mean values during the 2 to 3 weeks immediately before the eruption. The strain anomalies were observed as movements in the middle of the Klyuchevskoy volcanic group: a radial (relative to the eruption) compression and an extension in the tangential direction. The strain had reached ~ 10^–7 by the beginning of the eruption. The durations of the seismic and strain anomalies were comparable in value (~ 4 months before the eruption), thus providing evidence of a common origin. We can classify them as belonging to the same time scale of precursors (the intermediate�term in the accepted terminology).

Sheveluch volcano is the most active volcano in Kamchatka. The paroxysmal explosive eruption of the volcano that destroyed the lava dome in the volcanic crater continued on April 10–13, 2023. According to various satellite data, the height of the separate eruptive clouds probably exceeded 15 km a. s. l. A powerful cyclone, which dominated the entire Kamchatka Peninsula, pulled the eruptive cloud to the west, turned it to the south, stretched it to the north and directed it to the east from the volcano. The dynamics of the development of ash and aerosol clouds of this eruption is reflected in the animations made from a series of Himawari-9 satellite images in the VolSatView IS from 08:00 UTC (Coordinated Universal Time) on April 10 to 07:50 UTC on April 14 (http://d33.infospace.ru/jr_d33/materials/2023v20n2/283-291/1683110898.webm) and of the Arctica-M1 satellite from 16:00 to 21:30 UTC April 10 (http://d33.infospace.ru/jr_d33/materials/2023v20n2/283-291/1683821166.webm). It was noted that the eruptive column was not vertical: for example, at the initial moment of the eruption on April 10 at 13:20 UTC, it deviated to the north-northeast, on April 11 at 12:00 UTC to the northwest, and on April 12 at 07:00 UTC to the southwest. During the paroxysmal eruption, sulfur dioxide continuously entered the atmosphere, the maximum amount of which was released on April 10–11, as a result of the explosive destruction of the lava dome of the Sheveluch volcano. Ash clouds along with aerosol clouds on April 10–13 were stretched into a strip more than 3500 km long from west to northeast. On April 21–22, the Sheveluch aerosol cloud was observed in the region of the Scandinavian Peninsula. The total area of the territory of Kamchatka and the Pacific Ocean where ash and aerosol plumes and clouds were observed during the April 10–13 eruption was about 3280 thousand km2. The paroxysmal eruption of Sheveluch volcano belongs to the sub-Plinian type because it is characterized by a big height of eruptive cloud and a long event duration. For this eruption, the VEI (Volcanic Explosivity Index) is estimated to be 3–4. A detailed description of the paroxysmal explosive eruption of Sheveluch volcano and the spread of the eruptive cloud was performed based on data from various satellite systems (Himawari-9, NOAA-18/19, GOES-18, Terra, Aqua, JPSS-1, Suomi NPP, Arctica-M1 etc.) in the information system “Remote monitoring of the activity of the volcanoes of the Kamchatka and the Kuriles” (VolSatView, http://kamchatka.volcanoes.smislab.ru).

Bezymianny is one of the most active volcanoes in Kamchatka and the world. Its previous eruption occurred on March 15, 2019. This paper describes the explosive eruption of the volcano on October 21, 2020, and the events preceding it based on the study of video and various satellite data. Satellite monitoring of the volcano has been carried out using the information system “Remote monitoring of the activity of Kamchatka and Kurile volcanoes” (VolSatView) since 2014. Explosions raised ash up to 10–11 km above sea level, in connection with a cyclone in the Kamchatka region, the eruptive cloud was divided into two, the northern part of which was over the Klyuchevskoy group of volcanoes during October 21–23, and the southern part moved more than 1000 km southeast of the volcano. The main area of the territory where ashfalls were noted at 10:11 GMT on October 22, 2020, was about 111.5 thousand km2, including 60.8 thousand km2 on land. An animated image of the ash cloud movement from the volcano is shown, made according to a series of images of Himawari-8 in the VolSatView (http://kamchatka.volcanoes.smislab.ru/animation/1603972936.webm). The VEI for this eruption is 2.

Daily monitoring of Kamchatka volcanoes has been carried out since 1993, Kuril - since 2003. Since 2009, using modern information technologies and methods, informa tion systems equipped with modern tools for data analysis have been developed, with the help of which there are carried out in the IVS FEB RAS comprehensive studies of volcanogenic processes in the Kuril - Kamchatka region, including the most dangerous explosive eruptions for humans, as well as products of volcanic eruptions. The created systems allow volcanologists to work with various satellite data together with weather and video information for continuous monitoring and research of volcanic activity; simulate the spread of ash clouds and plumes to assess their danger to aviation; combine and systematize various information about volcanoes and their eruptions.

This book is the first work that provides the ultimate data about chemical composition of the Kamchatka Quaternary andesites. Besides the book provides data about a phase analysis of andesites, geochemical composition, REE composition and isotopic analysis of strontium, neodymium and oxygen. The analyses are prominent for their stratification and accurate geological positioning. This allows understanding how the geological events alternated. The paper is focused on the petrogenetic peculiarities of tholeiitic (the 1st type of mantle genesis) and calc-alkali (the 2nd type of mantle-crust genesis) andesites. The book stresses that petrochemical, petrological and isotopic-geochemical correlators play a great role in distinguishing of those two types of andesites. On the basis of petrochemical database we distinguished three trends of the volcanites differentiation: stable, unstable and intermediate. These trends are supposed to be used for the determination of the volcanic activity character and types of the volcanic eruptions.
This book will be helpful as a reference guide to volcanologists, petrographers, geochemists and geologists, to those who study the genesis of volcanic rocks.