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This paper considers the propagation of ash during the paroxysmal eruption of Sheveluch Volcano which occurred April 10–13, 2023, and its impact on the water resources of the affected area. We characterize ash thicknesses at various population centers and describe the grain-size composition of the ash. We show that the propagation of ash plumes is primarily driven by the eruption dynamics, but atmospheric circulation actually controls the spatial distribution of deposit thickness. The water-soluble salts contained in the ash and the dynamics of their washing out under natural conditions have been determined. The water-soluble part of fresh ash is dominated by calcium and magnesium sulfates, sodium chloride, with minor amounts of chlorides and fluorides of aluminum, potassium, and ammonium. The first substances to be washed out from ashes are well-soluble chlorides, to be followed by sulfates. As time goes on, the total concentration of soluble salts is decreasing, and their qualitative composition changes: hydrogen carbonates of calcium, magnesium, and sodium begin to dominate. Several months after the eruption, the impact of the ashfall on water resources of the settlements, including open springs at the ground surface, was leveled out. [ABSTRACT FROM AUTHOR]

The results of instrumental observations carried out at observatories of the INTERMAGNET network and at the Wakkanai ionospheric sounding station were used to show that the vigorous effusion–explosion eruption of Shiveluch Volcano occurring on April 10, 2023 was accompanied by variations in the Earth's magnetic field, as well as by changes in the critical frequency of the ionospheric F 2 layer. [ABSTRACT FROM AUTHOR]

In recent decades Bezymianny Volcano, Kamchatka, one of the most threatening volcanic objects of Russia, has produced an average of 1–2 short-lived, but strong, explosive–effusive eruptions per year. The most reliable source of data for identifying a precursory situation before such an eruption seems to be seismicity, with continuous data being supplied by the Kamchatka seismicity monitoring system. The formalized method developed by the present author for predicting Bezymianny eruptions based on a statistical estimation of seismicity level (SESL'09) has performed satisfactorily in real time as well, with the precursory processes before all the eight eruptions of Bezymianny in 2015–2020 being detected. Revision of all characteristics the method involves (efficiency, reliability, and validity) showed that they remained stable when new data were added. The prediction method was supplemented with a new parameter, lead time, which provides a formal procedure to estimate the expectation time for a prediction to come true. [ABSTRACT FROM AUTHOR]

This paper discusses the data of instrumental observations conducted at the Mikhnevo Observatory, at INTERMAGNET observatories, and at the Geophysical Monitoring Center of the Institute of Geosphere Dynamics (IGD), Russian Academy of Sciences (RAS) during the explosive eruption of Hunga Tonga-Hunga Ha'apai Volcano of January 15, 2022. It is shown that the explosion of the volcano produced a series of wave disturbances in the atmosphere, as well as electrical and magnetic variations at large epicentral distances. The atmospheric disturbances were recorded as Lamb waves emitted by a source at the center of the explosion, as well as by a virtual source situated at the antipode. The latter source was formed by convergence and summing of signals propagating on the terrestrial sphere. In addition to primary waves, the recorded phenomena also include secondary and tertiary waves due to multiple passage of the explosion-produced signal around the terrestrial sphere. We evaluated the source energy based on the characteristic frequency in the spectrum of the signal, resulting in the value ~1018 J, which corresponds to ~200 MT of TNT, when converted to an explosive source. It is shown that a volcanic explosion is accompanied by electrical and magnetic variations both at the time of the explosion and at the time when the recording site receives atmospheric wave disturbances. [ABSTRACT FROM AUTHOR]

This paper reviews the results of fundamental importance achieved by the Institute of Volcanology and Seismology (IV&S), Far East Branch (FEB), Russian Academy of Sciences (RAS) for the period 1962‒2021. We consider the most important achievements classified under the following headings: Volcanological research includes petrologic and geochemical features of ejecta by volcanoes in the Kuril–Kamchatka region; the age of volcanoes and the phases of volcanogenic catastrophism in Kamchatka; hydrothermal systems and geothermal reserves of Kamchatka; hydrothermal metasomatism and volcanogenic mineral generation and mineralization; Geophysical research includes the seismology of volcanoes; deformation at active volcanoes; tectonic earthquakes and tsunamis; the internal structure of volcanic systems. [ABSTRACT FROM AUTHOR]

The early post-eruptive activity is described on the Third Cone, one of the New Tolbachik volcanoes, formed during the eruption at the Northern Breakthrough during the Great Tolbachik Fissure Eruption, which occurred in Kamchatka in 1975–1976. Changes in temperature, exhalation mineral generation, and rock alteration in the fumarole areas of the northern and southern craters of the Third Cone are characterized. [ABSTRACT FROM AUTHOR]

A short-lived but violent explosive eruption occurred on the small volcanic island Raikoke in June 2019 (central Kuril Islands). The culmination of the eruption lasted 3.5 h and the ash cloud rose to a height of 13 km. An analysis of a sequence of satellite images in combination with ground-based observations gave information on the pyroclastic deposits of the eruption and allowed us to estimate the associated impact on the island ecosystems. We found that this eruption had a phreatomagmatic, sub-Plinian to Plinian character. The phreatomagmatic mechanism of the eruption occurred due to interaction between the rising basaltic andesite magma and ground waters, which were mostly represented by sea water that percolated through the permeable rocks of the volcanic island. The eruption produced numerous pyroclastic flows. The hot deposits of the pyroclastic flows and tephra covered the entire island, destroying the vegetation and the habitat of birds and sea mammals. Much of the pyroclasts was deposited in the form of fans of pyroclastic flows at the base of the volcanic slopes, considerably displacing the shoreline seaward. As a result, the island area increased by 15%. The pyroclastic deposits were intensely eroded and redeposited during the first year after the eruption, making new areas of the island coast. The recovery of Raikoke's ecosystems will be enhanced by erosion of the pyroclastic deposits and gradual resettling of birds, which would bring new plant species to the island. The succession would be accelerated by areas of survived vegetation. Overall, we see periodic dramatic disruptions in the island ecosystems caused by violent explosive eruptions with subsequent rapid recovery that with high probability will be interrupted by new eruption. [ABSTRACT FROM AUTHOR]

Alaid Volcano on Atlasov Island is the northernmost and highest volcano of the Kuril island arc. The first time lavas were discharged by the terminal eruption of 2015–2016 was in October 2018. The samples were studied by petromagnetic, petrogeochemical, and microprobe techniques. The chemical composition of the 2015–2016 ejecta is very similar to that of the 1933–1934, 1972, and 1981 eruptions, attesting to a common deep source of magmas. That source can be inferred to lie at a depth greater than 50 km, judging from their potassium–sodium products and from estimates of the P–T conditions that prevailed during the precipitation of rock-forming mineral phases from the melt. It was for the first time that data were obtained concerning the structure and composition of the magnetic fraction in the Alaid igneous rocks, and the depth was determined for the last equilibrium state of magma during the 2015–2016 eruption. A joint analysis of the petromagnetic and petrogeochemical characteristics of the Alaid trachybasalts studied here revealed significant correlative relationships between (a) concentrations of Ti and Cu and petromagnetic concentration characteristics, (b) alkali elements (Li, Rb, Cs) and rare-earth elements and coercive petromagnetic parameters. [ABSTRACT FROM AUTHOR]

The early 21st century saw increased eruption activity of major volcanoes in the Northern Group of Kamchatka, namely, Sheveluch, Klyuchevskoy, Bezymianny, and the Tolbachik Fissure Zone. The growth of an extrusive dome on Sheveluch andesitic volcano has occurred, with the dome reaching a height of 600 m after 38 years of nearly uninterrupted eruption activity. An 8-year period of relative quiet was followed by ten summit eruptions and two lateral vent openings on the Klyuchevskoy basaltic volcano. Explosive–effusive eruptions were observed nearly every year on the Bezymianny andesitic volcano. A 36-year quiet period gave way to a new eruption in the Tolbachik regional fissure zone. [ABSTRACT FROM AUTHOR]

This paper gives measured quantities, inclined distances, and elevations between geodetic monuments on the northeastern slope of Klyuchevskoi Volcano for the period from 1978 through 2014. Parasitic and summit eruptions were generally preceded by uplifts of the slope, while the termination of an eruption was accompanied by subsidence. The data from the longest series of observations of vertical displacements on the Kirgurich radial line during the period from 1979 to 2014 were used to determine an uplift of the slope that was increasing nearer to the crater. The maximum displacements occurred 2 years before the start of the 1983 parasitic eruption on the Predskazannyi vent and before the 2003–2004 and 2007 summit eruptions. A ground uplift of 12.5 microradians measured on a 17.8-km baseline was recorded in 2007. Farther from the crater, at a distance of 27 km from it, the vertical displacements were insignificant. We show that the measurement stations at heights of 2000 m to 3000 m were subject to deep creep, i.e., a sliding movement. The rates of movement at these stations reached 5–20 cm/yr. Significant horizontal displacements of geodetic monuments occurred near the parasitic eruptions of March 6, 1980 and March 8, 1983. All lines of measurements were observed to shrink by 5 to 20 mm in 1989‒1993 to 2014, indicating a compression for the northeastern slope of Klyuchevskoi Volcano. [ABSTRACT FROM AUTHOR]