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The Tatun Volcano Group (TVG) is located at the northern end of Taiwan, ~ 15 km from the center of Taipei, a metropolitan area of over seven million inhabitants. A volcanic eruption by the TVG of any type or scale could cause catastrophic human and economic impacts. This paper summarizes previous geochemical, geophysical, and geochronological reports and highlights why the widely accepted age model does not comport with the latest observations. This study also reports novel 40Ar/39Ar ages for two andesite samples and one basalt sample from the TVG. A sample collected from Chihsingshan yields a robust 40Ar/39Ar age of 0.081 ± 0.005 Ma. This provides the first direct evidence of TVG volcanic activity after 0.1 Ma. Two samples yield 0.28 ± 0.02 Ma for Tatunshan and 0.159 ± 0.017 Ma for Honglushan. The younger ages refute previously proposed age models for the TVG. Along with new drone photos and LiDAR images, the age data help resolve eruptive history and advance understanding of volcanic hazards and hazard mitigation in Taiwan and surrounding areas. [ABSTRACT FROM AUTHOR]

Abstract The Tatun Volcano Group (TVG) is located at the northern end of Taiwan, ~ 15 km from the center of Taipei, a metropolitan area of over seven million inhabitants. A volcanic eruption by the TVG of any type or scale could cause catastrophic human and economic impacts. This paper summarizes previous geochemical, geophysical, and geochronological reports and highlights why the widely accepted age model does not comport with the latest observations. This study also reports novel 40Ar/39Ar ages for two andesite samples and one basalt sample from the TVG. A sample collected from Chihsingshan yields a robust 40Ar/39Ar age of 0.081 ± 0.005 Ma. This provides the first direct evidence of TVG volcanic activity after 0.1 Ma. Two samples yield 0.28 ± 0.02 Ma for Tatunshan and 0.159 ± 0.017 Ma for Honglushan. The younger ages refute previously proposed age models for the TVG. Along with new drone photos and LiDAR images, the age data help resolve eruptive history and advance understanding of volcanic hazards and hazard mitigation in Taiwan and surrounding areas.

Volcanic eruptions have varied and complex impacts on small-scale livestock farming located in volcanic hazard-prone areas due to diverse stock, rearing, and feeding practices. The study was aimed to clarify the critical factors for designing forage recovery and sustainable livestock production in highrisk-prone areas of active volcanic mountains. A total of seventy-five ruminant livestock farmers located in the eruption-impacted areas of five active volcanoes were surveyed on flock size, rearing, and feeding practices. They were interviewed about their experiences of the eruption's impact on the animals, forage feed, and livestock mitigation regarding survival efforts. Forage plants and soil samples were collected to analyze dry matter and crude nutrient composition and estimate the botanical composition, biomass production, and carrying capacity. Results showed that there were five species of ruminant animals reared in small flock size (< 7 heads/farm): beef cattle, buffalo, horses, goat, and sheep. Beef cattle and goats were the most popular farm animals raised in different breeds, rearing, and feeding systems. The volcanic eruption caused animal loss and health problems due to exposure to volcanic materials, forage damages, and animal mitigation constraints, resulting in flock size decrease and economic loss. The impact of the eruption on farm animals and forage plants varied among the volcanoes due to diverse eruptive characteristics, stock breed, rearing, and feeding practices. Livestock farming recovery post-eruption depended largely on the survival flock and the regrowth of forage plants. In conclusion, sustainable beef cattle farming in volcanic hazard-prone areas might be realized by effective livestock mitigation efforts, selecting appropriate types of animals and rearing/feeding systems based on agroecological conditions, and improving forage capacity and survival rate during and posteruption. [ABSTRACT FROM AUTHOR]

Volcanic eruptions have varied and complex impacts on small-scale livestock farming located in volcanic hazard-prone areas due to diverse stock, rearing, and feeding practices. The study was aimed to clarify the critical factors for designing forage recovery and sustainable livestock production in highrisk-prone areas of active volcanic mountains. A total of seventy-five ruminant livestock farmers located in the eruption-impacted areas of five active volcanoes were surveyed on flock size, rearing, and feeding practices. They were interviewed about their experiences of the eruption's impact on the animals, forage feed, and livestock mitigation regarding survival efforts. Forage plants and soil samples were collected to analyze dry matter and crude nutrient composition and estimate the botanical composition, biomass production, and carrying capacity. Results showed that there were five species of ruminant animals reared in small flock size (< 7 heads/farm): beef cattle, buffalo, horses, goat, and sheep. Beef cattle and goats were the most popular farm animals raised in different breeds, rearing, and feeding systems. The volcanic eruption caused animal loss and health problems due to exposure to volcanic materials, forage damages, and animal mitigation constraints, resulting in flock size decrease and economic loss. The impact of the eruption on farm animals and forage plants varied among the volcanoes due to diverse eruptive characteristics, stock breed, rearing, and feeding practices. Livestock farming recovery post-eruption depended largely on the survival flock and the regrowth of forage plants. In conclusion, sustainable beef cattle farming in volcanic hazard-prone areas might be realized by effective livestock mitigation efforts, selecting appropriate types of animals and rearing/feeding systems based on agroecological conditions, and improving forage capacity and survival rate during and posteruption.

Very Long Period (VLP) signals with periods longer than 2 s may occur during eruptive or quiet phases at volcanoes of all types (shield and stratovolcanoes with calderas, as well as other stratovolcanoes) and are inherently connected to fluid movement within the plumbing system. This is supported by observations at several volcanoes that indicate a correlation between gas emissions and VLPs, as well as deformation episodes due to melt accumulation and migration that are followed by the occurrence of VLPs. Moment tensors of VLPs are usually characterized by large volumetric components of either positive or negative sign along with possibly the presence of single forces that may result from the exchange of linear momentum between the seismic source and the Earth. VLPs may occur during a variety of volcanological processes such as caldera collapse, phreatic eruptions, vulcanian eruptions, strombolian activity, and rockfalls at lava lakes. Physical mechanisms that can generate VLPs include the inflation and deflation of magma chambers and cracks, the movement of gas slugs through conduits, and the restoration of gravitational equilibrium in the plumbing system after explosive degassing or rockfalls in lava lakes. Our understanding of VLPs is expected to greatly improve in the future by the use of new instrumentation, such as Distributed Acoustic Sensing, that will provide a much denser temporal and spatial sampling of the seismic wavefield. This vast quantity of data will then require time efficient and objective processing that can be achieved through the use of machine learning algorithms. [ABSTRACT FROM AUTHOR]

The study area is Diyadin, which is situated 71 km ESE of Ağrı very close to the Turkish-Iranian State border. It is one of several type localities of promising geothermal fields in the Eastern Anatolia. The neotectonic regime and related structures are dominated by a strike-slip tectonic regime governed by a stress field in the Eastern Anatolia where the greatest principal stress (σ1) is operating in NNW direction (N22°W) while the least principal stress (σ3) is N68°E. This stress field state was proved once more by the tensor solution of the 12 June 2022 Akçift (Muradiye-Van) earthquake of Mw = 5.1. The strike-slip neotectonic regime started at the time of latest Pliocene-early Quaternary and then triggered the first occurrence of the fissure eruption along the NNW trending Kaletepe open fracture. This event was followed by the development of both the two-peaked Tendürek strato-shild volcano and the Diyadin geothermal field (DGF). The geothermal potential of the DGF is high and its most common manifestations are the active tectonic regime and related faults (extensional horse tail strucure), active volcanoes (Tendürek and Ağrı volcanoes), fumeroles, numerous hot water springs to artesian wells, widespread iron-rich alteration zones, actively growing fissure-ridge travertines and the probable presence of the unroofed hypabyssal felsic to intermediate intrusions of Quaternary age at the roots and their near environs of the isolated Quaternary volcanoes in the Eastern Anatolia. In addition, some significant similarities and contrasts are seen between the DGF and the IGF when they are compared.

The presented work is based on the study of material collected by F.A. Romanyuk in the surroundings of Sarychev Peak active volcano on Matua Island, middle Kurils in 2017. Two families – Physciaceae and Caliciaceae – were sorted out from the collection and studied at first. As a result, seven species of the families were found: two species of the genus Rinodina, two species of the genus Physcia, two species of the genus Buellia and the species Tetramelas chloroleucus. All found species of the studied families were first identified for Matua Island. Matua Island is the northernmost location point in Eurasia for the species Rinodina ascociscana. Buellia badia is a new registered species for the Sakhalin Region.

Abstract The correct absolute time of a seismogram is an important prerequisite for many seismological processing methods. Recently, seismic interferometry has been applied to continuously estimate instrumental clock errors in certain regions. However, previous studies have focused on estimating clock errors in only one target region for each study, and data processing methods that provide more stable results in different regions have not been explored. This study presents a new method to estimate clock errors that are more stable in various regions based on seismic interferometry with windowed cross-correlation and least absolute deviation regression. The applicability of this method was validated by its application to 50 active volcanoes in Japan. We found clock errors at 23 stations at 13 volcanoes between January 2017 and December 2021. The maximum amplitude of the clock errors ranged between 0.24 and 18.27 s. This value range is significantly larger than the amplitude of the background fluctuation in the estimated values of clock errors, which is less than 0.05 s for most volcanoes. A comparison of different approaches for the estimation of clock error shows that our proposed method that uses windowed cross-correlation and least absolute deviation regression can reduce the effect of waveform changes in seismic ambient noise cross-correlation functions, probably because of noise source fluctuations. Managing the time stamps of data using the method proposed in this study will contribute to data quality assurance and ensure the reliability of analysis using time information in various study regions. Graphical Abstract

Abstract Nishiyama volcano on Hachijojima Island is an active basaltic volcano located in the Izu–Bonin arc. In this study, petrological and geochemical analyses were conducted on mafic lavas and pyroclastics to understand the magma plumbing system and pre-eruption magmatic processes. Whole-rock major element compositions show significant variations (49.4–54.9 wt.% SiO2), and the samples contain variable amounts of plagioclase phenocrysts (1–40 vol.%). The whole-rock Sr, Nd, and Pb isotopic compositions of samples from the youngest volcanic stage (

Diyadin is situated 71 km ESE of Ağrı nearby the Turkish-Iranian State border in the east Anatolian tectonic block. It is only one of several type localities of promising geothermal fields in eastern Anatolia. The neotectonic regime and related fault zones in the eastern Anatolia are dominated by a strike-slip tectonic regime governed by a stress field state, in which the greatest principal compressive stress (s1) is operating in NNW direction (N22°W) while the least principal stress axis (s3) or extension direction is N68°E. This stress field state was proved once more by the tensor solution of the 12 June 2022 Akçift (Muradiye-Van) earthquake of Mw = 5.1. The strike-slip neotectonic regime started at the time of latest Pliocene-early Quaternary and then triggered the first occurrence of the fissure eruption along the NW trending Kaletepe open fracture. This event was followed by the development of both the two-peaked Tendürek strato-shild volcano and the Diyadin geothermal field (DGF). The most common manifestations of the DGF are the active tectonic regime and related faults, active volcanoes, fumeroles, numerous hot water springs to artesian wells, widespread ironrich alteration zones, actively growing fissure-ridge travertines and the probable presence of the shallow-seated and unroofed hypabyssal felsic to intermediate intrusions of Quaternary age. [ABSTRACT FROM AUTHOR]

The correct absolute time of a seismogram is an important prerequisite for many seismological processing methods. Recently, seismic interferometry has been applied to continuously estimate instrumental clock errors in certain regions. However, previous studies have focused on estimating clock errors in only one target region for each study, and data processing methods that provide more stable results in different regions have not been explored. This study presents a new method to estimate clock errors that are more stable in various regions based on seismic interferometry with windowed cross-correlation and least absolute deviation regression. The applicability of this method was validated by its application to 50 active volcanoes in Japan. We found clock errors at 23 stations at 13 volcanoes between January 2017 and December 2021. The maximum amplitude of the clock errors ranged between 0.24 and 18.27 s. This value range is significantly larger than the amplitude of the background fluctuation in the estimated values of clock errors, which is less than 0.05 s for most volcanoes. A comparison of different approaches for the estimation of clock error shows that our proposed method that uses windowed cross-correlation and least absolute deviation regression can reduce the effect of waveform changes in seismic ambient noise cross-correlation functions, probably because of noise source fluctuations. Managing the time stamps of data using the method proposed in this study will contribute to data quality assurance and ensure the reliability of analysis using time information in various study regions. [ABSTRACT FROM AUTHOR]

Nishiyama volcano on Hachijojima Island is an active basaltic volcano located in the Izu–Bonin arc. In this study, petrological and geochemical analyses were conducted on mafic lavas and pyroclastics to understand the magma plumbing system and pre-eruption magmatic processes. Whole-rock major element compositions show significant variations (49.4–54.9 wt.% SiO2), and the samples contain variable amounts of plagioclase phenocrysts (1–40 vol.%). The whole-rock Sr, Nd, and Pb isotopic compositions of samples from the youngest volcanic stage (< 0.7 ka) are homogeneous, whereas some samples from the older stage (3–1 ka) have relatively low Pb isotopic ratios. This observation suggests that the younger magmas were derived from a single parental magma, but another parental magma with distinct geochemical features was involved in the magmatic system before 1 ka. The temporal variation in the FeO*/MgO ratios of the volcanic products is complex and is considered to reflect the intermittent injection of primitive magmas into the main magma chamber in which fractional crystallization occurred. Two-pyroxene geobarometry suggests that the main magma chamber was located at a depth of 9–12 km. The core region of some plagioclase phenocrysts consists of a glass inclusion-free inner core and an inclusion-rich outer mantle, suggesting that some plagioclase crystallized in the main magma chamber, which was followed by overgrowth during magma ascent because of increasing liquidus temperatures due to decompression-induced water exsolution from the melt. The whole-rock compositions of some eruption units with different Al2O3/MgO ratios exhibit distinct plagioclase-controlled trends, which negates the possibility that plagioclase accumulation occurred in a stable magma chamber. In addition, the density of plagioclase was higher than that of the melt during the magma ascent to the surface. From these observations, it is suggested that the accumulation of plagioclase phenocrysts occurred in ascending magmas as the plagioclase settled relative to the surrounding melt. The estimated depth of 9–12 km for the main magma chamber coincides with the depth range over which earthquake swarms occurred in 2002, suggesting that the magma chamber is still active, and that the earthquake swarms may reflect the injection of primitive magma into the magma chamber. [ABSTRACT FROM AUTHOR]

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The Sciara del Fuoco (SdF) collapse scar at Stromboli is an active volcanic area affected by rapid morphological changes due to explosive/effusive eruptions and mass-wasting processes. The aim of this paper is to demonstrate the importance of an integrated analysis of multi-temporal remote sensing (photogrammetry, COSMO-SkyMed Synthetic Aperture Radar amplitude image) and marine geophysical data (multibeam and side scan sonar data) to characterize the main morphological, textural, and volumetric changes that occurred along the SdF slope in the 2020–2021 period. The analysis showed the marked erosive potential of the 19 May 2021 pyroclastic density current generated by a crater rim collapse, which mobilized a minimum volume of 44,000 m3 in the upper Sciara del Fuoco slope and eroded 350,000–400,000 m3 of material just considering the shallow-water setting. The analysis allowed us also to constrain the main factors controlling the emplacement of different lava flows and overflows during the monitored period. Despite the morphological continuity between the subaerial and submarine slope, textural variations in the SdF primarily depend on different processes and characteristics of the subaerial slope, the coastal area, the nearshore, and "deeper" marine areas. [ABSTRACT FROM AUTHOR]

Copyright of Revista de la Asociación Geológica Argentina is the property of Asociacion Geologica Argentina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper explored the relationship between acidic sulfate alteration, geostructural frameworks, and geomorphological changes that can be observed in active volcanic hydrothermal systems. The target area was Pisciarelli in the Campi Flegrei volcano, where diffuse acidic sulfate alteration and hydrothermal dynamics have been growing since 2012, causing a progressive deterioration of landscapes. Terrestrial Laser Scanner (TLS), photogrammetry of proximity survey, geological field work, mineralogical and geochemical analysis with Optical Microscopy (OM), electron microscopy, and energy dispersive micro-analysis (BSEM-EDS) and X-ray Powder Diffraction (XRPD) to characterize (and monitor) altered rock outcrops were repeatedly carried out in the area. We present the multi-temporal acquisition and analysis referring to Terrestrial Laser Scanning (TLS) datasets (2014 survey) with 3D-point clouds obtained from the Structure for Motion (SfM) photogrammetry (2021 survey) with a high-resolution digital camera aimed at evaluating volumetric changes on the mostly damaged and altered fault scarp. For each survey, we obtained a vertical Digital Elevation Model (DEM) and a true color RGB orthomosaic that provided the setting of the area at the different times and its evolution through their comparison. Changing sites were examined in the field and characterized for mineralogical and geochemical purposes. The investigated slope lost up to about 4 m3 of deposits between 2014 and 2021, mostly related to hydrothermal alteration induced by gas emissions and meteoric infiltration. Our methodological approach appears promising to evaluate evolution and rock-fall susceptibility of solfataric terrains subjected to hydrothermal dynamics. [ABSTRACT FROM AUTHOR]

The identification of anomalies in seismic wave interferometry data is important in the prediction of imminent volcanic eruptions. Herein, we propose using the local outlier probability (LoOP) method to evaluate the degree of anomaly in seismic wave velocities and scattering properties, estimated via seismic wave interferometry. LoOP is the likelihood that an observation is anomalous and is always in the range of 0–1 (0–100%). We quantitatively evaluated the degree of anomaly in seismic wave velocities and scattering properties before and after the eruption of Mt. Aso, Japan, in October 2016 and Mt. Shinmoedake, which lies within the Mt. Kirishima cluster of volcanoes, Japan, in 2017 and 2018. We found that LoOP exceeded 70% 2 to 3 days before Mt. Aso erupted on October 8, 2016, and it exceeded 70% 1 to 5 days before Mt. Shinmoedake erupted on October 11, 2017 and March 6, 2018. Adjusting the reference and quiet periods for the estimation of changes in seismic velocity/scattering property and LoOP calculations can allow the tracking of repeated, significant LoOP increases during times of high volcanic activity. The quantitative evaluation of temporal anomalies in seismic datasets will improve the precision of predictions of imminent volcanic eruptions. [ABSTRACT FROM AUTHOR]

Microorganisms in extreme volcanic environments play an important role in the development of plants on newly exposed substrates. In this work, we studied the structure and diversity of a bacterial community associated to Andropogon glomeratus and Cheilanthes aemula at El Chichón volcano. The genetic diversity of the strains was revealed by genomic fingerprints and by 16S rDNA gene sequencing. Furthermore, a metagenomic analysis of the rhizosphere samples was carried out for pioneer plants growing inside and outside the volcano. Multifunctional biochemical tests and plant inoculation assays were evaluated to determine their potential as plant growth-promoting bacteria (PGPB). Through metagenomic analysis, a total of 33 bacterial phyla were identified from A. glomeratus and C. aemula rhizosphere samples collected inside the volcano, and outside the volcano 23 bacterial phyla were identified. For both rhizosphere samples, proteobacteria was the most abundant phylum. With a cultivable approach, 174 bacterial strains were isolated from the rhizosphere and tissue of plants growing outside the volcanic complex. Isolates were classified within the genera Acinetobacter, Arthrobacter, Bacillus, Burkholderia, Cupriavidus, Enterobacter, Klebsiella, Lysinibacillus, Pantoea, Pseudomonas, Serratia, Stenotrophomonas and Pandoraea. The evaluated strains were able to produce indole compounds, solubilize phosphate, synthesize siderophores, showed ACC deaminase and nitrogenase activity, and they had a positive effect on the growth and development of Capsicum chinense. The wide diversity of bacteria associated to pioneer plants at El Chichón volcano with PGPB qualities represent an alternative for the recovery of eroded environments, and they can be used efficiently as biofertilizers for agricultural crops growing under adverse conditions. [ABSTRACT FROM AUTHOR]

Polygenetic volcanoes and calderas produce eruptions of a wide variety of magnitudes, chemistries, and recurrence times. Understanding the interplay between long- and short-term and deep and shallow processes associated with accumulation and transfer of eruptible magma is essential for assessing the potential for future eruptions to occur and estimating their magnitude, which remains one of the foremost challenges in the Earth sciences. We review literature and use existing data for emblematic volcanic systems to identify the essential data sets required to define the state of activity of volcanoes and their plumbing systems. We explore global eruptive records in combination with heat flux and other geological and geophysical data to determine the evolutionary stage of plumbing systems. We define a Volcanic Activity Index applicable to any volcano that provides an estimate of the potential of a system to erupt in the future, which is especially important for long-quiescent volcanoes. Magmatic plumbing systems that feed volcanic activity extend across Earth's crust and are long-lived at depth and ephemeral in their shallowest portions. We revise and update the definitions of active, quiescent, and extinct volcanoes based on physical proxies for the architecture, longevity, amount, and distribution of eruptible magma in the crust. We propose a Volcanic Activity Index, which provides a relative measure of the state of activity of a volcano with respect to all other volcanoes in the world. New imaging and monitoring strategies are required to improve our ability to detect lower and middle crust magmatic processes and forecast eruptions and their potential size. [ABSTRACT FROM AUTHOR]

Abstract Kusatsu–Shirane Volcano is an active Quaternary andesitic-to-dacitic volcano located in the Central Japan Arc. We conducted a detailed petrological investigation of orthopyroxene (opx)–magnetite (mt) symplectites associated with olivine in the Sessho lava, an andesitic lava flow from Kusatsu–Shirane. We concluded that the symplectites are pseudomorphs after olivine and were formed through the breakdown of olivine in a mafic magma as a result of oxidation during mixing with a felsic magma. Various olivines and opx–mt symplectites that show different stages of the progressive breakdown reaction of olivine coexist in a single lava flow. We suggest that basaltic recharge into the magma reservoir beneath Kusatsu–Shirane occurred repeatedly, leading to a hybrid andesite magma with different types of olivine and symplectite being erupted at Kusatsu–Shirane Volcano.

The Sciara del Fuoco (SdF) collapse scar at Stromboli is an active volcanic area affected by rapid morphological changes due to explosive/effusive eruptions and mass-wasting processes. The aim of this paper is to demonstrate the importance of an integrated analysis of multi-temporal remote sensing (photogrammetry, COSMO-SkyMed Synthetic Aperture Radar amplitude image) and marine geophysical data (multibeam and side scan sonar data) to characterize the main morphological, textural, and volumetric changes that occurred along the SdF slope in the 2020–2021 period. The analysis showed the marked erosive potential of the 19 May 2021 pyroclastic density current generated by a crater rim collapse, which mobilized a minimum volume of 44,000 m3 in the upper Sciara del Fuoco slope and eroded 350,000–400,000 m3 of material just considering the shallow-water setting. The analysis allowed us also to constrain the main factors controlling the emplacement of different lava flows and overflows during the monitored period. Despite the morphological continuity between the subaerial and submarine slope, textural variations in the SdF primarily depend on different processes and characteristics of the subaerial slope, the coastal area, the nearshore, and “deeper” marine areas.

Abstract Definite increases in the components ratios of CO2/H2O, CO2/H2S, CO2/CH4 and He/CH4 were observed at the fumarolic gases from Owakudani geothermal area located at the center of Hakone volcanic caldera (Honshu Island, Japan), synchronized with the earthquake swarm in 2015. Such variations were due to the dominance of a magmatic component over a hydrothermal component, suggesting the earthquake swarm was produced by the injection of magmatic gases into the hydrothermal system. The CO2/H2O ratio of magmatic gas was estimated to be 0.0045 before the earthquake swarm, which increased up to 0.013 during the earthquake swarm, likely produced by the pressurization of magma as a result of magma sealing where the pressure increment in magma was estimated to be 3% to the lithostatic pressure. The H2O and CO2 concentration in magma were estimated to be 6.3 wt% and 20 wt ppm, respectively, assuming a temperature 900 °C and a rhyolitic composition. In May 2015, a few months prior to the earthquake swarm in May 2015, a sharp increase in the Ar/CO2 and N2/He ratios and a decrease in the isotopic ratio of H2O were observed at the fumarolic gas. The invasion of air into the hydrothermal system increased the Ar/CO2 and N2/He ratios. The decrease in the isotopic ratio of H2O was induced by partial condensation of H2O vapor.

Microorganisms in extreme volcanic environments play an important role in the development of plants on newly exposed substrates. In this work, we studied the structure and diversity of a bacterial community associated to Andropogon glomeratus and Cheilanthes aemula at El Chichón volcano. The genetic diversity of the strains was revealed by genomic fingerprints and by 16S rDNA gene sequencing. Furthermore, a metagenomic analysis of the rhizosphere samples was carried out for pioneer plants growing inside and outside the volcano. Multifunctional biochemical tests and plant inoculation assays were evaluated to determine their potential as plant growth-promoting bacteria (PGPB). Through metagenomic analysis, a total of 33 bacterial phyla were identified from A. glomeratus and C. aemula rhizosphere samples collected inside the volcano, and outside the volcano 23 bacterial phyla were identified. For both rhizosphere samples, proteobacteria was the most abundant phylum. With a cultivable approach, 174 bacterial strains were isolated from the rhizosphere and tissue of plants growing outside the volcanic complex. Isolates were classified within the genera Acinetobacter, Arthrobacter, Bacillus, Burkholderia, Cupriavidus, Enterobacter, Klebsiella, Lysinibacillus, Pantoea, Pseudomonas, Serratia, Stenotrophomonas and Pandoraea. The evaluated strains were able to produce indole compounds, solubilize phosphate, synthesize siderophores, showed ACC deaminase and nitrogenase activity, and they had a positive effect on the growth and development of Capsicum chinense. The wide diversity of bacteria associated to pioneer plants at El Chichón volcano with PGPB qualities represent an alternative for the recovery of eroded environments, and they can be used efficiently as biofertilizers for agricultural crops growing under adverse conditions.

This paper explored the relationship between acidic sulfate alteration, geostructural frameworks, and geomorphological changes that can be observed in active volcanic hydrothermal systems. The target area was Pisciarelli in the Campi Flegrei volcano, where diffuse acidic sulfate alteration and hydrothermal dynamics have been growing since 2012, causing a progressive deterioration of landscapes. Terrestrial Laser Scanner (TLS), photogrammetry of proximity survey, geological field work, mineralogical and geochemical analysis with Optical Microscopy (OM), electron microscopy, and energy dispersive micro-analysis (BSEM-EDS) and X-ray Powder Diffraction (XRPD) to characterize (and monitor) altered rock outcrops were repeatedly carried out in the area. We present the multi-temporal acquisition and analysis referring to Terrestrial Laser Scanning (TLS) datasets (2014 survey) with 3D-point clouds obtained from the Structure for Motion (SfM) photogrammetry (2021 survey) with a high-resolution digital camera aimed at evaluating volumetric changes on the mostly damaged and altered fault scarp. For each survey, we obtained a vertical Digital Elevation Model (DEM) and a true color RGB orthomosaic that provided the setting of the area at the different times and its evolution through their comparison. Changing sites were examined in the field and characterized for mineralogical and geochemical purposes. The investigated slope lost up to about 4 m3 of deposits between 2014 and 2021, mostly related to hydrothermal alteration induced by gas emissions and meteoric infiltration. Our methodological approach appears promising to evaluate evolution and rock-fall susceptibility of solfataric terrains subjected to hydrothermal dynamics.

The crater lake of El Chichón active volcano represents one of the most important extreme ecosystems in the world due to its high temperatures, low pH and the appearance of high concentrations of heavy metals because of volcanic activity. The latter is of great importance in nearby volcano sites due to heavy metal pollution, which is one of the worst types of environmental problems in the world. In this study, the concentration of heavy metals was evaluated in soils and sediments from different sections in the crater lake of El Chichón volcano. Representative samples were collected from four sediments and soils in 2015 and 2017. These samples were analyzed for 20 metals by inductively coupled plasma-optical emission spectrometry (ICP-OES). The most abundant elements in sediments of the crater lake of "El Chichón" volcano were Fe, Na, Si, Ca, K and Al and not found in soil samples. Be and Tl were more abundant in the soil, but the concentration of Se was higher in soil without showing statistically significant differences. Principal component analysis (PCA) showed that the abundance of metals was influenced by sample type. That is, a higher concentration of heavy metals and trace elements was found in volcanic sediments as compared to soil samples. This difference may be related to metals originating from the magma, which is partially transported in the water stream that gives way to the volcano lake. The most toxic heavy metals identified and quantified in high concentrations in crater soils and sediments were As and Cd. This study suggests that sediments and soils of El Chichón crater lake could be an important source of heavy metals and toxic elements such as As and Cd. [ABSTRACT FROM AUTHOR]

Kusatsu–Shirane Volcano is an active Quaternary andesitic-to-dacitic volcano located in the Central Japan Arc. We conducted a detailed petrological investigation of orthopyroxene (opx)–magnetite (mt) symplectites associated with olivine in the Sessho lava, an andesitic lava flow from Kusatsu–Shirane. We concluded that the symplectites are pseudomorphs after olivine and were formed through the breakdown of olivine in a mafic magma as a result of oxidation during mixing with a felsic magma. Various olivines and opx–mt symplectites that show different stages of the progressive breakdown reaction of olivine coexist in a single lava flow. We suggest that basaltic recharge into the magma reservoir beneath Kusatsu–Shirane occurred repeatedly, leading to a hybrid andesite magma with different types of olivine and symplectite being erupted at Kusatsu–Shirane Volcano. [ABSTRACT FROM AUTHOR]

Abstract We investigate the three-dimensional P- and S-wave attenuation ( $$Q_{\text{P}}^{ - 1}$$ Q P - 1 and $$Q_{\text{S}}^{ - 1} )$$ Q S - 1 ) structures of the crust around the source region of the 2016 Kumamoto earthquakes, Japan. To estimate the attenuation structures, the path-averaged attenuation factor $$t^{*}$$ t ∗ is estimated from the amplitude decay rate of the P- and S-wave spectra corrected for the source spectrum. The $$Q_{\text{P}}^{ - 1}$$ Q P - 1 and $$Q_{\text{S}}^{ - 1}$$ Q S - 1 structures are estimated by tomography using $$t^{*}$$ t ∗ for the P- and S-waves, respectively. Several features are found in the attenuation structures as follows: In the source region, two high- $$Q_{\text{P}}$$ Q P and high- $$Q_{\text{S}}$$ Q S zones exist along the Futagawa and the Hinagu fault segments in the upper crust. The high- $$Q_{\text{P}}$$ Q P and high- $$Q_{\text{S}}$$ Q S zone along the Futagawa fault segment is found to include the large-slip area of the mainshock obtained from a source inversion study. In the lower crust, the low $$Q_{\text{P}}$$ Q P is distributed beneath the entire source region. A low- $$Q_{\text{P}}$$ Q P and low- $$Q_{\text{S}}$$ Q S zone also exists beneath the Kuju and Aso volcanoes, which is consistent with the shallow limited depth extent of the seismogenic zone due to high temperature. The western edge of this zone adjoins the eastern edge of the high- $$Q_{\text{P}}$$ Q P and high- $$Q_{\text{S}}$$ Q S area, including the large-slip area. Graphical Abstract .

An expedition to the Kavachi submarine volcano (Solomon Islands) in January 2015 was serendipitously timed with a rare lull in volcanic activity that permitted access to the inside of Kavachi’s active crater and its flanks. The isolated location of Kavachi and its explosive behavior normally restrict scientific access to the volcano’s summit, limiting previous observational efforts to surface imagery and peripheral water-column data. This article presents medium-resolution bathymetry of the main peak along with benthic imagery, biological observations of multiple trophic levels living inside the active crater, petrological and geochemical analysis of samples from the crater rim, measurements of water temperature and gas flux over the summit, and descriptions of the hydrothermal plume structure. A second peak was identified to the southwest of the main summit and displayed evidence of diffuse-flow venting. Microbial samples collected from the summit indicate chemosynthetic populations dominated by sulfur-reducing ε-proteobacteria. Populations of gelatinous animals, small fish, and sharks were observed inside the active crater, raising new questions about the ecology of active submarine volcanoes and the extreme environments in which large marine animals can exist.

We investigate seismic velocity changes in response to the tidal strain at Izu‐Oshima volcano, Japan, by analyzing the data of permanent seismic stations and a small seismic array to evaluate the characteristics of strain sensitivity of velocity changes. We estimate the seismic velocity changes by phase differences between cross‐correlations functions of ambient noises at the frequency of 2–4 Hz stacked for time periods with different tidal strain amplitudes. The seismic velocity changes decrease and increase during dilatation and contraction periods, respectively, when analyzing the cross‐correlations functions at early lapse times ranging from 2 to 7 s. The strain sensitivity of seismic velocity changes is estimated to be −2.1±0.2×104 at the early lapse times. However, we find that strain sensitivity of the seismic velocity changes decreases when analyzing the cross‐correlation functions at later lapse times from 7 s to 35 s. Applying an array analysis to the cross‐correlation functions, we observe apparent velocities of about 1 km/s at the early lapse times and those of higher than 1 km/s at the late lapse times. Since the group velocity of Rayleigh waves is 1.1 km/s at Izu‐Oshima volcano, the apparent velocities at the late lapse times may indicate the scattered or reflected body waves incident from a deeper region. Decrease of strain sensitivity with the lapse times therefore results from the emergence of body waves on the late lapse times. These results highlight the need to pay attention to wave types of cross‐correlation functions and their paths to interpret seismic velocity changes. Key Points: Seismic velocity decreases and increases during dilatation and contraction periods, respectively, at lapse times from 2 to 7 sArray analysis enables us to understand wave properties of cross‐correlations functions accuratelyStrain sensitivity of seismic velocity changes decreases with lapse times because scattered body waves contaminate the cross‐correlation functions [ABSTRACT FROM AUTHOR]

The Izu-Oshima volcano is one of the most active volcanoes in Japan, and has generated relatively large-scale eruptions every 30–40 years for the past 200 years. As more than 30 years have passed since the last eruptions in 1986–87, volcanic activity is expected to resume in the near future. To help elucidate the current and future state of the volcano’s magma system, the temporal evolution of the recent magma plumbing system was investigated through a petrological and geochemical analysis of its basaltic lavas and pyroclastics (