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The physiochemical properties of volcanic ash are determined by magma ascent and eruption dynamics and provide important insights into controls on the timing and style of volcanic eruptions. However, linking petrological observations to monitoring parameters remains challenging. Here we investigate the relationships between geophysical, geochemical and satellite remote sensing data with the physiochemical properties of volcanic ash to better understand eruptive dynamics at El Reventador volcano, Ecuador. Between 2016 and 2019, eruptive activity at El Reventador was characterised by frequent explosions interspersed with effusive activity from two summit vents. We found that: (1) periods of predominantly effusive behaviour were defined by ash samples with the lowest proportions of juvenile grains, frequent, more intense thermal anomalies and frequent (ca. every 25 min) but low-energy explosions that produced lower average ash column heights (< 1200 m above the summit) and; (2) periods of predominantly explosive behaviour were defined by ash samples with the highest proportions of juvenile grains and also vesicular juvenile grains, low thermal anomalies and less frequent (ca. every 70 min), higher-energy explosions that produced higher average eruption column heights (> 1500 m above the summit). Our study shows that there are strong correlations between the physiochemical properties of erupted material and the multiparametric monitoring data which in turn link to the type of surface activity observed. As a result, the development of physical conduit models and interpretations of eruptive dynamics are made more robust combining both monitoring data and the physical properties of eruptive products. [ABSTRACT FROM AUTHOR]

Using recycled waste for soil improvement is a sustainable strategy that can reduce resource consumption. In this paper, recycled polyester fiber (RPF) is proposed to improve the engineering performance of red mud- improved volcanic ash (RV). A series of mechanical test were performed for RVs with five different content of RPF. And the microstructure was also investigated using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and mercury intrusion porosimetry (MIP) tests. Results show that RPF significantly reinforces the mechanical strength and toughness of RV and the optimum content of RPF is 0.9%. The Unconfined compressive strength (UCS), cohesion (c) and internal friction angle (φ) of reinforced soil enhanced by up to 122%, 40% and 8% compared to untreated soil at the optimum incorporation and optimum water content, respectively. The failure model of RPF-reinforced RV is converted from brittle to ductile, and the toughness parameters are significantly improved. Microscopic investigations reveal that RPF forms a complex three-dimensional structure within the reinforced soil. Adhesion and friction interactions at the fiber-matrix interface are the main reasons for the enhancement of strength and toughness. However, the performance of composites does not continue increasing with RPF content. Excessive fibers gather and twist to form weak zones, reducing the strength and stiffness of material. In practice, the optimal fiber content needs to be controlled to ensure the best mechanical properties. This eco-friendly soil improvement can promote the harmless utilization of red mud and waste polyester materials contributing to ground improvement techniques in volcanic areas. [ABSTRACT FROM AUTHOR]

Volcanic eruptions can release large amounts of tephra, lava, and gases, drawing attention due to their magnitude, energy, and impact on life and the environment. Among the most documented and sometimes dramatic effects of volcanic ashes are those linked to the input of diverse elements in the environment, which are released as a consequence of ash weathering. Laboratory studies have been conducted to investigate and predict the environmental input of chemical elements from volcanic ashes. This research paper describes the optimization of batch leaching tests used to investigate the release of ions from ashes collected in the Andes Cordillera after the eruption of the Puyehue volcano in 2011. Chemometric multivariate strategies were employed to evaluate the influence of variables affecting the leaching of volcanic ash. The effects of the main variables, namely contact time, the acidity of the leaching agent, the solid/liquid ratio, the particle size, and the stirring speed, were studied in leaching tests. To determine the optimal conditions for selected metal determinations, we employ Darringer's desirability function, which allows for the simultaneous optimization of the selected responses (element concentrations during the leaching process). Multielemental analysis (Na, Mg, Al, Si, P, Cl, K, Ca, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Cd, Hg, Tl, and Pb) was quantified by ICP-MS (inductively coupled plasma-mass spectrometry) following adequate dilution of test leaching. These results established the optimal experimental conditions for leaching volcanic ash. The most significant variables were the solid/liquid ratio and the stirring speed, resulting in two groups of elements with an adequate global desirability function (D) value. [ABSTRACT FROM AUTHOR]

A systematic study on the dissolution in concentrated alkali of two volcanic ashes from Cameroon, denoted as DAR and VN, is presented here. One volcanic ash, DAR, was 2 wt% richer in Fe and Ca and 4 wt% lower in Si than the other, designated as VN. Such natural raw materials are complex mixtures of aluminosilicate minerals (kaersutite, plagioclase, magnetite, diopside, thenardite, forsterite, hematite, and goethite) with a good proportion of amorphous phase (52 and 74 wt% for DAR and VN, respectively), which is more reactive than the crystalline phase in alkaline environments. Dissolution in NaOH + sodium silicate solution is the first step in the geopolymerisation process, which, after hardening at room temperature, results in solid and resistant building blocks. According to XRD, the VN finer ash powders showed a higher reactivity of Al-bearing soluble amorphous phases, releasing Al cations in NaOH, as indicated by IPC-MS. In general, dissolution in a strong alkaline environment did not seem to be affected by the NaOH concentration, provided that it was kept higher than 8 M, or by the powder size, remaining below 75 µm, while it was affected by time. However, in the time range studied, 1–120 min, the maximum element release was reached at about 100 min, when an equilibrium was reached. The hardened alkali activated materials show a good reticulation, as indicated by the low weight loss in water (10 wt%) when a hardening temperature of 25 °C was assumed. The same advantage was found for of the room-temperature consolidated specimens' mechanical performance in terms of resistance to compression (4–6 MPa). The study of the alkaline dissolution of volcanic ash is, therefore, an interesting way of predicting and optimising the reactivity of the phases of which it is composed, especially the amorphous ones. [ABSTRACT FROM AUTHOR]

Northwest North America has unique high elevation Picea–Abies forests and parkland classified in British Columbia as the Engelmann Spruce–Subalpine–fir (ESSF) Biogeoclimatic zone. These ecosystems occur on a topographically and climatically complex landscape, juxtaposed with diverse vegetation types including alpine tundra, inland rain forest, dry conifer forest, and grasslands. Spatio-temporal ecosystem disturbance is varied, driven by factors such as climate variation, wildfire, volcanic eruptions, and insect herbivory. A pollen and charcoal record derived from a lake sediment core from the ESSF reveals a unique late-glacial to modern vegetation history progressing from alpine steppe through dry open conifer forest to moist spruce–fir ecosystems, the latter arising only 4600 years ago, late by comparison to other ESSF sites in the region. Repeated disturbance in the mid Holocene by wildfire coupled with volcanic ash deposition and increased climatic variation resulted in recurring Pinus contorta-dominated seral forest stands before cooling and moistening in the late Holocene led to stable Picea–Abies forest. With rapid climate change, changing disturbance regimes, and timber harvest, the management of dry ESSF forests needs to consider that this forest-type could transform into parkland or open seral pine stands, with a high frequency disturbance regime. [ABSTRACT FROM AUTHOR]

This paper presents a method for retrieving optical parameters from volcanic sulfate aerosols from the AHI radiometer on board the Himawari-8 satellite. The proposed method is based on optical models for various mixtures of aerosol components from volcanic clouds, including ash particles, ice crystals, water drops, and sulfate aerosol droplets. The application of multi-component optical models of various aerosol compositions allows for the optical thickness and mass loading of sulfate aerosol to be estimated in the sulfuric cloud formed after the Karymsky volcano eruption on 3 November 2021. A comprehensive analysis of the brightness temperatures of the sulfuric cloud in the infrared bands was performed, which revealed that the cloud was composed of a mixture of sulfate aerosol and water droplets. Using models of various aerosol compositions allows for the satellite-based estimation of optical parameters not only for sulfate aerosol but also for the whole aerosol mixture. [ABSTRACT FROM AUTHOR]

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Terra Sirenum, a region of Noachian highlands southwest of the Tharsis volcanic complex, is unique in the number, proximity, and diversity of orbital detections of secondary minerals, as the sole region found to date hosting large‐scale deposits of all of Mars' major salts (chlorides, sulfates, carbonates) as well as diverse hydrated silicates. We combine mineralogical information, high‐resolution imagery, and elevation models to investigate the geologic context of these secondary minerals to understand the sources of water and ions for each type of deposit and their spatial/temporal relationships. Carbonates, where present, are part of Noachian basement rocks exposed through cratering and do not appear associated with evaporative sequences. Numerous small detections of the acid sulfate minerals alunite and jarosite mirror the dominant clay cation in the localities they are found—Al phyllosilicates and Fe phyllosilicates, respectively—suggesting in situ formation. We interpret a previously discovered kaolinite‐rich unit overlying Fe/Mg clays across northeast Terra Sirenum as remnants of a widespread ash unit rather than a pedogenic weathering sequence. Sulfate and chloride detections are decoupled, with sulfates in topographic lows likely precipitated from volcanism‐associated groundwaters, while chloride detections are consistent with surface water runoff, in some instances clearly post‐dating volcanic units capping sulfate detections. Volcanic resurfacing of craters in the region is progressively younger from west to east, and crater statistics‐based ages indicate localized sulfate‐ and chloride‐forming processes continue to occur from ∼3.5 to ∼1.4 Ga. We hypothesize that their decoupling points to disconnected, episodic surface and groundwater reservoirs, perhaps separated by a permafrost layer. Plain Language Summary: A major question is how Mars evolved from a water‐rich planet to a dry planet. We study a region southwest of Mars' largest volcanoes with multiple types of water‐related minerals. We use their detections to infer the properties of the water that deposited them and imagery to understand if/how the minerals are related to each other. Chlorides (e.g., table salt) are found in ponds and channels over a wide elevation range. Sulfates are present only in deep basins with signs of volcanic activity. On Earth, sulfates and chlorides are often together, forming during evaporation of a body of water; however, on Mars, the occurrences seem to be separated, which suggests different water sources and that groundwater with sulfur added from volcanic gases was involved in sulfate formation. The deposits both get progressively younger, as young as ∼2 billion years ago, toward the large volcanic region. Furthermore, aluminum clays on top of iron/magnesium clays in this area have been previously interpreted as weathering sequences, which implies a large volume of water. Instead, we find most aluminum clays are part of a volcanic ash layer deposited on top of older iron/magnesium clays, which needs a smaller amount of water to create the observed layering. Key Points: Thick, layered deposits with Al clays in upper strata thin with distance from Arsia Mons, suggesting volcanic ash parent lithologiesChlorides are decoupled from sulfates in deep basins; sulfates likely precipitated from upwelling groundwater with magmatic volatilesAssociated volcanic units have ages pointing to episodic volcanic springs and surface melt waters into the early Amazonian [ABSTRACT FROM AUTHOR]

Late Permian to middle Triassic volcanic activities were very strong, however, volcanic records in the early Triassic strata are less reported than those of the Permo-Triassic boundary and the Triassic Olenekian-Anisian boundary in the Yangtze plate, especially within the Sichuan basin. We conduct zircon U-Pb dating and geochemical analysis of the tephra which was first found in the early Triassic Jialingjiang Formation from the Maliuping section, Hechuan, Chongqing. The volcanic ash in the paper yields the new 248.5 ± 0.7 Ma U-Pb age consistent with those of volcanic ashes in these contemporaneous strata in the Yangtze plate. Geochemical characters of whole-rock samples show lower contents in SiO2, K2O and higher components in Al2O3, CaO, MgO, relatively enriched LREE and depleted HREE with distinct negative Eu anomaly, and conspicuous Ba, Nb, Ta, Sr, P, Ti depletion and Th, U, K, Nd enrichment, which is similar to those of the Mung Bean rock of the Triassic Olenekian-Anisian boundary, and those of acidic volcanics from the Sanjiang orogenic belt and Shiwandashan-Qiangfang suture zone during the Early-Middle Triassic. Trace elements of whole rock and analysed zircons of the tuff imply its primary magma derived from Rhyodacite/Dacite and its tectonic setting of volcanic arc granite with continental crust affinity. The early Triassic volcanism during the syn-collision stage of the Paleo-Tethys evolution was less active than those of the Permo-Triassic boundary and the Triassic Olenekian-Anisian boundary, while the volcanic event may have a crucial effect on prolonging fully biotic recovery and entirely ecosystem turnover soon after the Permian-Triassic mass extinction. [ABSTRACT FROM AUTHOR]

Lahars are hazardous mixtures of rock and water that flow rapidly in the form of debris flows or mudflows. The continuous eruptions at Sakurajima supply volcanic ash to form on the surface, reducing the permeability of the ground. As the surface permeability decreases, surface runoff occurs and eventually lahar starts. Therefore, Sakurajima Island suffers from lahars triggered by heavy rains every year. Sheet erosion by surface runoff decreases the thickness of volcanic ash on the ground and subsequently increases hydraulic conductivity. This cycle continues due to the eruptions of the Sakurajima volcano and the lahars formed by heavy rains. Depending on the lahar type and amount of surface runoff, the flow density and block sizes carried in the lahar vary. In this study, the relationship between the volcanic ash thickness and the hydraulic conductivity of the ground was investigated in the Arimura River basin of Sakurajima volcano between 2015 and 2020. Monthly volcanic ash thickness was measured 2 km from the craters. The dynamic change of volcanic ash thickness due to accumulation and erosion was investigated by the Universal Soil Loss Equation and the newly developed Discharge Dependent Erosion methods. Block sizes of the lahars were estimated by vibrographs and CCTV camera. The hydraulic conductivity of the ground was calculated with a Kinematic Wave Model developed specifically for this study. Based on the relationship between volcanic ash thickness and hydraulic conductivity, a risk assessment chart was created considering the block sizes carried by the lahars. [ABSTRACT FROM AUTHOR]

One of the challenges in construction on poor clay soils is their low compressive strength and high settlement. Therefore, geotechnical engineers are always trying to improve the characteristics of this type of soil using different soil stabilization methods. Estimation of the efficiency of different soil stabilization methods requires numerous experimental tests, which can be time-consuming and costly. This article examines the performance of various machine learning methods, including linear regression (LR), multilayer perceptron neural network (MLP), K-nearest neighbor, support vector machine regressor (SVR), decision tree, random forest, and gradient boosting machine in estimating the unconfined compressive strength of stabilized clay soil using two types of pozzolans under different curing conditions. The input variables for the machine learning algorithms include time and curing conditions, the molarity of the alkaline activator, the binder replacement, the type of pozzolan, and ratio of the activator to the optimal moisture content. To optimize and speed up the performance of the algorithms, hyperparameter tuning was performed using a grid search method. In addition, to reduce the variability of the results with respect to data division into training and testing sets, a 10-fold cross- validation method was used. The performance of the algorithms was evaluated using three criteria, namely mean square error, coefficient of determination, and mean absolute percentage error. Given the very close results of the SVR method to the MLP method, these algorithms can be confidently recommended for the estimation of UCS of the studied soil. Moreover, based on the performance evaluation criteria, the linear regression method has the worst results among the models used on the experimental data. Also, the sensitivity analysis of the models shows that, in order of preference, the input variables of binder replacement, molarity and curing time have the highest effect on the predicted compressive strength. The results of parametric analysis represent that by increasing the curing time, for both types of binders, namely cement and volcanic ash, uniaxial compressive strength increases. In addition, by increasing the percentage of binders under the optimum water condition, the uniaxial strength of soil increases, while in dry condition with increasing the binder replacement, for volcanic ash stabilized soil, the UCS decreases and for cement stabilized soil it fluctuates. It is observed that the compressive strength has a direct relationship with the amount of molarity. The results indicate also that by increasing the alkali activator/optimum water content up to 1.2, for the curing time of 28 days, the compressive strength increases and then it will be constant. [ABSTRACT FROM AUTHOR]

The phreatomagmatic eruption of Taal Volcano in Batangas, Philippines, in January 2020 resulted in a massive ash plume covering a large portion of nearby provinces, including Metro Manila. This event caused damage and disruptions to various sectors, including agriculture, the environment, health, infrastructure, and aviation. The challenge of managing the vast amount of collected tephra environmental waste prompted the initiative of converting it into a useful material. This study characterizes and evaluates the quality of the collected tephra as a potential raw material for the construction industry, based on the Philippine National Standard (PNS) 07:2018, to ensure structural integrity and public safety. Four ashfall samples from strategic locations, identified by the Philippine Institute of Volcanology and Seismology (PHIVOLCS), were obtained and analysed for specific chemical parameters using various analytical techniques. The results suggest that tephra has potential as a raw material for ground-level structures. However, further treatment is necessary to reduce the concentration of certain constituents. The material met the standard specifications for SiO2, MgO, and SO3. However, the levels of Al2O3, Fe2O3, total alkali, loss on ignition, and water-soluble and acid-soluble Cl– exceeded the threshold limits set by PNS 07:2018 and EN 197-1:2000. [ABSTRACT FROM AUTHOR]

Background: Sudden volcanic eruptions can lead to volcanic ash entering the eyes, causing severe discomfort and complicating evacuation efforts. The specific effects of volcanic ash on ocular tissues, especially when wearing soft contact lenses (SCLs), are not well documented, prompting this experimental investigation. Methods: White rabbits with normal eyes were randomly divided into three groups: (1) a bare eye group: bare eye + volcanic ash exposure + eye washing, (2) an SCL group: SCL-wearing eye + volcanic ash exposure + eye washing, and (3) a control group: eye washing only. In groups 1 and 2, volcanic ash was applied to one eye under topical anesthesia, followed by immediate saline rinsing. Slit-lamp microscopy and histopathological analysis were conducted after euthanasia. Results: Slit-lamp and histopathological examinations revealed more significant corneal and conjunctival erosion in the bare eye group compared to the SCL group, which showed limited damage. The control group displayed no ocular damage. Conclusions: Guidelines from the "Volcanic Ash Health Effects: A Guide for the Public" by the National Research Institute for Earth Science and Disaster Resilience recommend removing SCLs during ashfall. Our findings suggest that the damage to the corneal and conjunctival epithelium is less severe in SCL-wearing eyes than in bare eyes, recommending that SCL wearers prioritize evacuation over lens removal during sudden ashfall. [ABSTRACT FROM AUTHOR]

Volcanic eruption is known as multi-hazards to the surrounding environment and society causing the formation of lahar as the frequent hazards that shortly occurred due to airborne tephra after an eruption. Erosion triggered by rainfall on unconsolidated tephra material, such as volcanic ash, is the primary lahar initiation mechanism. The time and scale of lahars vary based on eruptions and watershed conditions. The variability of the erosion process is driven by a set of local factors including the grain size and spatial distribution of volcanic ash thickness, slope, and rainfall intensity. Laboratory simulation experiments were conducted in a 3.00 m long, 0.75 m wide, and 0.50 m deep flume to study the relationship of volcanic ash erosion rate to three driven parameters, namely slope, rainfall intensity, and volcanic ash thickness. Three slope gradients were selected to represent gentle (14.1%), mild (26.8%), and steep (46.6%) slopes. Meanwhile, the rainfall intensity ranged from 0.65 to 1.85 mm.min-1, and the variations of volcanic ash layer thickness were 1.00 cm; 2.50 cm; and 5.00 cm. The erosion rate model was generated from a dimensional analysis accommodating slope, rainfall intensity, flow discharge, and the ratio of critical and applied boundary shear stress as independent variables. The variable coefficients were obtained by parameter optimization of experiment data through nonlinear regression analysis. The erosion rate model performance was tested using the Nash-Sutcliffe model Efficiency (NSE), Index of Agreement (IOA), and Root Mean Square Error (RMSE). The performance of the volcanic ash erosion rate model was proven to be satisfactory with the NSE>0.75, IOA>0.95, and RMSE values ranging from 0.005 to 0.009. This model has proven applicable better for volcanic ash erosion than other erosion models which are sandy soil material-based experiments because of the specific characteristics of volcanic material itself. The volcanic ash erosion model in this study can be implemented to predict the sediment yield of tephra as part of volcanic disaster mitigation. [ABSTRACT FROM AUTHOR]

The East Asia black cotton soil (BCS) cannot be used as embankment filling directly due to its high clay content, liquid limit, plasticity index, and low CBR strength (CBR < 3%). This study evaluates the effects of treating East Asia BCS with lime, volcanic ash, or a combination of both on its engineering properties. Experiments were conducted to analyze the basic physical properties, swelling characteristics, and mechanical properties of the treated soil. Results indicate that lime addition significantly reduces the free swelling rate, improves limit moisture content, increases optimum moisture content, decreases maximum dry density, and enhances CBR value. Although volcanic ash also improves BCS performance, its effects are less pronounced than those of lime. The combined treatment with lime and volcanic ash exhibits superior performance, greatly reducing expansion potential and significantly increasing soil strength. Specifically, a mixture of 3% lime and 15% volcanic ash optimizes the liquid limit, plasticity index, and CBR value to 49.2%, 23.8, and 24.7%, respectively, meeting the JTG D30-2015 requirements and reducing construction costs. The treatment mechanisms involve hydration exothermic reactions, volcanic ash reactions, and semipermeable membrane effects, which collectively enhance the soil's properties by producing dense, high-strength compounds. [ABSTRACT FROM AUTHOR]

In the present work, the electrical and dielectric properties of ceramic samples prepared from volcanic ash were investigated. For this purpose, ceramic samples were prepared using milled volcanic ash with a binder material at a sintering temperature of 950 °C for 2 h. The chemical content of the milled volcanic ash was investigated using XRF. Differential thermal analysis and thermogravimetry were performed to determine the firing conditions. The crystalline phases and microstructures of the ceramic samples were investigated using XRD and SEM, respectively. Finally, the electrical and dielectric properties of the obtained samples were evaluated at a frequency ranging from 1 × 102 to 4 × 106 Hz and temperatures ranging from room temperature to 800 °C. The XRD results revealed that the ceramic samples contained three main phases: albite, hematite, and augite. Moreover, the microstructures of the samples exhibited a large crystal size with a dense surface. The conductivities and dielectric constants of the samples remained stable up to 500 °C. The real and imaginary parts of the dielectric constant decreased with an increase in frequency and increased with an increase in temperature. The results indicated that ceramics based on volcanic ash are promising for use in technological applications such as high-voltage power insulators. [ABSTRACT FROM AUTHOR]

The 2021 Tajogaite eruption was marked by intense pyroclastic fallout that covered a substantial portion of La Palma island, with maximum thicknesses in the central-western part. This, combined with lava flows, resulted in widespread damage to public and private properties. In this study, we investigated if volcanic ash from this eruption could serve as a raw material in the synthesis of alkali activated materials (AAMs) and contribute to the construction of eco-friendly buildings and the restoration of those damaged by the eruption. Volcanic ash-based AAMs were synthesized using NaOH and Na2SiO3 as alkaline solutions and by adding metakaolin to enhance ash reactivity and enable processing at ambient temperatures. Lightweight porous AAMs were also produced using H2O2 and metallic aluminum as foaming agents. Chemical, textural, physical, and mechanical analyses on the final products assessed their suitability as environmentally friendly materials to be used in the reconstruction of the island infrastructure, opening new perspectives on recovery actions that can be undertaken after disastrous eruptions. Of all the islands in the Canary Archipelago, La Palma has experienced the highest number of eruptions (8) in historical times, all of which showing considerable similarity in terms of eruptive mechanisms and composition to the most recent Tajogaite event. Although this study investigated fresh Tajogaite ash, similar perspectives can be envisaged for both other recent eruptions at La Palma and other similar volcanic scenarios worldwide.

The report presents the results of the fieldwork (July 2024) aimed at studying the traces of prehistoric ashfalls in the city of Kurilsk and nearby settlements: the villages of Kitovy, Rybaki, and Reydovo (Iturup, South Kuril Islands). The work was traditionally based on tephrostratigraphic studies, during which the sections of the soil-pyroclastic cover were studied. In total, more than 10 sections were studied. The materials obtained during the fieldwork, after carrying out radiocarbon dating and material composition studies, will be used in further regional studies on young volcanism of the South Kuril Islands, as well as in studies on assessing volcanic hazard and volcanic zoning.

The petrographical, mineralogical, whole-rock geochemical, and zircon U-Pb geochronological and Lu-Hf isotopic studies were carried out for investigating the provenance and genetic mechanism of the high-grade coal-bearing kaolin within the coal seams of the Permo-Carboniferous Taiyuan Formation in the Xiaoyu mine of the Datong coalfield, Shanxi Province. The coal-bearing kaolin is composed mainly of well-ordered kaolinite with no detrital quartz, feldspars and muscovite. Some samples contain boehmite that were formed through the desilication of kaolinite. The zircons in the coal-bearing kaolin are typically igneous origin with only one age population of ca. 300 Ma, same with the depositional age of the coal, confirming that the coal-bearing kaolin was altered from volcanic ash. Besides, the coal-bearing kaolin commonly contains tabular/columnar and vermicular kaolinite that are also diagnostic feature of alteration from volcanic ash. These coarse-grained kaolinites are thought to be pseudomorphic kaolinite altered from crystal fragments in volcanic ash, such as plagioclase and biotite. The zircon εHf(t) is dominant by a wide range of negative values, indicative of their formation from magma generated by substantial remelting of ancient continental crust, coinciding with that of contemporaneous magmatic rocks formed from continental arc volcanism in the Inner Mongolia Paleo-Uplift at the northern margin of North China. This suggests their cognate relationship. The geochemical fingerprints of trace element of zircons also indicate that they were crystalized from continental arc magma. The northern margin of the North China Craton (NCC) is an Andean-type continental margin in the late Paleozoic. During the coal-accumulating period of the Late Carboniferous to Early Permian in North China, the Paleo-Asian Ocean (PAO) plate was continuously southward subducted beneath the NCC, resulted in a frequent continental arc volcanism. The emitted volcanic ash fell into peat swamps developed in a paralic environment in North China, which were subjected to an intensive leaching and altered to the coal-bearing kaolin.

The phreatomagmatic eruption of Taal Volcano in Batangas, Philippines, in January 2020 resulted in a massive ash plume covering a large portion of nearby provinces, including Metro Manila. This event caused damage and disruptions to various sectors, including agriculture, the environment, health, infrastructure, and aviation. The challenge of managing the vast amount of collected tephra environmental waste prompted the initiative of converting it into a useful material. This study characterizes and evaluates the quality of the collected tephra as a potential raw material for the construction industry, based on the Philippine National Standard (PNS) 07:2018, to ensure structural integrity and public safety. Four ashfall samples from strategic locations, identified by the Philippine Institute of Volcanology and Seismology (PHIVOLCS), were obtained and analysed for specific chemical parameters using various analytical techniques. The results suggest that tephra has potential as a raw material for ground-level structures. However, further treatment is necessary to reduce the concentration of certain constituents. The material met the standard specifications for SiO2, MgO, and SO3. However, the levels of Al2O3, Fe2O3, total alkali, loss on ignition, and water-soluble and acid-soluble Cl− exceeded the threshold limits set by PNS 07:2018 and EN 197-1:2000.

Abstract The color of pyroclasts is fundamental, because it reflects various magma properties and eruption processes, including particle morphology, chemistry, and petrological characteristics. However, deriving the componentry ratio (CR) of pyroclasts for ongoing eruption monitoring remains challenging due to the lack of a robust quantitative standard. The derivation of the CR, as well as other petrological analyses, is too laborious and time-consuming to introduce as a sustainable monitoring method. To address this, we employed spectroscopic colorimetry to rapidly and quantitatively describe eruptive product colors, enabling CR derivation based on clear, objective standards for ash particle classification. Through color spectroscopy of bulk and sieved ash samples, we analyzed the major size fraction for time-series samples during the waxing stage of the 2017–2018 Shinmoe-dake eruption in Kirishima volcano, Southwest Japan. Our findings reveal that the color changes in bulk ash systematically changed with the evolution of componentry. This temporal color change was due to an increase in the amount of vesicular particles with clear glass against dark angular lava particles, as well as a grain size change, which we interpret as an indication of a transition from phreatic/phreatomagmatic to magmatic eruption. Subsequently, the color of the ash changed when the amount of different lava particles increased gradually, coinciding with a shift toward a more dominant effusion of lava. As the lava effusion continued, a slight reddening of the ash, indiscernible to the naked eye, was clearly detected by the spectrometer before the onset of intermittent Vulcanian eruptions. We interpreted this reddening as oxidation resulting from decreased ascent speed and caprock formation, which accumulates overpressure for Vulcanian explosions. These results highlight the potential of rapid, objective color value and componentry derivation for sustainable quasi-real-time monitoring of ongoing eruption materials. Graphical Abstract

This study investigated the potential of porous silica material extracted from volcanic ash of Mount Sinabung, Indonesia, as a corrosion inhibitor. The new material was subjected to comprehensive analysis using the X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Search Engine Marketing (SEM), and Atomic Absorption Spectrophotometry (AAS). Corrosion test was conducted by coating the metal surface with synthesized silica. XRD data showed the presence of amorphous silica, while SEM indicated a rough and irregular pore cavity. Based on AAS characterization, the concentration of silica in the Mount Sinabung volcanic ash was 79.23 % (v/v) with a yield of 29.73 %(w/w). Furthermore, coated and uncoated iron plates, with grit variations of 800, 1200, 1500, and 2000, were tested against HCl 15 % (v/v) and NaCl 3.5 % (w/v) as model corrosive solutions. The SEM results showed that coated plates had fewer holes and cracks formation while the XRD analysis of the same samples presented a slight decrease in the intensity of iron phase. Among silica-coated iron plates, the 1500 grit variation had the lowest corrosion rate and the highest corrosion inhibitor efficiency in both HCl 15 % (v/v) and NaCl 3.5 % (w/v) corrosive solutions, recording efficiencies of 26.3 and 91.8 %, respectively.

Several samples of fossilized wood (charcoal) were collected in the Papayita archaeological site, in coastal Ecuador. This carbonized material was encountered inside a layer of volcanic ash that sealed the site. The ash-sized tephra was produced by a sub-Plinian eruption from the Guagua Pichincha volcano contemporaneous with the late Valdivia phases during the Formative Period. Each of the samples was sectioned into 10 to 15 subsamples and examined under a Scanning Electron Microscope (SEM), producing high-resolution images with a large depth of field where the anatomical structures and their geochemical composition were vividly discernible. Each sample corresponds to organic matter of vegetable origin, that is, carbonized wood in the form of small rocks, whose appearance is that of carbonized woody tree trunks and or branches. We were able to observe vascular structures, specifically bundles of xylem. It was possible to conclude that these tracheids underwent a physicochemical transformation typical of petrification processes, leaving the molds intact. This allowed us to determine structural elements that support the identification of the group of plants to which these samples belong, through the methodology of comparison of the anatomical components of current species. The fossilized wood structures are three-dimensional and present characteristics that correspond to the group of higher plants, Gymnosperms, of the Podocarpaceae group. Among them, quadrangular tracheids, circular hole-shaped pits in the vascular system, and absent resin canals stand out. Central to the analysis is the presence of transverse parenchyma, which can be ascertained to correspond to vegetation from climates that are temperate or cold.

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]

Volcanic ash dispersed in the air adheres to thermal barrier coatings (TBCs) on the hot section components of gas turbines, posing a severe threat to aviation safety. Here, we report a novel strategy inspired by lotus leaf for mitigating the molten volcanic ash adhesion and corrosion. A hierarchical micro-nano structure composed of arrayed micro-conoids and numerous nanoparticles were constructed on the surface of NdYbZr 2 O 7 ceramic pellet by ultrafast laser direct writing technology, whose morphology could be changed by optimizing the processing parameters. The laser-ablated pellet exhibits larger contact angle of molten volcanic ash than the original one, revealing an enhanced resistance repelling volcanic ash. This phenomenon is primarily attributed to the air trapped in the micro-grooves, together with these nanoparticles. Note that the evolution of viscous force and capillary force with time accelerates the transition of molten volcanic ash from the Cassie state to the Wenzel state and reduces its contact angle. Also, this structure effectively inhibits the infiltration of molten volcanic ash by rapidly developing a reaction layer. These findings are an important step toward the design and development of next-generation silicate ash-repellent TBCs. [ABSTRACT FROM AUTHOR]

Antibiotic contamination of water sources is a significant environmental and public health concern. This contamination is classified among the most dangerous types of pollution currently because of their harmful effects. Therefore, it is essential to identify effective and environmentally friendly ways to deal with those dangerous compounds. Within this context, this work looked into whether soils made from volcanic ash could be used as cost-effective adsorbents to remove the antibiotic trimethoprim (TRM) from aqueous solutions. To examine the impacts of the main operating parameters on TRM removal, which are the initial antibiotic concentration (C), contact time (t), stirring speed (S), and solid-to-liquid ratio (R), a Central Composite Design (CCD) based on the Response Surface Methodology (RSM) was employed. Full quadratic polynomial models were used to correlate the experimental data, allowing for the estimation of each factor's influence. With a predicted removal efficiency of 77.59%, the removal process optimization yielded the following set of optimal conditions: C = 4.5 mg/L, t = 45.5 min, S = 747 rpm, and R = 0.04 g/mL. Experiments conducted under predicted ideal conditions supported both the result and the previously developed model's capacity for prediction. Additionally, the adsorption mechanism was also proposed based on the characterization of the adsorbent before and after the treatment. The study's findings provide the possibility of using soils formed from volcanic ash as a cost-effective adsorbent material for the removal of TRM and likely other similar pollutants from contaminated waters. [ABSTRACT FROM AUTHOR]

Portland cement products are extensively used as parent materials in construction projects. However, the production and consumption of these products result in various environmental pollutants, including the emission of carbon dioxide gas and excessive water usage. Geopolymer products have emerged as a promising alternative to Portland cement and its products due to their diverse mechanical and chemical properties. Therefore, in this study, we aim to investigate the potential of geopolymer products as a replacement for Portland cement. To this end, the optimal mixing design was obtained by performing uniaxial compressive strength and flow table tests. Nailing is a commonly used method for stabilizing soil excavations and slopes, often involving the use of Portland cement as grout. Geopolymer is used as a potential replacement for cement grout in this system. Pullout tests were conducted to investigate the interaction between the soil and grout, considering the effect of curing conditions and environmental factors such as temperature, humidity, and overburden pressure for both the geopolymer and cement grouts. The results indicate that, in general, the pullout force of geopolymer samples is lower than that of cement samples. However, raising the temperature in geopolymer samples results in an increase in the pullout force, whereas an increase in temperature in cement samples leads to a decrease in pullout force. It can be concluded that geopolymer samples need to be modified by using an additive, such as sodium silicate, to achieve proper pullout force and suitable interlocking with soil grains. [ABSTRACT FROM AUTHOR]

The color of pyroclasts is fundamental, because it reflects various magma properties and eruption processes, including particle morphology, chemistry, and petrological characteristics. However, deriving the componentry ratio (CR) of pyroclasts for ongoing eruption monitoring remains challenging due to the lack of a robust quantitative standard. The derivation of the CR, as well as other petrological analyses, is too laborious and time-consuming to introduce as a sustainable monitoring method. To address this, we employed spectroscopic colorimetry to rapidly and quantitatively describe eruptive product colors, enabling CR derivation based on clear, objective standards for ash particle classification. Through color spectroscopy of bulk and sieved ash samples, we analyzed the major size fraction for time-series samples during the waxing stage of the 2017–2018 Shinmoe-dake eruption in Kirishima volcano, Southwest Japan. Our findings reveal that the color changes in bulk ash systematically changed with the evolution of componentry. This temporal color change was due to an increase in the amount of vesicular particles with clear glass against dark angular lava particles, as well as a grain size change, which we interpret as an indication of a transition from phreatic/phreatomagmatic to magmatic eruption. Subsequently, the color of the ash changed when the amount of different lava particles increased gradually, coinciding with a shift toward a more dominant effusion of lava. As the lava effusion continued, a slight reddening of the ash, indiscernible to the naked eye, was clearly detected by the spectrometer before the onset of intermittent Vulcanian eruptions. We interpreted this reddening as oxidation resulting from decreased ascent speed and caprock formation, which accumulates overpressure for Vulcanian explosions. These results highlight the potential of rapid, objective color value and componentry derivation for sustainable quasi-real-time monitoring of ongoing eruption materials. [ABSTRACT FROM AUTHOR]

Acid deposition is widespread in Japan, but acidification of stream water is rare in forest ecosystems. Bedrock‐derived cations, including those released into the soil by weathering of bedrock minerals, generally act to neutralize acid deposition and flow out into streams. Volcanic ash, which is widespread in Japan, may also release cations and neutralize acids, but the contribution of volcanic‐ash‐derived cations is currently poorly explored. To assess the importance of volcanic ash as a source of base cations, we examined strontium in two catchments underlain by chert bedrock at Mount Amamaki, Japan. Additionally, we obtained comparative data from two sandstone‐bedrock catchments in the same area. We measured 87Sr/86Sr ratios in samples of stream water, bulk precipitation, riverbed rock, and soil from the catchments. We used the 87Sr/86Sr data to analyze the relative contributions of atmospheric deposition, bedrock, and volcanic ash in soil as sources of Sr in the stream waters. We estimated volcanic ash in soil to contribute between 46% and 78% of stream‐water Sr for one chert‐bedrock catchment, and between 0% and 52% for the other. We conclude that volcanic ash in soil is an important source of Sr in stream water. Thus, volcanic ash can act as a source of base cations and hence contribute to the acid‐neutralizing capacity of soil in forest ecosystems in Japan. [ABSTRACT FROM AUTHOR]

Eruption source parameters (ESPs) are crucial for characterising volcanic eruptions and are essential inputs to numerical models used for hazard assessment. Key ESPs of explosive volcanic eruptions include plume height, mass eruption rate, eruption duration, and grain-size distribution. Some of these ESPs can be directly observed during an eruption, but others are difficult to measure in real-time, or indeed, accurately and precisely quantify afterwards. Estimates of ESPs for eruptions that cannot be observed, for example, due to the remote location of a volcano or poor weather conditions, are often defined using expert judgement and data from past eruptions, both from the volcano of interest and analogue volcanoes farther afield. Analysis of such information is time intensive and difficult, particularly during eruption response. These difficulties have resulted in the production of datasets to aid quick identification of ESPs prior to or during an eruption for use in operational response settings such as those at volcano observatories and Volcanic Ash Advisory Centres. These resources include the Mastin et al. (2009a) ESP dataset and the Catalogue of Icelandic Volcanoes and European Catalogue of Volcanoes aviation tables. Here, we review and compare these resources, which take different approaches to assigning ESPs. We identify future areas for development of these resources, highlighting the need for frequent updates as more knowledge of volcanic activity is gained and as modelling capabilities and requirements change. [ABSTRACT FROM AUTHOR]

Rare-earth silicates are promising environmental barrier coatings (EBCs) that can protect SiCf/SiCm substrates in next-generation gas turbine blades. Notably, RE2Si2O7 (RE = Yb and Ho) shows potential as an EBC due to its coefficient of thermal expansion (CTE) compatible with substrates and high resistance to water vapor corrosion. The target operating temperature for next-generation turbine blades is 1400°C. Corrosion is inevitable during adhesion to molten volcanic ash, and thus, understanding the corrosion behavior of the material is crucial to its reliability. This study investigates the high-temperature corrosion behavior of sintered RE2Si2O7 (RE = Yb and Ho). Samples were prepared using a solid-state reaction and hot-press method. They were then exposed to volcanic ash at 1400°C for 2, 24, and 48 h. After 48 h of exposure, volcanic ash did not react with Yb2Si2O7 but penetrated its interior, causing damage. Meanwhile, Ho2Si2O7 was partially dissolved in the molten volcanic ash, forming a reaction zone that prevented volcanic ash melts from penetrating the interior. With increasing heat treatment time, the reaction zone expanded, and the thickness of the acicular apatite grains increased. The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb2Si2O7 but decreased considerably over time for Ho2Si2O7. The Ca in volcanic ash was consumed and formed apatite, indicating that RE3+ ions with large ionic radii (Ho > Yb) easily precipitated apatite from the volcanic ash. [ABSTRACT FROM AUTHOR]

To tackle the ever-increasing operating temperature of aero-engines, a La2Ce2O7 (LCO)/yttria partially stabilized zirconia (YSZ) double-layer thermal barrier coating (TBC) was investigated. The LCO/YSZ double-layer samples were annealed with volcanic ash (VA) at 1250 °C to assess their stability in comparison with that of standard single-layer YSZ. The findings showed that the double-layer system exhibited greater resistance to VA damage than the single-layer YSZ coating. The corrosion mechanism was characterized by a rapid crystallization reaction between LCO and VA, where the kinetics of the solution's reprecipitation reaction outpaced the penetration rate into the coating's open pores. [ABSTRACT FROM AUTHOR]

This study investigated the potential of porous silica material extracted from volcanic ash of Mount Sinabung, Indonesia, as a corrosion inhibitor. The new material was subjected to comprehensive analysis using the X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Search Engine Marketing (SEM), and Atomic Absorption Spectrophotometry (AAS). Corrosion test was conducted by coating the metal surface with synthesized silica. XRD data showed the presence of amorphous silica, while SEM indicated a rough and irregular pore cavity. Based on AAS characterization, the concentration of silica in the Mount Sinabung volcanic ash was 79.23 % (v/v) with a yield of 29.73 %(w/w). Furthermore, coated and uncoated iron plates, with grit variations of 800, 1200, 1500, and 2000, were tested against HCl 15 % (v/v) and NaCl 3.5 % (w/v) as model corrosive solutions. The SEM results showed that coated plates had fewer holes and cracks formation while the XRD analysis of the same samples presented a slight decrease in the intensity of iron phase. Among silica-coated iron plates, the 1500 grit variation had the lowest corrosion rate and the highest corrosion inhibitor efficiency in both HCl 15 % (v/v) and NaCl 3.5 % (w/v) corrosive solutions, recording efficiencies of 26.3 and 91.8 %, respectively. [ABSTRACT FROM AUTHOR]

The year 2021 marked a decade of holopelagic sargassum (morphotypes Sargassum natans I and VIII, and Sargassum fluitans III) stranding on the Caribbean and West African coasts. Beaching of millions of tons of sargassum negatively impacts coastal ecosystems, economies, and human health. Additionally, the La Soufrière volcano erupted in St. Vincent in April 2021, at the start of the sargassum season. We investigated potential monthly variations in morphotype abundance and biomass composition of sargassum harvested in Jamaica and assessed the influence of processing methods (shade-drying vs. frozen samples) and of volcanic ash exposure on biochemical and elemental components. S. fluitans III was the most abundant morphotype across the year. Limited monthly variations were observed for key brown algal components (phlorotannins, fucoxanthin, and alginate). Shade-drying did not significantly alter the contents of proteins but affected levels of phlorotannins, fucoxanthin, mannitol, and alginate. Simulation of sargassum and volcanic ash drift combined with age statistics suggested that sargassum potentially shared the surface layer with ash for ~50 d, approximately 100 d before stranding in Jamaica. Integrated elemental analysis of volcanic ash, ambient seawater, and sargassum biomass showed that algae harvested from August had accumulated P, Al, Fe, Mn, Zn, and Ni, probably from the ash, and contained less As. This ash fingerprint confirmed the geographical origin and drift timescale of sargassum. Since environmental conditions and processing methods influence biomass composition, efforts should continue to improve understanding, forecasting, monitoring, and valorizing sargassum, particularly as strandings of sargassum show no sign of abating. [ABSTRACT FROM AUTHOR]

Globally, most organic-rich shales are deposited with volcanic ash layers. Volcanic ash, a source for many sedimentary basins, can affect the sedimentary water environment, alter the primary productivity, and preserve the organic matter (OM) through physical, chemical, and biological reactions. With an increasing number of breakthroughs in shale oil exploration in the Bohai Bay Basin in recent years, less attention has been paid to the crucial role of volcanic impact especially its influence on the OM enrichment and hydrocarbon formation. Here, we studied the petrology, mineralogy, and geochemical characteristics of the organic-rich shale in the upper submember of the fourth member (Es4 1) and the lower submember of the third member (Es3 3) of the Shahejie Formation, aiming to better understand the volcanic impact on organic-rich shale formation. Our results show that total organic carbon is higher in the upper shale intervals rich in volcanic ash with enriched light rare earth elements and moderate Eu anomalies. This indicates that volcanism promoted OM formation before or after the eruption. The positive correlation between Eu/Eu* and Post-Archean Australian Shale indicates hydrothermal activity before the volcanic eruption. The plane graph of the hydrocarbon-generating intensity (S1þS2) suggests that the heat released by volcanism promoted hydrocarbon generation. Meanwhile, the nutrients carried by volcanic ash promoted biological blooms during Es4 1 and Es3 3 deposition, yielding a high primary productivity. Biological blooms consume large amounts of oxygen and form anoxic environments conducive to the burial and preservation of OM. Therefore, this study helps to further understand the organic-inorganic interactions caused by typical geological events and provides a guide for the next step of shale oil exploration and development in other lacustrine basins in China. [ABSTRACT FROM AUTHOR]

Sulfur-containing ejecta of Plinian-type eruptions can be transported to great distances in gas pores of ash particles. The mean concentration of sulfur in the rhyolite tephra of the ca. 1500 BP Opala eruption is 310 ppm. The maximum concentration can reach 800 ppm. We have found a relationship between sulfur concentration in bulk samples and grain-size composition: sulfur is mostly found in the 0.25‒0.50 mm fraction consisting of elongate ash particles with elongate gas pores 1.0‒10.0 µm long. The most likely cause why sulfur concentration depends on the structure of ash particles consists in the fact that sulfur compounds of the water-soluble complex are preserved inside gas pores; sulfur-containing compounds that have been sorbed on the surface of ash particles were removed by precipitation during the time the tephra resided in continental settings. When ash particles that contain sulfur compounds on the inner surface of gas pores come into bottom sediments during Plinian-type eruptions like that on Opala Volcano ca. 1500 BP, that can affect the geochemistry of lithogeny and rearrange the mineral phases that are sensitive to the presence of oxide-sensitive agents in the sedimentary sequence during diagenesis. [ABSTRACT FROM AUTHOR]

The eruption of Mount Semeru at the end of 2021 was responsible for emitting volcanic ash with specific characteristics. These unique mineralogy and chemical properties have both positive and negative effects on soil fertility, as excessive heavy metals adversely affect soil, plants, and the environment. Therefore, this study aimed to determine the distribution of volcanic ash cover from the eruption of Mount Semeru and investigate elemental composition as well as mineral characteristics of volcanic ash and soil covered by volcanic ash. The investigation was carried out in Supiturang village, Pronojiwo District, Lumajang, East Java, Indonesia. Sampling was carried out following the toposequence method, covering agricultural land within approximately ± 15 km from Mount Semeru. Pure volcanic ash was collected at sites not contaminated with soil. At the site location, it was found that the depth of volcanic ash cover ranged from “thin” (10 cm). The results of SEM and XRD analyses showed that of the pure volcanic ash contained quartz (50%), rock fragments (15%), plagioclase (12%), hornblende (10%), opaque (8%), and pyroxene (5%) minerals. The results of XRF analysis showed that the dominant elements in volcanic ash and soil were silica (Si), aluminum (Al), calcium (Ca), iron (Fe), and potassium (K). Several non-essential heavy metal elements found were Pb, Sn, and As, while rare minerals discovered were Y, Nb, Eu, and Yb at relatively low concentrations. The SEM analysis showed the structure of volcanic ash dominated by prismatic and blocky.

In 2014, Kelud, an active volcano in East Java, ejected ashes (hereafter termed KA; Kelud ash) that reportedly reached as far as Central Java and the Special Region of Yogyakarta (DIY). The KA deposits are observable in, among others, the coastal sand dune area in Parangtritis. Due to the active aeolian process, the KA layers can be found at different depths five years after the eruption. Thus, the KA can be used as a marker of the post-2014 aeolian activities at the Parangtritis dune, which was once classified as a degraded land and later recognized as a coastal geosite, ultimately allowing us to calculate the volume and sand transport rate. The research surveys performed at 25 points discovered volcanic ash layers at 1 cm to 26 cm below the surface. At some observed points, the ash deposits were found on the surface and continuously transported. This research observed an area of 60,000 m2 with an average of 8.5 cm thick sand layers lying above the KA layer. Based on the calculation, the total volume of the transported sand at the Parangtritis sand dune from 2014 to 2019 was approximately 5,100 m3. This volume is considerably small owing to various obstacles in the transport zones. Based on the five-year dynamic of the sand dune, this study suggested that restoration needs to be conducted immediately particularly in eliminating vegetation barriers to maintain the sediment balance (erosion-transport-sedimentation) of the coastal sand dune area.

Lightning‐induced volcanic spherules (LIVS) are glasses produced by the rapid melting and solidification of molten volcanic ash grains. High temperatures generated by lightning will alter the physical and chemical properties of minerals exposed to the discharge. Laboratory experiments reveal that LIVS glass composition varies depending on the starting material, exhibiting heterogeneous compositional features common in other glasses created by cloud‐to‐ground lightning, nuclear explosions, and high velocity impact events. This study uses scanning electron microscopy, energy dispersive spectroscopy, and Raman spectroscopy to investigate the structure and Raman signatures of lightning‐induced glass spherules manufactured from five igneous minerals (<32 μm powders of albite, labradorite, augite, hornblende, and magnetite). LIVS were created through high‐current impulse experiments using peak currents of 25 and 40 kA. Analysis of the post‐experimental albite, labradorite, augite, and hornblende LIVS reveal primarily homogeneous silicate or aluminosilicate glasses with limited heterogeneity. Their amorphous Raman spectra are comparable to rhyolitic and mafic natural glasses along with Na2O‐K2O‐Al2O3‐SiO2, CaCO3‐Al2O3‐SiO2, and CaO‐MgO‐SiO2 synthetic glass networks. A few of the augite and hornblende LIVS spectra exhibit premelting effects, which occur below the melting point and represent the onset of cation disordering in phases that remain crystalline. Magnetite samples produced crystal‐rich, glass‐poor LIVS characterized by the growth of dendritic microcrystals and crystalline spectra that also contain a few bands alluding to the composition of their silicate–phosphate glass matrix. By understanding these chemical changes induced by lightning, we can extract information from other types of glasses produced during high temperature, short duration events. Plain Language Summary: High temperatures generated by volcanic lightning melt and fuse airborne volcanic ash grains consisting of mineral crystals and glassy fragments. Molten grains will rapidly quench into solid or hollow glass spheres termed lightning‐induced volcanic spherules, thereby altering the chemical and structural properties of the ash grains. This study utilizes Raman spectroscopy to characterize the structural properties of glass spherules produced from five common minerals (albite, labradorite, augite, hornblende, and magnetite) through lightning simulation experiments. Results reveal that lightning can alter these mineral samples irrevocably by transforming them into glass with complex compositions and Raman signatures corresponding to mineral and glass phases. The four minerals with a higher abundance of silica, a glass‐forming element, primarily produced chemically complex glass spheres with compositions representing a mixture of different melted minerals, and Raman signals similar to synthetic and naturally occurring glasses. In contrast, the post‐experimental spheres created from the silica‐poor, iron‐rich mineral magnetite are composed of newly formed iron micrometer‐sized crystals, limited amounts of glass, and Raman signals indicative of crystalline material. Although specific to volcanic ash, the impact of lightning on mineral fragments has broader implications for a wide range of geoscientists and planetary scientists. Key Points: Lightning simulation experiments conducted on powdered minerals produce particles containing both glass and crystalline phasesRaman spectroscopy of lightning‐induced spherules reveal spectra comparable to naturally occurring and synthetic multicomponent glassesCrystalline spectra derive from surviving mineral fragments and lightning‐induced crystallization of iron oxide dendrites [ABSTRACT FROM AUTHOR]

Small-to-moderate explosive eruptions involve VEIs ≤ 3, tephra volumes ≤ 0.1 km3 and often eject a significant amount of ash-sized pyroclastic material. This reduces the preservation potential of associated deposits and leads to an underrepresentation of these low- to mid-intensity explosive eruptions in long-term, frequency-magnitude datasets. Mt. Ruapehu is one of New Zealand’s most active volcanoes, having produced at least 32 small-to-moderate eruptions over the past 1800 years. The largest of these eruptions deposited the widespread T13-sequence and lasted several months to years. The cumulative deposit volume is estimated at 0.15 km3, thus being an order of magnitude larger than the average deposit volumes of the last 1800 years at Ruapehu. The sequence of pyroclastic fall deposits can be subdivided into six depositional sub-units representing at least five eruption phases of variable intensity and magnitude. The ash-lapilli sequence displays variable dispersal, deposit textures and pyroclast characteristics. While the initial phase is characterised by dispersal limited to the proximal 11 km and a tephra volume of 8.5 × 105 m3 (± 3%), the following high-intensity “peak” phase is estimated at 8.8 × 107 m3 (± 37.8%), representing about ⁓60% of the cumulative tephra volume. The combination of deposit characteristics with textural analysis of different types of juvenile clasts suggests that changes in eruption style and intensity were mainly controlled by shallow processes in the conduit, such as degassing and crystallisation and changes in conduit geometry. Multilobate, irregular dispersal patterns and laterally variable pyroclast assemblage indicate unsteady eruption conditions characterised by weak eruption plumes controlled by prevailing winds. This study testifies the complexity of tephra sequences associated with long-lasting, small-to-moderate eruptions, and describes the key eruption parameters that can be obtained through a detailed characterisation and identifies the main limitations related to the classification of these eruptive styles. [ABSTRACT FROM AUTHOR]

Early detection of volcanic ash clouds is crucial to aviation safety and airspace surveillance. With the increase in air traffic and the frequency of volcanic eruptions, the need for effective warning procedures and improved detection methods has become obvious. The eruption of the Eyjafjallajökull volcano in 2010 showed that air traffic operations were severely disrupted and highlighted the importance of effective communication strategies between stakeholders. To improve monitoring capabilities, satellite techniques have become essential due to their wide coverage and rapid response. This article presents the HOTVOLC 3.0 web-Geographic Information System (GIS) interface, an enhanced version of the French operational monitoring platform developed at the Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) and certified by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS-INSU). By integrating data from the Meteosat Second Generation (MSG) satellites, HOTVOLC 3.0 enables early detection of volcanic activity and monitoring of ash plumes and clouds. The HOTVOLC service is designed to support volcanic observatories, volcano research institutes, Volcanic Ash Advisory Centers (VAAC), and other operational actors who play a crucial role in decision-making and the implementation of effective risk management strategies for aviation safety. After a description of how the system works, we provide details of the updated web interface, which enhances the user experience by offering an interface with an operational mode and an archive mode, enabling easy access to past eruptions for training purposes. In the second part, we look at the various ash-related observation products (detection algorithms and quantitative products) that are disseminated via the new interface. Finally, we explore future developments of the platform, including the use of machine learning for ash detection, the integration of data from other geostationary satellites to improve product quality, and the forthcoming arrival of data from Meteosat Third Generation (MTG) satellites. [ABSTRACT FROM AUTHOR]

In the view of the recycling and upscaling processes of waste materials, three different precursors, namely metakaolin, fly ash and volcanic ash, were mixed with Na- or K-silicate to produce binders aimed for the synthesis of geopolymer mortars based on construction and demolition wastes (CDWs). These later, used as aggregates in amount of 50 wt.%, were sampled in two geologically different Italian areas. A comparative study was carried out through a multidisciplinary approach using mineralogical–chemical analyses and physical–mechanical tests for the characterization of six binders and twelve mortars. The aim was to verify the effects of CDW interactions on binders as well as the extent of their compositional influences on the final properties. The chemical and mineralogical results evidenced strong compositional differences among the CDWs, differently influencing the physical–mechanical performances (i.e., compressive strength, density, water absorption and porosity) of the mortar samples. Regardless of the types of precursors and CDWs used, a better influence of K-silicate than sodium on the synthetised samples was observed. Furthermore, the higher versatility of metakaolin mortars with any type of CDW used was noted. Contrary, fly ash and volcanic ash mortars showed better properties with CDWs based on their high silica content and volcanic minerals. The study highlighted the critical roles of the CDW composition and precursor selection in mortar production. It confirmed that CDWs can be recycled for geopolymeric synthesis through proper characterisation and binder selection. Optimising these parameters allows for the successful integration of CDWs into geopolymeric materials. This process supports the advancement of a circular economy in the construction industry. [ABSTRACT FROM AUTHOR]

Monitoring changes in species composition near active volcanoes is important to identify environmental factors that maintain biological diversity after major disturbances. We investigated the taxonomic composition of epigaeic beetles' assemblages in five mountains in north‐western Patagonia (Argentina) in the aftermath of the 2011 Puyehue Cordón‐Caulle Volcanic Complex eruption.The associations of beetle composition with the thermal environment, vegetation structure and soil characteristics were analysed using 10 m × 10 m plots with nine pitfall traps each, established 100 m apart in altitude on each mountain in 2005, 2006 (pre‐eruption) and 2012, 2015 and 2016 (post‐eruption).We found significant differences in beetle composition between forests and high‐Andean steppes before and after the eruption. The beetle composition of forests and high‐Andean steppes differed due to higher plant cover and lower pH and herb richness in forests. Six months after the eruption, the herbs almost disappeared and forests showed high ash accumulation and lower temperature than the high‐Andean steppes. In the medium term, plant cover, temperature and soil conditions—but not ash accumulation—remained as important correlates of beetle composition. Before the eruption, forest assemblages showed higher beetle diversity and Leiodidae indicator species, but Curculionidae predominated post‐eruption. Tenebrionidae and Carabidae were high Andean steppes indicators. Post‐eruption, the beetle composition in high‐Andean steppes did not change significantly except for an increase in Tenebrionidae indicator species.We concluded that the conservation of landscape diversity and environmental gradients maintaining the differentiation between ecoregions is essential to protect epigaeic beetle composition and for species survival after volcanic disturbances. [ABSTRACT FROM AUTHOR]

In 2014, Kelud, an active volcano in East Java, ejected ashes (hereafter termed KA; Kelud ash) that reportedly reached as far as Central Java and the Special Region of Yogyakarta (DIY). The KA deposits are observable in, among others, the coastal sand dune area in Parangtritis. Due to the active aeolian process, the KA layers can be found at different depths five years after the eruption. Thus, the KA can be used as a marker of the post-2014 aeolian activities at the Parangtritis dune, which was once classified as a degraded land and later recognized as a coastal geosite, ultimately allowing us to calculate the volume and sand transport rate. The research surveys performed at 25 points discovered volcanic ash layers at 1 cm to 26 cm below the surface. At some observed points, the ash deposits were found on the surface and continuously transported. This research observed an area of 60,000 m2 with an average of 8.5 cm thick sand layers lying above the KA layer. Based on the calculation, the total volume of the transported sand at the Parangtritis sand dune from 2014 to 2019 was approximately 5,100 m3. This volume is considerably small owing to various obstacles in the transport zones. Based on the five-year dynamic of the sand dune, this study suggested that restoration needs to be conducted immediately particularly in eliminating vegetation barriers to maintain the sediment balance (erosion-transportsedimentation) of the coastal sand dune area. [ABSTRACT FROM AUTHOR]

The manufacture of natural pozzolans as cement products is economically affordable and contributes to CO2 mitigation in the cement-based materials industry. Through two experimental stages, this study evaluates the feasibility of using volcanic ash (VA) to partially substitute portland cement (PC) in mortar production. In Stage 1, the effectiveness of different activation methods, such as calcination, alkali activation, and lime addition, in enhancing VA reactivity was assessed when the mortars were produced using 35% VA. The compressive strength (fcm) and physical properties of the mortars produced were determined at 7 and 28 days and compared with those of mortars without activated VA. In Stage 2, the most effective treatments obtained from Stage 1 were applied to produce mortars with 50% and 75% of VA replacements, focusing on their physical and mechanical properties. The findings revealed promising results, particularly when mortars were produced with up to 50% calcined VA (CVA) at 700 °C and 20 wt% lime addition, reaching a higher fcm than 45 MPa. Chemical activation with 2% CaCl or 1% NSi enhanced early-age strength in 35% VA-based mortars. Additionally, NSi-activated CVA-lime-based mortar at 50% VA achieved a notable fcm of 40 MPa at 28 days. Even mortars with 75% VA replacement achieved an adequate compressive strength of 33MPa at 28 days. This study determined that VA-based mortars have the potential for construction applications. [ABSTRACT FROM AUTHOR]

Natural volcanic soils containing pumice particles are commonly found in Hokkaido, Japan, and this type of soil is prone to landslides, internal erosion, and liquefaction. Therefore, the purpose of this paper is to summarise the hydro-mechanical response of volcanic ash soil subjected to internal erosion using the modified erosion triaxial apparatus, based on the literature and additional investigations. The results of the study show that the rate of erosion and shear strain during the erosion process are influenced by initial density, stress state, and hydraulic gradient. Notably, anisotropic consolidation is experienced by specimens under seepage flow. Additionally, the removal of fines leads to a slight decrease in the grading state index. Moreover, suffosion increases the maximum shear modulus and Poisson’s ratio of the soil, while increasing seepage time stabilises the peak shear strength of eroded specimens. Furthermore, the critical state line does not change much with internal erosion. To sum up, this study offers valuable insights into the behaviour of volcanic ash soil subjected to internal erosion and provides an integrated interpretation of hydro-mechanical response of volcanic ash on removal of fines.