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Volcanic oil and gas resources are abundant and have been one of the principal focuses of research in the oil and gas industry for a long time. Due to the complexity of the volcanogenesis and the non-homogeneity of the reservoir, the construction of a reasonable volcanic rock petrophysical model to guide the reservoir prediction is the key to success or failure. Unlike conventional sedimentary reservoirs, volcanic rock skeletons have diverse mineralogical compositions and pore structures, making the construction of equivalent petrophysical models highly complicated. This paper proposes a method to construct equivalent petrophysical models of complicated volcanic rocks with multiple mineral components and pore structures utilizing conventional logging curves. In the middle basal volcanic rock development area of the Songnan Fault, the errors in mineral content calculation and transverse wave estimation are less than 10% when comparing the results of elemental capture spectroscopy (ECS) logging and core test analysis; meanwhile, it directs the volcanic rock phase-controlled pre-stack inversion work and upgrades the accuracy of volcanic rock well seismic multi-scale reservoir prediction. [ABSTRACT FROM AUTHOR]

The 2050 ± 50 14C yBP caldera-forming eruption of Okmok volcano, Alaska, had a global atmospheric impact with tephra deposits found in distant Arctic ice cores and a sulfate signal found in both Greenland and Antarctic ice cores. The associated global climate cooling was driven by the amount of sulfur injected into the stratosphere during the climactic phase of the eruption. This phase was dominated by pyroclastic density currents, which have complex emplacement dynamics precluding direct estimates of the sulfur stratospheric load. We simulated the dynamics of the climactic phase with the two-phase flow model MFIX-TFM under axisymmetric conditions with several combinations of mass eruption rate, jet water content, vent size, particle size and density, topography, and emission duration. Results suggest that a steady mass eruption rate of 1.2–3.9 × 1011 kg/s is consistent with field observations. Minimal stratospheric injections occur in pulses issued from the central plume initially rising above the caldera center and from successive phoenix ash-clouds caused by the encounter of the pyroclastic density currents with topography. Most of the volcanic gas is injected into the stratosphere by the buoyant liftoff of dilute parts of the currents at the end of the eruption. Overall, 58–64 wt% of the total amount of gas emitted reaches the stratosphere. A fluctuating emission rate or an efficient final liftoff due to seawater interaction is unlikely to have increased this loading. Combined with petrological estimates of the degassed S, our results suggest that the eruption injected 11–20 Tg S into the stratosphere, consistent with the subsequent climate response and Greenland ice sheet deposition. Our results also show that the combination of the source Richardson number and the mass eruption rate is able to characterize the buoyant–collapse transition at Okmok. We extended this result to 141 runs from 10 published numerical studies of eruptive jets and found that this regime diagram is able to capture the first-order layout of the buoyant–collapse transition in all studies except one. An existing multivariate criterion yields the best predictions of this regime transition. [ABSTRACT FROM AUTHOR]

The isotopic fractionation of carbon between CO 2 gas and silicate melts is a crucial parameter to understand the carbon cycle at the planetary scale that requires accurate quantification. In this study, we conducted experiments to determine the carbon isotope fractionation between CO 2 gas and carbon dissolved in silicate melt at 350 – 420 MPa and 1160 – 1225 °C, across a range of melt compositions. A linear relationship emerges between the fractionation coefficient and the degree of polymerization of the melt (NBO/T; non–bridging oxygens per tetrahedral cation) with the fractionation coefficient increasing for depolymerized melts (e.g., basalt) and decreasing for polymerized melts (e.g., rhyolite): 1000 ln α gas - m e l t = 3.251 × N B O / T + 0.026 R 2 = 0.74 or 1000 ln α gas - m e l t = - 0.087 × Si O 2 + A l 2 O 3 w t % + 7.968 R 2 = 0.74 . These equations enable the calculation of carbon fractionation coefficients in silicate melts, providing a mean to interpret δ13C–value measurements in natural volcanic gases and melts through forward and backward modelling of degassing paths from mantle to surface. We hypothesize that the ratio of CO 3 2–/CO 2 dissolved in the melt is the key parameter behind this relationship. Carbon dissolved as CO 2 molecular transfers to the gas phase with a fractionation coefficient of 0 ‰ whilst carbon dissolved as CO 3 2– transfers with a fractionation coefficient of 2.9 ‰. The relationship is calibrated from NBO/T=0 to 0.88, covering most major melt compositions. However, at NBO/T>0.88, as the CO 3 2–/CO 2 ratio reaches its maximum in silicate melt, correspondingly the fractionation coefficient reaches its maximum of 2.9 ‰, both are expected to stabilize and remain constant. Carbon isotopic fractionation might hence offer a window into carbon speciation in natural melts. [ABSTRACT FROM AUTHOR]

India-Asia continental collision–induced volcanic gas emissions are thought to have played an important role in driving Cenozoic atmospheric CO2 variations, yet the details of how the deep carbon cycle may influence volcanic CO2 degassing are not understood. We present a novel study employing Mg-Zn-Mo isotopic compositions of Cenozoic ultrapotassic lavas from NW Tibet. The negative Mg-Zn isotope correlation (δ26Mg = −0.39‰ to −0.19‰; δ66Zn = +0.27‰ to +0.36‰), bolstered by petrographic analysis of mantle-derived xenoliths from these lavas, demonstrates that the ultrapotassic magmas originated from a lithospheric mantle source that had been enriched by recycled carbonate-bearing sediments rich in calcite and dolomite. Very low δ98Mo values (−0.78‰ to 0‰) relative to the average continental crust (δ98Mo = +0.10‰ to +0.35‰) further indicate that the sedimentary components were derived from the subducted Indian continental crust after its dehydration. Monte Carlo modeling estimates that the input flux of carbon (elemental C) from such sediments into the lithospheric mantle is ∼5.6 Mt/yr, with a predicted CO2 emission rate of ∼15.5 Mt/yr. We suggest that the still ongoing subduction of the Indian tectonic plate has played a crucial role in introducing substantial quantities of carbonate-rich sediments into the Tibetan lithospheric mantle, leading to the sequestration of large amounts of CO2 via carbonatite metasomatism. Hence, partial melting of such a carbon-rich mantle reservoir in an orogenic setting provides the positive feedback mechanism that can explain the high flux of volcanic CO2 during IndiaAsia collision. These findings not only highlight the importance of continental subduction, sediment recycling, and mantle metasomatism by carbon-rich melts/fluids in the generation of Tibetan ultrapotassic volcanism, but they also show how the deep carbon cycle influences volcanic CO2 degassing. [ABSTRACT FROM AUTHOR]

Carbon dioxide is a key gas to monitor at volcanoes because its concentration and isotopic signature can indicate changes to magma supply and degassing behavior prior to eruptions, yet carbon isotopic fluctuations at volcanic summits are not well constrained. Here we present δ13C results measured from plume samples collected at Stromboli volcano, Italy, by Uncrewed Aerial Systems (UAS). We found contrasting volcanic δ13C signatures in 2018 during quiescence (−0.36 ± 0.59‰) versus 10 days before the 3 July 2019 paroxysm (−5.01 ± 0.56‰). Prior to the eruption, an influx of CO2‐rich magma began degassing at deep levels (∼100 MPa) in an open‐system fashion, causing strong isotopic fractionation and maintaining high CO2/St ratios in the gas. This influx occurred between 10 days and several months prior to the event, meaning that isotopic changes in the gas could be detected weeks to months before unrest. Plain Language Summary: Volcanoes produce gases which change composition depending on how active the volcano is. One of these gases, carbon dioxide, is known to change in proportion to other gases before an eruption occurs, but little is known about how the isotopes of carbon change leading up to an eruption. Using drones to reach the gaseous plume of Stromboli volcano, Italy, we have captured carbon dioxide both during an inactive phase in 2018 and during the lead‐up to a highly explosive eruption called a paroxysm in 2019. There is a stark difference in the carbon isotopes measured 10 days before the 3 July 2019 paroxysm as opposed to those measured in 2018. This is caused by the arrival of CO2‐rich magma which progressively degassed, leading to lighter carbon isotopes in the residual magma over time. This process could have started anywhere from 10 days to several months before the paroxysm. This provides a warning signal which can be detected weeks to months before an active period begins. Key Points: Rapid collection of volcanic plume CO2 enabled by Uncrewed Aerial SystemsA carbon isotopic anomaly was present two weeks prior to the Stromboli 2019 paroxysmHigh CO2 concentrations, elevated CO2/St, and light δ13C‐CO2 may precede paroxysms on timescales of months to weeks [ABSTRACT FROM AUTHOR]

The 1999 basaltic eruption of Shishaldin volcano (Alaska) displayed a transition between Subplinian and Strombolian activity. Strombolian bubbles indicate the presence of a periodically unstable foam at the top of magma reservoir. In contrast, a long foam, whose rupture led to the eruptive column, was also able to collect in the conduit. Laboratory experiments show that long foams can be produced in a conduit by the spreading of a stable foam accumulated at the top of the reservoir. The existence of a Taylor bubble at the onset of the Subplinian phase, also reproduced by my laboratory experiments, suggests that the foam in the reservoir was just at the transition between stable and unstable. This constrains the bubble diameter prior to the Subplinian phase to be 0.034–0.038 mm when using the foam dimensionless analysis and the underlying gas flux (0.52–0.80 m3/s). The increase in bubble diameter and potentially gas flux prior to the Strombolian activity, 0.81–1.4 m3/s, is sufficient to explain the foam in transition to be unstable. The radius of the magma reservoir is small, 200–210 m, as expected. The bubble diameter is the smallest of those estimated for classical basaltic eruptions (Etna, Kı̄lauea, Erta 'Ale), while the gas flux is among the largest. A dilute suspension of small and isolated bubbles cannot explain the large gas flux at Shishaldin. This implies numerous bubbles with a gas volume fraction ≥0.63−2%, a regime for which the bubbles form bubble clusters. The diameter of these bubble clusters, 3.0–5.4 mm, is sufficient to explain large gas fluxes. Plain Language Summary: Basaltic eruptions, producing high eruptive columns, 16 km of ashes and volcanic gases, are rare and not yet well understood. The goal of this paper is to use the chronology of the 1999 Shishaldin eruption in Alaska, the estimates of expelled gas volumes obtained by previous studies of infrasound to understand this rare but dangerous eruptive regime. An analog volcano, no more than a few tens of centimeters, filled by viscous oils and small bubbles, was used to estimate key degassing parameters in the magma reservoir, that is, the diameter of the small bubbles and the gas flux at 3 km depth. The strength of this model is to be able to understand the four main basaltic eruptive patterns at the surface by a single set of parameters in the magma reservoir, the magma viscosity, the bubble diameter and the underlying gas flux. Key Points: The basaltic Subplinian eruption of Shishaldin is due to a very large underlying gas flux and tiny bubble diameter in the magma reservoirFour main basaltic regimes (weak and typical Strombolian, fire fountains, subplinian) can explained by foam behavior in magma reservoirThe large gas flux in magma reservoir can be explained by the rise of tiny bubbles, agregated in bubble clusters, hence rising much faster [ABSTRACT FROM AUTHOR]

The results of studies of a basaltic andesite sample (complicated by the mineralized fracture and voids, as well as fracture and gas voids filled with secondary mineralization) dredged on the submarine Esmeralda Volcano are presented. A detailed comparative study of the mineral composition of the substance lining the fracture, the near-fracture space, and the basaltic andesite part unaffected by secondary alterations made it possible to discover the presence of a mineral assemblage, which is atypical for the unaltered volcanic rocks, in the submarine Esmeralda Volcano. In the intra-fracture space and adjacent basaltic andesite zones, wide variation ranges of the plagioclase composition are recorded; isomorphism in the Fe–Ca pyroxene series is studied; REE oxides, hydroxides, and fluorohydroxides are studied; and variability in the composition of minerals of the magnetite–hematite series is shown. Tectonic movements in the previously formed basaltic andesites likely promoted the emergence of permeable zones, through which new portions of the melt leaked. In a limited space, high fluid gas saturation, temperature, and pressure fostered the extraction of metal compounds from the melt and host rocks. [ABSTRACT FROM AUTHOR]

Abstract Volcanic eruptions can emit large quantities of sulphur dioxide (SO2) into the atmosphere, which can be harmful to people and the environment. Aircraft encounters with a volcanic SO2 cloud could represent a health hazard to crew and passengers onboard. In this study we have assessed concentration levels of volcanic SO2 in the atmosphere following eight historic eruptions and use four-dimensional dispersion model simulation data to calculate when and where the World Health Organisation (WHO) health protection guideline for SO2 of 500 μgm-3 over 10 minutes is exceeded. The time and area of exceedance varies and depends on the eruption characteristics: the amount, duration and height of the SO2 release. The WHO-based guideline value is exceeded for all historic eruptions considered. In several cases, the area delineated by the WHO-based guideline, here called the SO2 hazard area, can be considerably larger than the volcanic ash hazard area for the same eruption. SO2 hazard areas also often extend over a longer period of time compared to the equivalent ash advisories. For example, following the 2019 eruption of Raikoke, the SO2 hazard area reached up to 1.7 million km2 and the WHO-based guideline value was exceeded for about two weeks, while volcanic ash was considered hazardous to aviation for about five days. These results will help the aviation industry to better understand the potential risks to their passengers and crew from volcanic SO2, and aid in defining concentration thresholds for any potential volcanic SO2 forecasts for aviation.

We investigate ten of the most recent tephra-fall deposits emplaced between ≤21 and 2 ka from the Pacheco stage of Misti volcano, Peru, to elucidate magma dynamics and explosive eruption triggers related to magma storage, recharge, and remobilization. Whole-rock, glass, and mineral textures and compositions indicate the presence of broadly felsic, intermediate, and mafic magmas in a chemically and thermally stratified magma storage system (Zones 1–3) that interact to differing extents prior to eruption. Intermediate magmas are defined by plagioclase + amphibole + two-pyroxenes + Fe-Ti oxides and phase equilibria indicate they formed at ~300 to 600 MPa and ~950°C to 1000°C. Intermediate magmas dominate the Pacheco stage and either erupted alone as hybridized magmas or mingled with minor volumes of cool felsic magmas (~800°C) in which only plagioclase + Fe-Ti oxides are stable. Felsic magmas do not exclusively comprise any tephra-fall deposit emplaced during the Pacheco stage but were remobilized by recharge and mixing with intermediate magmas in order to erupt. Furthermore, felsic-hosted amphibole cognate to the intermediate magmas are reacted despite the felsic magmas being water saturated, which suggests they are staged above the amphibole stability limit (≤200 MPa). The cryptic presence of mafic magmas is indicated by high-An plagioclase cores (An74–88), rare anhedral olivine (Fo77–80), and possibly high Mg# augite and amphibole (up to Mg# 84 and 77, respectively). The dearth of basalt to basaltic andesite melts recorded in erupted glasses and exclusivity of high-An plagioclase to crystal cores signals mafic magmas are staged deeper in the crust than the intermediate magmas. Periodic interactions between these magmas tracked via glass compositions and crystal exchange reveal an alternation between the production of mingled magmas and their eruption shortly after a recharge event, followed by a period of homogenization and eruption of hybridized magmas. As such, we identify magma recharge as a key mechanism by which half of the explosive eruptions were triggered in the Pacheco stage. A >100°C increase in Misti's fumarole temperatures from 1967 to 2018 coincident with changes in fumarolic gas compositions is consistent with degassing of a mafic recharge magma, signaling that Misti could produce similar explosive eruptions in the future. [ABSTRACT FROM AUTHOR]

Recycling of oxidized sulfur from subducting slabs to the mantle wedge provides simultaneous explanations for the elevated oxygen fugacity (fO2) in subduction zones, their high hydrothermal and magmatic sulfur outputs, and the enriched sulfur isotopic signatures (i.e., δ34S > 0‰) of these outputs. However, a quantitative understanding of the abundance and speciation of sulfur in slab fluids consistent with high pressure experiments is lacking. Here we analyze published experimental data for anhydrite solubility in H2O‐NaCl solutions to calibrate a high‐pressure aqueous speciation model of sulfur within the framework of the deep earth water model. We characterize aqueous complexes, required to account for the high experimental anhydrite solubilities. We then use this framework to predict the speciation and solubility of sulfur in chemically complex fluids in equilibrium with model subducting mafic and ultramafic lithologies, from 2 to 3 GPa and 400 to 800°C at log fO2 from FMQ‐2 to FMQ+4. We show that sulfate complexes of calcium and sodium markedly enhance the stability of sulfate in moderately oxidized fluids in equilibrium with pyrite at fO2 conditions of FMQ+1 to +2, causing large sulfur isotope fractionations up to 10‰ in the fluid relative to the slab. Such fluids could impart oxidized, sulfur‐rich and high δ34S signatures to the mantle wedge that are ultimately transferred to arc magmas, without the need to invoke 34S‐rich subducted lithologies. Plain Language Summary: Subducting oceanic plates (or "slabs") release aqueous fluids when subjected to high pressures and temperatures, driving the magmatism that produces volcanic arcs. These fluids carry high concentrations of solutes, and thus play an important role in the geologic cycling of elements. Sulfur is of particular interest, since the transfer of sulfur‐rich fluids could explain the oxidized nature of arc magmas, their often high sulfur concentrations, as well as their heavy sulfur isotope signatures (i.e., enriched in 34S relative to bulk Earth). However, there is conflicting evidence about sulfur's oxidation potential and the origin and significance of its isotopic enrichment. To address this problem, we need to understand which sulfur‐bearing chemical species are important at high pressures and temperatures relevant to subduction zone conditions. To do this, we analyzed high‐pressure experimental data, and found that they required the presence of aqueous species such as CaHSO4+ and Na2SO40, previously uncharacterized at high temperatures and pressures, in which sulfur is in its oxidized form. We further predict that these species would be important in natural subduction zone fluids and would carry enrichments in 34S, which can explain the enriched sulfur isotope signatures typically observed in arc volcanic rocks and gases. Key Points: We analyzed high pressure experimental solubility of anhydrite to calibrate the properties of aqueous S species in the Deep Earth Water modelWe provide a template for the solubility and speciation of S and other rock‐forming elements in a wide hypothetical range of subduction fluidsFluids in equilibrium with pyrite can be 34S‐rich relative to slabs due to high concentrations of sulfate complexes [ABSTRACT FROM AUTHOR]

Open‐Path Fourier‐Transform Infrared (OP‐FTIR) absorption spectroscopy is a powerful method for remote characterization of volcanic plume composition from safe distances. Many studies have used it to examine the composition of volcanic gas emitted at the surface, which is influenced by initial volatile contents and magma ascent/storage processes, and help to reveal the dynamics controlling surface activity. However, to evaluate the health hazard threats associated with volcanic emissions and their potential impact on wider atmospheric conditions, near‐source particle measurements are also key. Here we present a forward model and fitting algorithm which allows quantification of particle size and abundance. This was successfully applied to radiometrically uncalibrated OP‐FTIR spectra collected with a highly dynamic radiation source during the Fagradalsfjall eruption, Iceland, on 11 August 2021. Quantification of plume temperatures ranging from 350 to 650 K was essential to characterize the emission‐absorption behavior of SO2, enabling retrievals of particulate matter in the thermal infrared spectral window (750–1250 cm−1) in each spectrum. For the first time, we observe the rapid formation of primary aerosols in young plumes (only a few seconds old) with OP‐FTIR. Temperature‐dependent SO2/SO42− molar ratios range from 100 to 250, consistent with a primary formation mechanism controlled by cooling and entrainment of atmospheric gases. This novel aerosol spectrum retrieval opens new frontiers in field‐based measurements of sulfur partitioning and volcanic plume evolution, with the potential to improve volcano monitoring and quantification of air quality hazard assessments. Plain Language Summary: Open‐Path Fourier‐Transform Infrared (OP‐FTIR) spectroscopy is often used during volcanic eruptions to identify and quantify the amounts of different gases released during eruptions from a safe distance. This is important because gas compositions contain information about where magma came from and how it rose to the surface and erupted, and help us understand the impact of eruptions on air quality and climate. This paper presents a new way of analyzing spectra which allows us to quantify the amount and composition of aerosols, small droplets of water and other chemicals such as sulfuric acid. These aerosols can have important impacts on air quality and local climate, or even global climate in the case of large eruptions. We used this new approach during an eruption in 2021 on Iceland, pointing the instrument directly at the erupting vent, and were able to observe the formation of aerosols very close to their emission point, where they undergo rapid cooling. This is the first time we have been able to directly measure this aerosol formation process during an eruption. Our work opens new opportunities to re‐analyze older data to extract further insights and provides new opportunities to better understand the impacts of future eruptions. Key Points: We present a new method for retrieving water and sulfate aerosol column densities from Open‐Path Fourier‐Transform Infrared measurements of near‐source volcanic plumesTemperature‐dependent SO2/SO42− ratios range from 100 in colder plumes to 250 in hotter plumesThis method enables quantitative observation of primary aerosol formation in young plumes, a few seconds after emission [ABSTRACT FROM AUTHOR]

Lava flows have presented the greatest hazard to human property during the most recent eruptions of Hawaiian volcanoes, and lava fountains are a source of these lava flows. The height of Hawaiian lava fountains reflects the exsolved gas content of the magma that controls eruption intensity. However, fountain height is not always observed, so we sought a proxy to estimate fountain heights of eruptions that were older or otherwise unobserved. Here, methods are described to empirically derive a relationship between the modal diameter of vesicles within Pele's tears and spheres and lava fountain height, using samples of Pele's tears produced during the last eruptions of Kīlauea Iki (1959) and Mauna Ulu (1969). The tears used to develop these relationships were approximately 1 to 4 mm in diameter. Additionally, since lava fountains 50-580 m high were used, the relationships we describe may only describe lava fountains in this height range. The strongest empirical relation follows the trendline Hmax = -2575d + 820, where Hmax is maximum lava fountain height and d is modal vesicle diameter. This empirical relationship may be applied to sub-Strombolian eruptions of tholeiite basalt that were not directly measured or observed to assess long-term shifts in lava fountain heights and thus the exsolved gas contents of a volcanic system. While the same conceptual framework can be applied beyond Hawai'i, the quantitative empirical relation may be slightly different in different systems, depending on total dissolved volatiles, magma chemistry and other factors. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of sulfur dioxide (SO2) degassing is of primary importance for tracking temporal variations in volcanic activity. Here we introduce the novel "disk method," which aims at estimating the daily volcanic SO2 mass flux from satellite images (such as those provided by Sentinel‐5P/TROPOspheric Monitoring Instrument [TROPOMI]). The method calculates a "proto‐flux" using a regression, as a function of distance, of SO2 mass integrated in a series of nested circular domains centered on a volcano. After regression, a single multiplication by plume speed suffices to deduce the SO2 mass flux, without requiring a subsequent regression. This way, a range of plume speed and plume altitude scenarios can be easily explored. Noise level in the image is simultaneously evaluated by the regression, which allows for estimating posterior uncertainties on SO2 flux and improving the level of detection for weak sources in noisy environments. A statistical test is also introduced to automatically detect occurrences of volcanic degassing, lowering the risk of false positives. Application to multi‐year time‐series at Etna (2021) and Piton de la Fournaise (2021–2023) demonstrates (a) a reliable quantification of SO2 emissions across a broad range of degassing styles (from passive degassing to effusive or paroxysmal events), and (b) a reasonable day‐to‐day correlation between SO2 flux and seismic energy. The method is distributed as an open‐source software, and is implemented in an interactive web application within the "Volcano Space Observatory Portal," facilitating near‐real‐time exploitation of the TROPOMI archive for both volcano monitoring and assessment of volcanic atmospheric hazards. Plain Language Summary: Volcanic eruptions emit sulfur dioxide gas (SO2) into the atmosphere, which may cause harm to populations and the environment, and need to be monitored. Tracking volcanic emissions is also important for volcanologists to detect changes on a given volcano, and anticipate eruptions. SO2 can be observed by satellites every day, but exploitation of satellite imagery requires complex procedures. Wind speed is a crucial ingredient, but it is often poorly known, leading to large uncertainties in estimated SO2 emissions. Here, a simple algorithm is proposed for analyzing SO2 images provided by satellites. The mass of SO2 is extracted in an area surrounding a volcano (typically 500 km) to estimate the SO2 emission rate, as well as associated uncertainty. Plume speed information can be incorporated after running the algorithm, which facilitates testing different plume speed scenarios. Application to Etna and Piton de la Fournaise volcanoes shows that temporal variations of SO2 emissions follow the same pattern as seismic energy recorded by ground seismometers, which gives confidence in the results. The algorithm is made available to all as open‐source code and in an open‐access interactive web application "SO2 Flux Calculator" within the framework of the "Volcano Space Observatory Portal." Key Points: Daily volcanic SO2 flux is deduced from TROPOspheric Monitoring Instrument satellite imagery by mass‐to‐distance regression, including a noise estimation procedureSO2 emission rates at Etna, during episodes of passive, and eruptive degassing, demonstrate a good correlation with seismic energyThe algorithm is made available to all as an open‐source Python package and on the interactive web application "SO2 Flux Calculator" [ABSTRACT FROM AUTHOR]

​​​​​​​The 21 June 2019 Raikoke eruption (48° N, 153° E) generated one of the largest amounts of sulfur emission to the stratosphere since the 1991 Mt. Pinatubo eruption. Satellite measurements indicate a consensus best estimate of 1.5 Tg for the sulfur dioxide (SO 2) injected at an altitude of around 14–15 km. The peak Northern Hemisphere (NH) mean 525 nm stratospheric aerosol optical depth (SAOD) increased to 0.025, a factor of 3 higher than background levels. The Volcano Response (VolRes) initiative provided a platform for the community to share information about this eruption which significantly enhanced coordination efforts in the days after the eruption. A multi-platform satellite observation subgroup formed to prepare an initial report to present eruption parameters including SO 2 emissions and their vertical distribution for the modeling community. It allowed us to make the first estimate of what would be the peak in SAOD 1 week after the eruption using a simple volcanic aerosol model. In this retrospective analysis, we show that revised volcanic SO 2 injection profiles yield a higher peak injection of the SO 2 mass. This highlights difficulties in accurately representing the vertical distribution for moderate SO 2 explosive eruptions in the lowermost stratosphere due to limited vertical sensitivity of the current satellite sensors (± 2 km accuracy) and low horizontal resolution of lidar observations. We also show that the SO 2 lifetime initially assumed in the simple aerosol model was overestimated by 66 %, pointing to challenges for simple models to capture how the life cycle of volcanic gases and aerosols depends on the SO 2 injection magnitude, latitude, and height. Using a revised injection profile, modeling results indicate a peak NH monthly mean SAOD at 525 nm of 0.024, in excellent agreement with observations, associated with a global monthly mean radiative forcing of - 0.17 W m -2 resulting in an annual global mean surface temperature anomaly of - 0.028 K. Given the relatively small magnitude of the forcing, it is unlikely that the surface response can be dissociated from surface temperature variability. [ABSTRACT FROM AUTHOR]

Abstract Auckland city (pop. 1.7 M) is Aotearoa New Zealand’s largest city and an important economic hub. The city is built upon the active intraplate basaltic Auckland Volcanic Field (AVF). An AVF eruption would cause considerable impacts. An important component of volcanic risk management is assessing the likely volcanic hazards to help inform emergency planning and other preparedness activities. Previous volcanic hazard assessments for the AVF, particularly those for emergency planning scenarios, have modeled multiple volcanic hazards including lava flows, pyroclastic density currents, ballistic projectiles and tephra fall. Despite volcanic gas being an important and impactful hazard from intraplate basaltic field eruptions, there has been limited consideration of volcanic gas in AVF hazard assessment to date. This project is one of the first to quantitatively assess potential volcanic gas hazards for an explosive eruption scenario. For basaltic volcanism, sulfur dioxide (SO2) gas is typically the most consequential volcanic gas emitted. The aim of this exploratory study was to model SO2 dispersion from a high impact eruption during weather conditions conducive to high ground level pollutant concentrations. Since ground level SO2 concentrations are influenced by complex wind patterns resulting from interactions of locally driven flow circulations and topographically influenced weather, we modeled SO2 dispersion using the HYSPLIT model, a state-of-the art hybrid Eulerian and Lagrangian dispersion model widely used for volcanic gases, using high-resolution meteorological forcing fields given by the Weather Research and Forecasting (WRF) model. Modeled air parcel trajectories and ground level SO2 concentrations illustrate the effect of the converging sea breeze winds on SO2 dispersion. Under worst-case dispersion conditions, extensive areas of up to hundreds of square kilometers to the north and northwest of the eruption location would exceed New Zealand short-term (24 h) air quality standards and guidelines for SO2, indicating heightened health risks to downwind communities. Using this numerical modeling approach, this work presents a methodology for future applications to other AVF eruption scenarios, with a wider range of meteorological conditions that can help in exploring consequences for health services such as anticipated emergency department respiratory admissions.

The thermal activity of a magmatic–hydrothermal system commonly changes at various stages of volcanic activity. Few studies have provided an entire picture of the thermal activity of such a system over an eruptive cycle, which is essential for understanding the subsurface heat transport process that culminates in an eruption. This study quantitatively evaluated a sequence of thermal activity associated with two phreatic eruptions in 2021 at Aso volcano. We estimated plume-laden heat discharge rates and corresponding H2O flux during 2020–2022 by using two simple methods. We then validated the estimated H2O flux by comparison with volcanic gas monitoring results. Our results showed that the heat discharge rate varied substantially throughout the eruptive cycle. During the pre-eruptive quiescent period (June 2020–May 2021), anomalously large heat discharge (300–800 MW) were observed that were likely due to enhanced magma convection degassing. During the run-up period (June–October 2021), there was no evident change in heat discharge (300–500 MW), but this was accompanied by simultaneous pressurization and heating of an underlying hydrothermal system. These signals imply progress of partial sealing of the hydrothermal system. In the co-eruptive period, the subsequent heat supply from a magmatic region resulted in additional pressurization, which led to the first eruption (October 14, 2021). The heat discharge rates peaked (2000–4000 MW) the day before the second eruption (October 19, 2021), which was accompanied by sustained pressurization of the magma chamber that eventually resulted in a more explosive eruption. In the post-eruptive period, enhanced heat discharge (~ 1000 MW) continued for four months, and finally returned to the background level of the quiescent period (< 300 MW) in early March 2022. Despite using simple models, we quantitatively tracked transient thermal activity and revealed the underlying heat transport processes throughout the Aso 2021 eruptive activity. [ABSTRACT FROM AUTHOR]

At many dormant volcanoes, magmatic gases are not channeled through preferential degassing routes as fumaroles and only percolate through the flanks of the volcano in a diffuse way. This type of volcanic gas emission provides valuable information, even though the soil matrix contains an important atmospheric component. This study aimed to demonstrate that chemical ratios such as He/CO2 in soil gases provide excellent information on the evolution of volcanic unrest episodes and help forecast the volcanic eruption onset. Before and during the occurrence of the October 2011–March 2012 submarine of El Hierro, Canary Islands, more than 8500 soil He analyses and diffuse CO2 emission measurements were performed. The results show that the soil He/CO2 emission ratio began increasing drastically one month before eruption onset, reaching the maximum value 10 days before. During the eruptive period, this ratio also showed a maximum value several days before the period with the highest magma emission rate. The He/CO2 ratio was also helpful in forecasting the eruption onset. We demonstrate that this tool can be applied in real-time during volcanic emergencies. Our results also encourage a reevaluation of the global He emission from the subaerial volcanism. [ABSTRACT FROM AUTHOR]

Giant impacts can generate transient hydrogen-rich atmospheres, reducing atmospheric carbon. The reduced carbon will form hazes that rain out onto the surface and can become incorporated into the crust. Once heated, a large fraction of the carbon is converted into graphite. The result is that local regions of the Hadean crust were plausibly saturated with graphite. We explore the consequences of such a crust for a prebiotic surface hydrothermal vent scenario. We model a surface vent fed by nitrogen-rich volcanic gas from high-temperature magmas passing through graphite-saturated crust. We consider this occurring at pressures of 1– 1000 bar and temperatures of 1500– 1700   ∘ C . The equilibrium with graphite purifies the leftover gas, resulting in substantial quantities of nitriles ( 0.1 % HCN and 1 ppm HC3N) and isonitriles ( 0.01 % HNC) relevant for prebiotic chemistry. We use these results to predict gas-phase concentrations of methyl isocyanide of ∼1 ppm. Methyl isocyanide can participate in the non-enzymatic activation and ligation of the monomeric building blocks of life, and surface or shallow hydrothermal environments provide its only known equilibrium geochemical source. [ABSTRACT FROM AUTHOR]

This work reviews possible signatures and potential detectability of present-day volcanically emitted material in the atmosphere of Venus. We first discuss the expected composition of volcanic gases at present time, addressing how this is related to mantle composition and atmospheric pressure. Sulfur dioxide, often used as a marker of volcanic activity in Earth's atmosphere, has been observed since late 1970s to exhibit variability at the Venus' cloud tops at time scales from hours to decades; however, this variability may be associated with solely atmospheric processes. Water vapor is identified as a particularly valuable tracer for volcanic plumes because it can be mapped from orbit at three different tropospheric altitude ranges, and because of its apparent low background variability. We note that volcanic gas plumes could be either enhanced or depleted in water vapor compared to the background atmosphere, depending on magmatic volatile composition. Non-gaseous components of volcanic plumes, such as ash grains and/or cloud aerosol particles, are another investigation target of orbital and in situ measurements. We discuss expectations of in situ and remote measurements of volcanic plumes in the atmosphere with particular focus on the upcoming DAVINCI, EnVision and VERITAS missions, as well as possible future missions. [ABSTRACT FROM AUTHOR]

Continuous monitoring of volcanic gas emissions is crucial for understanding volcanic activity and potential eruptions. However, emissions of volcanic gases underwater are infrequently studied or quantified. This study explores the potential of Distributed Acoustic Sensing (DAS) technology to monitor underwater volcanic degassing. DAS converts fiber-optic cables into high-resolution vibration recording arrays, providing measurements at unprecedented spatio-temporal resolution. We conducted an experiment at Laacher See volcano in Germany, immersing a fiber-optic cable in the lake and interrogating it with a DAS system. We detected and analyzed numerous acoustic signals that we associated with bubble emissions in different lake areas. Three types of text-book bubbles exhibiting characteristic waveforms are all found from our detections, indicating different nucleation processes and bubble sizes. Using clustering algorithms, we classified bubble events into four distinct clusters based on their temporal and spectral characteristics. The temporal distribution of the events provided insights into the evolution of gas seepage patterns. This technology has the potential to revolutionize underwater degassing monitoring and provide valuable information for studying volcanic processes and estimating gas emissions. Furthermore, DAS can be applied to other applications, such as monitoring underwater carbon capture and storage operations or methane leaks associated with climate change. [ABSTRACT FROM AUTHOR]

Carbonate sediments transported into the mantle at subduction zone settings account for the majority of the carbon flux into the Earth's interior and are thus critical to the deep carbon cycle. Understanding carbon storage volumes in the deep earth requires knowledge of the degree to which carbonate sediments are stored in the arc lithosphere or descend to the deep mantle. Here, we use petrological‐thermomechanical modeling to indicate that solid‐state diapirs dominate the removal of carbon from subducting plates, which may be the principal carbon‐release mechanism for the Cyclades (Greece) and Costa Rican forearcs. We find that forearc diapirs remove up to ∼80% of subducting carbon and develop diagonally upward, resulting in massive carbon storage in the subarc lithosphere. Outgassing from the carbon storage may cause high carbon outputs and explain volcanic gas with high δ13C at some subduction zones, affecting atmospheric CO2 concentration. Plain Language Summary: Whereas many concepted models for the fate of subducting carbon, mainly from the sedimentary carbonates, have been proposed, it remains unclear to which extend these ideas are consistent with carbon balance between the shallow and deep reservoirs. The dynamic processes by which carbon release from subducting sediments and the transit into the shallow reservoirs above subarc depths remain largely unanswered. In this study, we account for metamorphic decarbonation and coupled with thermomechanical models, to investigate the dynamics of subducting sediments and associated carbon flux. Results show that solid‐state diapirs formed in the forearc remove substantial amounts of sedimentary carbon, which are much more than that via subarc diapirs and metamorphic reactions, and indicate that they dominate the carbon release from subducting sediments. The massive carbon stored in the overlying lithosphere reservoir is formed via the diagonal transport of forearc diapirs provided that a thick sediment, a young oceanic plate, and slow convergence are present. We argue that the remobilization of sedimentary carbon in the subarc lithosphere can provide an efficient mechanism for the abnormally high decarbonation efficiency of the volcanism in subduction zones, therefore regulating the Earth's climate. Key Points: We conduct 2D petrological‐thermomechanical models to explore the sediment subduction and recycling in subduction zonesYoung oceanic plates, slow convergence rates, and thick sediments promote forearc diapirs and cause high decarbonation efficiencyForearc diapirs dominate removal of carbon from the subducting plate and reduce the proportion of the carbon released at subarc depths [ABSTRACT FROM AUTHOR]

Arc volcanoes are significant natural sources of trace chalcophile elements to the atmosphere via gas and aerosol plumes. Villarrica volcano, part of the Andean arc, erupts basaltic magmas and is characterised by a persistent volcanic gas plume and therefore presents an opportunity to quantify volcanic chalcophile processing in a subduction zone from slab to surface. Here we present geochemical data for olivine-hosted melt inclusions, as well as for the gas and aerosol plume. We show that melts erupted at Villarrica are enriched (over mid-ocean ridge basalts) in a suite of fluid-mobile elements comprising the large ion lithophiles, including Cs, and chalcophile elements W, Tl, Pb and Sb. Volcanic gas and aerosol samples show that the chalcophile elements, and Cs, are strongly enriched in the gas phase over the silicate melt, 103 to 106 times more so than the non-volatile Rare Earth Elements. Volatilities (the percentage of an element that degasses from a melt on eruption) reach ∼ 45 % for Tl, with Pb, Sn and Mo exhibiting volatilities of up to 0.3 % and Cu up to 0.08 %. Many of the chalcophile elements (e.g. Cu, Ag, Zn) have an affinity for chloride in the gas phase and we observe that the volatility of chloride-speciating trace metals is linked strongly to the availability of chlorine in volcanic plumes globally. Overall, we show that the trace element composition of the volcanic gas—and hence probably also the deeper, denser and more saline fluids in the subsurface—is sensitive to both the availability of chloride in the gas phase and the composition of the melt, which is controlled by the slab flux and may be variable between subduction zones. [ABSTRACT FROM AUTHOR]

To monitor the volcanoes at a high spatiotemporal resolution, we introduce the singular value decomposition‐based Wiener filter and the three‐component waveforms in ambient noise velocity monitoring. The continuous ambient noise data from 63 stations around Mt. Fuji and Mt. Hakone, Japan, during the January‐September 2011 were analyzed to estimate the seismic velocity variations at a 1‐day temporal resolution, allowing us to distinguish the velocity drops caused by the 2011 Mw 9.0 Tohoku‐oki and the Mw 6.0 East Shizuoka earthquake. The velocity drop during the Tohoku‐oki earthquake was large in volcanic areas and was larger around Mt. Hakone than Mt. Fuji. This difference is possibly due to the existence of fluid‐ and gas‐rich zones at shallower depths and a higher crack density around Mt. Hakone. In addition, the velocity drop at Mt. Fuji during the Tohoku‐oki and the East Shizuoka earthquake was the same level, despite larger static stress changes beneath Mt. Fuji during the East Shizuoka earthquake. We interpret this inconsistency between the velocity drops and static stress changes to arise from incomplete recovery of the generated cracks during the Tohoku‐oki earthquake when the East Shizuoka earthquake occurred. This study also investigates the spatial variations in recovery speed and recovery amount, finding slow recovery speeds in the volcanic areas and fault areas, possibly due to larger crack densities in the crust. Furthermore, we observe the lowest velocity recovery amount in the volcanic areas, which is likely attributed to the maintained increase in pore pressure due to the volcanic gas bubbles. Plain Language Summary: Ambient noise monitoring is a useful tool to estimate the dynamic behaviors of subsurface conditions, such as crustal stress and pore pressure. In recent years, this monitoring technique has been applied to volcanic eruption prediction, however, the temporal resolution is about 5 or 10 days, which is still insufficient for volcanic eruption prediction. Therefore, we introduce denoising techniques with combination of singular value decomposition and Wiener filter to stably estimate the velocity change in high temporal resolution. As a result, we are able to estimate velocity changes with 1‐day temporal resolution and distinguish the velocity changes caused by the 2011 Mw 9.0 Tohoku earthquake and the Mw 6.0 East Shizuoka earthquake that occurred 4 days after the Tohoku earthquake. The high temporal resolution of this monitoring approach could contribute to volcano monitoring systems, particularly through providing additional information on the state of the volcanic system. Moreover, we model the velocity changes and estimate the spatial variation of recovery speed and recovery amount, which is important to predict the postseimic recovery of velocity changes. We found slow recovery speed in volcanic areas and fault areas, and small recovery amount in volcanic areas. Key Points: Ambient noise monitoring with high temporal resolution (1 day) was applied to volcanic areas (Mt. Fuji and Hakone area)Slow velocity recovery speeds in the volcanic areas and fault areas, possibly due to larger crack densities in the crustThe lowest velocity recovery amount in the volcanic areas could attribute to the maintained high pore pressure due to the volcanic gas [ABSTRACT FROM AUTHOR]

This study combines volcanic gas compositions, SO2 flux and satellite thermal data collected at Nevado del Ruiz between 2018 and 2021. We find the Nevado del Ruiz plume to have exhibited relatively steady, high CO2 compositions (avg. CO2/ST ratios of 5.4 ± 1.9) throughout. Our degassing models support that the CO2/ST ratio variability derives from volatile exsolution from andesitic magma stored in the 1–4 km depth range. Separate ascent of CO2-rich gas bubbles through shallow (< 1 km depth), viscous, conduit resident magma causes the observed excess degassing. We infer that degassing of ~ 974 mm3 of shallow (1–4 km) stored magma has sourced the elevated SO2 degassing recorded during 2018–2021 (average flux ~ 1548 t/d). Of this, only < 1 mm3 of magma have been erupted through dome extrusion, highlighting a large imbalance between erupted and degassed magma. Escalating deep CO2 gas flushing, combined with the disruption of passive degassing, through sudden accumulation and pressurization of bubbles due to lithostatic pressure, may accelerate volcanic unrest and eventually lead to a major eruption. [ABSTRACT FROM AUTHOR]

Active volcanoes often discharge hot (T ≫ 100 °C) magmatic gases whose original composition has been modified through partial interaction with an externally fed hydrothermal system. The study of methane (CH 4) in these volcanic discharges may provide useful information on the interplay between deep magmatic gases and shallow circulation of hydrothermal fluids. However, the origin of CH 4 in high-temperature volcanic gases and the factors exerting control on its abundance and stable isotope composition are still largely unknown. Here, we present the abundances and stable isotopic composition of CH 4 in hot (99–387 °C) volcanic gases from the La Fossa volcanic crater of Vulcano Island (Southern Italy). Our investigation revealed low (<1.5 μmol/mol) CH 4 concentrations and an extraordinarily large variability in CH 4 stable isotopic composition, with δ13C and δ2H values being positively correlated and varying from −35 to −9.2 ‰ and −670 to −102 ‰, respectively. Notably, CH 4 isotopes measured at Vulcano almost encompasses the global-scale variability observed in natural fluids, with δ2H values ≤ −500 ‰ being the first ever reported in nature. Gases showing extremely negative δ13C-CH 4 and δ2H-CH 4 values systematically display higher CH 4 abundances. We propose two possible scenarios in order to explain the observed huge variation in δ13C and δ2H: (1) mixing of 13C- and 2H-depleted CH 4 with 13C- and 2H-enriched CH 4 of thermogenic origin formed under hydrothermal conditions; (2) post-genetic removal and isotopic alteration of 13C- and 2H-depleted CH 4 occurring during the ascent of volcanic gases. Comparing our dataset with available isotopic data from naturally occurring and artificially produced CH 4 , a thermogenic origin for the isotopically light CH 4 seems unlikely. We postulate that the 13C- and 2H-depleted CH 4 may have formed via kinetically-controlled abiotic synthesis through CO (or CO 2) hydrogenation reactions in the hot ascending gas phase, possibly at temperatures intermediate between those typical of magmatic and hydrothermal conditions. Further investigations of methane in high-temperature volcanic gases are necessary to test this hypothesis. [ABSTRACT FROM AUTHOR]

Băile Lăzărești, located 16 km north-east from Băile Tușnad, is a representative area for post-volcanic regions where gases emitted at the surface contain over 85% carbon dioxide. Nineteen stations were set up for collecting soil samples for analysis of heavy metals, TOC, carbonates, and lithology and four water stations for nutrient analysis in July and August 2022. The impact of increased CO2 emissions on the soil is evident through the exceeding normal concentrations of heavy metals such as Cr, Cu, Hg, and Ni in areas with high CO2 emissions and their reduction in areas with lower volcanic gas emissions. Water sample analysis, all with high CO2 concentrations, showed elevated levels of nitrites, inorganic phosphorus, and sulphates, classifying the water quality into categories II and III, according to national classification. The impact of high CO2 concentrations is clearly visible in the vegetation, which is absent at CO2 concentrations above 20%, predominantly consists of grasses, and shows distinct colorations at concentrations below 20%. These observed and analysed elements could serve as surface indicators for potential CO2 leaks from anthropogenic storage sites. [ABSTRACT FROM AUTHOR]

This article presents the results of a comparative analysis of the isotopic–geochemical composition of gases from igneous/hydrothermal and sedimentary volcanic systems in various regions of the world based on a large amount of literature data and the results of the author's own research. The purpose of the study is to evaluate the nature of gases of various volcanic systems using known genetic criteria developed as a result of many years of research by a number of scientists from around the world. Data processing for the purpose of comparative analysis and corresponding graphical constructions have been performed using standard computer programs. A comprehensive analysis of the isotopic composition of carbon-rich gases and the isotopic ratio of helium (R/Ra) allows us to draw the following main conclusions: (1) hydrocarbon (HC) gases of the studied volcanic systems have different genetic sources: (a) abiogenic in igneous and carbonic sedimentary volcanic systems, (b) predominantly abiogenic–biogenic in the hydrothermal system, and (c) biogenic (thermogenic–microbial) in sedimentary volcanoes; (2) the content of abiogenic methane in the magmatic/hydrothermal system is insignificant and does not exceed 1%; (3) the isotope composition of CO2 and the ratio of isotopes of radiogenic and air argon (40Ar/36Ar) in igneous volcanoes varies within very narrow limits when compared with sedimentary volcanoes. However, the use of these parameters as an unambiguous genetic criterion is not possible. [ABSTRACT FROM AUTHOR]

This article provides an overview of the use of remote sensing technology to monitor and study volcanic emissions. It explains the use of Differential Optical Absorption Spectroscopy (DOAS) to measure the concentration of sulfur dioxide (SO2) gas in volcanic plumes. The article emphasizes the importance of technological advancements and interdisciplinary research in improving our understanding of volcanism and its impact on the atmosphere. However, it also cautions that seasonal snow cover can potentially lead to overestimations of SO2 emissions. Overall, this article offers valuable insights into the role of remote sensing in volcano monitoring and research. [Extracted from the article]

Volcanic activity and the associated gas emissions into the atmosphere often result in adverse air quality conditions and present a hazard to human health and the environment. Building on a decade‐long effort to provide operational surface sulfur dioxide and sulfate aerosol forecasts for the State of Hawai'i, we present an air quality modeling framework called VogCast. VogCast is designed to simplify ensemble air quality prediction on a regional scale by linking together multiple state‐of‐the‐art models of meteorology, emissions, and dispersion. The framework is open‐source and introduces a new dynamic plume‐rise algorithm for distributing pollutants vertically. Using radar and satellite data, we demonstrate that VogCast reasonably captured the mean injection height, the location, and the general envelope of the vog plume during Mauna Loa's 2022 eruption. The results suggest that during the 12‐day eruption period model performance varied between days with trade and non‐trade wind conditions. Our findings also highlight the importance of sulfur dioxide emission rate and vent parameter inputs for improving forecast accuracy. The broad goal of this work is to better our understanding of vog dispersion and improve air quality prediction for impacted communities. Plain Language Summary: Volcanic activity often results in poor air quality for communities downwind of active eruptions. In Hawai'i, forecasts of volcanic air pollution (vog) are used to provide early warning and help reduce negative impacts from vog exposure. In this paper, we introduce a new air quality modeling framework called VogCast designed to simplify and improve the accuracy of existing surface air quality forecasts in Hawai'i. We use radar and satellite data to assess the ability of VogCast to capture vog dispersion during the 2022 Mauna Loa eruption. Our findings suggest VogCast is able to reasonably predict the height and general location of the vog plume. We also show that both volcanic gas emission rates and meteorology have a strong impact on model performance. The broad goal of this work is to better our understanding of vog dispersion and improve air quality prediction for impacted communities. Key Points: VogCast is a Python‐based modular open‐source air quality modeling framework for volcanic gas emissionsVogCast incorporates a dynamic plume‐rise scheme for estimating plume injection heightComparison with remotely sensed data from 2022 Mauna Loa eruption suggests VogCast is able to accurately capture regional‐scale vog dispersion [ABSTRACT FROM AUTHOR]

Lava fountains are a common manifestation of basaltic volcanism. While magma degassing plays a clear key role in their generation, the controls on their duration and intermittency are only partially understood, not least due to the challenges of measuring the most abundant gases, H2O and CO2. The 2021 Fagradalsfjall eruption in Iceland included a six-week episode of uncommonly periodic lava fountaining, featuring ~ 100–400 m high fountains lasting a few minutes followed by repose intervals of comparable duration. Exceptional conditions on 5 May 2021 permitted close-range (~300 m), highly time-resolved (every ~ 2 s) spectroscopic measurement of emitted gases during 16 fountain-repose cycles. The observed proportions of major and minor gas molecular species (including H2O, CO2, SO2, HCl, HF and CO) reveal a stage of CO2 degassing in the upper crust during magma ascent, followed by further gas-liquid separation at very shallow depths (~100 m). We explain the pulsatory lava fountaining as the result of pressure cycles within a shallow magma-filled cavity. The degassing at Fagradalsfjall and our explanatory model throw light on the wide spectrum of terrestrial lava fountaining and the subsurface cavities associated with basaltic vents. This study of volcanic gas chemistry during pulsatory lava fountaining at Fagradalsfjall volcano in Iceland reveals that the intermittency stems from pressure cycles and gas-melt separation within a shallow magma-filled cavity. [ABSTRACT FROM AUTHOR]

Pyroclastic density currents (PDCs) are hazardous, multiphase currents of heterogeneous volcanic material and gas. Moisture (as liquid or gas) can enter a PDC through external (e.g., interaction with bodies of water) or internal (e.g., initial eruptive activity style) processes, and the presence of moisture can be recorded within distinct deposit layers. We use analogue experiments to explore the behaviour of pyroclastic material with increasing addition of moisture from 0.00–10.00% wt. Our results show that (1) the cohesivity of pyroclastic material changes with the addition of small amounts of moisture, (2) small increases in moisture content change the material properties from a free-flowing material to a non-flowable material, (3) changes in moisture can affect the formation of gas escape structures and fluidisation profiles in pyroclastic material, (4) gas flow through a deposit can lead to a moisture profile and resulting mechanical heterogeneity within the deposit and (5) where gas escape structure growth is hindered by cohesivity driven by moisture, pressure can increase and release in an explosive fashion. This work highlights how a suite of varied gas escape morphologies can form within pyroclastic deposits resulting from moisture content heterogeneity, explaining variation in gas escape structures as well as providing a potential mechanism for secondary explosions. [ABSTRACT FROM AUTHOR]

Over the past decade, we have conducted geochemical and isotopic monitoring of the fumarolic gases of the Peteroa volcano (Argentina‐Chile). Using the resulting data set, we constructed a conceptual model that describes the evolution of the magmatic‐hydrothermal system and identifies precursory geochemical signals of the last eruption. Our data set includes new chemical and isotopic analyses of fumarolic gas samples collected from 2016 to 2021, as well as previously published data from the 2010–2015 period. After an eruptive period in 2010–2011, the activity was characterized by low degassing rates and seismic activity. However, an increase in seismic activity and fumarolic gas emissions was observed from 2016 to 2018–2019 eruptive episode, leading to a major phreato‐magmatic eruption. Fumarole gases show different compositions during quiescent versus unrest/eruptive degassing related to the interaction of deep (magmatic) and shallow (hydrothermal) fluid contributions. During quiescent periods, fumaroles exhibited low SO2/H2S, HF/CO2, and HCl/CO2 ratios (<0.1), revealing a dominant hydrothermal contribution. In contrast, during pre‐and syn‐eruptive periods, fumaroles showed ratios up to 100 times higher indicative of an enhanced magmatic input. When compared to the evolution of the seismic activity, the increment of magmatic‐related strong acidic gases suggests repeated inputs of hot magmatic fluids, which are only partially dissolved into the hydrothermal system feeding the fumaroles. Interestingly, the 3He/4He and δ13C‐CO2 values remained relatively constant during the magmatic and hydrothermal degassing in 2016–2021, suggesting that the deep magmatic gas source did not significantly change throughout variations in Peteroa's activity.Plain Language Summary: The Peteroa volcano is an active volcano located in the southern Andes Mountains of South America. It has erupted multiple times in recent years, but there is limited knowledge about its behavior and potential damage it could cause. To address this, we have been studying the volcano for the past decade using special techniques to examine the gases that come out of the openings in the ground, known as fumaroles. These fumaroles allow volcanic gases to escape, and by collecting data on fumarolic gas samples from 2010 to 2021, we have developed a model that helps us understand how the volcano changes over time and identify warning signs of an upcoming eruption. Our research found increased seismic activity and fumarolic gas emissions starting in 2016, leading to a significant eruption from 2018 to 2019. We also discovered that the composition of the fumarolic gases varies depending on whether the volcano is in a quiet or unrest period. During quiet periods, the gases show compositions with a stronger influence from underground water, but before and during the 2018–2019 eruption, the gas compositions showed changes indicating a more significant influence of magma. This study is vital as it enhances our understanding of volcano behavior and provides valuable insights for forecasting future eruptions. This is particularly important in the region as there are many potentially dangerous volcanoes with limited available information, but the findings can be applied to improve our understanding of other volcanoes, ultimately contributing to the global knowledge base on volcanic processes.Key Points: Geochemical and isotopic monitoring of Peteroa volcano allowed us to elaborate a conceptual model that explains the evolution of the magmatic‐hydrothermal systemFumarolic gases exhibit different compositions during quiescent and unrest/eruptive periods, allowing the identification of precursory signals of the last eruptionDespite variations in activity, the deep magmatic gas source of Peteroa volcano remained relatively constant, as indicated by consistent He and C isotopic values [ABSTRACT FROM AUTHOR]

Hydrogen (H$_{2}$) and hydrogen sulphide (H$_{2}$S) are typically present at only minor to trace levels in volcanic gas emissions, and yet they occupy a key role in volcanic degassing research in view of the control they exert on volcanic gas reducing capacity (e.g., their ability to remove atmospheric O$_{2}$). In combination with other major compounds, H$_{2}$ and H$_{2}$S are also key to extracting information on source magma conditions (temperature and redox) from observed magmatic gas compositions. Here, we use a catalogue, compiled by extracting from the geological literature a selection of representative analyses of magmatic to mixed (magmatic–hydrothermal) gases, to review the processes that control H$_{2}$ and H$_{2}$S abundance in volcanic gases. We show that H$_{2}$ concentrations and H$_{2}$/H$_{2}$O ratios in volcanic gases both exhibit strong positive temperature dependences, while H$_{2}$S concentrations and H$_{2}$S/SO$_{2}$ ratios are temperature insensitive overall. The high H$_{2}$ concentrations (and low H$_{2}$S/SO$_{2}$ compositions, of ${\sim }$0.1 on average) in high-temperature (${>}$1000 °C) magmatic gases are overall consistent with those predicted thermodynamically assuming external redox buffering operated by the coexisting silicate melt, at oxygen fugacities ranging from ${\Delta }$FMQ $-$1 to 0 (non-arc volcanoes) to ${\Delta }$FMQ 0 to ${+}$2 (arc volcanoes) (where ${\Delta }$FMQ is oxygen fugacity expresses as a log unit difference relative to the Fayalite–Magnetite–Quartz oxygen fugacity buffer). Lower temperature (${

This short report introduces one of the ways to quickly and accurately aim melt inclusions in phenocryst using NanoSIMS. [ABSTRACT FROM AUTHOR]

Abstract Over the past decade, we have conducted geochemical and isotopic monitoring of the fumarolic gases of the Peteroa volcano (Argentina‐Chile). Using the resulting data set, we constructed a conceptual model that describes the evolution of the magmatic‐hydrothermal system and identifies precursory geochemical signals of the last eruption. Our data set includes new chemical and isotopic analyses of fumarolic gas samples collected from 2016 to 2021, as well as previously published data from the 2010–2015 period. After an eruptive period in 2010–2011, the activity was characterized by low degassing rates and seismic activity. However, an increase in seismic activity and fumarolic gas emissions was observed from 2016 to 2018–2019 eruptive episode, leading to a major phreato‐magmatic eruption. Fumarole gases show different compositions during quiescent versus unrest/eruptive degassing related to the interaction of deep (magmatic) and shallow (hydrothermal) fluid contributions. During quiescent periods, fumaroles exhibited low SO2/H2S, HF/CO2, and HCl/CO2 ratios (

During a volcanic eruption, copious amounts of volcanic gas, aerosol droplets, and ash are released into the stratosphere, potentially impacting radiative feedback. One of the most significant volcanic gases emitted is sulphur dioxide, which can travel long distances and impact regions far from the source. This study aimed to investigate the transport of sulphur dioxide and sulphate aerosols from the Tonga volcanic eruption event, which occurred from the 13th to the 15th of January 2022. Various datasets, including Sentinel-5 Precursor (TROPOMI), the Ozone Monitoring Instrument (OMI), and the Ozone Mapping and Profiler Suite (OMPS), were utilized to observe the transport of these constituents. The TROPOMI data revealed westward-traveling SO2 plumes over Australia and the Indian Ocean towards Africa, eventually reaching the Republic of South Africa (RSA), as confirmed by ground-based monitoring stations of the South African Air Quality Information System (SAAQIS). Moreover, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) demonstrated sulphate aerosols at heights ranging from 18 to 28 km with a plume thickness of 1 to 4 km. The results of this study demonstrate that multiple remote sensing datasets can effectively investigate the dispersion and long-range transport of volcanic constituents. [ABSTRACT FROM AUTHOR]

The eruptions of Eyjafjallajökull volcano in 2010 (including its initial effusive phase at Fimmvörðuháls and its later explosive phase from the central volcano) and Bárðarbunga volcano in 2014–2015 (at Holuhraun) were widely reported. Here, we report on complementary, interdisciplinary observations made of the eruptive gases and lavas that shed light on the processes and atmospheric impacts of the eruptions, and afford an intercomparison of contrasting eruptive styles and hazards. We find that (i) consistent with other authors, there are substantial differences in the gas composition between the eruptions; namely that the deeper stored Eyjafjallajökull magmas led to greater enrichment in Cl relative to S; (ii) lava field SO2 degassing was measured to be 5–20% of the total emissions during Holuhraun, and the lava emissions were enriched in Cl at both fissure eruptions—particularly Fimmvörðuháls; and (iii) BrO is produced in Icelandic plumes in spite of the low UV levels. [ABSTRACT FROM AUTHOR]

We quantified the redox state of magma recorded in volcanic glass particles from an ash-forming eruption at Bromo volcano, Indonesia, to obtain insights into its degassing process. An ash sample was collected by real-time sampling from the ash-forming eruption on 24 March 2011. The ash sample contains juvenile glass particles with a brown-colored, transparent appearance. Detailed observations of texture under a field-emission–electron probe micro analyzer show that the brown glasses lack nanoscale crystals in their groundmass. The compositions of groundmass glass (trachy-andesite) and phenocrysts in the brown glass particles indicate a pre-eruptive magma temperature of 1060 ± 20 °C. The Fe3+/ΣFe ratios of the brown glasses were determined to be 0.15–0.24 using synchrotron-based Fe–K edge micro X-ray absorption near-edge structure spectroscopy. From the chemical composition, temperature, and Fe3+/ΣFe data, the oxygen fugacity of the magma is estimated to be in the range of 10−10.3 to 10−8.9, yielding a redox state of ΔQFM = 0.57 ± 0.70. The redox state of magma estimated from the brown glasses is more reduced than that of volcanic gas emitted during the open-vent degassing phase (~ 700 °C and ΔQFM of 1.8). The low temperature and oxidized condition of the volcanic gas can be explained by closed-system cooling from 1060 to 700 °C in the gas phase after outgassing, suggesting that the magma head was located deeper during the open-vent degassing phase than during the ash-forming eruption. The comparison between the redox states of volcanic glass and gas reported in this study gives valuable insights into the degassing process driving volcanic activity. [ABSTRACT FROM AUTHOR]

The La Fossa volcano is near the inhabited zone of the island of Vulcano and is a suitable case for studying gas sources of different geological origins. Since the last eruption, fumarolic-solfataric activity has interested this area with fumarolic emissions, mainly at the top of the volcanic cone and at Vulcano Porto. In recent decades, the anomalous degassing zones on the island have not significantly changed their location. On the contrary, there have been several significant changes in the emission rate due to the addition of volcanic gas. In these zones, CO2 flux from the ground is responsible for a decrease in the indoor air quality. A recent increase in volcanic degassing led to an increase in the gas hazard in the inhabited area of Vulcano Island, and people were temporarily displaced from Vulcano Porto. The results of this study show that a monitoring system can be used for the early detection of transients in soil CO2 flux (φCO2) in the anomalous degassing zone of Vulcano. Synchronous monitoring of φCO2 and outdoor air CO2 concentration has shown variations in volcanic degassing that affect outdoor air CO2 concentration in the populated zone of Faraglione. [ABSTRACT FROM AUTHOR]

A pyroclastic density current (PDC) is characterized by its strong stratification of particle concentration; it consists of upper dilute and lower dense currents, which generally control the dynamics and deposits of PDCs, respectively. To explain the relationship between the dynamics and deposits for magmatic and phreatomagmatic eruptions in a unified way, we developed a two‐layer PDC model considering thermal energy conservation for mixing of pyroclasts, external water, and air. The results show that the run‐out distance of dilute currents increases with the mass fraction of external water at the source (wmw) owing to the suppression of thermal expansion of entrained air. For wmw ∼ 0.07–0.38, the particle concentration in the dilute current becomes too low to generate the dense current so that the deposits directly form at the bottom of the dilute current in the entire area. These results capture the diverse features of natural PDCs in magmatic and phreatomagmatic eruptions. Plain Language Summary: Explosive volcanic eruptions eject mixtures of hot fragmented magma and gas from the volcanic vent and form eruption columns, which can collapse and propagate along the ground surface as pyroclastic density currents (PDCs). The dynamics and deposits of PDCs are extremely diverse depending on the amount of external water (e.g., groundwater, lakes, and oceans) that mixes with magma. To explain the diverse features of the dynamics and deposits of PDCs for various amounts of external water, we developed a two‐layer model for PDCs considering thermal energy conservation for mixing of magma and external water. The two‐layer model successfully reproduces the dynamics and deposits of PDCs with strong stratification of particle concentrations in a unified way. The results show that the run‐out distance of upper dilute currents increases with the increasing amount of external water. For a relatively small proportion of external water, the lower dense current tends to be absent, resulting in the direct formation of the deposits from the dilute current in the entire area. These model predictions are useful to mitigate the diverse hazards caused by natural PDCs under various geological conditions. Key Points: A two‐layer pyroclastic density current model with heat conservation for mixing of pyroclasts, external water, and air is developedIn phreatomagmatic eruptions, the upper dilute current flows over longer distances and the lower dense current tends to be absentOur results explain the diverse features of the dynamics and deposits of natural pyroclastic density currents in a unified way [ABSTRACT FROM AUTHOR]

Shear thinning and brittle failure of silicate melt control the dynamics of volcanic eruptions, but their molecular‐scale origin is still unclear. Here, we conducted tension and compression experiments on silicate melts, using time‐resolved X‐ray diffraction. Our experiments revealed that the intermediate‐range ordering of silicate structures, that is, the ring size formed by the SiO4 tetrahedra, demonstrated elastic and anisotropic dilation under tension and shrinkage under compression in the non‐Newtonian regime. In contrast, there were no significant changes in short‐range ordering, such as Si–O and Si–Si distances. Based on these findings, we inferred that shear thinning observed under high stress originates from the formation of anisotropically deformed large and small rings in silicate structures that are energetically unfavorable and unstable. Brittle failure occurred under high‐stress conditions, in both tension and compression. We propose a stress criterion as a necessary and sufficient condition for magma failure, rather than a strain rate criterion. Plain Language Summary: Explosive volcanic eruptions occur when magma fragments and volcanic gases are released to the surface. However, magma is originally a continuous fluid that behaves like a liquid in the crust. To understand how magma fails during volcanic eruptions, we need to uncover the underlying mechanisms. This challenge was identified over four decades ago, and researchers proposed conducting molecular‐scale experiments on magma deformation to shed light on its complex behavior, including brittle failure. However, this has been difficult to achieve experimentally. In this study, we used powerful X‐ray sources at SPring‐8 in Japan to address this challenge. Our findings reveal that the complex behavior of magma originates from previously unrecognized molecular‐scale elastic and anisotropic deformation. Finally, we propose a criterion for magma failure that can help determine whether an eruption will be explosive. Key Points: Molecular‐scale elastic and anisotropic deformation of the silicate melt was observed under tension (dilation) and compression (shrinkage)Formation of large and small rings by the SiO4 tetrahedra could be the origin of shear thinning and brittle failure in the silicate meltStress condition is "the necessary and sufficient condition" for the magma failure criterion [ABSTRACT FROM AUTHOR]

Injecting volcanic gas into the air leads to an increase in carbon dioxide (CO2) levels compared with background concentrations and may establish gas hazard conditions. This study reports the results of five stable isotope (i.e., δ13C‐CO2 and δ18O‐CO2) surveys of airborne CO2 on Vulcano from August 2020 to November 2021. To measure CO2 in the air, a mobile laboratory was equipped with a laser‐based spectrophotometer that can selectively detect different CO2 isotopologues. Volcanic CO2 has a different isotopic signature than atmospheric CO2 and both δ13C‐CO2 and δ18O‐CO2 can help trace the injections of volcanic gases into the air. An isotopic mass balance model was developed for partitions CO2 between atmospheric background and volcanic CO2. The results of these studies show that volcanic CO2 emissions and atmospheric circulation deeply affected the concentration of CO2 in the air at Vulcano Porto. Studies of δ13C‐CO2 and δ18O‐CO2 provide an estimate of volcanic CO2 in the air. These results help identify spatially some points of interest for mitigating volcanic gas emission‐related hazards on Vulcano. Plain Language Summary: In volcanic areas, the concentration of CO2 in the air increases due to the dispersion of volcanic gases, as CO2 dominates among the local gas source components. Identifying variations in gas hazard due to changes in volcanic degassing is difficult when estimates of volcanic gases in air are based only on measurements of CO2 concentration. In this study, the effects of volcanic degassing on airborne CO2 are thoroughly evaluated by analyzing the isotopic composition of airborne CO2 during five onsite measurement surveys between August 2020 and November 2021. To quantify the contribution of volcanic CO2 to total CO2 in air, we developed a model based on the collected data using mass balance calculations. In 2021, a massive increase in volcanic degassing caused a clear increase of airborne CO2 concentration at Vulcano. We find that the effects of volcanic degassing depend on air turbulence, which changes throughout the day. The spatial variations in CO2 allow us to track the dispersion of volcanic gases in the air and their effects on gas hazards and atmospheric composition with unprecedented accuracy. Key Points: Spatial isotope monitoring enables the identification of the origin of CO2 in the airCalculating the stable isotope mass balances enables quantifying the volcanic CO2 in the total CO2 in the airSignificant changes in volcanic degassing increased air CO2 concentration and gas hazard on Vulcano—Italy—in 2021 [ABSTRACT FROM AUTHOR]