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We report the free energy barriers for the elementary reactions in the 2e− and 4e− oxygen reduction reaction (ORR) steps on Au(100) in an alkaline solution. Due to the weak adsorption energy of O2 on Au(100), the barrier for the association channel is very low, and the 2e− pathway is clearly favored, while the barrier for the O–O dissociation channel is significantly higher at 0.5 eV. Above 0.7 V reversible hydrogen electrode (RHE), the association channel becomes thermodynamically unfavorable, which opens up the O–O dissociation channel, leading to the 4e− pathway. The low adsorption energy of oxygenated species on Au is now an advantage, and residue ORR current can be observed up to the 1.0–1.2 V region (RHE). In contrast, the O–O dissociation barrier on Au(111) is significantly higher, at close to 0.9 eV, due to coupling with surface reorganization, which explains the lower ORR activity on Au(111) than that on Au(100). In combination with the previously suggested outer sphere electron transfer to O2 for its initial adsorption, these results provide a consistent explanation for the features in the experimentally measured polarization curve for the alkaline ORR on Au(100) and demonstrate an ORR mechanism distinct from that on Pt(111). It also highlights the importance to consider the spin state of O2 in ORR and to understand the activation barriers, in addition to the adsorption energies, to account for the features observed in electrochemical measurements. [ABSTRACT FROM AUTHOR]

Imagine that you and your traveling companion are toming the ruins of the ancient city of Pompeii. Your historically uninformed companion asks you, 'So, what caused the destruction of Pompeii?' [...]

High need for precision agriculture today has been associated with the completeness of the data available. The application of smart technology becomes the main alternative for fulfilling incomplete data and predicting future data. This paper presents the results of a research that aims to monitor and to predict water availability for determining conservation strategy on water availability using time series data from satellite rainfall, spanning from 2007 to 2022. We employed the innovative use of remote sensing technology, global rainfall measurement (GPM) and Climate Hazards Group InfraRed Rainfall with Station data (CHIRPS), to assess and correct satellite-derived rainfall estimates against ground-based observations. Conducted in the Serang watershed of Mount Merbabu’s volcanic landscape, the research employs a quantitative descriptive approach. We used coupled climate models MIROC6 and MRI-ESM2-0 in the CMIP-6 Framework for rainfall projections 2023–2030, then continued with the F.J. Mock model simulations for water availability projection. Our findings reveal a significant impact of climate change on water availability over the decade, with the most extreme conditions observed in 2029 and 2030, where the increasing of water availability reaching 10 m3 /s. The results showed that CHIRPS performed well in describing rainfall data. The novelty of this research highlighting the potential of: firstly, the use of satellite rainfall data for this specific region has not been extensively studied before; secondly, the discovered impacts of climate change to the water availability are particularly noteworthy, and thus contributing to the sustainability of agricultural practices in response to climate change. A limitation of this study is the short investigation period of just one decade, which does not fully capture the long-term impacts of climate change. Future research is recommended to utilize satellite data over extended periods to better represent extreme climate events and derive drought and wetness patterns over durations exceeding one decade. [ABSTRACT FROM AUTHOR]

A basaltic lava flow erupted from the Tajogaite volcano on 4 December 2021, in La Palma (Canary Islands, Spain) was sampled to find out to what extent reliable and correct information on both intensity and direction of the Earth's magnetic field can be obtained from the palaeomagnetic signal recorded in a lava flow which erupted under known conditions. Samples were taken every few centimetres across a flow up to a total of 27 oriented cores. Palaeomagnetic experiments showed a strong viscous overprint in many samples. Nevertheless, the mean palaeomagnetic direction obtained agrees well with the actual value from IGRF-13. Rock magnetic experiments were performed to obtain additional information about the quality and reliability of the results and the reasons for unsuccessful determinations. Analysis of mostly irreversible thermomagnetic curves showed that the carriers of remanence were magnetite and titanomagnetite of low and/or intermediate Curie-temperature. Hysteresis parameter ratios showed a pronounced variability across the flow. Analyses of frequency dependent susceptibility, IRM acquisition coercivity spectra and FORCs showed a noticeably presence of very low coercivity grains (multidomain and superparamagnetic-single domain boundary). Multimethod palaeointensity experiments were performed with the Thellier-Coe, multispecimen and Tsunakawa-Shaw methods. Only three of 25 cores from the flow yielded successful Thellier-Coe determinations, in agreement with the expected field value of 38.7 μT (IGRF-13). However, palaeointensities of 60 per cent of the specimens agree with the expected value performing an informal analysis without considering criteria thresholds. Four of six Tsunakawa-Shaw determinations performed on samples from the flow yielded correct results, but three multispecimen determinations providing apparently successful determinations largely underestimate the expected field intensity. Combination of three Thellier-Coe and four Tsunakawa-Shaw successful determinations yields a multimethod palaeointensity result B = (36.9 ± 2.0) μT in good agreement with the expected field intensity. [ABSTRACT FROM AUTHOR]

Computationally derived volcano curve has become the gold standard in catalysis, whose practical application usually relies on empirical interpretations of composition or size effects by the identical active site assumption. Here, we present a proof-of-concept study on disclosing both the support- and adsorbate-induced restructuring of Pt-Co bimetallic catalysts, and the related interplays among different interfacial sites to propose the synergy-dependent volcano curves. Multiple characterizations, isotopic kinetic investigations, and multiscale simulations unravel that the progressive incorporation of Co into Pt catalysts, driven by strong Pt-C bonding (metal-support interfaces) and Co-O bonding (metal-adsorbate interfaces), initiates the formation of Pt-rich alloys accompanied by isolated Co species, then Co segregation to epitaxial CoOx overlayers and adjacent Co3O4 clusters, and ultimately structural collapse into amorphous alloys. Accordingly, three distinct synergies, involving lattice oxygen redox from Pt-Co alloy/Co3O4 clusters, dual-active sites engineering via Pt-rich alloy/CoOx overlayer, and electron coupling within exposed alloy, are identified and quantified for CO oxidation (gas-phase), ammonia borane hydrolysis (liquid-phase), and hydrogen evolution reaction (electrocatalysis), respectively. The resultant synergy-dependent volcano curves represent an advancement over traditional composition-/size-dependent ones, serving as a bridge between theoretical models and experimental observations in bimetallic catalysis. Volcano curves have become the gold standard in catalyst design. Here, the authors propose synergy-dependent volcano curves by disclosing both support- and adsorbate-induced catalyst restructuring, ideally bridging the gap between theoretical models and experimental observations. [ABSTRACT FROM AUTHOR]

Dual‐atom catalysts (DACs) often exhibit superior electrocatalytic activity, due to their versatile combinations and synergistic effects. However, the neglect of both dynamic axial adsorption of the active site upon working potential and the reactant adsorption as a rate‐determining step hinders the establishment of an accurate high‐throughput screening strategy. Here, the oxygen reduction reaction (ORR) of 42 kinds of 3d–3d metal DACs by density functional theory (DFT) calculations are systematiclly investigated and demonstrated that the ORR kinetics can be limited by O2* adsorption besides the proton–electron transfer step and the active center of DACs may be reconstructed by axial pre‐adsorption of intermediates under working potential. Therefore, the ORR volcano plot is proposed by using both the O2* and OH* adsorption as activity descriptors. Then, a high‐throughput screening method is constructed and 38 promising ORR DACs are screened out from 267 DACs containing 3d, 4d, or 5d metals. Importantly, the previously unexplored MnCoN6 DAC is also experimentally synthesized, and exhibits ultrahigh ORR activity outperforming Pt/C, perfectly matching with theoretical prediction. In short, this work not only proposes a volcano plot‐based high‐throughput screening method but also provides a proof‐of‐concept of experimental verification of theoretical prediction to heuristically design electrocatalysts for other reactions. [ABSTRACT FROM AUTHOR]

Seismicity at active volcanoes provides crucial constraints on the dynamics of magma systems and complex fault activation processes preceding and during an eruption. We characterize time‐dependent spectral features of volcanic earthquakes at Axial Seamount with unsupervised machine learning (ML) methods, revealing mixed frequency signals that rapidly increase in number about 15 hr before eruption onset. The events migrate along pre‐existing fissures, suggesting that they represent brittle crack opening driven by influx of magma or volatiles. These results demonstrate the power of unsupervised ML algorithms to characterize subtle changes in magmatic processes associated with eruption preparation, offering new possibilities for forecasting Axial's anticipated next eruption. This analysis is generalizable and can be employed to identify similar precursory signals at other active volcanoes. Plain Language Summary: Our research used observations of small earthquakes to understand the dynamic behaviors of magma and fault systems before and during a volcano eruption. Specifically, we used ML techniques to search for patterns in the waveforms that may inform us of their associated physical processes. At Axial Seamount, an active underwater volcano, we discovered distinct patterns in earthquake signals preceding and during the 2015 eruption. Based on event spectral patterns, we identified signals of mixed‐frequency earthquakes that rapidly increase in number about 15 hr before the eruption starts and migrate along pre‐existing eruptive fissures. The spectral pattern involves a mixture of low frequency energy following the first arrivals, which we interpret to represent opening of cracks and being filled with magma or gases. Our study demonstrates that we can use ML algorithms to detect subtle changes in volcanic signals and help us better understand the processes leading up to an eruption. This may help us in forecasting Axial's upcoming eruption and can be applied to other active volcanoes too. Key Points: Unsupervised learning separated regular earthquakes and precursory mixed frequency earthquakes (MFEs) based on different spectral patternsThe regular earthquakes have strong tidal modulation, corresponding to failures on the caldera ring faults triggered by tidal stress changesThe MFEs intensify 15 hr before eruption and migrate along pre‐existing fissures, likely associated with eruption preparation processes [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials exhibiting both second-harmonic generation (SHG) and ferroelectric properties are promising candidates for high-performance optoelectronic devices. However, the relationship between SHG response and ferroelectric polarization and bandgap in such materials has not been revealed clearly. Therefore, by using first-principles calculations based on many-body theory, we comprehensively study the structural, electronic, linear and nonlinear (SHG) properties of ferroelectric NbOCl2 monolayer under strain regulation to clarify the influence of ferroelectric polarization (Ps) and bandgap on the SHG coefficient. Our results show a ferroelectric to nonpolar phase transition under compressive strain larger than 5% along the polar direction. Moreover, under strain, the electronic bandgap, optical gap E o , and SHG coefficient can be modified to a large extent and show different variation tendencies before and after phase transition. Importantly, a volcano relationship between SHG coefficient and a combined parameter (β1 = Ps* E o ) is established. Our findings unambiguously demonstrates the correlation between structural distortion, spontaneous polarization, and SHG property and have important implications for developing ferroelectric and nonlinear optical devices. [ABSTRACT FROM AUTHOR]

Changbaishan volcano (CBV), located on the border between China and North Korea, has undergone violent eruptions since the Oligocene, making it one of the most captivating and explosive volcanoes on Earth. However, the lack of precise characterization regarding the magmatic system makes it difficult to decipher its eruption risk and mechanism, despite its significant size and past devastating effects. In this study, we employed newly developed teleseismic receiver function techniques, including Ps and Sp waves, to construct a lithospheric structure model beneath the CBV region. The results show a thick crust (~37 km) and a weak, thin lithosphere under the CBV, with a low-amplitude width of 80 km at the Moho depth and 200 km at the depth of the lithosphere-asthenosphere boundary. These features depict the seismological response of a translithospheric magmatic system beneath the CBV, where hot upwelling material rises through the lithospheric mantle, underplates at the base of the crust, and forms the magma chamber(s) at shallow depth. Such magmatic system features can be taken as a unifying paradigm for large volcanic regions worldwide. [ABSTRACT FROM AUTHOR]

Using the images of the Sentinel-1A satellite, taken from May 1 to September 22, 2023, and the differential interferometry method (DInSAR) we calculated successive displacement fields in time, which clearly show a dome-shaped uplift on the western slope of Shiveluch volcano, 8‒8.5 km west of its active crater. The uplift grew especially intensely at the satellite acquisition intervals of May 1‒13, 2023; May 13‒25, 2023; and May 25‒June 6, 2023. To confirm the hypothesis on the formation of the displacement region due to magma intrusion beneath the western slope of the volcano, numerical modeling was carried out and the parameters of the sill-like magma body, which forms the displacements on the surface that best match the displacement observed from satellite radar interferometry data, were determined. It is assumed that, after the eruption on April 11, 2023, magma rose from a depth of 20‒25 km through a fissure formed under the western slope of the volcano and intruded horizontally beneath the slope at a depth of 1‒2 km in the north-northwesterly direction. Within the precision of data on slope displacements, the size of the magma body varies from 6.0 × 3.0 km at 1 km depth to 5.25 × 1.4 km at 2 km depth, while its height ranges from 0.5 to 1.75 m and its volume, from 0.009 to 0.0129 km3. Thus, based on radar interferometry data together with the data on the distribution of seismic activity accompanying the movement of magma, the model of the magma body that intruded beneath the western slope of Shiveluch volcano in the postparoxysmal phase of the eruption on April 11, 2023, was constructed. The formation of a new extrusive dome on the western slope of Shiveluch volcano at the end of April 2024 confirms the hypothesis about the intrusion of magmatic material beneath the western slope of the volcano and allows estimating the rate of magma rise to the surface. [ABSTRACT FROM AUTHOR]

The Changbai volcano, a globally recognized hotspot of volcanic activity, has garnered significant attention due to its persistent seismicity and ongoing magma activity. The volcano's discontinuities and magma dynamics have raised concerns about the likelihood of future eruptions, which would likely result in substantial ecological, climatic, and economic impacts. Consequently, a comprehensive understanding of the Changbai volcanic system is essential for mitigating the risks associated with volcanic activity. In recent years, the P-wave coda autocorrelation method has gained popularity in lithosphere exploration as a reliable technique for detecting reflection coefficients. Additionally, the Common Reflection Point stacking approach has been employed to superimpose reflection signals in a spatial grid, enabling continuous observation of reflection coefficients in the study area. However, the accuracy of this approach is heavily reliant on better spatial data coverage. To better understand the internal dynamics of the Changbai volcano, we applied this approach to a densely packed short-period seismic array with an average station spacing of less than 1 km. Our results were constrained using waveform data of reflection coefficients and Moho dip angles. Our findings revealed a discontinuity in the Moho, which may indicate a conduit for mantle magma entering the crust. Furthermore, we identified two low-velocity anomalies within the crust, likely representing a magma chamber comprising molten and crystallized magma. Notably, our results also provided a clear definition of the lithosphere–asthenosphere boundary. [ABSTRACT FROM AUTHOR]

Iceland is a unique example where the rift zone of the Mid-Atlantic Ridge emerges at the surface, and whose morphology and tectonic structure differ considerably from typical rift zones of mid-oceanic ridges. The morphology and geodynamics of the western branch of Icelandic rifts are largely controlled by the thermal influence of the Iceland plume that has created the North Atlantic large igneous province. The western branch of Icelandic rifts is characterized by ceasing tectonic and magmatic activity. Overlapping the Eastern Rift Zone, it forms the rotating Hreppar microplate block, which results in a northward decrease of its tectono-magmatic activity. Based on a morphometric analysis of fault scarps, we identified the degree of present-day activity for individual areas of volcanic systems, and determined its variation during Late Quaternary for some areas. The inferences drawn here demonstrate distinct differences in the present-day tectonic structure and dynamics of rift zones and individual volcanic systems within them. The southernmost, transtensional Reykjanes Rift Zone shows tectono-magmatic activity decreasing to the east, which is due to a lower influence exerted by the Reykjanes Ridge that is adjacent to it to the southwest. We observed its gradual eastward diminution, which is probably due to an analogous southward movement of the most active Eastern Rift Zone and to the formation of a new transtensional zone that combines the present-day Reykjanes Rift Zone and South Iceland Seismic Zone. The Western Rift Zone is developing independently of the Reykjanes Rift Zone, having a major extension center in the area of Lake Thingvallavatn. The Holocene manifestations of tectono-magmatic activity in its northern part, as is the case in the Central Rift Zone, are very weak, being mostly due to glacio-isostatic reactivation of older structures. The identified structural inhomogeneities can also be traced in the morphological aspect of rift zones. As an example, the Western and Central Rift Zones typically contain well-developed shield volcanoes that are largely composed of hyaloclastites, while individual lava shield edifices are observed within fissure swarms. In contrast to this, the Reykjanes Rift Zone is characterized by an absence of central volcanoes expressed in topography, and chains of small volcanic vents are observed within fissure swarms. [ABSTRACT FROM AUTHOR]

With the advent of new terminologies to categorize and characterize the simple and complex monogenetic volcanoes, also came the semantic issues, which caused a predicament for the usage of terms like simple, complex, polycyclic, polymagmatic, complex monogenetic volcanoes with polygenetic inheritance. To analyse and validate this nomenclature, we studied an overlapping volcanic structure located south of the present‐day town of Irapuato, Central Mexico, that appears to be a monogenetic complex at first sight. Field observations, tephra stratigraphy, petrography and geochemistry of the tephra deposits confirms that the structure is in fact a cluster of three simple (San Joaquin tuff ring and two scoria mounds) and one complex, polycyclic, polymagmatic (La Sanabria‐San Roque tuff ring) monogenetic volcanoes formed by independent events, governed by distinct conduits and magma bodies of different origin (subduction‐related, OIB and E‐MORB origin) and separated by different tephra sequences of dissimilar components and depositional characteristics. We estimate the magma volumes (using the juvenile content and their vesicularity percentage) to be at 0.40–1.31 × 108, 0.25 × 108 and 0.42–0.90 × 108 m3 for San Joaquin, La Sanabria and San Roque, reckoning an eruption duration of 77 and 48 and 81 days, respectively (considering an average eruption rate of 6 m3/s from the well‐documented shallow crater (<30 m), Ukinrek maars in Alaska) occurring within the age range of 40–70 k years (crater diameter and depth ratio). This study not only aided to validate the above‐mentioned terms for monogenetic volcanoes, but also reconsider a few of them and avoid confusion with the polygenetic counterparts. [ABSTRACT FROM AUTHOR]

Summary: The cases of fake Moutai‐flavour liquor have occurred frequently, seriously disrupting market economic order, therefore it is of great significance to realise the Moutai‐flavour liquor identification. Herein, an approach based on GC–MS technology coupled with chemometrics was established to achieve products identification and origins traceability. The normalised metabolite data were analysed by PCA, OPLS‐DA and volcano plot to screen differential metabolites. The heatmap visualisation and boxplot were used to explore the correlation between chemical markers and liquor samples. PLS‐DA model realised the accurate classification of Moutai‐flavour liquor samples using the screened chemical markers. All Moutai‐flavour liquor samples of the prediction set were accurately differentiated with 100% accuracy during the external verification. This study indicated that an approach based on GC–MS coupled with chemometrics has great potential for products identification and source tracing, thus providing technical support for combating crime of fake Moutai‐flavour liquor. [ABSTRACT FROM AUTHOR]

Jimibong is a north-facing horseshoe-shaped scoria cone in the northeast of Jeju Island that released lava flows to form a semicircular lava plateau. Sixty volcanic hummocks comprising scoria, spatter, and volcanic bombs are found on the lava plateau. The hummocks can be classified into Type 1 and Type 2 according to clast components, distance from the vent, and internal structure. Type 1 hummocks, distributed within approximately 1,000 m of the vent, comprise scoria deposits mixed with volcanic bombs and relatively few dykes that rise from the underlying lava. In contrast, Type 2 hummocks, distributed 1,000–1,300 m from the vent along the coast, comprise spatter/scoria and volcanic bomb deposits. The spatter/scoria of the Type 2 hummocks is highly agglutinated with abundant squeezing dykes that originated from the underlying lava and locally extruded over the hummocks. Although both the Type 1 and Type 2 hummocks comprise parts of the collapsed and rafted spatter/scoria blocks, their differences in shape, clast components, and structures are explained by changes in the eruption style (from spatter to scoria) and rheological changes in the lava with distance from the vent. Lava flows breached the cone following spatter-dominated eruptions in the early stages of Hawaiian eruption. Through this partial cone collapse, spatter blocks were transported with the lava flow away from the cone. The lava surface then cooled and hardened as the lava temperature decreased and viscosity increased. The contraction of the lava due to cooling caused the rafted cones to fragment into various sizes as they cracked, fractured, and rotated. Hot liquid lava from within the flow was squeezed-up because of the volcanic load of the rafted blocks, intruding into the fractures in the rafted blocks before locally flowing over them, creating the characteristic Type 2 hummocks. In contrast, Type 1 hummocks formed in the later stages of Strombolian activity, when scoria-dominant eruptions caused collapsed scoria blocks to be rafted with the lava flow. These scoria blocks were deposited in areas proximal to the cone and show few dyke intrusions due to the limiting effects of edifice load on dyke development. The Jimibong volcano provides an example of changing hummock structures in relation to changing eruption styles of scoria cones, deepening our understanding of the geomorphic development in volcanic regions. [ABSTRACT FROM AUTHOR]

Temporary seismic networks on Mt. Halla and Ulleung Island volcanoes were deployed, which employ broadband and geophone arrays to monitor potential volcanic activities and to estimate high-resolution magmatic structures beneath these volcanoes. The purpose of this paper is to introduce these networks and present early results through basic seismic analyses, suggesting the potential for future comprehensive seismological studies. The array in Mt. Halla volcano consists of five broadband sensors (JH array), and it has been operational around the Baengnokdam summit crater since October 2020. There was an additional linear geophone array (HL array) installed in September 2021 for detailed shallow subsurface imaging. Ulleung Island volcano had been under observation for two years since June 2021 with a network of nine broadband sensors (UL array) along its coast and in the Nari crater basin, complemented by a 52-geophone array (UG array) deployed in May 2022 for high-resolution subsurface studies. Despite the noisy environments typical of temporary setups, power spectral density analyses confirmed the quality of data as comparable to established reference noise models in permanent stations. Our study aimed to initiate studies uncovering seismic activities and structures beneath Mt. Halla and Ulleung Island volcanoes, specifically regarding volcanic activity. This approach detected no clear sign of volcanic seismicity on both islands, suggesting a period of magmatic dormancy. Seismic velocity variation (dv/v) analyses further indicated that environmental factors, rather than volcanic processes, influenced the changes in the physical properties of the underground structures. Conversely, the receiver function analysis and ambient noise data processing hinted at the presence of complex subsurface structures, potentially indicative of volcanic features, such as partial melting. Despite the lack of direct evidence for active magmatic processes, the collected seismic data provides a crucial baseline for future monitoring and a deeper understanding of the magmatic and tectonic dynamics beneath these volcanoes, offering valuable insights for ongoing volcanic research. [ABSTRACT FROM AUTHOR]

Lava tubes are powerful heat insulators, allowing lava to practically keep the initial temperature and travel longer distances than when freely flowing on the ground surface. It is thus extremely important to recognize how, when and where these structures form within a lava flow field for hazard assessment purposes, in order to plan possible interventions should a lava flow approach inhabited areas. Often being formed within thick and complex lava flow fields, lava tubes are difficult to detect, study and explore. In this study, we analyse the 1792-93 Etna lava flow field emplaced on a steep slope (>4°) which comprises several lava tubes located at different distances from the eruptive fissure, at different levels within the lava flow field, and showing various inner morphologies, with peculiar inner features related to their maturity and eruptive history. Our aim is to verify whether it is possible to connect the underground features with features observed on the lava flow surface in order to reconstruct the extension of the tube network and unravel the genetic processes. Our results show that, in the studied lava flow field, a clear correspondence is possible between shallow tubes emplaced late during the lava flow field growth and surface textures. In addition, vertical and horizontal tube capture is very widespread, and might be the primary process for lava tube persistence and long life. Our results might be applicable to other lava tubes on Earth and other rocky planets. [ABSTRACT FROM AUTHOR]

Leopardus wiedii and Leopardus pardalis are endangered small felids. Its main altitudinal range expands from sea level to 1,500 m. Camera traps were placed in the Matawi Indigenous Park on the Nevado de Toluca Volcano. Photographic records were obtained of L. wiedii at 3,207 masl and of L. pardalis at 3,307 masl. This is the highest altitudinal record for margay in its distribution, and for ocelot is the highest in the northern hemisphere. [ABSTRACT FROM AUTHOR]

This paper presents and interprets two new self-potential data measured over a hydrothermally active field associated with a Quaternary rhyolitic volcano, Oomuro-dashi, in the northern Izu-Ogasawara Arc, south of Japan. The measured data show a pair of positive and negative anomalies of the order of one millivolt at 5 m above the seafloor. The observation of a positive self-potential near a seafloor hydrothermal system is new, in spite that negative self-potential anomalies have been regularly reported in various studies for different locations. Determining the dominant mechanism(s) is therefore key to further understanding the subseafloor structure of seafloor hydrothermal systems. To this end, we also conducted long-term observations of subseafloor temperatures at two sites in the area of the self-potential anomaly to estimate the Darcy velocity. We found a downward fluid flow of the order of tens of metres per year at both sites. The flow in the area of the negative self-potential anomaly is stronger than in the area of the positive anomaly. Based on these observations, we propose two end-member models to explain the paired self-potential anomaly. The first model considers a horizontal geo-battery, in which part of a subhorizontal electrically conductive body is crossed by a subvertical redox front. In this model, the oxidised part of the geo-battery causes a negative self-potential anomaly, as in the previous observations, while the reduced counterpart of the geo-battery, which is normally buried, is exposed near the seafloor and causes a positive anomaly. In this case, a conductive body is expected to lie beneath both anomalies, and we could access the reduced part of the geo-battery. This model is consistent with the results of the Darcy velocity estimation if the strong hydrothermal circulation would cause the redox horizon to deepen. The second model is a combination of the thermal and streaming potentials causing both positive and negative self-potential anomalies. This model does not necessarily require a buried conductive body beneath the self-potential anomalies. These end-member models could be distinguished by resistivity imaging, which identifies the distribution of conductive bodies beneath self-potential anomalies, although they would overlap in natural systems. [ABSTRACT FROM AUTHOR]

Juno has allowed clear, high‐resolution imaging of Io's polar volcanoes using the Jovian Infrared Auroral Mapper (JIRAM) instrument. We have used data from JIRAM's M‐band (4.78 μm) imager from 11 Juno orbits to construct a global map of volcanic flux. This map provides short‐term insight into the spatial distribution of volcanoes and the ways in which high‐ and low‐latitude volcanoes differ. Using spherical harmonic analysis, we quantitatively compare our volcanic flux map to the surface heat flow distribution expected from models of Io's tidal heat deposition (summarized in de Kleer, Park, et al. (2019, https://doi.org/10.26206/d4wc‐6v82). Our observations confirm previously detected systems of bright volcanoes at high latitudes. Our study finds that both poles are comparably active and that the observed flux distribution is inconsistent with an asthenospheric heating model, although the south pole is viewed too infrequently to establish reliable trends. Plain Language Summary: Our study uses data from an infrared camera on Juno called the Jovian Infrared Auroral Mapper (JIRAM) to image Io, the innermost Galilean moon of Jupiter. Io is the most volcanically active body in the Solar System. Io's volcanoes are powered by both the extreme tides from Jupiter and the gravitational interactions between it and Jupiter's other moons. These tides generate friction inside Io. Simulations of Io's interior suggest that, depending on how deep that friction is being generated, the surface heat flow will be higher in certain areas (de Kleer, Park, et al., 2019, https://doi.org/10.26206/d4wc‐6v82). Using JIRAM, we have mapped where volcanoes are producing the most power and compared that to where we expect higher heat flow from the interior models. Our map doesn't agree with any of these models very well. JIRAM observed more volcanic activity at the poles than we expected to see based on previous observations. However, since the south pole was only observed twice, it's possible that these observations don't represent the average volcanic activity of the south pole. Very bright volcanoes that may have been continuously active for decades were also imaged during these Juno fly‐bys, some of which are nearer the poles than the equator. Key Points: We have produced a global volcanic flux map of Io using data from 11 Juno fly‐bysOur flux map doesn't agree well with tidal heat flow models reported in de Kleer, Park, et al. (2019, https://doi.org/10.26206/d4wc‐6v82)The M‐band flux is anti‐correlated with the asthenospheric heating model and has only very weak agreement with the global magma ocean model [ABSTRACT FROM AUTHOR]

Interdecadal variations of the global land monsoon have been previously attributed to internal fluctuations of the climate system, but the role of natural external forcings was underexplored. Here, we investigate this issue by using the Community Earth System Model ensemble simulations over the last millennium (LM) (AD 950–1850). Our analysis reveals that the surface temperature, with two dominant structures (global cooling/warming and longitudinal sea surface temperature gradient in the tropical Pacific, which affects the Walker circulation), predominantly shapes the leading forced mode of the global land monsoon. This mode, representing 19% of the total variance, manifests as consistent features across South Asia, the southern part of East Asia, North Australia, South America, and western South Africa, contrasting with other monsoon regions. Under global cooling conditions, the monsoon intensity is enhanced in the northern parts of the East Asian and eastern parts of the North and South African monsoons, but it decreases in the other monsoon regions. Under weak Walker circulation conditions, changes in atmospheric circulation in response to the sea surface temperature gradient in the tropical Pacific are associated with a substantial attenuation of almost all land monsoon regions. It was further shown that the global mean surface temperature and the tropical Pacific temperature gradient jointly account for 75% of the total variance in the leading mode of the global land monsoon, with 29% and 46% as their respective contributions. Furthermore, our results suggest that volcanic eruptions are the dominant external forcing for these variations. These findings provide valuable insights for future research on global monsoon dynamics. Significance Statement: Our study using the Community Earth System Model reveals that surface temperature significantly impacts decadal global land monsoon (GLM) variations during the last millennium. Two key factors in relation to global-scale cooling/warming and changes in the tropical Pacific sea surface temperature gradient affect the GLM's leading forced mode. The leading forced GLM features remain consistent across regions like South Asia, southern East Asia, North Australia, South America, and western South Africa. Under global cooling, monsoon intensities in most land monsoon regions are enhanced, while they are reduced in northern East Asian land monsoon regions. In contrast, weak tropical Pacific temperature gradient conditions cause a decrease in intensities in almost all land monsoon regions. Additionally, the global mean surface temperature and the tropical Pacific temperature gradient account for 75% of the total variance in the leading forced GLM variations, contributing 29% and 46%, respectively. Notably, volcanic eruptions emerge as the key external factor influencing these variations. [ABSTRACT FROM AUTHOR]

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

In May 2018, an unprecedented long and intense seismic-volcanic crisis broke out off the island of Mayotte (Indian Ocean) and was associated with the birth of an underwater volcano (Fani Maoré). Since then, an integrated observation network has been created (REVOSIMA), with the given objective of monitoring and better understanding underwater volcanic phenomena. Recently, an unmanned submarine glider (SeaExplorer glider) has been deployed to supplement the data obtained during a series of oceanographic surveys (MAYOBS) carried out on an annual basis. Operated by ALSEAMAR, the glider performed a continuous monitoring of 30 months of the water column from the sea surface to 1250 meters water depth with the objective to acquire hydrological properties, water currents and dissolved gas concentrations. This monitoring already showed that it is feasible and valuable to measure autonomously, continuously and at a high spatio-temporal scale, physical (temperature, salinity, ocean current) and biogeochemical parameters (O 2, CH 4, CO 2, bubbles/droplets, vertical speeds anomalies related to droplets) over several months from a glider. In particular, innovating sensing capabilities (e.g., MINICO2, ADCP) have shown a great potential in the context of the Mayotte seismic volcano crisis, despite technical challenges (complex algorithms, sensor capabilities, etc.). [ABSTRACT FROM AUTHOR]

Research with gravity data in the area of Semeru volcano has been undertaken. The study aims to determine the subsurface fault structure of the Semeru volcano by utilizing derivative analysis of gravity data anomalies. A comprehensive dataset of 1,929 measurement points, spaced 500 m apart, was analyzed to identify variations in the Bouguer anomaly. Complete Bouguer anomaly values ranged from 37 to 111 mGal. The contrast of Bouguer anomaly variations effectively delineates the boundaries of different rock formations: Mandalika, Wuni, Quarter Volcanic Semeru and Quarter Volcanic Jembangan. These formations are instrumental in causing significant variations in gravity anomalies, indicating an underlying geological structure. The derivative analysis, encompassing horizontal (FHD) and vertical (SVD) anomalies, unveiled a pronounced fault structure southeast of the Semeru crater, characterized by a NESW orientation. Advanced modeling, informed by residual anomaly incision lines and depth estimates derived from the radial spectrum, revealed a complex subsurface stratigraphy consisting of 5 types: Volcanic clastics, tuff, breccia, basaltic lava and andesitic lava. This research advances our understanding of the Semeru volcano's subsurface architecture. It introduces an enhanced methodology for fault detection and characterization in volcanic areas, showcasing the potential of gravity data in geological investigations. [ABSTRACT FROM AUTHOR]

The 2022 eruption at Mauna Loa, Hawai'i, marked the first extrusive activity from the volcano after 38 years of quiescence. The eruption was preceded by several years of seismic unrest in the vicinity of the volcano's summit. Characterizing the structure and dynamics of seismogenic features within Mauna Loa during this pre‐eruptive interval may provide insights into how pre‐ and co‐eruptive processes manifest seismically at the volcano. In particular, the extent to which seismicity may be used to forecast the location and timing of future eruptions is unclear. To address these questions, we construct a catalog of relocated seismicity on Mauna Loa spanning 2011–2023. Our earthquake locations image complex, sub‐kilometer‐scale seismogenic structures in the caldera and southwest rift zone. We additionally identify a set of streaks of seismicity in the volcano's northwest flank that are radially oriented about the summit. Using a rate‐and‐state friction model for earthquake occurrences, we demonstrate that the seismicity rate in this region can be modeled as a function of the stressing history caused by magma accumulation beneath the summit. Finally, we observe a mid‐2019 step change in the seismicity rate in the Ka'oiki region that may have altered the stress state of the northeast rift zone in the three years before the eruption. Our observations provide a framework for interpreting future seismic unrest at Mauna Loa. Plain Language Summary: In 2022, Mauna Loa erupted for the first time in 38 years. In the years before this eruption, the volcano had been generating a large number of earthquakes. We looked back at seismic data between 2011 and 2023 to detect and locate many more small earthquakes than were previously identified. Mapping out the locations of these earthquakes allows us to identify structures inside the volcano with high resolution. We also find evidence that the large number of earthquakes before the eruption was caused by accumulation of magma beneath the volcano's summit. Key Points: We construct a new catalog of 91,770 relocated earthquakes at Mauna Loa volcano spanning 2011–2023The new catalog details a decade of nonstationary inflation‐related seismicity and detailed structure in the caldera and rift zonesOur observations can provide a framework for understanding future episodes of pre‐eruptive seismic unrest at Mauna Loa [ABSTRACT FROM AUTHOR]

South‐central Alaska features a history of massive volcanic activity. How the Denali volcanic gap (DVG) formed and why the Wrangell volcanoes are clustered remain vigorously debated. Investigating the crustal thermal structure can be crucial for understanding subsurface magmatic activity. We present a high‐resolution broadband Lg‐wave attenuation model to constrain crustal thermal anomalies beneath Alaska. Strong Lg attenuation is observed beneath the volcanoes in south‐central Alaska, indicating thermal anomalies and possible melting in the crust. In contrast, the central Yakutat terrane (YT) and DVG are characterized by weak Lg attenuation, suggesting the existence of a cool crust that prevents hot mantle materials from invading the crust. This cool crust is likely the reason for the DVG. Quarter‐toroidal crustal melting with strong attenuation is revealed around the YT. This curved zone of crustal melting, possibly driven by toroidal mantle flow, weakly connects the Wrangell and Buzzard Creek‐Jumbo Dome magmatic chambers. Plain Language Summary: The Alaskan mainland is located at the western end of the North American plate. This region is adjacent to the Bering Sea to the west and overlies the subducting Pacific Plate to the south. The Yakutat microplate subducts northward below Alaska with a velocity similar to that of the Pacific plate but with a lower angle. Many volcanoes have developed in south‐central Alaska, including those in the Aleutian arc, the Buzzard Creek‐Jumbo Dome, and the Wrangell volcanic field (WVF). However, the origins, storage and transport patterns of the magmas feeding these volcanoes are still unclear and under debate. In this study, we conduct Lg‐wave attenuation tomography on the Alaskan mainland and use the results to investigate the regional crustal thermal structure. The imaging results reveal a cold Yakutat terrane and hot crustal features beneath the volcanoes. The Denali volcanic gap is characterized by weak crustal attenuation, indicating that cool crust may have inhibited volcanic activity. Quarter‐toroidal crustal melting is revealed by a curved belt of strong attenuation. The crustal magmatic chambers may weakly connect the WVF and the Buzzard Creek‐Jumbo Dome volcanoes. Key Points: A high‐resolution broadband Lg‐wave attenuation model is obtained for the Alaskan mainlandStrong Lg‐wave attenuation beneath the volcanoes indicates crustal thermal anomalies and meltingA quarter‐toroidal crustal melting belt weakly connects the magmatic chambers beneath the Buzzard Creek‐Jumbo Dome and Wrangell volcanoes [ABSTRACT FROM AUTHOR]

During the last 20 kyr, the Etna volcano has been characterized by almost continuous summit eruptions and by less frequent—yet definitely more destructive—flank eruptions issuing at <1,000 m asl altitudes and reaching the Ionian Sea. The chronological framework of pre‐historic (pre‐2,750 yr BP) flank eruptions is supported only by few radiometric and paleomagnetic ages. Here we paleomagnetically investigated 15 Holocene lava flows from SE Etna lower slopes and dated 12 of them. Paleomagnetic dating at Etna relies on best method pre‐requisites: European location where reference geomagnetic models are well defined, and detailed stratigraphic evidence is available. We sampled 45 sites (450 oriented cores) from lavas loosely constrained in the 19,000–2,000 yr BP age window. Ten eruptions yielded a minimum 40% refinement with respect to initial age constraints, with four lava flows achieving refinement up to 90%. We obtained 620–1,398 yr (998 yr on average) dating accuracy for three flows bracketed in relatively short (1,398–1,644 yr) independent age constraints. By contrast, five flows characterized by longer 6,567–7,439 yr initial age windows yielded multiple age solutions. Finally, four lava flows with 1,644–6,567 yr‐long initial age windows were tightly dated with 120–680 yr age ranges. We conclude that at volcanoes where best paleomagnetic dating pre‐requisite are fulfilled, singular solutions are expected for 30% of the analyzed flows and, significant refinements for the others. Seven kyr seems to represent an independent age window threshold length to get or not significant dating refinements. Plain Language Summary: Reconstructing a volcano's past eruptive activity, particularly over the last few centuries or millennia, is essential for conducting comprehensive long‐term hazard assessments. Mount Etna (Sicily, Italy) is an active basaltic volcano characterized by infrequent but highly destructive flank eruptions whose lava flows historically have impacted the populated lower slopes of the volcano. As the timing of the Etna prehistoric flank eruptions currently remains poorly determined, we used the paleomagnetic dating method, which offers a high level of precision that is challenging to achieve using alternative radiometric techniques in Holocene (i.e., last ca. 14 ky) basaltic products. Out of a total of 15 Holocene lava flows investigated, which are distributed over the Etna SE lower slopes, we paleomagnetically dated 12 flows by comparing their flow‐mean paleomagnetic directions with Paleo‐Secular Variation (PSV) reference curves, the latter showing the changes of the geomagnetic field over time. Our data show that for most of the studied eruptions, the paleomagnetic ages significantly reduce their independent age constraints, thus providing an improvement to the understanding of Etna Holocene eruptive activity. Key Points: Paleomagnetic dating of 12 Etna Holocene flank lava flows provided 40%–90% refinement of independent age constraints for 10 eruptionsAt Etna, where best method pre‐requisites are satisfied, paleomagnetic dating provides singular age solutions for ca. 30% of the dated flowsPaleomagnetism reduce by more than 40%–50% the eruptions' age windows for flows with independent age intervals lower than 7,000 years [ABSTRACT FROM AUTHOR]

Open‐vent volcanoes continuously emit magmatic products and frequently feature multiple adjacent craters. Temporal shifts of thermal emissions between craters are especially detectable by InfraRed satellites. Here, SENTINEL‐2 and LANDSAT‐8/9 Short Wave InfraRed (SWIR) high‐spatial resolution satellite data, are combined to investigate 10 years (2013–2023) of thermal activity at Stromboli volcano (Italy). The correlation between Volcanic Radiative Power (VRP, in Watts) and Volcanic Radiative Energy (VRE, in Joules), retrieved by moderate MODIS and VIIRS Middle InfraRed (MIR) data, with the Thermal Index SWIR (TISWIR) data, allows us to quantify long‐term series of heat fluxes (VRPSWIR) and energy (VRESWIR). Combining moderate and higher spatial resolution data and fitting cumulative trends of TISWIR with VREMIR allows to measure thermal activity sourced by single craters during Strombolian activity. Long‐term results highlight that thermal emissions are clustered in the northern and southern parts of the crater terrace, with total energy emitted (∼12 × 1014 J) equally distributed. The thermal increase since April 2017 marked a reactivation of shallow magma transportation and an intensification of the activity after the 2014 eruption. Distinct thermal behaviors are shown by the NE, C, and SW craters, related to mechanisms of explosions. We found that short‐term thermal variations match well those resolved by ground‐based signals, and the NE crater as the most sensitive to the transition to higher‐intensity activity. Our multispatial/multisensory investigation allows, for the first time, the long‐term quantification of heat flux from Stromboli's craters, with an improved understanding of open‐vent dynamics and a new approach to monitor multiple active craters. Plain Language Summary: Stromboli is a volcano in southern Italy, historically well‐known, considered unique and fascinating for its persistent emission of magma and gas through multiple adjacent craters lasting for millennia. This study focuses on tracking the thermal activity of Stromboli using modern satellite data over 2013–2023, with unprecedented levels of detail able to distinguish the heat released by single craters. The analysis revealed that most thermal emissions at Stromboli were concentrated in two primary sectors of the summit terrace. Notably, a significant increase in thermal activity was observed since April 2017, indicating a resurgence in volcanic activity after a period of relatively calm following the previous eruption. Distinct thermal behaviors of the three historically active craters of Stromboli have been recognized and reconciled with different styles of volcanic explosions. Furthermore, the study identified patterns of heat release within Stromboli's main craters which agreed with the fluctuations in gas emissions and explosive activity characterizing the volcano. Overall, this comprehensive analysis provides valuable insights to scientists and volcano‐involved communities into the long‐term quantification of heat flux from multiple craters at Stromboli, contributing to a better understanding of open‐vent eruptive dynamics and enhancing continuous monitoring of Stromboli and similar volcanoes. Key Points: Ten years (2013–2023) quantification of heat flux VRPSWIR from active craters at Stromboli using Sentinel‐2 and Landsat‐8/‐9 SWIR imagesTwo main thermal clusters emitting ∼12 × 1014 J. Thermal increase since April 2017 marks a reactivation of intense Strombolian activityNE, C, and SW craters show distinct thermal behavior, with the NE as the most energetic. VRPSWIR tracks transition to more explosive phases [ABSTRACT FROM AUTHOR]

The Ecuadorian arc is composed of an unusually high number of volcanoes, organized as along-arc alignments and across-arc clusters, in a relatively small area. Although several geochronological studies have been carried out in the last three decades, the eruptive history of the central zone of the arc remains poorly documented, preventing analysis of the initiation of volcanism of the whole arc. In this study, we present new K–Ar ages obtained from this central area, referred to as the Quito segment. These results were then incorporated into an updated comprehensive geochronological database of about 250 ages, allowing us to describe, at the arc scale, the spatial and temporal evolution of Quaternary volcanism in Ecuador. About eighty Quaternary volcanoes have been identified in the Ecuadorian Andes, 45 of which have been radioisotopically dated and/or identified as active or potentially active. The volcanic arc developed in three stages, characterized by an increase in the total number of active volcanoes. During the oldest Plio-Early Pleistocene stage, documented volcanic activity was mostly concentrated in the Eastern Cordillera of the Quito segment, with minor effusive eruptions in the southern Back-Arc. Since ~ 1.4 Ma, activity has spread to the surroundings of the Quito segment, and new edifices also appeared in the Western Cordillera and the Inter-Andean Valley. Towards the end of this intermediate stage (i.e., ~ 800 ka), volcanism occurred in isolated areas north and south of the Inter-Andean Valley. Finally, the late and current has been characterized by a remarkable increase in volcanic activity since ~ 600 ka. About 50 volcanoes were active during this stage. The spatial distribution of the Ecuadorian arc volcanism seems to be guided by deep mechanisms (i.e., slab geometry and age, amount and composition (fluids and melts) of slab input, mantle heterogeneities) and old crustal tectonic structures of the Western Cordillera, while neotectonics seems to influence the development of stratovolcanoes. In addition, we note that the spatial and temporal evolution of volcanism highlights the influence of the Carnegie Ridge and the young Nazca crust on the thermal regime of the subduction system, which in turn increases of volcanic activity in Ecuador. [ABSTRACT FROM AUTHOR]

The International Network for Volcanology Collaboration (INVOLC) is a network formalised by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) with the specific ambition to enhance volcanology globally through improved international collaboration. IAVCEI-INVOLC was created with a focus on volcano scientists working in resource-constrained contexts, including those based in low- or middle-income countries. After a community-wide online survey and inaugural workshop during which INVOLC's ambitions were discussed, a series of challenges, as commonly experienced by those working in resource-constrained settings, were identified. These challenges may present barriers to participation in volcano science in an international context and are related to both organisational resources (financial, human, technical) and inclusion in research collaborations. In this perspectives paper, we present a series of 15 guidelines for best-engagement protocols in international collaboration in volcanology that may be adopted during times of quiescence, volcanic unrest and/or an eruption and its aftermath. Our aspiration is that these guidelines will help build more respectful, equitable and sustainable partnerships that will ultimately advance the science of volcanology. [ABSTRACT FROM AUTHOR]

Using data from the regional broadband dense temporary array deployed by the ChinArray project, we applied the three-dimensional (3D) Kirchhoff migration method of the teleseismic P-wave receiver function to investigate discontinuity structures of the mantle transition zone (MTZ) in the central and western parts of the North China Craton (NCC) using a high-resolution 3D velocity model of the East Asian region. The results show that the 410-km discontinuity beneath the Datong Volcano is depressed by ∼10 km, indicating the presence of a high-temperature anomaly near the depth of 410 km, which is likely related to small-scale mantle upwelling caused by the dehydration of the stagnant Pacific Plate in the MTZ. The upwelling of hot material provides a heat source for surface magmatic activity. Beneath the Bohai Bay Basin, significant subsidence of the 660-km discontinuity is observed, and the transition zone here is extensively thickened. It's suggested that the anomalies in this region are related to the stagnation of the Pacific slab in the MTZ. Although the thickness of the transition zone west of the North-South Gravity Lineament appears normal, we propose that the subducting front of the Pacific slab did not cross the gravity lineament in the NCC. In comparison, the small-scale subsidence of the 660-km discontinuity and the thickening of the MTZ observed north of the Hannuoba Volcano likely indicate that the slab crossed the gravity lineament at its turning point and remained in the MTZ. Furthermore, a local thickening of the MTZ is observed in the Dabie orogenic belt of the Qinling Mountains. This is believed to be a combined effect of lithospheric delamination into the transition zone in the lower Yangtze region and the stagnation of the Pacific Plate. [ABSTRACT FROM AUTHOR]

In volcanic belts, magma influx into magma chambers generates excess pressure, amplifying the initial stress field to cause crustal deformation with significant ground displacements, which manifests in topographic relief. Quantifying such volcano-driven ground surface displacements is a fundamental requirement to embark on a criticality analysis of volcanotectonic events and associated hazard monitoring strategies. This study theoretically examines the underlying dynamics of surface displacements in a volcanic plumbing system comprising multiple magma chambers. The classical Mogi equation is extended to derive a set of analytical solutions to evaluate surface displacements as a function of separations between two off-axis chambers, measured along both horizontal and vertical directions. The resulting surface displacement plots, from the analytical solutions are compared with those calculated from a set of finite element (FE) model simulations run with the same parameters considered for the analytical formulations. Both the analytical and FE results suggest that horizontal (Sh) and vertical (Sv) separations of magma chambers largely control the vertical (Uz) and lateral (Ur) ground-displacement components. Spatially varying Uz attains its peak value at a specific location above the chambers, but increasing horizontal separation (Sh ~ 10 km) transforms the single-peak Uz pattern to a weakly developed double-peak Uz pattern, which eventually give way to two prominent high-amplitude peaks above the chambers when Sh ~ 25 km. Similarly, a large vertical separation (Sv ~ 6 km) yields double peaks in the Uz profile, which merge to form a single peak for small Sv (~ 1.5 km). The FE model results are used to map the stress fields around the two magma chambers to show that inter-chamber mechanical interaction can influence the deformation behaviour around the chambers, depending on Sh and Sv magnitudes. Finally, the model estimates are evaluated using available reports on the naturally occurring volcanoes: Teide volcano (Tenerife, Spain) and Long Valley Caldera (USA). [ABSTRACT FROM AUTHOR]

The early Jurassic syn-rift phase generated a significant set of half-grabens, calderas, and pull-apart basins along the southwestern margin of South America. In particular, the Loncon Complex, located in the western Extra-Andean region of North Patagonia (∼40°S), forms part of such structures. In the present contribution, we characterize and define the Early Jurassic extensional architecture of the Loncon Complex, constituted of a small-scale pull-apart basin associated with polygenetic volcanism, based on outcrop-scale kinematic data from strike-slip faults, and stratigraphic analysis. Lithofacies analysis, texture, componentry, and structural data allow us to distinguish four stages during the evolution of the Complex; the three early stages are followed by a deformational phase, and crowned by a limited felsic monogenetic volcano; stages consist of a) A continental alluvial to fluvial sedimentation related with an early pull-apart basin phase; b) local phreatomagmatic explosions with syn-eruptive sedimentation periods of a medium life cycle (~104-105 years), b) effusive andesitic stage generated by strike-slip transtension, resulting in partial deformation and development of a local unconformity, and c) a final short-term silicic tuff ring volcano construction (days to months' time span). The measured faulting pattern is synchronous with the Loncon Complex's sedimentation and volcanism. Kinematic data allow us to characterize the Loncon Complex evolution under NNE-NNW minimum horizontal stress (SHmin). This local NNE-oriented extension is interpreted as a consequence of a regional process, in a similar way to the report for the Neuquén Basin and the surrounding region in Patagonia. New U-Pb data indicate the onset of volcanism began in the Sinemurian (193.08 ± 1.13 Ma) also supporting an equivalent timing with the vicinity half-grabens areas of the North Patagonia region and the Neuquén Basin (Figure S1a). The process that occurred during the Sinemurian, and probably during the Pliensbachian, affected the entire back-arc basin developed along the southwestern border of Gondwana. [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]

A major challenge in mantle geochemistry is determining the source composition and melt fraction involved in melting. We provide a new Rare‐Earth Element (REE) inverse model that provides source concentration, source and melt mineral modes, and melt fraction based on the difference between separate determinations of bulk distribution coefficients and constrained by boundary conditions. An analytical inverse of the batch melting equation provides expressions for source, Coi ${C}_{o}^{i}$, and bulk distribution coefficient of the mantle, Doi ${D}_{o}^{i}$, with two unknowns, the initial concentration of La in the mantle, CoLa ${C}_{o}^{La}$, and Pi, the bulk distribution coefficient of the melt. We traverse through a range of CoLa ${C}_{o}^{La}$ steps and examine thousands of melt modes, Pi, at each step. Thousands of trial melt modes fail by generating Doi ${D}_{o}^{i}$ that are inconsistent with partition coefficients. Many surviving trials cannot be inverted to estimate a mantle mode. Other boundary conditions eliminate even more trials. Surviving trials are ordered by the difference between Doi ${D}_{o}^{i}$ calculated from the REE data of a lava suite and Dci ${D}_{c}^{i}$ calculated from partition coefficients and mantle mode. We select the solution with the closest fit that passes all the boundary conditions. We tested our new model with lava suites from Hawaii where different lines of evidence suggest that they melted from different mantle sources, Mauna Kea representing shield‐stage lava and submarine Kiekie representing rejuvenated stage lava. Our inverse determination of mantle composition and melting parameters was consistent with earlier models based on assumptions of HREE composition. Plain Language Summary: Determining the composition of our planet's interior is a major goal of geochemistry. The most common approach is to make forward models based on reasonable assumptions about the source composition and the melting process to calculate synthetic compositions that match the observed lava. Successful forward models may be difficult to achieve, but nevertheless remain dependent on initial assumptions. In principle, inverse models make fewer assumptions and achieve more objective results. Even so, most published inverse models for mantle melting require assumptions about the source. The inverse modeling described here relies on boundary conditions and the match between observed and calculated bulk distribution coefficients to determine the behavior of mantle parameters as a function of the initial lanthanum concentration (CoLa ${C}_{o}^{La}$). Certain behavior patterns allow determination of the optimum CoLa ${C}_{o}^{La}$, allowing a complete inverse. Successful inverse models for Hawaiian lava suites define two distinct mantle types, in agreement with past observations about these volcanoes. Key Points: Melt modes and mantle La concentrations generate trial source and bulk distribution profiles, but most solutions fail boundary conditionsTrial solutions are ranked by comparing observed and calculated bulk distribution profiles. The best fit over a range of La is the solutionOptimum source and bulk distribution profiles provide melt extents for shield stage Hawaiian tholeiites and rejuvenated basalts [ABSTRACT FROM AUTHOR]

This study explores the dynamic evolution of the Hunga Volcano in the Kingdom of Tonga and covers two volcanic unrests, focusing on the creation and subsequent disappearance of a new island between Hunga Tonga (HT) and Hunga Ha'apai (HH) between 2013 and 2023. The island expanded in 2015 and vanished in January 2022 due to a massive eruption (VEI = 6), featuring a 57 km high volcanic cloud and generating multiple tsunamis that caused damage across the Pacific Ocean. Utilizing remote sensing techniques, including multispectral imaging from Sentinel 2, Landsat 8-9, and synthetic aperture radar (SAR) imaging from Sentinel 1, the research employs a supervised random forest classification algorithm to individuate the changing subaerial surface area of the volcano. This approach documents size variations in the islands, particularly during weeks surrounding two volcanic unrests. The classifier, trained on nearly cloud-free multispectral images, automatically delineates surface area changes over the years. The temporal resolution of area change, limited to images with less than 5% cloudiness, encompasses about 50% of Landsat and 20% of Sentinel 2 images between 2013 and 2023, selected from 739 available images. The multispectral observations are complemented by 215 Sentinel 1 SAR images, penetrating clouds, though with limited bands. Despite higher noise, the classifier on Sentinel 1 successfully distinguishes land from ocean. Sentinel 1 observations, starting in 2014, cover the volcano unrest of 2014/2015. Earth Engine, a cloud computing data facility, is used for processing. Analysis indicates a slight decrease in the area change post-2015 island formation and identifies the disappearance of the island bridge connecting HT and HH, along with two smaller islands south of HT and HH in 2022. The 2022 explosion is preceded by an increase in island area in the weeks before the eruption. Global satellite coverage could automatically detect changes in oceanic areas and distinguish water from new volcanic islands, offering a means of identifying volcanic unrests and documenting their evolution. [ABSTRACT FROM AUTHOR]

Volcanic eruptions carry essential information on the dynamics of volcanic systems. Studies have documented variable eruption styles and eruptive surface deformation. However, co‐eruptive subsurface structural changes remain poorly understood. Here we characterize the seismic velocity changes from July 2019 to July 2023 at Great Sitkin Volcano in the central Aleutian volcanic arc, using single‐station ambient noise interferometry at five three‐component seismic stations. Coincident with the lava effusion since late July 2021, about two months after the explosive eruption on 26 May 2021, we observe a sustained velocity increase, most prominently to the northwest of the caldera. We attribute this velocity increase to the structural changes with magma extrusion, with the spatial variation controlled by the geometry of the magma system or the property of shallow volcaniclastics. Our findings offer insights into understanding co‐eruptive structural modifications at active volcanoes. Plain Language Summary: Volcanic eruptions provide important insights into how volcanoes work and the potential risks they pose. This study looks at the ongoing eruption at Great Sitkin Volcano in the central Aleutian volcanic arc to better understand the changes happening beneath the surface. We measure the changes in the velocity of seismic waves, with data from five seismometers on the island. We collected data from July 2019 to July 2023, covering different eruptive stages and multiple lava effusion episodes during the eruption that started on 26 May 2021. Coincident with the lava effusion since late July 2021, we notice a significant increase in seismic velocities, most prominently at a station northwest of the volcano's central crater. We conclude that this increase reflects the structural change in the shallow subsurface due to magma extrusion, with deflation of the edifice and closure of cracks. The findings in this study help to improve our understanding of how volcanoes behave during eruptions. Key Points: We observe prominent, spatially variable increases in seismic velocity during lava effusions at Great Sitkin Volcano since late July 2021The sustained co‐eruptive increase in seismic velocity reflects structural changes with crack closures as the consequence of magma extrusionThe distinct spatial variation of the velocity increase may be controlled by reservoir geometry or the strength of shallow volcaniclastics [ABSTRACT FROM AUTHOR]

Simple Summary: Male anurans attract conspecific females for reproduction by giving advertisement calls. As calling implies high energetic costs, theory predicts that in mixed-species assemblages call features differ among species to reduce acoustic interference. Each species occupies a distinct acoustic niche in the soundscape. In equatorial wetlands water bodies for reproduction are available all over the year, therefore, we expect that diel and seasonal partitioning of acoustic space should be less important than differences in call structure to reduce competition and niche overlap. Additionally, acoustic communities should be species-saturated. We tested these predictions in four communities at 2546–3188 m a.s.l. in the Volcanoes National Park, Rwanda. Using automated recording devices from September 2019 to March 2020, we obtained an extensive dataset on call activity. The communities included 4–6 species, depending on the wetland structure, with a common stock of three species (Hyperolius castaneus, H. glandicolor, Leptopelis kivuensis). Independent of elevation, niche breadth for call features was similar and overlap reduced by partitioning the frequency range used. The diel and seasonal niche breadth of specific call activity varied according to the local temperature regime at different altitudes. We conclude that stochastic niche theory describes accurately the processes shaping equatorial highland communities. The soundscape is a complex arrangement of sounds originating from animals and the environment. It is considered a reliable proxy for ecosystem niche structure at the community level. Acoustic communities of anuran species include advertising males, which compete in acoustic space for conspecific females. Stochastic niche theory predicts that all local niches are occupied, and the acoustic community is species-saturated. Acoustic niches, which include the spectral and temporal call structure and diel and seasonal patterns of call activity, are of similar breadth with small overlap. We tested these predictions in four communities inhabiting pristine wetlands at 2546–3188 m a.s.l. in the Volcanoes National Park, Rwanda. We sampled 74 days of hourly 5 min recordings of the local soundscape (September 2019–March 2020) using passive automated monitoring devices (Songmeter SM4). We identified species based on the advertisement call features and measured call activity as calls per minute. The communities included 4–6, species depending on wetland structure, with a shared stock of three species (Hyperolius castaneus, H. glandicolor, Leptopelis kivuensis). Independent of elevation, niche breadth for call features was similar among species and overlap reduced by partitioning the frequency range used. The diel and seasonal niche breadth of specific call activity varied according to the local temperature regime at different altitudes representing the variable part of the acoustic niche. We conclude that communities are indeed species-saturated and acoustic niches differ primarily by the fixed call features remaining locally adaptable by the modulation of the call activity pattern, corroborating the predictions of the stochastic niche theory. [ABSTRACT FROM AUTHOR]

Offshore volcanic activity occurs when an underwater volcano erupts. These volcanoes can be located underwater or on land and can be very dangerous to marine life. The aim of this study is to examine whether the influence of two volcanoes has an effect on the concentrations of metals and trace elements in the Atlantic mackerel Scomber colias in the Canary Islands. For the study, ten specimens of S. colias were obtained from each sampling area in March 2022. Metal concentrations were determined by inductively coupled plasma optical emission spectrophotometry (ICP-OES). The specimens of Scomber colias from the area affected by the Tajogaite volcano (La Palma) showed higher concentrations of all metals and trace elements analyzed than those from the other study areas. The specimens from the area of influence of the Tagoro Volcano (El Hierro) showed the second highest concentration of the elements studied, although this volcanic process is in a state of degassing. [ABSTRACT FROM AUTHOR]

The studies are focused in the Mara–Kamenka–Uvat interfluve of the Biryusa Uplift of the basement of the Siberian Platform, where the Mara paleovolcano was recognized during the prospecting works for manganese more than 50 years ago. The specific volcano-sedimentary rocks are considered in the structure of the Late Riphean Karagas Group. Our mineralogical and petrographic studies allowed us to establish abundant high-K pyroclastic rocks, ignimbrites, and trachybasalts, which indicate a subaerial explosive character of the Mara volcano. The age of high-K volcanism of 640 Ma is based on U–Th–Pb dating of zircon. The Lu–Hf isotope systematics of zircon indicates a link of volcanism with mantle magmas. The composition and the period of the formation of rocks prevent their correlation (as was considered before) with sedimentary Late Riphean quartz and quartz–feldspar sandstones of the Karagas Group and dolerites of the Nersa intrusive complex. Specific mineralogical–petrographic features of rocks allow their use as a regional stratigraphic reference. [ABSTRACT FROM AUTHOR]

Seamount eruptions alter the bathymetry and can occur undetected due to lack of explosive character. We review documented eruptions to define whether they could be detected by a future satellite gravity mission. We adopt the noise level in acquisitions of multi-satellite constellations as in the MOCAST+ study, with a proposed payload of a quantum technology gradiometer and clock. The review of underwater volcanoes includes the Hunga Tonga Hunga Ha'apai (HTHH) islands for which the exposed surface changed during volcanic unrests of 2014/2015 and 2021/2022. The Fani Maoré submarine volcanic eruption of 2018–2021 produced a new seamount 800 m high, emerging from a depth of 3500 m, and therefore not seen above sea surface. We review further documented submarine eruptions and estimate the upper limit of the expected gravity changes. We find that a MOCAST+ type mission should allow us to detect the subsurface mass changes generated by deep ocean submarine volcanic activity for volume changes of 6.5 km3 upwards, with latency of 1 year. This change is met by the HTHH and Fani Maoré volcanoes. [ABSTRACT FROM AUTHOR]

The morphology of the shield volcanoes on Bioko, a volcanic island in central Africa, is controlled both by tectonic and volcanic processes, but the complex interplay of these regional and local mechanisms is poorly understood. Using a TanDEM-X digital elevation model, we are able to create an inventory of 436 vents and monogenetic cones, and over 1330 structural elements and lineaments, and perform a comprehensive morphological and geospatial analysis. We provide detail on the general geomorphology of Bioko Island, and describe its flat top, apical graben-like structures, and the setting of the structural inventory created. Based on vent density and lineament mapping, we are able to identify volcanic rift zones that are governed by vent clustering and the asymmetry of associated monogenetic cones. Specifically, we find that eruption vents are not only clustered but aligned and follow the principal NE-SW axis, although we also highlight evidence for complex structures such as side-stepping alignments and en échelon patterns indicative of strike-slip contributions to the volcano-tectonic fabrics. We discuss possible volcano-tectonic and regional tectonic contributors, such as the Cameroon Volcanic Line and intersecting fracture zones, as well as gravity-tectonic processes dominant at Bioko Island. In this view, our results are relevant for understanding the past and recent volcanic activity and discuss the influence of regional and local volcano-tectonic architectures. [ABSTRACT FROM AUTHOR]

The gravitational instability of hot material deposited during eruptive activity can lead to the formation of glowing avalanches, commonly known as deposit-derived pyroclastic density currents (PDCs). These currents can travel hundreds of metres to several kilometres from the source at exceptionally high temperatures, posing a catastrophic hazard to areas surrounding steep-slope volcanoes. The occurrence of deposit-derived PDCs is often associated with crater rim failure, which can be triggered by various factors such as magma thrust from dike injection, magma fingering, bulging or less commonly, powerful explosions. Here, the in-depth study of data from the multi-parametric monitoring network operating on Stromboli (Italy), including video surveillance, seismicity and ground deformation data, complemented by remote topographic sensing data, has facilitated the understanding of the events leading to the crater rim collapse on 9 October and 4 December 2022. The failures resulted in the remobilisation of 6.4 ± 1.0 × 103 m3 and 88.9 ± 26.7 × 103 m3 of material for the 9 October and the 4 December 2022, respectively, which propagated as PDCs along the NW side of the volcano and reached the sea in a few tens of seconds. These events were characterised by a preparatory phase marked by an increase in magmatic pressure in the preceding weeks, which correlated with an increase in the displacement rate of the volcano's summit. There was also an escalation in explosive degassing, evidenced by spattering accompanied by seismic tremors in the hours before the collapse. These events have been interpreted as an initial increase in magma vesicularity, followed by the release of gas once percolation threshold was reached. The degassing process induced densification of the magma, resulting in increased thrust on the conduit walls due to increased magmastatic pressure. This phase coincided with crater rim collapse, often followed or accompanied by the onset of lava overflow phases. A mechanism similar to the one proposed may shed light on similar phenomena observed at other volcanoes. The analysis performed in this study highlights the need for a multi-parametric and multi-platform approach to fully understand such complex phenomena. By integrating different data sources, including seismic, deformation and remote sensing data, it is possible to identify the phenomena associated with the different phases leading to crater rim collapse and the subsequent development of deposit-derived PDCs. [ABSTRACT FROM AUTHOR]