Search

Observing in‐conduit physical mechanism underlying the switching of eruptive activity between the craters of multi‐vent volcanoes could contribute to hazard assessment at these complex volcanic edifices. We performed monitoring of mass density changes beneath two active craters of Sakurajima volcano in Kyushu, Japan between September 2018 and July 2023 with cosmic‐ray muography. From December 2022, the mass density decreased beneath Minamidake crater and increased beneath Showa crater in accordance with a switch of eruptive activity from Minamidake crater to Showa crater. Plug formation and convective magma degassing processes have been observed with muography in accordance with the deformation of the surface of volcanic edifice measured by Interferometric Synthetic Aperture Radar. We found a moderate inverse correlation with a Pearson's coefficient of −0.52 between the mass densities observed beneath the two active craters throughout the entire period. The inverse correlation of mass densities indicates a magmatic gas flux dynamics which characterizes a branched conduit structure. Muography thus reveals the shallow magmatic processes during switching of eruptive activity between the craters of multi‐vent volcanoes and allows to infer to the conduit structure. Plain Language Summary: Observing the changing of structure and amount of materials in the upper plumbing systems of active volcanoes can contribute to the visualization the ongoing volcanic phenomena and assessing of related hazards. For instance, the increase in mass density indicates the uprise of deep volcanic materials in the conduit that may result in the onset of eruption. We measured the directional dependent yield of naturally occurring cosmic‐ray muon particles across the active Sakurajima volcano in Kyushu, Japan. We utilized muography to visualize the changes in mass density structure beneath the erupting craters over time. The captured muon images revealed that the mass densities varied inversely underneath the Minamidake and Showa craters throughout the measurement period. The observed inverse correlation between the mass densities indicates a branched linkage between the conduits of the two active craters. Key Points: Muography is utilized for visualizing and monitoring the mass density changes beneath the active craters of Sakurajima volcano, Kyushu, JapanInverse correlation is found between the mass densities observed beneath the two active cratersA branched linkage between the conduits of active craters inferred from the changes of eruptive activity and mass densities [ABSTRACT FROM AUTHOR]

Constraining stresses in the Earth's crust in volcanic regions is critical for understanding many mechanical processes related to eruptive activity. Dike pathways, in particular, are shaped by the orientation of principal stress axes. Therefore, accurate models of dike trajectories and future vent locations rely on accurate estimates of stresses in the subsurface. This work presents a framework for probabilistic constraint of the stress state of calderas by combining three‐dimensional physics‐based dike pathway models with observed past vent locations using a Monte Carlo approach. The retrieved stress state is then used to produce probability maps of future vent opening across a caldera. We test our stress inversion and vent forecast approach on synthetic scenarios, and find it successful depending on the distribution of the available vents and the complexity of the volcano's structural history. We explore the potential and limitations of the approach, show how its performance is sensitive to the assumptions in the models and available prior information, and discuss how it may be applied to real calderas. Plain Language Summary: Many processes at volcanoes are influenced by the stress state in the subsurface, which results from various forces, such as the gravitational loading due to redistribution of mass following the formation of topographic features. In particular, magma often opens its own pathway from a magma chamber to the surface along trajectories that are sensitive to the distribution of stress within the rocks. Therefore, knowledge of the stress state in volcanoes is critical to understand, and possibly forecast, magma pathways and the locations where they may reach the surface. In this work, we develop a framework to constrain the stress state at calderas. We estimate the stress field so that it is consistent with pathways that link the magma chamber with the eruptive vents of past eruptions. Then, we employ the estimated stress state to simulate future magma pathways and study the expected distribution of the resulting eruptive vents across the caldera, identifying the areas which are more likely to host future eruptions. We test our approach on artificially generated scenarios and explore the potential, limitations, and possible future applications of our work. Key Points: We use past vent locations and a Bayesian framework to constrain the stress state at calderas with a physics‐based model of dike pathwaysWe exploit the posterior information on stress state at calderas to produce probability maps of future vent opening locationsWe test the stress inversion and vent forecast on synthetic calderas, exploring the potential and limitations of the strategy [ABSTRACT FROM AUTHOR]

The Alaska Volcano Observatory (AVO) uses multidisciplinary data to monitor and study dozens of active and potentially active volcanoes. Here, we provide an overview of internally and externally generated data types, tools and resources used in their management, and challenges faced. Data sources include the following: (1) a multiparameter (seismic, infrasound, GNSS, web cameras) ground-based monitoring network that spans 3000 km and transmits data in real time; (2) a variety of satellite-borne sensors that provide information about surface change and volcanic emissions; (3) geologic and gas field campaigns; and (4) other external data products that provide situation awareness. Each data type requires distinct acquisition, processing, storage, visualization, and archiving approaches. AVO uses a variety of externally and internally developed tools to handle individual data types as well as multidisciplinary volcanological data. A primary tool is the Geologic Database of Information on Volcanoes in Alaska (GeoDIVA), which stores detailed, searchable information on more than 140 volcanoes and over 1000 eruptions and unrest events, including images, eruption descriptions, and geologic station and sample data, metadata, and analyses. It interacts with other internal tools that store monitoring reports and other operational records. Additional data management resources used by AVO assist with alarms and alerts, state-of-health monitoring, and multiparameter visualization. Requirements for 24/7 accessibility, the ever-expanding portfolio of data, and transitioning new tools from development to operations are all challenges faced by AVO and other volcano observatories. AVO strives to meet FAIR data practices and ensure that data are available to national and international community efforts using external repositories as well as those hosted by AVO and its parent institutions. [ABSTRACT FROM AUTHOR]

El Chichón volcano is the most active volcano in the state of Chiapas, México, and experienced its last Plinian eruption (VEI = 5) in 1982. To better assess its volcanic hazard, we studied its readiness to erupt by estimating changes in its internal stress state. These stress changes are difficult to calculate accurately, for example in the absence of focal mechanisms, but their existence can be indirectly revealed by the presence of volcano-tectonic earthquakes, for example following a large tectonic earthquake. We show that the seismic rate recorded at El Chichón volcano increased slightly after the large Mw8.2 Tehuantepec earthquake of 8 September 2017, Chiapas. However, this rate quickly returned to its background level after only 2 months, without any external volcanic manifestations, suggesting that the volcano is not ready to erupt in the near future. Previous observations of slight increases in the volcanic seismicity rate following large earthquakes have been explained by the presence of active hydrothermal systems in the vicinity of the volcano. We propose a similar explanation for El Chichón volcano which is known for its large hydrothermal system. Furthermore, the characteristics of the 2017 seismicity (spatial and magnitude distributions), and the horizontal-to-vertical spectral ratio also confirm the presence of high amounts of water near the volcano. We show that the 2017 volcano-tectonic seismicity is of hydrothermal rather than magmatic origin, in agreement with recent independent geochemical and aeromagnetic studies. [ABSTRACT FROM AUTHOR]

Effective volcanic impact and risk assessment underpins effective volcanic disaster risk management. Yet contemporary volcanic risk assessments face a number of challenges, including delineating hazard and impact sequences, and identifying and quantifying systemic risks. A more holistic approach to impact assessment is required, which incorporates the complex, multi-hazard nature of volcanic eruptions and the dynamic nature of vulnerability before, during and after a volcanic event. Addressing this need requires a multidisciplinary, integrated approach, involving scientists and stakeholders to co-develop decision-support tools that are scientifically credible and operationally relevant to provide a foundation for robust, evidence-based risk reduction decisions. This study presents a dynamic, longitudinal impact assessment framework for multi-phase, multi-hazard volcanic events and applies the framework to interdependent critical infrastructure networks in the Taranaki region of Aotearoa New Zealand, where Taranaki Mounga volcano has a high likelihood of producing a multi-phase explosive eruption within the next 50 years. In the framework, multi-phase scenarios temporally alternate multi-hazard footprints with risk reduction opportunities. Thus, direct and cascading impacts and any risk management actions carry through to the next phase of activity. The framework forms a testbed for more targeted mitigation and response planning and allows the investigation of optimal intervention timing for mitigation strategies during an evolving eruption. Using 'risk management' scenarios, we find the timing of mitigation intervention to be crucial in reducing disaster losses associated with volcanic activity. This is particularly apparent in indirect, systemic losses that cascade from direct damage to infrastructure assets. This novel, dynamic impact assessment approach addresses the increasing end-user need for impact-based decision-support tools that inform robust response and resilience planning. [ABSTRACT FROM AUTHOR]

Real-time analysis of fine ash in volcanic plumes, which represent magma fragments expelled from the crater during explosive eruptions, is a valuable tool for volcano monitoring and hazard assessment. To obtain the chemical characterization of the juvenile pyroclastic material emitted in volcanic plumes, many analytical techniques can be used. Among them, laser-induced breakdown spectroscopy (LIBS) is the one that can most easily be adapted to advanced applications in extreme environments. In this paper, LIBS experiments based on self-calibrated approaches are used to determine the elemental composition of suspended volcanic ash. To simulate the conditions of dispersed volcanic ash in the atmosphere, different sizes of volcanic ash samples are suspended in the air by laser-induced shockwaves in a dedicated chamber, and a parametric study is carried out to establish the optimal experimental conditions for recording usable plasma emission spectra for each ash size. The quantitative analysis is performed using a self-calibrated analytical method, including calibration-free LIBS, which is based on the calculation of the spectral radiance of a uniform plasma in local thermodynamic equilibrium. The method accounts intrinsically for self-absorption since it modifies the intensity of spectral lines and thus leads to an underestimation of the elemental fraction. An intensity calibration of the spectra based on the measurements of Fe lines intensities was also used in this work to deduce the apparatus response from the spectrum itself and avoid the use of standard calibration lamps. Results demonstrate the potential of real-time measurements of elemental fractions in volcanic ash with good agreement with the literature composition. [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]

Simulation of a potential collapse on Koryaksky Volcano showed the most likely direction of movement for a debris avalanche. The periodic fumarolic activation of the volcano provides evidence of the circulation of meteoric waters and of favorable conditions for replacement of the bedrock in the volcanic edifice resulting in landslide deposits. Satellite data were used to study surface ground deformation. The northeastern slopes of Koryaksky are rising relative to the subsiding southwestern slopes. Recalling that Koryaksky volcano stands at a distance of 10 km from Avachinsky Volcano which has produced massive explosive debris deposits during its history, the present study is of utmost urgency. The Elizovo–Petropavlovsk agglomeration (which includes the town of Elizovo and Petropavlovsk-Kamchatsky, as well as adjacent population centers in Elizovo District), which is in immediate vicinity of Koryaksky Volcano, harbors more than a half of all population of Kamchatka, as well as facilities that produce over half of all income in the region. Consequently, the assessment of naturally occurring processes on the volcano with a view to further development of a plan to minimize their negative impact is critically important for the economy of Kamchatka. [ABSTRACT FROM AUTHOR]

During the last 10 kyr, significant subsidence and uplift occurred on Mayotte Island in the Comoros archipelago (Indian Ocean), but the role of volcanic processes in Holocene vertical movements has been neglected in the research so far. Here, we show that an abrupt subsidence of 6–10 m occurred between 9.4 and 10 kyr ago, followed by an uplift of the same amplitude at a rate of 9 mm/yr from 8.1 to 7 kyr ago. A comparison of the relative sea level of Mayotte and a reference sea level curve for the global ocean has been conducted using a modeling approach. This shows that an increasing and decreasing pressure at depth, equivalent to the process caused by a deep magma reservoir (50–70 km), was responsible for ~6–10 m subsidence and 6–10 m uplift, whereas loading by new volcanic edifices caused subsidence during the last few thousand years. Surface movements and deep pressure variations may be caused by pulses from the deep mantle, related to superplume activity, but uncertainties and unknowns about these phenomena are still present and further studies are needed. A better understanding of the volcano-tectonic cycle may improve assessments of volcanic hazards. [ABSTRACT FROM AUTHOR]

Tsunamis generated by volcanic eruptions have risen to prominence since the December 2018 tsunami generated by the flank collapse of Anak Krakatau during a moderate eruption and then the global tsunami generated by the explosive eruption of the Hunga volcano in the Tongan Archipelago in January 2022. Both events cause fatalities and highlight the lack in tsunami warning systems to detect and warn for tsunamis induced by volcanic mechanisms. Following the Hunga Tonga—Hunga Ha'apai eruption and tsunami, an ad hoc working group on Tsunamis Generated by Volcanoes was formed by the Intergovernmental Oceanographic Commission of UNESCO. Volcanic tsunamis differ from seismic tsunamis in that there are a wide range of source mechanisms that can generate the tsunamis waves and this makes understanding, modelling and monitoring volcanic tsunamis much more difficult than seismic tsunamis. This paper provides a review of both the mechanisms behind volcanic tsunamis and the variety of modelling techniques that can be used to simulate their effects for tsunami hazard assessment and forecasting. It gives an example of a volcanic tsunami risk assessment undertaken for Stromboli, outlines the requirement of volcanic monitoring to warn for tsunami hazard and provides examples of volcanic tsunami warning systems in Italy, the Hawaiian Island (USA), Tonga and Indonesia. The paper finishes by highlighting the need for implementing monitoring and warning systems for volcanic tsunamis for locations with submarine volcanoes or near-shore volcanoes which could potentially generate tsunamis. [ABSTRACT FROM AUTHOR]

Outgassing of sulfur (as SO2) is one of the principal hazards posed by volcanic eruptions. However, S emission potentials of most volcanoes globally are poorly constrained due to a short observational record and an incomplete understanding of the magmatic processes that influence pre‐eruptive S concentrations. Here, we use a compilation of published and new data from melt inclusions (MIs)—which can preserve magmatic S concentrations prior to eruptive degassing—from the Iceland hotspot to evaluate the effects of mantle melting and crustal magmatic processes on the S budgets of Icelandic melts. We use MI data to estimate S emission potentials (ΔSmax, in ppm S) for 73 eruptions from 22 of Iceland's presently active ∼33 volcanic systems. We show that the S systematics of Icelandic melts are strongly regulated by the sulfide solubility limit. Sulfide‐saturated conditions during lower‐degree mantle melting, prevalent at off‐rift zones, likely explains observed decoupling between S and Cl. During magmatic differentiation, a local maximum in modeled sulfide solubility occurs in evolved basalts (4–6 wt.% MgO), coinciding with highest MI S concentrations. Highest ΔSmax values (2,100–2,600 ppm) are found in the Hekla 1913 CE, Eldgjá 939 CE, and Surtsey 1963–1967 CE eruptions in the South Iceland Volcanic Zone. Our results extend the record of volcanic sulfur emissions back in time and can be used to assess volcanic gas hazards at Icelandic volcanoes where no direct measurements are available. Broadly, the results underline the governing role of sulfide saturation during melting and magma differentiation in controlling the eruptible S contents of Icelandic magmas. Key Points: Maximum eruptible S contents (ppm S) are estimated for 73 Icelandic eruptions based on melt inclusion dataPre‐eruptive S contents are mostly controlled by sulfide saturation during both melting and crustal magmatic differentiationIcelandic basalts often erupt at compositions close to a compositional maximum in sulfide solubility, leading to relatively high S emissions [ABSTRACT FROM AUTHOR]

Determining the time spans of processes related to the assembly of eruptible magma at active volcanoes is fundamental to understand magma chamber dynamics and assess volcanic hazard. This information can be recorded in the chemical zoning of crystals. Nevertheless, this kind of study is still poorly employed for the active volcanoes of the Neapolitan area (Southern Italy), in particular, for Ischia island where the risk is extremely high and this information can provide the basis for probabilistic volcanic hazard assessment. For these reasons, we acquired chemical composition on clinopyroxene crystals erupted at Ischia during the Zaro eruption (6.6 ± 2.2 ka) and performed numerical simulations of the input of mafic magma into a trachytic reservoir, in order to investigate various aspects of pre-eruptive dynamics occurring at different timescales. This event emplaced a ~ 0.1 km3 lava complex, in which the main trachytic lava flows host abundant mafic to felsic enclaves. Previous petrological investigation suggested that mafic magma(s) mixed/mingled with a trachytic one, before the eruption. In this work, the clinopyroxene zoning patterns depict the growth of crystals in different magmatic environments, recording sequential changes occurred in the plumbing system before the eruption. The evolution of the plumbing system involved a hierarchy of timescales: a few hours for magma mingling caused by mafic recharge(s) and likely occurred multiple times over a decade during which a dominant magmatic environment was sustained before the eruption. Such timescales must be considered in volcanic hazard assessment at Ischia and similar active volcanoes in densely populated areas. [ABSTRACT FROM AUTHOR]

Silicic caldera volcanoes present major volcanic and seismic hazards but also host dynamic hydrothermal and groundwater systems and a rich but largely unexplored subsurface biosphere. Many of these volcanoes are hosted in rift settings. The intricate connections and feedbacks among magmatism, rifting, hydrothermal processes, and the biosphere in these complex systems remain poorly understood, necessitating subsurface joint observations that are only enabled by scientific drilling. The CALDERA (Connections Among Life, geo-Dynamics and Eruptions in a Rifting Arc caldera) project workshop funded by the International Continental Scientific Drilling Program (ICDP) gathered multi-disciplinary international experts in January 2023 to advance planning of a scientific drilling project within one of these dynamic, rift-hosted calderas, the Okataina Volcanic Centre (OVC), Aotearoa New Zealand. The OVC's high eruption rate, frequent unrest events and earthquake swarms, location in a densely faulted rapidly extending rift, abundant groundwater–geothermal fluid circulations, and diverse surface hot spring microbiota make it an ideal location for exploring a connected geo-hydro-biosphere via scientific drilling and developing a test bed for novel volcano monitoring approaches. Drilling configurations with at least two boreholes (∼ 200 and ∼ 1000–1500 m deep) were favoured to achieve the multi-disciplinary objectives of the CALDERA project. Decadal monitoring including biosphere activity and composition has the potential to evaluate the response of the hydro-bio system to volcano-tectonic activity. In addition to the OVC caldera-scale datasets already available, site surveys will be conducted to select the best drilling locations. The CALDERA project at the OVC would provide, for the first time, an understanding of volcanic–tectonic–hydrological–biological connections in a caldera–rift system and a baseline for global comparisons with other volcanoes, rifts, and hydrothermal systems. CALDERA would serve as an unprecedented model system to understand how and how quickly the subsurface biosphere responds to geologic activities. Discoveries will improve assessment of volcanic and seismic hazards, guide the sustainable management and/or conservation of groundwater and geothermal resources and microbial ecosystems, and provide a forum for interweaving mātauranga Māori and Western knowledge systems. [ABSTRACT FROM AUTHOR]

In this paper we present a new model for the simulation of lahars based on the depth-averaged code IMEX-SfloW2D with new governing and constitutive equations introduced to better describe the dynamics of lahars. A thorough sensitivity analysis is carried out to identify the critical processes (such as erosion and deposition) and parameters (both numerical and physical) controlling lahar runout using both synthetic and real case topographies. In particular, an application of the model to a syn-eruptive lahar from a reference size eruption from Somma–Vesuvius, affecting the Campanian Plain (southern Italy), described in Di Vito et al. (2024), is used in this work for the sensitivity analysis. Effects of erosion and deposition are investigated by comparing simulations with and without these processes. By comparing flow thickness and area covered by the flow and their evolution with time, we show that the modelling of both the processes is important to properly simulate the effects of the bulking and debulking as well as the associated changes in rheology. From a computational point of view, the comparisons of simulations obtained for different numerical grids (from 25 to 100 m), scheme order, and grain size discretization were useful to find a good compromise between resolution and computational speed. The companion paper by Sandri et al. (2024) shows an application of the presented model for probabilistic volcanic hazard assessment for lahars from Vesuvius deposits in the Neapolitan area. [ABSTRACT FROM AUTHOR]

In this study we present a novel general methodology for probabilistic volcanic hazard assessment (PVHA) for lahars. We apply the methodology to perform a probabilistic assessment in the Campanian Plain (southern Italy), focusing on syn-eruptive lahars from a reference size eruption from Somma–Vesuvius. We take advantage of new field data relative to volcaniclastic flow deposits in the target region (Di Vito et al., 2024b) and recent improvements in modelling lahars (de' Michieli Vitturi et al., 2024). The former allowed defining proper probability density functions for the parameters related to the flow initial conditions, and the latter allowed computationally faster model runs. In this way, we are able to explore the effects of uncertainty in the initial flow conditions on the invasion of lahars in the target area by sampling coherent sets of values for the input model parameters and performing a large number of simulations. We also account for the uncertainty in the position of lahar generation by running the analysis on 11 different catchments threatening the Campanian Plain. The post-processing of the simulation outputs led to the production of hazard curves for the maximum flow thickness reached on a grid of points covering the Campanian Plain. By cutting the hazard curves at selected threshold values, we produce a portfolio of hazard maps and probability maps for the maximum flow thickness. We also produce hazard surface and probability maps for the simultaneous exceeding of pairs of thresholds in flow thickness and dynamic pressure. The latter hazard products represent, on one hand, a novel product in PVHA for lahars and, on the other hand, a useful means of impact assessment by assigning a probability to the occurrence of lahars that simultaneously have a relevant flow thickness and large dynamic pressure. [ABSTRACT FROM AUTHOR]

One of the most intriguing questions of modern volcanology is the inception of an eruption. Despite efforts to detect premonitory signals, numerous unpredicted eruptions have occurred recently. It has been suggested that these unpredicted eruptions might be explained by viscosity variations in elemental sulfur accumulated within the hydrothermal systems present in several volcanic settings under the influence of organics, hydrocarbons, hydrogen sulfide, halogens, and ammonia. Changes in impure sulfur viscosity are more complex than those in pure S, invoked decades ago to trigger eruptions by system sealing in volcanoes hosting a crater lake. Growing evidence suggests that sulfur accumulation is a common process, not restricted to crater lakes. Moreover, both types and amounts of gas species released at the surface, critical for volcano monitoring, would be altered, following chemical reactions involving impure S, invalidating signals used to issue alerts. Impure sulfur behavior may explain puzzling degassing and contrasting signals reported at volcanoes and restless calderas worldwide, with implications for hazard assessment and volcanic-risk-mitigation strategies. [ABSTRACT FROM AUTHOR]

We hereby present VolcFire, a new cellular automaton model for fire propagation aimed at the creation of fire hazard maps for fires of volcanic origin. The new model relies on satellite-derived input data for the topography, land-use, fuel, and humidity information, and produces probabilistic maps of fire propagation simulating fire spread. The model contains several simplifications compared to the current state-of-the-art, limiting its usability to plan fire-fighting interventions during an event in favour of a reduced computational load. The accuracy and reliability of the model are also discussed by presenting its ability to reproduce two recent fires on Stromboli island, with good spatial fit (Brier score of 0.146 ± 0.002 for the 3 July 2019 volcanic fire, and of 0.073 ± 0.001 for the 25 May 2022 anthropogenic fire) and less than 1.5 % variation across multiple simulations for the same event. [ABSTRACT FROM AUTHOR]

During explosive eruptions, tephra fallout represents one of the main volcanic hazards and can be extremely dangerous for air traffic, infrastructures, and human health. Here, we present a new technique aimed at identifying the area covered by tephra after an explosive event, based on processing PlanetScope imagery. We estimate the mean reflectance values of the visible (RGB) and near infrared (NIR) bands, analyzing pre- and post-eruptive data in specific areas and introducing a new index, which we call the 'Tephra Fallout Index (TFI)'. We use the Google Earth Engine computing platform and define a threshold for the TFI of different eruptive events to distinguish the areas affected by the tephra fallout and quantify the surface coverage density. We apply our technique to the eruptive events occurring in 2021 at Mt. Etna (Italy), which mainly involved the eastern flank of the volcano, sometimes two or three times within a day, making field surveys difficult. Whenever possible, we compare our results with field data and find an optimal match. This work could have important implications for the identification and quantification of short-term volcanic hazard assessments in near real-time during a volcanic eruption, but also for the mapping of other hazardous events worldwide. [ABSTRACT FROM AUTHOR]

Accurate volcanic hazard assessments rely on a detailed understanding of the timing of past eruptions. While radiometric methods like 40Ar/39Ar or K/Ar are by far the most conventional lava flow dating tools, their low resolution for young (<20 ka) deposits interferes with the development of precise recent effusive chronologies on most volcanoes. Mt. Ruapehu (New Zealand) has produced many lava flows throughout its history, but the precise timing of many recent eruptions remains largely unknown. In this study, we use cosmogenic 3He exposure dating to provide 23 eruption ages of young lava flows at Ruapehu. We then compare our results with existing 40Ar/39Ar and palaeomagnetic constraints, highlighting the value of cosmogenic nuclides exposure dating in refining recent eruptive chronologies. Of the 23 sampled flows, 16 provided robust eruption ages (5–20 % internal 2σ; n≥3) between ca 20 and 8 ka, except for one lava erupted at around 43 ka, and their age distribution indicates that, during the last 20 thousand years, effusive activity at Ruapehu peaked at 17–12 ka and at 9–7.5 ka. Nearly identical eruption ages of lavas located in different flanks of the volcanic edifice suggest concurrent activity from multiple vents during relatively short time intervals (0–2 kyr) at around 13, 10 and 8 ka. We analysed four lavas previously dated by 40Ar/39Ar, two of which yielded eruption ages older than the older limit of the 2σ interval of the radiometric dates, but the good clustering of individual samples from our sites suggests that our results better represent these lava flows' real eruption ages. Our 3He-based dates show excellent agreement with palaeomagnetic constraints, suggesting that production rate uncertainties are unlikely to impact the accuracy of our eruption ages. This study demonstrates how cosmogenic nuclides dating can provide greater detail on the recent effusive chronology of statovolcanoes, helping to resolve the low resolution and difficulty in applying radiometric dating methods to young lava flows. [ABSTRACT FROM AUTHOR]

Volcanic eruptions can cause significant impacts on communities and infrastructure. There is an increasing need for effective risk assessments to inform decision-making and minimise the impact of volcanic hazards. Vulnerability models play a crucial role in these assessments, connecting the intensity of the hazard with the elements that are exposed to it, allowing for the calculation of potential impact or risk. There has been a large increase in the number of vulnerability models being developed for volcanic risk applications, and there is now a need to identify knowledge gaps for the field to take a strategic approach moving forward. This review aims to provide a high- level overview of the current state of volcanic vulnerability modelling and identify areas for future development. We evaluated 594 vulnerability models covering a range of elements and sectors, including buildings, critical infrastructure, transportation networks, agriculture, and human vulnerability. We reviewed the types of hazard intensity metrics and impact/risk metrics used in the models, modelling methodologies, underpinning data requirements, and uncertainty characterisation. A global clearinghouse for volcanic vulnerability models would be advantageous for the volcanic risk community to identify appropriate vulnerability models quickly and efficiently for their needs. As a first step towards such a clearinghouse, we have uploaded this volcano vulnerability model compilation to a repository and encourage additions/suggestions from the community on its future development. The results of this study will contribute to the advancement of the field and provide valuable insights for future research and development in volcanic risk assessment. [ABSTRACT FROM AUTHOR]

The Central Volcanic Zone of the Andes (CVZA) extends from southern Peru, through the altiplano of Bolivia, to Puna de Atacama of northern Chile and Argentina, between latitudes 14-28°S of the Andean cordillera, with altitudes raising up to more than 4,000 m above sea level. Given the large number of active volcanoes in this area, which are often located close to both urban areas and critical infrastructure, prioritization of volcanic risk reduction strategies is crucial. However, the identification of hazardous active volcanoes is challenging due to the limited accessibility. Here, we identify the riskiest volcanoes based on complementary strategies including i) a regional mapping based on volcanic hazard parameters and surrounding density of elements at risk combined with ii) the application of the recently developed Volcanic Risk Ranking methodology that integrates hazard, exposure and vulnerability as factors that increase risk, and resilience as a factor that reduces risk. The method identifies 59 active and potentially active volcanoes that not only highlights the volcanic centers with the most intense and frequent volcanic eruptions (e.g., El Misti and Ubinas volcanoes (Peru)) and the highest density of exposed elements (e.g., the cities of Arequipa and Mequegua (Peru)), but also those with the highest potential impact requiring risk mitigation actions (i.e., Cerro Blanco (Argentina), Yucamane, Huaynaputina, Tutupaca, and Ticsani (Peru)). [ABSTRACT FROM AUTHOR]

Submarine volcano monitoring is vital for assessing volcanic hazards but challenging in remote and inaccessible environments. In the vicinity of Kita‐Ioto Island, south of Japan, unusual M ∼ 5 non‐double‐couple volcanic earthquakes exhibited quasi‐regular recurrence near a submarine caldera. Following the earthquakes in 2008 and 2015, a distant ocean bottom pressure sensor recorded distinct tsunami signals. In this study, we aim to find a source model of the tsunami‐generating earthquake and quantify the pre‐seismic magma overpressure within the caldera's magma reservoir. Based on the earthquake's characteristic focal mechanism and efficient tsunami generation, we hypothesize that submarine trapdoor faulting occurred due to highly pressurized magma. To investigate this hypothesis, we establish mechanical earthquake models that link pre‐seismic magma overpressure to the size of the resulting trapdoor faulting, by considering stress interaction between a ring‐fault system and a reservoir of the caldera. The trapdoor faulting with large fault slip due to magma‐induced shear stress in the submarine caldera reproduces well the observed tsunami waveform. Due to limited data, uncertainties in the fault geometry persist, leading to variations of magma overpressure estimation: the pre‐seismic magma overpressure ranging approximately from 5 to 20 MPa, and the co‐seismic pressure drop ratio from 10% to 40%. Although better constraints on the fault geometry are required for robust magma pressure quantification, this study shows that magmatic systems beneath calderas are influenced significantly by intra‐caldera fault systems and that tsunamigenic trapdoor faulting provides rare opportunities to obtain quantitative insights into remote submarine volcanism hidden under the ocean. Plain Language Summary: Monitoring submarine volcanoes is essential to understand and prepare for potential volcanic hazards in/around oceans, but it's challenging because these volcanoes are located in inaccessible environments. In a submarine volcano with a caldera structure in the south of Japan, unusual volcanic earthquakes took place every several years. After one of these earthquakes in 2008, a pressure sensor deployed on the sea bottom recorded a clear signal of tsunami waves. By utilizing the tsunami signal from the earthquake, we attempt to measure how much magma pressure was building up beneath the volcano before the earthquake. Assuming that the earthquake happened with sudden rupture on an intra‐caldera fault system due to highly pressurized magma beneath the volcano, we develop a method to assess the built‐up magma pressure through quantification of the earthquake and tsunami sizes. By applying the method, we estimate that the volcanic edifice was under a highly stressed condition before the earthquake, suggesting the active magma accumulation process that has continued beneath the volcano. Signals emitted from volcanic earthquakes under oceans shed light on the activity of poorly monitored submarine volcanoes. Key Points: Non‐double‐couple earthquakes with seismic magnitudes of 5.2–5.3 recurred in the vicinity of a submarine caldera near Kita‐Ioto IslandA mechanical model of trapdoor faulting based on tsunami data of the 2008 earthquake infers pre‐seismic overpressure in a magma reservoirUncertainty in fault geometry varies our estimate of pre‐seismic overpressure (5–20 MPa) and co‐seismic pressure drop ratio (10%–40%) [ABSTRACT FROM AUTHOR]

The Instituto Geofísico (IG-EPN) was created in 1983 by faculty of the Escuela Politécnica Nacional, a public university in Quito, Ecuador, with the objective of assessing volcanic hazard in the country. Since then, the IG-EPN has established and developed an instrumental monitoring network and from 1999 has faced the eruption of five continental-arc volcanoes (Guagua Pichincha, Tungurahua, Reventador, Cotopaxi, and Sangay) which displayed varied hazards, eruptive dynamics, eruption durations, and socio-economic contexts. At the same time, mainly effusive eruptions took place in Galápagos archipelago, which has undergone an increase in local population over the last two decades and hence in the risk posed by volcanic eruptions. The outstanding handling of these volcanic crises was the reason why IG-EPN was granted with the 2020 Volcanic Surveillance and Crisis Management IAVCEI Award. Now, the IG-EPN manages a country-wide network of about 500 instruments to monitor both volcanic and tectonic activity with a highly qualified staff of 80 people. This manuscript describes the history of IG-EPN, the main volcanic hazard studies and resulting hazard maps; the instrumental networks; and the volcanic crises that the IG-EPN faced during the last forty years. [ABSTRACT FROM AUTHOR]

Here, we review volcanic risk management at Mount St. Helens from the perspective of the US Geological Survey's (USGS) experience over the four decades since its 18 May 1980 climactic eruption. Prior to 1980, volcano monitoring, multidisciplinary eruption forecasting, and interagency coordination for eruption response were new to the Cascade Range. A Mount St. Helens volcano hazards assessment had recently been published and volcanic crisis response capabilities tested during 1975 thermal unrest at nearby Mount Baker. Volcanic unrest began in March 1980, accelerating the rate of advance of volcano monitoring, prompting coordinated eruption forecasting and hazards communication, and motivating emergency response planning. The destruction caused by the 18 May 1980 eruption led to an enormous emergency response effort and prompted extensive coordination and planning for continuing eruptive activity. Eruptions continued with pulsatory dome growth and explosive eruptions over the following 6 years and with transport of sediment downstream over many more. In response, USGS scientists and their partners expanded their staffing, deployed new instruments, developed new tools (including the first use of a volcanic event tree) for eruption forecasting, and created new pathways for agency internal and external communication. Involvement in the Mount St. Helens response motivated the establishment of response measures at other Cascade Range volcanoes. Since assembly during the early and mid-1990s, volcano hazard working groups continue to unite scientists, emergency and land managers, tribal nations, and community leaders in common cause for the promotion of risk reduction. By the onset of renewed volcanic activity in 2004, these new systems enabled a more efficient response that was greatly facilitated by the participation of organizations within volcano hazard working groups. Although the magnitude of the 2004 eruptive sequence was much smaller than that of 1980, a new challenge emerged focused on hazard communication demands. Since 2008, our understanding of Mount St. Helens volcanic system has improved, helping us refine hazard assessments and eruption forecasts. Some professions have worked independently to apply the Mount St. Helens story to their products and services. Planning meetings and working group activities fortify partnerships among information disseminators, policy and decision-makers, scientists, and communities. We call the sum of these pieces the Volcanic Risk Management System (VRMS). In its most robust form, the VRMS encompasses effective production and coordinated exchange of volcano hazards and risk information among all interested parties. [ABSTRACT FROM AUTHOR]

The article focuses on exploring the architecture of magma plumbing systems and how magmas move through them in the context of volcanic activity. It discusses the use of advanced seismic techniques to study the shallowest parts of magmatic systems beneath the East Pacific Rise (EPR) and provides insights into the complex network of crustal magma bodies, shedding light on their characteristics and potential links to volcanic eruptions.

The past decades have seen tremendous advances in analytical capabilities regarding the sensitivity, spatial selectivity, and instrumental precision of U-Th-Pb zircon geochronology. Along with improved zircon pretreatment to mitigate the effects of Pb-loss, these advancements have resulted in the emergence of U-Th-Pb dating as the most widely used geochronometer. In parallel, it became increasingly obvious that modern analytical techniques can resolve zircon age dispersal beyond instrumental uncertainties and that this dispersion cannot be attributed to Pb-loss or inheritance. Hence, there is a pressing need to refine statistical procedures for displaying and interpreting dispersed age data from volcanic and plutonic rocks, where zircon ages were traditionally assigned to the quasi-instantaneous events of eruption and magma emplacement, respectively. The ability to resolve zircon age spectra, which often range over timescales of 103-106 years, also offers new opportunities to monitor magmatic processes, because zircon crystallization directly relates to the temperature and composition of its host melt. This relation is, at least for typical subalkaline melt compositions, well calibrated by multiple zircon saturation experiments, although absolute saturation temperatures derived from them can vary by tens of degrees. Moreover, zircon saturation thermometry is supported by the trace element and isotopic inventory of zircon, which records the thermochemical and compositional evolution of melts at high fidelity. Here, we first review the properties of true zircon age spectra that are defined by a statistically robust overdispersion relative to analytical uncertainties. Secondly, we evaluate existing models and present new models that aim to quantitatively translate the properties of zircon age spectra into parameters controlling the longevity and thermal evolution of crustal magma bodies such as magma recharge flux and duration. These developing approaches, which aspire to capture all processes that affect the formation and dispersal of zircon in dynamic crustal magma systems, have the potential to foster an improved understanding of magmatism with implications for volcanic hazard assessment, geothermal energy uses, and the origins of ore deposits. [ABSTRACT FROM AUTHOR]

In this study we present a novel general methodology for Probabilistic Volcanic Hazard Assessment (PVHA) for lahars. We apply the methodology to perform a probabilistic assessment in the Campanian Plain (Southern Italy), focussing on syn-eruptive lahars from a reference-size eruption from Somma-Vesuvius. We take advantage of new field data relative to volcaniclastic flow deposits in the target region and recent improvements in modelling lahars. We explore the effect of uncertainty on the flow initial conditions on the invasion of lahar in the target area, by sampling coherent sets of values for the input model parameters and performing a large number of simulations. We analyse the simulation outputs to produce hazard curves, hazard maps and probability maps for the maximum flow thickness, and hazard surface and probability maps for joint thresholds in flow thickness and dynamic pressure. We believe the latter hazard products represent, on one hand, a novel product in PVHA for lahars, and, on the other hand, a useful means for impact assessment. [ABSTRACT FROM AUTHOR]

Accurate dating of young eruptions from explosive volcanoes is essential for forecasting future eruptions and for defining the hazardscape of volcanic fields. However, precise dating of Quaternary eruptions is often challenging due to limited number of applicable dating methods or lack of datable eruptive phases. Moreover, small volume eruptions (e.g., monogenetic type), despite their significance on regional scale, have traditionally deserved less attention than their large volume counterparts. Puketerata is a maar-lava dome complex in the central Taupō Volcanic Zone (New Zealand), encompassing mafic and silicic phreatomagmatic eruptions with well-preserved pyroclastic deposits sourced from closely spaced vents. Its most recent activity is estimated to ca. 16 ka based on medial and distal stratigraphic surveys. Here, we carried out two independent age determinations and an additional paleomagnetic analysis on the volcanic succession of the Puketerata maar-lava dome complex with an aim to unravel the timing of volcanic activity. Combined U-Th disequilibrium and (U-Th)/He dating of zircon from two lava domes yielded eruption ages of 11.3 ± 2.6 ka and 11.3 ± 1.7 ka, which are concordant with the radiocarbon ages of 11.3–11.7 ka obtained on charcoal from the base of the pyroclastic sequence. Paleomagnetic data on the lavas from the two lava domes suggest at least ~ 100 years difference between their emplacements. Our geochronological results and new stratigraphic observations suggest that the volcanic/magmatic history of the Puketerata is complex with multiple eruptions within a small, confined area, where the most recent eruptions occurred only at ca. 11.5 ka, which is significantly younger than previously thought. This provides an additional datum for volcanic hazards assessment and stratigraphic correlations in New Zealand. [ABSTRACT FROM AUTHOR]

In this paper we present a new model for the simulation of lahars, based on the depth-averaged code IMEX-SfloW2D with new governing and constitutive equations introduced to better describe the dynamics of lahars. A thorough sensitivity analysis is carried out to identify the critical processes (such as erosion and deposition) and parameters (both numerical and physical) controlling lahar runout, using both synthetic and real cases topographies. In particular, an application of the model to a syn-eruptive lahar from a reference-size eruption from Somma-Vesuvius, affecting the Campanian Plain (Southern Italy), described in Di Vito et al. (this issue), is used in this work for the sensitivity analysis. Effects of erosion and deposition are investigated by comparing simulations with and without these processes. By comparing flow thickness and area covered by the flow and their evolution with time, we show that the modelling of both the processes is important to properly simulate the effects of the bulking and debulking and the associated changes in rheology. From a computational point of view, the comparison of simulations obtained for different numerical grids (from 25 m to 100 m), scheme order, and grain size discretization were useful to find a good compromise between resolution and computational speed. The companion paper by Sandri et al. (this issue) shows an application of the presented model for probabilistic volcanic hazard assessment for lahars from Vesuvius deposits in the Neapolitan area. [ABSTRACT FROM AUTHOR]

In this paper we present a new model for the simulation of lahars, based on the depth-averaged code IMEX-SfloW2D with new governing and constitutive equations introduced to better describe the dynamics of lahars. A thorough sensitivity analysis is carried out to identify the critical processes (such as erosion and deposition) and parameters (both numerical and physical) controlling lahar runout, using both synthetic and real cases topographies. In particular, an application of the model to a syn-eruptive lahar from a reference-size eruption from Somma-Vesuvius, affecting the Campanian Plain (Southern Italy), described in Di Vito et al. (this issue), is used in this work for the sensitivity analysis. Effects of erosion and deposition are investigated by comparing simulations with and without these processes. By comparing flow thickness and area covered by the flow and their evolution with time, we show that the modelling of both the processes is important to properly simulate the effects of the bulking and debulking and the associated changes in rheology. From a computational point of view, the comparison of simulations obtained for different numerical grids (from 25 m to 100 m), scheme order, and grain size discretization were useful to find a good compromise between resolution and computational speed. The companion paper by Sandri et al. (this issue) shows an application of the presented model for probabilistic volcanic hazard assessment for lahars from Vesuvius deposits in the Neapolitan area. [ABSTRACT FROM AUTHOR]

The Main Ethiopian Rift is accompanied by extensive volcanism and the formation of geothermal systems, both having a direct impact on the lives of millions of inhabitants. Although previous studies in the region found evidence that asthenospheric upwelling and associated decompression melting provide melt to magmatic systems that feed the tectono‐magmatic segments in the rift valley, there is a lack of geophysical models imaging these regional and local scale transcrustal structures. To address this challenge, we use the magnetotelluric method and image subsurface electrical conductivity to examine the magmatic roots of Aluto volcano, quantify and interpret the melt distribution in the crust considering established concepts of continental rifting processes and constrain the formed geothermal system. Specifically, we combined regional (maximum 30 × 120 km2) and local (15 × 15 km2) magnetotelluric data sets and obtained the first multi‐scale 3‐D electrical conductivity model of a segment of the central Main Ethiopian Rift. The model unravels a magma ponding zone with up to 7 vol. % melt at the base of the crust (30–35 km b.s.l.) in the western part of the rift and its connection to Aluto volcano via a fault‐aligned transcrustal magma system. Melt accumulates at shallow crustal depths (≥4 km b.s.l.), thereby providing heat for Aluto's geothermal system. Our model suggests that different volcano‐tectonic lineaments in the rift valley share a common melt source. The presented model provides new constraints on the melt distribution below a segment of the rift which is important for future geothermal developments and volcanic hazard assessments in the region. Plain Language Summary: Continental rifting is a fundamental process of plate tectonics that breaks continents apart to ultimately form new oceans. The landscape of the Main Ethiopian Rift is characterized by abundant volcanism and hot springs, which indicate the presence of geothermal resources formed by magmatic heating of subsurface fluids. Here we present a new 3‐D subsurface electrical conductivity image of the magmatic system and geothermal reservoir beneath the Aluto volcano in the Main Ethiopian Rift. The model allows us to estimate the amount and distribution of magmatic melt. This is the first model that provides a high‐resolution image of the entire magmatic system below a central part (maximum 30 × 120 km2) of the Main Ethiopian Rift from the deep magmatic melt source up to the surface. The new model shows that the geothermal reservoir under Aluto has been formed as a consequence of rifting‐related volcanic activity thereby providing a geophysical illustration of fundamental geological processes. These results also have a high societal relevance by providing a basis for volcanic risk assessment and contributing to a better understanding of how the sustainable green geothermal energy resources form. Key Points: 3‐D multi‐scale magnetotelluric model imaging the entire transcrustal tectono‐magmatic system across a segment of the Main Ethiopian RiftA lower crustal magma ponding zone feeds a fault‐aligned magmatic mush column supplying heat for the geothermal system of Aluto volcanoEastern and western volcano‐tectonic lineaments likely share a lower crustal magma source with an estimated melt fraction of 7 percent [ABSTRACT FROM AUTHOR]

Gl The Tonga volcano eruption was the biggest submarine eruption in history. Potential hazards which would affect the settlement of Squamish include voluminous lava flows, pyroclastic density currents caused by lava dome collapse, tephra fallout, debris flows, lahars and potentially eruption-related forest fires. 'We found that the EPB formed by this eruption reached space even beyond the ionosphere, suggesting that we should pay attention to the connection between the ionosphere and the cosmosphere when extreme natural phenomenon, such as the Tonga event, occur'. Tonga eruption affected satellite signals An international team has used satellite- and ground-based ionospheric observations to demonstrate that an air pressure wave triggered by volcanic eruptions could produce an equatorial plasma bubble (EPB) in the ionosphere, severely disrupting satellite-based communications ( I ScienceDaily i , 22 May 2023). [Extracted from the article]

Nowadays, modeling of tephra fallout hazard is coupled with probabilistic analysis that takes into account the natural variability of the volcanic phenomena in terms of eruption probability, eruption sizes, vent position, and meteorological conditions. In this framework, we present a prototypal methodology to carry out the long-term tephra fallout hazard assessment in southern Italy from the active Neapolitan volcanoes: Somma–Vesuvius, Campi Flegrei, and Ischia. The FALL3D model (v.8.0) has been used to run thousands of numerical simulations (1500 per eruption size class), considering the ECMWF ERA5 meteorological dataset over the last 30 years. The output in terms of tephra ground load has been processed within a new workflow for large-scale, high-resolution volcanic hazard assessment, relying on a Bayesian procedure, in order to provide the mean annual frequency with which the tephra load at the ground exceeds given critical thresholds at a target site within a 50-year exposure time. Our results are expressed in terms of absolute mean hazard maps considering different levels of aggregation, from the impact of each volcanic source and eruption size class to the quantification of the total hazard. This work provides, for the first time, a multi-volcano probabilistic hazard assessment posed by tephra fallout, comparable with those used for seismic phenomena and other natural disasters. This methodology can be applied to any other volcanic areas or over different exposure times, allowing researchers to account for the eruptive history of the target volcanoes that, when available, could include the occurrence of less frequent large eruptions, representing critical elements for risk evaluations. [ABSTRACT FROM AUTHOR]

Understanding the crustal structure and the storage and movement of fluids beneath a volcano is necessary for characterizing volcanic hazard, geothermal prospects and potential mineral resources. This study uses local earthquake traveltime tomography to image the seismic velocity structure beneath Nabro, an off‐rift volcano located within the central part of the Danakil microplate near the Ethiopia‐Eritrea border. Nabro underwent its first historically documented eruption in June 2011, thereby providing an opportunity to analyze its post‐eruptive state by mapping subsurface fluid distributions. We use a catalog of earthquakes detected on a temporary seismic array using machine learning methods to simultaneously relocate the seismicity and invert for the three‐dimensional P‐ and S‐wave velocity structures (VP, VS) and the ratio between them (VP/VS). Overall, our model shows higher than average P‐ and S‐wave velocities, suggesting the presence of high‐strength, solidified intrusive magmatic rocks in the crust. We identify an aseismic region of low VP, low VS, and high VP/VS ratio at depths of 6–10 km b.s.l., interpreted as the primary melt storage region that fed the 2011 eruption. Above this is a zone of high VS, low VP, and low VP/VS ratio, representing an intrusive complex of fractured rocks partially saturated with over‐pressurized gases. Our observations identify the persistence of magma in the subsurface following the eruption, and track the degassing of this melt through the crust to the surface. The presence of volatiles and high temperatures within the shallow crust indicate that Nabro is a viable candidate for geothermal exploration. Plain Language Summary: Understanding the structure of the crust and the distribution and movement of fluids beneath a volcano allows for the assessment of volcanic hazard, geothermal potential and possible mineral extraction. To identify different regions of the crust and differentiate between fluids, we use the fact that the speed of seismic waves depends on the material they are traveling through. For example, seismic waves will travel through magma (molten, or liquid, rock) at lower speeds than in the surrounding rock. The focus of this study is Nabro volcano in Eritrea, which erupted in 2011. We use earthquakes that have been automatically detected following the eruption to image the structure of the crust in the form of 3D variations in seismic wave speeds. This identifies a volume of magma stored at depths of 6–10 km below sea level, which fed the eruption. Above this, we observe a region of rocks that are likely remnants of earlier eruptions at Nabro, with fractures containing gases at high pressure. The source of this high pressure is the release of gas from the magma storage zone. The presence of hot fluids means Nabro could be used as a source of geothermal power in the future. Key Points: 3D seismic modeling reveals the structure of the magmatic and hydrothermal systems beneath Nabro volcano in EritreaThe primary melt storage region feeding the 2011 eruption is located at depths of 6–10 km below sea levelDegassing from the magma storage zone causes overpressure in partially saturated, fractured intrusive complex above [ABSTRACT FROM AUTHOR]

Despite their global societal importance, the volumes of large-scale volcanic eruptions remain poorly constrained. Here, we integrate seismic reflection and P-wave tomography datasets with computed tomography-derived sedimentological analyses to estimate the volume of the iconic Minoan eruption. Our results reveal a total dense-rock equivalent eruption volume of 34.5 ± 6.8 km³, which encompasses 21.4 ± 3.6 km³ of tephra fall deposits, 6.9 ± 2 km³ of ignimbrites, and 6.1 ± 1.2 km³ of intra-caldera deposits. 2.8 ± 1.5 km³ of the total material consists of lithics. These volume estimates are in agreement with an independent caldera collapse reconstruction (33.1 ± 1.2 km³). Our results show that the Plinian phase contributed most to the distal tephra fall, and that the pyroclastic flow volume is significantly smaller than previously assumed. This benchmark reconstruction demonstrates that complementary geophysical and sedimentological datasets are required for reliable eruption volume estimates, which are necessary for regional and global volcanic hazard assessments. The authors use seismic and sedimentology data to estimate the volume of the Minoan eruption. The results show that the Plinian phase contributed most to the distal tephra fall, and that the pyroclastic flow volume is significantly smaller than previously assumed. [ABSTRACT FROM AUTHOR]

The rigorous assessment of volcanic hazards relies on setting contemporary monitoring observations within an accurate, longer-term geological context. Revealing that geological context requires the detailed fieldwork, mapping and laboratory analysis of the erupted materials. However, many of the world's most dangerous volcanic systems are located on or near coasts (e.g., the Phlegraean Fields and Vesuvius in Italy), islands (e.g., the volcanic archipelagos of the Pacific, south-east Asia, and Eastern Caribbean), or underwater (e.g., the recently erupting Hunga Tonga–Hunga Ha'apai volcano), meaning that much of their erupted material is deposited on the sea bed. The only way to sample this material directly is with seafloor sediment cores. This perspectives paper outlines how marine sediment cores are a vital yet underused resource for assessing volcanic hazards by: (1) outlining the spatio-temporal scope of the marine volcanic record and its main deposit types, (2) providing existing examples where marine sediments have contributed to volcanic hazard assessments; (3) highlighting the Sunda Arc, Indonesia as an example location where marine sediment cores are yet to contribute to hazard assessments, and (4) proposing that marine sediment cores can contribute to our understanding of very large eruptions that have a global impact. Overall, this perspectives paper aims to promote the utility of marine sediment cores in future volcanic hazard assessments, while also providing some basic information to assist researchers who are considering integrating marine sediment cores into their volcanological research. [ABSTRACT FROM AUTHOR]

After more than a year of unrest, a small effusive eruption commenced in Fagradalsfjall, Iceland, on 19 March 2021. The eruption lasted six months. The first six weeks were characterized by multiple fissure openings, and the remainder was dominated by effusive activity from a single crater. During the eruption, lava and low-level gases propagated over the complex terrain: a hyaloclastite massif with mountain peaks up to about 350 m asl with valleys in between. The area is uninhabited, but easily accessible at about 30 km distance from Reykjavík. While the eruption was ongoing, more than 356,000 tourists visited the eruptive site. To maintain low risk access to the area, it was critical to monitor the eruption (including opening of new fissures) in real-time, forecast the transport of gas and lava flow emplacement, and assess the evolving hazards. In addition to data accessibility and interpretation, managing this volcanic crisis was possible thanks to strong collaboration between the scientific institutions and civil protection agencies. The eruption presented an opportunity to tune, test and validate a variety of numerical models for hazard assessment as well as to refine and improve the delivery of information to the general public, communities living near the eruption site and decision makers. The monitoring team worked long hours during both the pre- and syn-eruptive phases for identifying low risk access areas to the eruption site and to provide a regular flow of information. This paper reviews the eruption and its associated hazards. It also provides an overview of the monitoring setup, the adopted numerical tools and communication materials disseminated to the general public regarding current exclusion zones, hazards and possible future eruptive scenarios. [ABSTRACT FROM AUTHOR]

Mapping fluid accumulation in the crust is pertinent for numerous applications including volcanic hazard assessment, geothermal energy generation, and mineral exploration. Here, we use seismic attenuation tomography to map the distribution of fluids in the crust below Uturuncu volcano, Bolivia. Seismic P wave and S wave attenuation, as well as their ratio (QP/QS), constrain where the crust is partially and fully fluid‐saturated. Seismic anisotropy observations further constrain the mechanism by which the fluids accumulate, predominantly along aligned faults and fractures in this case. Furthermore, subsurface pressure‐temperature profiles and conductivity data allow us to identify the most likely fluid composition. We identify shallow regions of both dry and H2O/brine‐saturated crust, as well as a deeper supercritical H2O/brine column directly beneath Uturuncu. Our observations provide a greater understanding of Uturuncu's transcrustal hydrothermal system, and act as an example of how such methods could be applied to map crustal fluid pathways and hydrothermal/geothermal systems elsewhere. Plain Language Summary: Locating where water/brines, gas, and molten rock are in the crust is important various applications, including assessing volcanic hazard, generating geothermal energy, and exploring for critical metals. Here, we map how seismic energy is absorbed (or attenuated) in Earth's crust, in order to look for fluids in the subsurface. We do this at Uturuncu volcano, Bolivia. This allows us to imagine whether the crust is partly or fully saturated with fluids. We also use seismic anisotropy to help us understand how the seismic energy is absorbed. We then use other data, including pressure, temperature, and electrical conductivity data to identify what fluids can be found where. We find that we can map where water/brines are and whether they contain carbon dioxide (i.e., are "sparkling") or not (i.e., "still"). Key Points: Seismic attenuation tomography can map crustal fluids and elucidate whether fluids are compressible, incompressible, or supercriticalS wave velocity anisotropy suggests that crustal fluids at Uturuncu migrate and/or accumulate along fracturesSeismic attenuation combined with temperature, pressure, and conductivity measurements can provide constraint on fluid composition [ABSTRACT FROM AUTHOR]

Valles Caldera was formed by large rhyolitic eruptions at ∼1.6 and 1.23 Ma and it hosts post‐caldera rhyolitic deposits as young as ∼69 ka, but the contemporary state of the magmatic system is unclear. Local seismicity beneath Valles Caldera is rare and shear‐velocity (Vs) structure has not been previously imaged. Here, we present the first local Vs tomography beneath Valles Caldera using ambient noise Rayleigh dispersion from a ∼71 km transect of nodal seismographs with mean spacing of ∼750 m. An ∼6 km wide low‐Vs anomaly (Vs < 2.1 km/s) is located at ∼3–10 km depth within the 1.23 Ma caldera's ring fracture. Assuming magma in textural equilibrium, the new tomography suggests that melt fractions up to ∼17%–22% may be present within the upper crustal depth range where previously erupted rhyolites were stored. Plain Language Summary: Silica‐rich magma stored in the shallow crust of the Earth can fuel eruptions that pose significant hazards to society. Valles Caldera was created by a large explosive eruption of silica‐rich magma 1.23 million years ago. Numerous smaller volcanic eruptions occurred following the large eruption event (as young as 69 thousand years ago) and the shallow subsurface at Valles remains hot indicating potential for modern magmatic storage at depth. Seismic shear waves are sensitive to the presence of magma and other variations in crustal structure. However, no local shear wave imaging has been conducted at Valles Caldera. Using new seismic data from densely spaced instruments and a technique known as ambient noise tomography, we produced the first shear velocity image beneath Valles Caldera. A region of significant low shear velocity is present in the upper crust beneath the caldera which we attribute to the presence of silica‐rich magma. These new results on shallow magma storage can contribute to assessing volcanic hazards more accurately near Valles Caldera. Key Points: The Valles Caldera magmatic system was imaged with ambient noise Rayleigh tomography using a dense temporary seismic transectA low‐Vs anomaly, Vs < 2.1 km/s is imaged within the caldera's ring fracture at ∼3–10 km depthThe upper crustal magma reservoir beneath Valles Caldera may contain up to ∼17%–22% rhyolitic melt [ABSTRACT FROM AUTHOR]

Next, challenge students to identify volcanoes in geographic regions recently studied in social studies, then investigate how living near a volcano can affect the culture of a region. As this resource is continually updated, the volcanoes that are reported will change, but the patterns resulting from student' plotted data will remain similar given the consistency in the locations of volcanoes. Whereas many students' initial reactions may be to question why people would choose to live somewhere so dangerous or even urge people to move away from volcanoes, they may be surprised that the cultures and ways of life experienced by populations living in the shadows of volcanoes can be quite rich! As students begin to understand the patterns of volcano locations, the implications of living near an active volcano, as well as the deep ties between volcanoes and the cultures of those living nearby, become apparent. [Extracted from the article]

Villarrica or Rukapillan (35.9°S; 2,847 m a.s.l.) is one of the most active volcanoes in South America and is the highest-risk volcano in Chile. It has an open conduit with a persistent lava lake. On the 3 March 2015, Strombolian activity rapidly progressed into a 1.5-km-high lava fountain, erupting at least ∼ 2.4 × 106 m3 of tephra. Soon after, the activity returned to mild Strombolian "background" explosions, which lasted until early 2017. Understanding the pre-eruptive conditions of such paroxysmal events is fundamental for volcanic hazard assessment. We present major and trace element geochemistry for glass and crystalline phases of basaltic andesite paroxysm pyroclasts (52–56 wt.% SiO2), and for the subsequent Strombolian "background" activity through February 2017 (54–56 wt.% SiO2). The lava fountain source magma was initially stored in a deeper and hotter region (9.4–16.3 km; ca. 1140 °C) and was then resident in a shallow (≤ 0.8 km) storage zone pre-eruption. During storage, crystallising phases comprised plagioclase (An66–86), olivine (Fo75–78) and augite (En46–47). Equilibrium crystallisation occurred during upper-crustal magmatic ascent. During storage in the shallower region, magma reached H2O saturation, promoting volatile exsolution and over-pressurization, which triggered the eruption. In contrast, subsequent "background" explosions involving basaltic-andesite were sourced from a depth of ≤ 5.3 km (ca. 1110 °C). Pre-eruptive conditions for the 2015 lava fountain contrast with historical twentieth-century eruptions at Villarrica, which were likely driven by magma that underwent a longer period of mixing to feed both effusive and explosive activity. The rapid transition to lava-fountaining activity in 2015 represents a challenging condition in terms of volcano monitoring and eruption forecasting. However, our petrological study of the pyroclastic materials that erupted in 2015 offers significant insights into eruptive processes involving this type of eruption. This aids in deciphering the mechanisms behind sudden eruptions at open conduit systems. [ABSTRACT FROM AUTHOR]

Starting from February 2021, Mt. Etna (Italy) experienced a period of intense explosive activity with 17 lava fountain episodes between 16 February and 1 April 2021. During the eruptive cycle, the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) issued 62 alert notifications known as VONAs (Volcano Observatory Notice for Aviation) to inform the aeronautical authorities about the volcanic activity. We present an automated VONA-based workflow aimed at real-time assessment of the volcanic hazard due to tephra fallout at Mt. Etna. When a VONA reporting tephra emission is issued by INGV-OE, numerical simulations accounting for atmospheric and eruptive uncertainties are automatically initialized to produce probabilistic hazard maps of tephra fallout and atmospheric dispersal. We applied the workflow to three lava fountains that occurred during the 2021 eruptive cycle. To test the modelling results, we compared the simulated ground load with field data, and the extent and position of the simulated volcanic cloud with the observed or estimated volcanic cloud from the Toulouse Volcanic Ash Advisory Center. Overall, we found a good match between simulated and observed quantities (tephra loads and volcanic cloud position), especially when accurate information on eruptive conditions (column height and duration) are supplied by the VONAs. Finally, through a statistical analysis, we found that column height and wind field are fundamental in determining tephra ground accumulation. For this reason, these parameters should be constrained by observational data as accurately as possible when performing numerical simulations, especially in the line of developing operational workflows. [ABSTRACT FROM AUTHOR]

The geological survey has been carried out in El Hierro with the aim to produce a new Geological Map at 1:12,500 scale for the Southern Rift. Almost 70 km² have been mapped providing a detailed stratigraphic and volcano-tectonic reconstruction of its evolution. Our work focused on the last Rift Volcanism phase, where hundreds of cinder cones, associated with thin lava flows, cover most of the island’s surface. Lava flows fields (40), monogenetic volcanic edifices (>90), and volcano–tectonic structures (69), such as dykes, eruptive fissures, and faults have been surveyed and stored in the Geological Map. The map poses fundamental constraints on the Southern Rift geological evolution, mainly concerning its recent activity and allowing the definition of 4 main stages during the last 40 ka. Moreover, this 1:12,500 scale detailed map represents a primary tool for the volcanic hazard assessment of the Island, volcanic monitoring, urban planning, and further stratigraphic data-based investigations. [ABSTRACT FROM AUTHOR]

Laterally directed explosive eruptions are responsible for multiple fatalities over the past decade and are an increasingly important volcanology problem. To understand the energy dynamics for these events, we collected field-scale explosion data from nine acoustic sensors surrounding a tiltable cannon as part of an exploratory experimental design. For each cannon discharge, the blast direction was varied systematically at 0°, 12°, and 24° from vertical, capturing acoustic wavefield directivity related to the tilt angle. While each event was similar in energy discharge potential, the resulting acoustic signal features were variable event-to-event, producing non-repetitious waveforms and spectra. Systematic features were observed in a subset of individual events for vertical and lateral discharges. For vertical discharges, the acoustic energy had a uniform radiation pattern. The lateral discharges showed an asymmetric radiation pattern with higher frequencies in the direction of the blast and depletion of those frequencies behind the cannon. Results suggest that, in natural volcanic systems, near-field blast directionality may be elucidated from acoustic sensors in absence of visual data, with implications for volcano monitoring and hazard assessment. [ABSTRACT FROM AUTHOR]

Mechanically weakened alteration zones in lava domes are thought to jeopardize their stability. Such zones can be hazardous when concealed within the dome, either because they formed by subsurface hydrothermal circulation or because they formed on the surface but were subsequently buried by renewed lava extrusion. We present a new suite of computational models showing how the size and position of a weakened brittle zone within a dome can affect large-scale fracture formation, displacement, and the collapse mechanism. By combining recent laboratory data for the mechanical behavior of dome rocks with discrete element method models, we show (1) the presence of a weak zone increases instability, which is exacerbated when the size of the zone increases or the zone is positioned off-center; (2) the position of the weak zone changes the deformation mechanism from slumping-type slope deformation when the zone is positioned centrally, compared with deep-seated rotational slope failure when the zone is positioned toward the dome flank; and finally, (3) dome-cutting tensile fractures form in the presence of a small weak zone (60 m diameter, -14% of dome width), whereas large weak zones (120 m diameter, -27% of dome width) promote the formation of longer and deeper fractures that jeopardize larger dome volumes. Our results corroborate previous field observations at lava domes and indicate that large fracture formation, which greatly influences dome stability and outgassing, can be explained by the presence of concealed alteration zones. This improved understanding of the mechanisms responsible for dome instability enables better hazard assessment at volcanoes worldwide. [ABSTRACT FROM AUTHOR]

In 2021, La Palma's southern volcanic complex Cumbre Vieja erupted for its longest period in historic times. Although the geological record shows no evidence for a collapse of Cumbre Vieja, ground deformation studies and field observations suggest that its western flank is moving seawards, following the direction of previous collapses of the island. To better estimate the hazard of a potential flank collapse of Cumbre Vieja, it is important to identify the lateral extent and depth of the mobile sector. Here, we analyse the volcano-tectonic deformation along Cumbre Vieja's western flank, based on geomorphological analysis of combined topographic and new ship-born bathymetric data as well as the analysis of shallow seismicity records associated with the 2021 eruption. In our interpretation, the shoreline-crossing Puerto Naos Ridge results from tectonic uplift accompanying transpressional deformation along the northern boundary of Cumbre Vieja's moving flank, therefore decoupling a stable sector in the north from the mobile sector farther south. The proposed moving sector is consistent in scale with previous ground deformation studies and documented flank collapses of structurally similar volcanoes. We present a workflow for semi-automatically detecting boundaries of unstable volcanic flanks based on morphological changes captured in digital elevation data. The method correctly delineated the known boundaries of the unstable flanks of Mt. Etna and Kilauea volcanoes. The ability to constrain potential boundaries of unstable volcanic flanks should inform the planning of future geophysical and geodetic campaigns aiming to identify precursory signals of potential flank failures. • Conceptual volcano-tectonic model of Cumbre Vieja's unstable western flank • Constraints on potential northern boundary of the moving flank • Shoreline-crossing geomorphological analysis using bathymetric and topographic data • Shallow seismicity indicate zones of structural weakness within the western flank • Semi-automated method for identifying unstable volcanic flanks for hazard assessment [ABSTRACT FROM AUTHOR]

• We present a new integrated seismic, magnetic, gravity and isostatic model across the Makran subduction zone. • Slow low-angle Makran subduction has 60–65% serpentinization in the peridotitic shallow mantle wedge. • A large volume of rheologically weak serpentinite reduces seismicity by lowering the slab friction. • Little fluid left in the slab at the melting depth (70–100 km) explains the limited arc magmatism. • Around 100 km depth, the low-angle subduction changes to an almost vertical dip. Subduction processes usually involve extensive seismicity and create voluminous magmatic arcs by mantle wedge melting caused by dehydration of the subducting slab, but the Makran subduction zone has anomalously low seismicity and magmatism. Here we explain these anomalous features by 60–65% serpentinization in the peridotitic shallow mantle wedge based on our new integrated seismic, magnetic, gravity and isostatic model across the Makran subduction zone. The low-angle, slow Makran subduction provides ample time for the slab to release sufficient amounts of fluids for creating a large volume of rheologically weak serpentinite. This reduces seismicity by lowering the friction between the slab and surrounding rocks. Further, very little fluid is left in the slab when it reaches the melting depth, which explains the limited arc magmatism. Around 100 km depth, the subduction switches from low-angle to almost vertical. Our model demonstrates the combined effects of subduction rate and dip on mantle serpentinization with implication for assessment of seismic and volcanic hazards in subduction systems. [ABSTRACT FROM AUTHOR]

Hazard assessments in monogenetic volcanic fields require estimates of the runout of pyroclastic surges that result from phreatomagmatic explosive activity. Previous assessments used runout distances of 1–4 km, with large cases up to 6 km. Surge deposits at Ubehebe Crater (∼2100 y.b.p., Death Valley, California) have been traced ∼9 km from the crater center, and likely originally extended 1–3 km farther. There is no evidence that the Ubehebe Crater activity was unusually energetic; rather, its distal deposits are better preserved than those at most maar volcanoes because of its young age and the arid environment. Numerical simulations illustrate how low temperatures facilitate long runout of phreatomagmatic surges due to reduced expansion of entrained air compared to hot surges, allowing cool surges to retain higher densities than ambient air. We suggest that hazard assessments for volcanic fields with phreatomagmatic, maar‐forming eruptions should consider runout distances in the range of 10–15 km. Plain Language Summary: Assessments of volcanic hazards in areas prone to small‐volume basaltic volcanoes includes consideration of the lateral extent of devastating pyroclastic surges from eruptions that are caused by magma‐water explosions. Previous assessments considered surge distances up to 6 km, but the deposits from Ubehebe Crater (Death Valley, California, USA) have been traced to 9 km and likely originally extended farther. This was not an unusual eruption, but its deposits are exceptionally preserved due to the arid environment. Pyroclastic surges from magma‐water explosions are likely to be cooler than other volcanic flows, and this facilitates long travel distances and hence far‐reaching potential impacts if the area is inhabited. We suggest that future assessments should consider pyroclastic surge distances of 10–15 km from the vent. Key Points: Hazard assessments in monogenetic volcanic fields have considered pyroclastic surge runout up to 6 km based upon preserved deposits of previous eruptionsSurge deposits from Ubehebe Crater extend to 9 km; this may not be unusual and such surges may have long runout facilitated by their low temperaturesWe suggest that future hazard assessments in monogenetic volcanic fields consider pyroclastic surge runout up to 10–15 km [ABSTRACT FROM AUTHOR]

Volcanic eruptions pose a great threat to humans. In this context, volcanic hazard and risk assessment constitute crucial issues with respect to mitigating the effects of volcanic activity and ensuring the health and safety of inhabitants. Lava flows directly affect communities living near active volcanoes. Nowadays, remote sensing advances make it possible to effectively monitor eruptive activity, providing immediate and accurate information concerning lava evolution. The current research focuses on the mapping of the surface deformation and the analysis of lava flow evolution occurred on the island of La Palma, during the recent (2021) eruptive phase of the volcano. Sentinel-1 data covering the island were collected throughout the entire eruptive period, i.e., September 2021 until January 2022. The processing was based on amplitude-based and phase-based detection methods, i.e., Synthetic Aperture Radar interferometry (InSAR) and offset tracking. In particular, ground deformation occurred on the island, while Line-Of-Sight (LOS) displacements were derived from Sentinel-1 interferograms. Moreover, the evolution of lava flow velocity was estimated using Sentinel-1 imagery along with offset tracking technique. The maximum lava flow velocity was calculated to be 2 m/day. It was proved that both approaches can provide rapid and useful information in emergencies, especially in inaccessible areas. Although offset tracking seems a quite promising technique for the mapping of lava flows, it still requires improvement. [ABSTRACT FROM AUTHOR]