Katla is an ice-covered central volcano in the southern part of Iceland’s Eastern Volcanic Zone. It is one of the country's most hazardous volcanoes due to its frequent explosive hydro-magmatic, basaltic eruptions and proximity to inhabited areas. The central volcano has a large ~100 km2, ice-filled caldera and an associated fissure swarm extending 70 km towards NE. Most frequently, eruptions are explosive and inside the caldera, but the largest effusive eruptions occur on the fissure swarm. In the last millennium, over 20 explosive eruptions have occurred inside the caldera, and these eruptions have been accompanied by large subglacial floods (jökulhlaups) causing severe flood risks in glacial rivers draining from the ice-cap. Several geothermal areas are located inside the caldera, where geothermal heat melts the overlying ice and meltwater accumulates at the glacier bed. These melt-water pockets regularly drain and cause smaller jökulhlaups in the surrounding glacial rivers. Manifestations of these areas are depressions, or ice cauldrons, on the overlying glacier surface and high seismicity, concentrated at shallow levels in the underlying crust. Research on the effects of glacial isostatic rebound of Katla on magma production in the underlying mantle has been ongoing in the ISVOLC project. In the presentation we focus on the analysis of seismicity recorded at Katla during the last 35 years and interpret the results together with other multidisciplinary observations during this period. Katla is a very seismically active volcano with nearly 38 thousand earthquakes recorded since the beginning of the national digital seismic network SIL (VI). Around 90% of this activity is equally divided between the caldera and the NW flank (Godabunga). The earthquakes are predominantly shallow, or 90% in the top 5 km and this is also the depth range of the largest earthquakes, whose magnitude can be up to Mw~4.5. Only 4% of the activity is below 10 km. To improve earthquake location-accuracy and enable mapping of the volcano’s subsurface plumbing, as well as evolution of the seismicity, relative relocations (DD), using cross-correlation of waveforms from 15 thousand earthquakes in the magnitude range 0.4<M<3, was carried out. The relocated shallow seismicity reveals several distinct clusters within the caldera and the time and spatial evolution of these clusters are interpreted together with observations of cauldron developments and drainage, as well as observations of deformation through GPS over the last three decades. The relocations also reveal a distinct vertically elongated earthquake cluster at 17-25 km depth under the eastern caldera rim. This activity, which often comes in bursts, is most prominent from 2011-2021, peaking in 2014-2015. We infer that this cluster represents magmatic intrusions into the crust from the mantle below.
How to cite: Vogfjord, K., Parks, M. M., O’Hara, C. G., and Sigmundsson, F.: Analysis of patterns and temporal behavior of seismic activity at Katla volcano, Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23255, 2026.
On 23 November 2025, the Hayli Gubbi volcano, located in the Danakil depression of Afar, northern Ethiopia, erupted with an unforeseen massive explosion. The volcano is situated approximately 15 km from Erta Ale, one of the most active volcanic systems in the region. This study provides the first seismic characterization of this event, recorded across a broad regional network including ten permanent seismological stations.
We find that the seismic recordings reveal an eruption sequence consisting of a minute-long precursor phase, a main explosion phase, and secondary events occurring hours later. Two separate wave trains indicate that the main eruption comprised two major explosions with a time delay of several minutes rather than a single distinct event. Accurate event localization is performed through joint inversion of origin time, epicentral coordinates, and wave velocity for independently picked surface wave arrivals from the explosions. Forward modeling strongly supports the assumption of an explosive sequence, as synthetic seismograms match the observed waveforms only when two sequential explosive sources are assumed. Higher-frequency and pulse-like precursor signals were detected within minutes before both main explosions, potentially reflecting early pressurization, conduit processes, or magmatic fracturing preceding failure.
The exceptional magnitude of this event provides valuable insights into the seismic emission of the large explosive eruption, while highlighting the challenges of monitoring active volcanoes in this remote and sparsely instrumented region. The unforeseen nature of the eruption underscores the need for improved local seismic monitoring to better constrain magmatic processes and enable more robust eruption prediction capabilities for volcanoes in Afar.
How to cite: Limberger, F., Alemayehu, S., Rümpker, G., and Ayele, A.: Seismic signature of the 23 November 2025 Hayli Gubbi eruption sequence in Afar, Ethiopia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9362, 2026.
Tenerife (Canary Islands, Spain) is an active oceanic volcanic island where low to moderate seismicity provides one of the few direct windows into the present stress state, hydrothermal, and volcanic activity. The island contains four main volcanic systems that interact in complex ways, and its seismic behaviour is also influenced by regional tectonic stresses, including the fault zone between Tenerife and Gran Canaria. Since 2016, small but persistent changes in the rate and spatial pattern of local earthquakes have been observed. These changes raise the question of how Gutenberg–Richter parameters and related metrics respond to an evolving volcanic–tectonic setting.
In this study, we use a catalogue-based, multi-parameter approach to investigate the factors controlling variations in the Gutenberg–Richter a and b values in Tenerife. The analysis is complemented by simple fractal measures that describe how earthquake hypocentres cluster in time and space. We track the spatial and temporal evolution of these parameters using moving windows at different scales, paying particular attention to magnitude completeness, as seismicity is strongly concentrated in a few areas of the island.
We explicitly separate background seismicity from well-defined swarm episodes. Swarms are analysed both independently and as part of the whole catalogue, allowing us to quantify the extent to which they influence overall estimates of a, b, and the fractal dimension.
By comparing the resulting parameter patterns with the main volcanic systems, rift zones, and structural lineaments, we explore how variations in b-value and clustering reflect differences in stress conditions and structural complexity. Special attention is given to areas and time periods in which, based on independent geochemical data, the hydrothermal system is known to have played an important role, as fluid circulation can enhances microseismicity in Tenerife
This work aims to provide observational constraints on the interpretation of Gutenberg–Richter parameters and fractal metrics in an ocean-island setting. We show how this simple but information-rich framework can help distinguish volcanic, tectonic, and hydrothermal contributions to seismicity in Tenerife, and can serve as a basis for future models that link b-value variability to underlying physical processes in interacting volcanic systems.
How to cite: García-Hernández, R., D’Auria, L., Álvarez-Hernández, A., Ortega-Ramos, V., M. van Dorth, D., López-Díaz, P., de Armas-Rillo, S., Calderón-Delgado, M., Rodríguez, Ó., Prieto, D., and Pérez, N. M. .: What controls b-value variability in an active oceanic volcanic island? A multi-parameter study of the seismicity of Tenerife (Canary Islands)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11624, 2026.
Volcanoes produce infrasound –acoustic waves below 20 Hz– during explosive eruptions. Often, these eruptions inject large amounts of ash into the atmosphere, reaching altitudes of commercial flights (~8-12 km), thus posing a direct threat to civil aviation worldwide. Infrasound can travel up to thousands of kilometers through the atmosphere and is therefore a promising tool to remotely (>250 km) detect volcanic eruptions and alert experts and authorities of the danger by an ash cloud. Long-range infrasound records have been investigated for many explosive eruptions, but its efficiency as a monitoring system has not been addressed in details yet.
The Volcanic Information System (VIS) was created within the Atmospheric dynamics Research InfraStructure in Europe (ARISE) projects under the European Commission’s programs FP7 and H2020), and originally in collaboration with the Toulouse Volcanic Ash Advisory Centre (VAAC), as a prototype monitoring system that uses long-range (>250 km) infrasound to remotely detect and notify of explosive eruptions. The integration of the VIS into the EPOS Thematic Core Service Volcano Observation (TCS-VO) or HOTVOLC web-GIS interface (OPGC, CNRS-INSU) is currently being discussed within the European Geo-INQUIRE project (HORIZON-INFRA-2021-SERV-01).
The VIS is designed to use global observations from the International Monitoring System (IMS) infrasound network (currently comprising 54 of 60 planned stations), and it can also incorporate non-IMS infrasound array data. To remotely detect an eruption, the VIS relies on the Infrasound Parameter (IP), which is a data-derived measure accounting for propagation effects, detection persistency, and amplitude at each detecting station.
The efficiency of this methodology has been investigated extensively considering 10 years of global explosive activity. Recently, we have expanded the VIS capabilities to use open-access streamlined and standardized IMS-derived infrasound array signal processing data products, and to allow the incorporation of pre-calculated propagation effects in the form of back-azimuth deviation interpolations for each source-station pair.
In the current study, we focus on two similar energetic explosive eruptions (June 2011 at Cordón Caulle and April 2015 at Calbuco, Chile) to assess the reliability of the VIS to detect, locate and raise automatic notifications for the VAACs. We base this on open-access data from 2011 to 2015 of IMS stations up to ~4800 km away from both volcanoes. With operability in mind, we show how this methodology could be implemented in different scenarios, e.g. for monitoring Mount Etna, Italy.
How to cite: De Negri, R., Marchetti, E., Gheri, D., Hupe, P., Le Pichon, A., Näsholm, S. P., and Labazuy, P.: Perspectives and Limitations of Long-Range Infrasound Monitoring of Volcanic Eruptions with the Volcanic Information System: Operational Insights from the Historical Analysis of June 2011 Cordón Caulle and 2015 Calbuco Eruptions, Chile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6516, 2026.
Episodes of volcanic unrest and eruptions are accompanied by various seismic signals, so seismic observations have become one of the most effective methods for monitoring volcanoes. Among them, to examine the potential of the seismic background level (SBL) technique for monitoring exceptionally active volcanoes with a limited number of stations, we applied it to seismic data recorded at the Northern group of volcanoes (NGV) in Kamchatka. NGV is an area with highly active and diverse volcanism formed by a dense cluster of active volcanoes, the Klyuchevskoy volcano group (KVG), and Shiveluch, the northernmost active volcano of Kamchatka.
For this work, we chose four stations located within a few tens of kilometers of the active volcanoes and calculated the SBL during the 2022--2023 eruptive sequence. We combined the results with more conventional Real-time Seismic Energy Measurement (RSEM) and the thermal anomalies detected by the Himawari-8/9 satellite. Because the Bezymianny and Klyuchevskoy volcanoes, separated only by 10 km, were erupting in the same period, it was impossible to distinguish between the two volcanoes using only a single SBL time series. By comparing the SBL amplitudes at the three stations at the KVG in various frequency bands, we were able to separate the unrest of Klyuchevskoy and Bezymianny. The results suggest continuous low-frequency tremor from a deep source beneath the KVG, which rose to the shallow depths beneath Klyuchevskoy before its eruptions. Also, we identified high-frequency continuous tremor at shallow depths beneath Bezymianny, indicating sustained unrest during the five major eruptions over 18 months.
On the other hand, the SBL variations at Shiveluch did not reflect the surface eruptive activity but a potential inflation event of this volcano after its catastrophic eruption. Based on these observations, it appears that SBL can detect both eruptive and non-eruptive processes in magmatic systems.
We also demonstrated that growing features of eruption precursors, consisting of volcanic earthquake events or discrete tremors, can be captured by the RSEM but not by the SBL. We emphasize that combining SBL and traditional approaches will better capture the precursors and significance of volcanic unrest.
How to cite: Galina, N., Ichihara, M., Horiuchi, T., Kaneko, T., Droznin, D., Senyukov, S., and Chebrov, D.: Exploring the 2022-2023 eruption sequence of the Northern group of volcanoes in Kamchatka with the seismic background level (SBL) technique and satellite images, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6452, 2026.
On 10 May 2018, a seismic crisis occurred near Mayotte (Comoros Archipelago, Indian Ocean), and was followed by a significant ground deformation and eastward displacement of the island. Combined with the records of very-long period (VLP) earthquakes, these observations were the first signs of a major submarine volcanic eruption, Fani Maoré, discovered in 2019 approximately 50 km east of Mayotte. The deployment of onshore seismometers and Ocean Bottom Seismometers (OBS) network since 2019 has allowed a better characterisation and classification of the seismicity, including various types of seismic and acoustic signals as volcano-tectonic (VT) earthquakes, long-period (LP) earthquakes, VLP, and hydro-acoustic signals.
In this study, we further investigated the seismic and hydroacoustic activity associated with the Fani Maoré submarine volcano by focusing on the characterization of rare and unconventional seismic signals that are poorly or previously not documented. We concentrated on the October–November 2019 period, when the OBS network was dense and included an OBS station deployed close to the active lava flows. To analyze this dataset, we applied a self-supervised learning (SSL) approach to four-channel time series data, comprising three-component seismometer recordings and a colocated hydrophone.
The SSL-based analysis resulted in the identification of multiple clusters, revealing distinct groups of seismic and acoustic signals. By aggregating these clusters into broader families, we distinguished signals originating from non-volcanic sources (e.g., motor induced signals and whale vocalizations), and families of events clearly associated with the volcanic activity of the Fani Maoré submarine volcano. These include VT and LP earthquakes, impulsive HA signals, drumbeat-like events, tremor-like events and additional signal types whose sources remain uncertain but are likely related to volcanic processes. These results bring new insights in the dynamic of the Fani Maoré volcano, and will allow a better characterization of the involved mechanisms in the seismo-acoustic activity, and improve its monitoring.
How to cite: Retailleau, L., Rimpot, J., Saurel, J.-M., and Hibert, C.: Unveiling Exotic Seismic and Hydroacoustic Events Associated with the Activity of the Fani Maoré Submarine Volcano, Mayotte, Indian Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13065, 2026.
Submarine volcanism is estimated to account for the vast majority of Earth’s total magma output, playing a critical role in crustal formation and ocean geochemical cycles. However, despite this dominance, global eruption catalogs remain heavily biased toward subaerial events, with less than 10% of documented eruptions occurring underwater. This discrepancy highlights a massive knowledge gap in our understanding of planetary volcanic rates and magnitude-frequency distributions. Hydroacoustic monitoring offers the most promising avenue to address this deficit, utilizing the International Monitoring System (IMS) of the CTBTO. While these stations routinely detect hydroacoustic signals from magmatic activity thousands of kilometers away, the sensitivity of the global array remains unquantified for specific volcanic arcs. Without understanding the detection threshold for any given location, it is challenging to convert individual detection logs into accurate global eruption rate estimates.In this study, we present a comprehensive framework for evaluating the detectability of submarine eruptions that accounts for the complex physics of sound propagation in a heterogeneous ocean. We utilize global 3D acoustic propagation modeling to calculate Transmission Loss (TL) from potential volcanic sources to IMS hydrophone stations. Unlike standard 2D approximations, this approach accounts for critical 3D effects, including bathymetric blockage by ridges and seamounts, horizontal refraction, and diffraction effects that severely impact signal continuity. Our results provide the first global "detectability maps," quantifying the minimum Source Level required for an eruption to be registered by the IMS network. This framework allows for a rigorous assessment of the "blind spots" in the current global catalog. Furthermore, we demonstrate how this 3D modeling facilitates the optimization of station selection. By analyzing signal-to-noise ratios and transmission paths, we identify which specific stations are best suited to analyze eruptions from a given volcano, thereby providing a method for robust cross-validation of eruption signals. Beyond simple detection, this approach enhances source characterization. We present maps of travel time estimates that account for 3D path deviations, allowing researchers to correct for data shifts and accurately locate sources even over trans-oceanic distances. Additionally, we explore the effects of frequency-dependent attenuation, demonstrating how 3D propagation modeling can help distinguish between different source mechanisms, such as sustained distinct magmatic jetting versus discrete explosive impulses. To validate this framework, we apply our 3D transmission loss analysis to the Hunga Tonga-Hunga Ha’apai eruption sequence. We demonstrate the utility of data fusion by integrating recordings from the far-field CTBTO global network with near-field data from the published regional MERMAID floating seismometer dataset. By correcting for long-range propagation effects, we show that it is possible to recover original volcanic source properties from distant hydroacoustic data. These results highlight the challenges posed by complex bathymetry and underscore the necessity of 3D acoustic sound propagation modeling. Ultimately, this work provides the robust framework required to move from individual eruption detections to a comprehensive, unbiased quantitative estimate of global submarine volcanism rates.
How to cite: Mittal, T., Heaney, K., Swar, S., and Olugboji, T.: A Global 3D Hydroacoustic Detectability Framework for Quantifying Submarine Volcanism Rates using CTBTO network, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14284, 2026.
We analyzed a muography dataset acquired at La Soufrière de Guadeloupe volcano, spanning more than three years from 2022 to the present, to investigate subsurface mass variations within the active volcanic system. Muography is a passive geophysical technique that exploits the attenuation of cosmic-ray muons to estimate the opacity of large geological structures. Muons are subatomic particles capable of traversing large amounts of matter. The flux of muons is measured along many distinct axes of observation, each corresponding to a specific trajectory through the subsurface. Because muons are absorbed according to the amount of matter they encounter, changes in the measured flux along each axis can be interpreted as variations in subsurface mass over time. This setup allows a single muon detector to investigate multiple regions of the volcanic edifice simultaneously, providing spatially and temporally resolved information on subsurface mass distribution. A key aspect in analyzing muon time series is deciding how to group the signals from different trajectories to calculate the flux through distinct regions, since combining trajectories that are not coherent could mask meaningful variations. To address this, we applied a PCA-based multivariate analysis to jointly analyze the time series from all trajectories and identify spatially coherent regions characterized by common temporal behavior. This study demonstrates how muography, combined with multivariate statistical analysis, can be used to investigate the spatial organization and temporal variability of subsurface mass in active volcanoes.
How to cite: Tramontini, M., Rosas-Carbajal, M., and Marteau, J.: Multivariate Temporal Analysis of Muography Data at La Soufrière de Guadeloupe Volcano, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18042, 2026.
How can experimental magnetotellurics and petrophysics provide critical constraints on the structure of magmatic plumbing systems? How can magnetotellurics contribute to volcanic monitoring? We present a workflow applied to two French volcanoes: Montagne Pelée (Martinique, West Indies) and Mayotte.
Montagne Pelée volcano has experienced renewed seismic activity since 2019, with earthquakes occurring below 10 km depth and more superficial activity within the first few kilometers. In 2023, a broadband magnetotelluric (MT) survey was conducted, allowing the construction of both finite-difference and finite-element 3D electrical conductivity models down to 20 km depth. These models reveal key features of the magmatic plumbing system, constrained by the joint interpretation of MT data and experimental petrophysics, using high-pressure laboratory measurements of electrical conductivity as a function of temperature on lava samples. In June 2025, an experimental array of three continuous MT monitoring stations was installed in strategically selected locations to track fluid migration and the progressive development of partial melt within the plumbing system. We describe the complete workflow, from 3D imaging to characterization and monitoring.
Since 10 May 2018, Mayotte has been experiencing one of the largest offshore seismovolcanic crises of the past three centuries. The MAYOBS1 scientific mission (2–19 May 2019, Marion Dufresne vessel) led to the discovery of a new 820-m-high volcanic edifice, named Fani Maore, with an estimated volume exceeding 6.55 km³. Between 2018 and 2021, geophysical observations revealed an eastward displacement of the island of 21–25 cm, combined with 10–19 cm of subsidence, as well as more than 100,000 earthquakes occurring at unusually large depths (22–45 km). A combination of broadband land and marine MT surveys enabled the construction of a 3D resistivity model down to 30 km depth, revealing two major conductive bodies at approximately 12 km and 22 km depth. The deeper conductor is interpreted as a magmatic mush zone with an estimated melt fraction of 22–42%. As part of the REVOSIMA (Réseau de Surveillance Volcanologique et Sismologique de Mayotte), a network of permanent MT stations is currently monitoring the magmatic plumbing system. The latest imaging results and monitoring developments will be presented.
How to cite: Wawrzyniak, P., François, B., Vedrine, S., Dubois, F., Gaillard, F., Andujar, J., Tarits, P., and Hautot, S.: Imaging, characterizing, and monitoring volcanic plumbing systems at Montagne Pelée and Mayotte using experimental petrophysics and land–marine magnetotellurics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21924, 2026.
Surface ground deformation at active volcanoes is commonly attributed to fluid processes at depth, such as magma storage, propagation, and geothermal activity. Geodetic modeling of ground deformation of these processes is important for understanding and assessing the potential hazard posed by volcanic unrest. However, changes in surface loading, such as ice retreat, can also cause ground deformation. Katla volcano in Iceland underlies Mýrdalsjökull, the fourth largest glacier in Iceland, which has been retreating since about 1890. Historically, Katla has had an average repose time of ~50 years, but the last confirmed eruption occurred in 1918. Katla has been continuously uplifting since the installation of GNSS in 1993. Over the past 10 years, Katla has had an average uplift rate of ~17 mm/yr, as recorded at a GNSS station located on a nunatak on the caldera rim. GNSS stations outside of the glacier record vertical deformation rates of ~10 mm/yr.
In this work, we investigate the effects of the long-term ice retreat and magmatic processes on the recorded ground deformation. It is necessary to understand the contribution of surface load changes on recorded ground deformation to be able to isolate and monitor volcanic signals. We model a long-term deformation source at Katla, using an analytical inversion of GNSS data, after the removal of seasonal signals, plate spreading, and estimated rates of deformation due to glacial retreat (glacial isostatic adjustment, GIA) at Mýrdalsjökull and other glaciers in Iceland. We find the best-fit deformation source parameters are highly dependent on the GIA correction, so evaluation of the GIA contributions to a surface deformation signal is needed. We generate a 3D Finite Element (FE) model, using COMSOL Multiphysics, including realistic topography and ice unloading, based on 10 years of GNSS data from Mýrdalsjökull, to investigate the contribution of ice retreat on the deformation signal. We furthermore evaluate the applicability of Iceland country-wide GIA models considering ice retreat in all of Iceland. A previous study of the seasonal snow loading signal at Katla was able to reproduce observed horizontal deformation, several mm/yr, at the edge of the glacier. This implies that long-term glacial retreat may contribute to the observed inflation at Katla, rather than deformation of only volcanogenic origin.
How to cite: O'Hara, C., Sigmundsson, F., Albino, F., Parks, M., Trasatti, E., Geirsson, H., Ófeigsson, B., Liebsch, J., Bellagamba, G., and Givens, T.: Interpreting Long-term Ground Deformation Signals at Subglacial Katla Volcano, Iceland: Combined Effects of Surface Loading and Magmatic Processes., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13062, 2026.
Hydrothermal alteration can modify the permeability of volcanic rocks, influencing the movement of fluids and volcanic hazard potential. Permeability increases could facilitate outgassing, promoting effusivity, and permeability decreases could result in overpressurisation, promoting explosivity and instability. We measured the permeability of 573 variably altered rocks from La Soufrière de Guadeloupe (Eastern Caribbean) using a calibrated field permeameter. Our data show a wide range of alteration (from pristine to extremely altered) and permeability (10–18–10–11 m²), and that more altered rocks have a higher average permeability, and a wider permeability range, than less altered rocks. We also find that alteration and permeability are spatially heterogeneous. Microstructural analysis reveals evidence for dissolution in plagioclase phenocrysts and void-filling precipitation. For high-permeability rocks, such alteration did not affect the well-connected flow-path: these rocks were simply altered without modifying their permeability. For low-permeability rocks, dissolution in isolated plagioclase phenocrysts did not decrease flow-path tortuosity, but precipitation blocked important pathways for flow: alteration reduced their permeability. Therefore, although the more altered rocks have a higher average permeability, we conclude that alteration reduces permeability. Alteration sites are, therefore, sites of high permeability undergoing permeability reduction. Downsampling our large dataset to test whether smaller datasets reproduce the observed trend highlights the problems associated with using small datasets to understand the influence of alteration on permeability. The results of our study can be used to improve volcano monitoring and hazard mitigation.
How to cite: Poganj, A., Heap, M. J., and Baud, P.: The influence of hydrothermal alteration on permeability: A field study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-341, https://doi.org/10.5194/egusphere-egu26-341, 2026.
Vulcano island, located in the Italian Eolian Archipelago, is an active hydrothermal volcanic system that last erupted in 1888-1890. Since then, activity has persisted at fumaroles, thermal ground and soil degassing at the Fossa crater, and also at the Baia di Levante (Levante Bay). The bay hosts a secondary geothermal system fed by a shallow hydrothermal aquifer that is heated by magmatic gases resulting in coastal/offshore low temperature fumaroles and soil CO2 degassing in the Acqua Calde beach. In 2021, Vulcano island entered a new phase of unrest marked by increased degassing, seismicity, heat release and deformation at the Fossa cone, followed by increased diffuse soil degassing at the Vulcano Porto area that prompted protective measures for residents. In May 2022, gas output at the Baia di Levante area rose significantly, coinciding with the first observed sea whitening event. This area, one of the main tourist attractions of the island, now faces heightened hazard from degassing and potential explosive activity. Other studies reported elevated CO2 and H2S fluxes (diffuse and convective), anomalous seawater pH, and extremely high dissolved CO2 concentrations, even in zones with limited visible hydrothermal activity. Since 2022, multiple sea whitening events were recorded, though their variable duration prevents construction of a continuous timeline from punctual surveys. For this study, we used the archives of three high spatial resolution sensors – Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Landsat 8 and 9 Operational Land Imager (OLI) and Sentinel-2 Multispectral instrument (MSI) – to detect and quantify the extent and intensity of these events. The sea anomalies are compared to the ground-based measurements of degassing and heat release, as well as thermal anomalies identified by the ASTAD machine learning algorithm, a convolutional neural network (CNN)-based model designed specifically for ASTER data. Preliminary work has detected thermal anomalies during three episodes in 2022, 2023 and 2025. The second phase of the study is using hyperspectral PRecursore IperSpettrale della Missione Applicativa (PRISMA) data to test whether geochemical species in the precipitates (e.g., carbonates, sulphates) can be identified and quantified. This work will provide new insights into the coupling between degassing, seawater chemistry, and volcanic hazards at Vulcano and ultimately is applicable globally with these orbital sensors.
How to cite: Pailot-Bonnétat, S., Corradino, C., Collins, E., and Ramsey, M.: Monitoring underwater hydrothermal degassing at Baia di Levante (Vulcano Island) using high‑resolution and hyperspectral satellite data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-888, https://doi.org/10.5194/egusphere-egu26-888, 2026.
Over the past few years, the development of ground-based Remote Sensing (RS) techniques has significantly enhanced our ability to monitor volcanic degassing. Among these, Thermal Infrared (TIR) imaging has emerged as a powerful tool for quantifying sulfur dioxide (SO2) flux and plume dynamics. This work summarizes a multi-year research activity (2021–2025) focused on the design, testing, and validation of a simplified TIR camera system across different field campaigns, including Etna (Italy), Stromboli (Italy), Sabancaya (Peru), Popocatépetl (Mexico) and Lastarria (Chile) volcanoes.
The results, validated through cross-comparison with traditional Ultra-Violet (UV) cameras and satellite data (e.g., TROPOMI), demonstrate that TIR systems offer several advantages as temporal continuity by providing crucial measurements also during night-time, a precise plume geometry retrievals (plume height, thickness, and speed) by exploiting the high thermal contrast with background clear sky and a good cost-effectiveness ratio obtaining high accuracy in SO2 columnar abundance and flux retrieval. However, some limitations remain. TIR measurements are highly sensitive to volcanic particles (ash and water vapour) and environmental temperature fluctuations, requiring rigorous calibration and site-specific error assessment.
Future developments will focus on the reduction of the effect of environment temperature, the correction of the influence of plume particles on SO2 retrievals and the use of Machine Learning (ML) for automated plume detection and real-time data processing. Such advancements will be pivotal for improving early warning systems and volcanic hazard mitigation on a global scale.
How to cite: Corradini, S., Guerrieri, L., Merucci, L., Naranjo, C., and Stelitano, D.: Simplified low cost ground-based Thermal InfraRed system for volcanic SO2 monitoring: Lessons Learned and Future Perspectives, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18125, 2026.
Detecting and tracking volcanic clouds using complementary GEO and LEO data is highly important for the mitigation of volcanic hazards. Here we present a new observation system that expands the Support to Aviation Control Service (SACS), currently using only LEO products, with observations from a suite of GEOs - like SEVIRI (onboard MSG), FCI (onboard MTG), ABI (onboard GOES-W and GOES-E), and AHI (onboard HIMAWARI-9), forming the so-called GEO-Ring.
The presentation is divided in two parts. First, we present our work on an improved GEO detection product for aerosols and SO2, largely inspired by an approach developed for IASI (Clarisse et al., 2013). We show that this technique improves the detection of hazardous clouds, particularly for thick plumes, and leads to fewer false detections. For several recent events, we compare the results to data from the IASI and TROPOMI instruments and show that similar patterns are found between LEO and GEO detections. New RGB imagery based on improved volcanic and cloud detection from GEO satellites will be presented. This is a great asset as it opens the perspective of high temporal resolution sensitive detection of aerosols and SO2, at nearly global scale. Second, we present a web-based data service under development, integrating near-real time data from the GEO-Ring and LEO sensors into a single system. With several examples, we illustrate the added value of this approach. Finally, we discuss our plans with respect to new sensors recently launched (onboard MTG-S and Metop-SG).
This work was performed as part of the Belgian Natural Hazards Monitoring from Satellites (NAMSAT) project, funded under the BELSPO Impulse Actions program (project IM/RT/23/NAMSAT of https://www.belspo.be/belspo/fedra/prog.asp?l=en&COD=IM).
Clarisse, L., Coheur, P.-F., Prata, F., Hadji-Lazaro, J., Hurtmans, D., and Clerbaux, C.: A unified approach to infrared aerosol remote sensing and type specification, Atmos. Chem. Phys., 13, 2195–2221, https://doi.org/10.5194/acp-13-2195-2013, 2013.
How to cite: Brenot, H., Theys, N., van Gent, J., de Buyl, P., Clarisse, L., Clerbaux, N., and Van Roozendael, M.: A global monitoring system to detect aerosols and SO2 using a combination of GEO and LEO satellite data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9540, 2026.
Shallow eruptions from submarine volcanoes can hinder the navigation of ships and alter the biological response of marine ecosystems. Hydrothermal vents and ash-laden plumes can spread across the sea surface for weeks, affecting the water column's optical properties. Systematic in situ observations (i.e., underwater observations and hydro-acoustic and seismic arrays) are logistically complicated to deploy and usually expensive to carry out before and during an eruptive event. Conversely, satellite remote sensing can provide timely and continuous information about volcanic activity around dangerous sites, contributing to the assessment of pre-, syn-, and post-eruptive phenomena. Sea-water discoloration is one of the most significant indicators of underwater volcanic activity, as its accurate, timely and continuous detection can help revealing possible precursor processes of submarine volcanic eruptions and tracking their evolution. Most published studies have characterized discolored water patches after major eruptions by assessing their reflectance patterns using multispectral ocean color data acquired by MODIS, VIIRS, and Sentinel-3 OLCI. While these sensors may enable the timely detection of submarine eruption features, their coarse spatial resolution makes them unsuitable for mapping discolored patches whose size and spatial dynamics are on a ten- or hundred-meter scale. The improved spatial resolution offered by Sentinel 2-MSI and Landsat 8/9-OLI data (10–60 m) ensures accurate mapping of sea-water discoloration, even for small and weak plumes. In this framework, we have proposed a novel, spectrally-derived method to accurately detect and map discolored plumes around submarine volcanoes in oligotrophic oceans by integrating Sentinel 2A/B-MSI and Landsat 8/9-OLI satellite data. The developed method, which combines two discoloration algorithms, was tested using a yearly (2022) MSI-OLI integrated dataset around a representative test case, namely the Kavachi Volcano (Solomon Islands, Southwest Pacific Ocean). It exhibited satisfactory validation metrics, recording overall accuracies (OAs) close to 90% for both single and integrated (multi-sensor) configurations. Despite omission errors (OEs) ranging from 18% to 20%, the very low (around 2%) commission errors (CEs) demonstrated its high level of reliability in mapping discolored waters of volcanic origin. Furthermore, the proven exportability of this method to the Kaitoku Volcano (Japan, Western Pacific Ocean) confirms its capability in detecting underwater volcanic activity regardless of geographic location or the chemical composition of discolored seawater. This method could serve as an automated early warning tool to support the operational monitoring of submarine volcanoes arranged by maritime surveillance systems.
How to cite: Ciancia, E., Marchese, F., Mazzeo, G., Plank, S., and Pergola, N.: A novel spectrally-derived method for detecting sea-water discoloration around submarine volcanoes by combining Sentinel 2A/B-MSI and Landsat 8/9-OLI data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10140, 2026.
Over the past decades, satellite-based thermal monitoring of volcanoes has undergone a major transformation driven by new Earth-observing missions and advances in spectroscopic surface analysis, revealing diverse thermal responses of volcanic surfaces to subsurface processes and showing that many eruptions are preceded by subtle thermal anomalies. This growing body of evidence underscores the need for robust methods capable of detecting and tracking diffuse thermal unrest using existing satellite archives while fully exploiting the capabilities of current sensors in orbit. To meet this need, we present SSTAR (Subtle Surface Thermal Anomalies Recognizer), a user-friendly application designed to detect and analyze diffuse thermal anomalies, i.e., subtle surface warming on the order of ~1 K over large areas (several km²), using MODIS satellite data. Building on the statistical thermal anomaly detection framework of Girona et al. (2021) [https://doi.org/10.1038/s41561-021-00705-4], SSTAR operates at the pixel level to track the temporal evolution of thermal anomalies at specific sites and to map their spatiotemporal distribution across broad regions, incorporating dedicated filtering strategies to identify both long-term (years) and short-term (weeks) signals with uncertainty quantified through bootstrapping. We demonstrate the capabilities of SSTAR through its application to Shishaldin Volcano (Alaska), where the four eruptions that occurred over the past two decades are shown to have been systematically preceded by diffuse, low-amplitude thermal anomalies, highlighting the potential value of such signals as eruption precursors. SSTAR is distributed as a standalone application with an interactive interface accessible to non-specialists, while also providing full script access for MATLAB users who wish to adapt or extend the methodology for specialized applications. Beyond volcanology, it is expected to be useful for geothermal exploration, where the detection of faint and spatially coherent thermal anomalies may help identify subsurface fluid pathways and guide early-stage site characterization. An upcoming version will enable near-real-time tracking of diffuse thermal unrest, positioning SSTAR as a forward-looking tool for advancing satellite-based thermal monitoring of volcanic activity in the coming decades.
How to cite: Girona, T. and Brenot, L.: SSTAR: A user-friendly application to track subtle thermal anomalies at volcanoes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16667, 2026.
Volcanoes that have been dormant for tens of thousands of years often have a long warm-up time before eruption onset. Magma and fluid migration are obstructed by closed fractures at depth, a sealed hydrothermal lens, and conduit blockage, all of which work against magma emplacement. Our first significant activity at Chiles-Potrerillos was a Mw 5.5 earthquake, followed by an intense seismic swarm in October 2014. Uplift occurred, perhaps in concert with movement on local faults. Subsequently, lulls in activity and little deformation or changes in the hydrothermal springs assuaged our concerns. Then, more seismic swarms registered in 2018-19, 2022-24, and in late 2025. Commonly, 2000-4000 VT events are registered each day. Overall seismic production is ~1.5 million events. While most events are VTs and are less than Mw= 1, numerous events fall into the 3-4 Mw category and are felt. Deformation detected by GPS and InSAR (Sentinel-1 and TerraSAR-X) exceeds 40 mm/yr and now involves the southern flank of Chiles volcano, as well as a rectangular zone 20 km to the SE, called Potrerillos, where several domes are located. Overall, and significantly, the deformation has presented strong, then lower rates of uplift, but values are rarely negative. Surface manifestations at hot springs have remained unchanged over the past 12 years. While we believe that magma is probably stressing the system, the seals of the hydrothermal system remain intact, which impedes the onset of explosions, strong exsolution of magmatic gases, and overall increased heat flow. We anticipate that before an eruption onset, deformation will become more abrupt and concentrated, with or without increased seismicity, since much of the country rock is already fractured.
How to cite: Mothes, P., Yepez, M., Cordova, A., Pacheco, D., Almeida, M., Sierra, D., Telenchana, E., Hidalgo, S., Ruiz, M., and Espin, P.: Long, episodic awakening of volcanoes: The case of Chiles-Potrerillos, Ecuador, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15697, 2026.
Based on mathematical analyses of the extensive historical and recent records of its explosive activity, this study presents the first probability hazard maps of the areas potentially affected by ballistic fallout from major explosions and paroxysms at Stromboli (Italy). These are more energetic explosions that punctuate the persistent explosive activity of the volcano, where the paroxysms are the greatest category, able to reach inhabited areas.
Conditional probability maps have been produced by adopting a novel approach that develops and integrates three statistical models of ballistic fallout patterns and the associated uncertainties. Model 1 mirrors the areas observed to be affected in the past, whereas Models 2 and 3 address data under-sampling and morphologic variations of craters and/or shallow part of conduits, respectively assuming independency between the categorical data of ballistic distance and dispersal direction, or radial symmetry. This approach could be applied to similar hazard mapping problems, where it is possible to represent the data in terms of distances and directions with respect to a relatively constrained geographical center.
Notably, this study is also based on a new method to map the areas affected by ballistic fallout of a sufficient number of major explosions and paroxysms from historical and recent records. This mapping method adopts a simplified description of the affected areas by a circular proximal area and up to three circular sectors with variable radius and width, and associated uncertainties. The dataset of maps includes a total of 67 events over ≈150 years, based on an extensive review of historical, observational, and monitoring data. The new mapping approach is less detailed than free-hand isopach drawing, and includes some elements of expert judgement to manage non-homogeneous and decades-old information. Nevertheless, all its steps are transparent and replicable, from the original excerpts of contemporaneous sources to the geographical mapping of the areas affected by ballistic fallout.
In addition to conditional maps of major explosions and paroxysms, the study presents temporal probability assessments of these phenomena. A comprehensive probability distribution of maximum ballistic distances at Stromboli should merge the major explosions and the paroxysms, but their assessments are based on two different catalogs, and therefore the estimates of their occurrence ratio are significantly uncertain. In fact, major explosions before 1970 are affected by likely under-recording issues. Vice versa, only 5 paroxysms occurred after 1970, and their time series is irregular and characterized by temporal clusters and a 44-year gap between 1959 and 2003. Moreover, the probability rates of major explosions and paroxysms are not constant in time, but significantly increase in the weeks/months after one of these events has occurred. Combining the maps with the variable occurrence rates of the events, cumulative estimates of ballistic fallout probability in the next years are presented, as well as hourly probabilities as a function of the time passed after the previous major explosion or paroxysm.
These findings open the way to individual and societal risk assessments for this phenomenon at Stromboli, and represent useful approaches for studying ballistic hazard, especially on island volcanoes.
How to cite: Bevilacqua, A., Neri, A., Landi, P., Del Carlo, P., Pompilio, M., and Baxter, P.: Ballistic fallout from major explosions and paroxysms at Stromboli (Italy): from the mapping of historically affected areas to probabilistic hazard assessment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10461, 2026.
All active volcanoes in Aotearoa New Zealand can erupt explosively, potentially dispersing volcanic ash across much of the country. Ash can be highly disruptive and damaging to the agricultural industry, critical infrastructure, and human health. Therefore, accurate and rapid ash dispersion and ashfall forecasts are necessary to enable timely and informed decisions for protecting New Zealanders and their property. While such forecasts do currently exist, they rely on poorly constrained input parameters (e.g., eruption start time, duration, mass eruption rate). Here we aim to develop a new purpose-built seismo-acoustic code package for volcano observatories to help constrain eruption source parameters as rapidly as possible after the start of an eruption. The package will include various theoretical and empirical models to link seismic and acoustic signal properties from eruptions of various sizes from local (< 100 km) to global (>5000 km) distances. Tests will be carried out on seismo-acoustic data from eruptions within Aotearoa New Zealand (e.g., Te Maari, Whakaari) and from across the SW Pacific. Ultimately this package will be part of a larger open-access software suite to constrain eruption source parameters that draws on a range of data (e.g., satellite, radar, GNSS, webcams) to help rapidly produce robust ash dispersion and ashfall forecasts.
How to cite: Jarvis, P., Lamb, O., and Perttu, A.: Near-real time quantification of volcanic ash plume parameters in Aotearoa New Zealand through seismo-acoustic methods, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15253, 2026.
In the week from 28 March to 4 April 1982, El Chichón volcano, located in south-eastern Mexico, produced the largest and deadliest eruptive episode in the modern history of that country. About a month later, a lake formed on the floor of the 1 km wide, 200 m deep crater carved on its summit by the intense explosions. Since then, irregular, yet persistent monitoring of some geophysical and geochemical parameters has unveiled different types of interaction between the lake and the underlying hydrothermal and magmatic systems. Identifying the causes of the area's non-seasonal large variations in the observed hydrogeochemical results is a critical problem for assessing volcanic hazards. A running correlation analysis of the hydrogeochemical data and the lake size variations suggested that a change in permeability of the interface between the lake and the underlying systems, probably related to the stabilization of the young lacustrine system and the decreasing magmatic influence, produced the first significant change in 1983. Other causes are proposed for the following changes, mainly related to the increasing influence of two underlying hydrothermal systems, probably fed by different aquifers. The degree of influence appears to be increasingly controlled by the seismicity around the volcano. For example, during the period 1990-2006, one M 4.0 earthquake was recorded in that area on October 9, 2002, when lake-area fluctuations began to increase. The recent mounting crater lake area variations and the increasing seismicity recorded from June to August 2025, suggest a growing degree of interaction between the lake water and the hydrothermal systems, probably through the stress and displacement changes in two fractures crossing the volcanic edifice, namely the Chichón-Catedral (NW-SE) and San Juan (E-W) faults. This could lead to an increased probability of phreatic explosions, which may be followed by lava dome emplacement on the crater floor. The coordinated management of volcanic risk between the Civil Protection System and the Advising Scientific Committee has designed a specific Traffic Light Alert System, along with an operational plan to keep the surrounding population aware and protected, considering these possibilities, as well as others of higher intensity but lower probability.
How to cite: De la Cruz-Reyna, S., Armienta Hernández, M. A., and Gómz-Vázquez, A.: Hazard scenarios associated with the El Chichón volcano crater lake increasing area fluctuations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8467, 2026.
Posters on site: Wed, 6 May, 16:15–18:00 | Hall X1
Tenerife, the largest and most populated island of the Canary Islands, hosts a complex volcanic system characterized by rift-related activity, long-lived magma reservoirs, and an active hydrothermal system. Although historically characterised by relatively sporadic eruptive activity, the island’s volcanic system remains active, as evidenced by historical eruptions, such as those of Siete Fuentes (1704) and Chinyero (1909), as well as the 2004-2005 unrest. After more than a decade of relative quiescence, the Instituto Geográfico Nacional (IGN) began detecting seismic and geochemical anomalies in 2016 and a continuous slow deformation in 2023, which has persisted to the present.
The IGN currently operates a geodetic monitoring network on Tenerife consisting of 16 continuous GNSS (cGNSS) stations, the first installed in 2007, together with other geodetic instrumentation used continuously for the monitoring of ground deformation associated with volcanic activity. These ground-based observations are complemented by the analysis of InSAR data, allowing the detection of spatially distributed deformation patterns.
Analysis of the geodetic data reveals the onset of slow, low-magnitude ground deformation affecting the central sector of the island since mid-2023. This deformation pattern had not been observed in previous years and coincides in time with the seismic and geochemical anomalies detected by the IGN, suggesting a common magmatic origin.
Time series derived primarily from cGNSS and InSAR analysis indicate an extensional deformation affecting the central part of Tenerife, with horizontal velocities of the order of a few millimeters per year. Focusing on the central sector of the island, and considering a NW–SE-oriented axis, stations located to the north of this axis show northwestward horizontal displacements, whereas those to the south exhibit southeastward movements, consistent with a regional extension pattern.
To date, no significant vertical deformation associated with the observed horizontal displacements has been identified. This absence may be explained by several factors, including the higher noise level of the vertical component due to atmospheric effects and/or the influence of the island’s aquifer system, as well as the possible influence of the island’s geological structures on the observed deformation, which may locally modify or redistribute strain. The analysis of the deformation processes developed since 2023, together with their temporal evolution, provides essential constraints for monitoring the ongoing volcanic unrest on Tenerife.
How to cite: García-Cañada, L., González-Alonso, E., Molina-Arias, A. J., Lamolda, H., Prieto-Llanos, F., Quirós, F., Domínguez-Valbuena, J., Fernández-García, A., Pereda de Pablo, J., Cezón Martínez, L. E., Fernández, L., D. Suarez, E., Meletlidis, S., del Fresno, C., and Domínguez Cerdeña, I.: Long-term volcanic unrest in Tenerife (Canary Islands): Ground deformations signals , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17293, 2026.
The chemical and isotopic composition of groundwater in active volcanic oceanic islands is highly sensitive to the input of magmatic gases. On Tenerife (2,034 km2), the absence of visible peripheral gas emissions, aside from the Teide summit fumaroles, makes the island’s extensive network of water galleries a “window” into the volcanic aquifer. Since 2016, following a significant long-period (LP) seismic swarm on October 2 (D'Auria et al., 2019), a multidisciplinary geochemical monitoring program has been maintained across ten representative galleries (horizontal drillings) to detect deep-seated magmatic signals.
Current results reveal a relatively homogeneous hydrochemical facies, primarily bicarbonate-sodium-calcium type, consistent with CO2-driven water-rock interaction. However, long-term time series analysis (2016–2025) across several galleries, including Fuente del Valle, San Fernando, Barranco de Vergara, and Buen Viaje, demonstrates significant temporal fluctuations in key volcanic tracers. High-frequency sampling during the study period identified distinct peaks in total alkalinity (HCO3−), pCO2, and Na+/Cl− ratios that correlate with episodes of increased seismicity, including volcano-tectonic (VT) and hybrid swarms.
Notably, Fuente del Valle and San Fernando galleries exhibited sustained increasing trends in HCO3− and SO42−/Cl− molar ratios (Amonte et al., 2021), particularly surrounding the hybrid seismic swarms of 2019, 2022, and late 2024. Furthermore, sharp increases in pCO2 and dissolved fluoride (F−) concentrations in galleries such as El Almagre and Barranco de Vergara coincide with periods of renewed seismic unrest, suggesting the pulsative injection of magmatic CO2 and acidic volatiles into the hydrothermal-volcanic aquifer.
These hydrogeochemical variations provide evidence of a dynamic hydrochemical connection between the Teide-Pico Viejo volcanic system and the underlying aquifer. By establishing robust baseline datasets and identifying pre-seismic geochemical anomalies, this monitoring approach serves as a critical early-warning tool. The integration of these hydrochemical "fingerprints" into the INVOLCAN volcano surveillance program enhances the ability to forecast changes in the volcanic system, ultimately contributing to volcanic risk reduction on Tenerife.
References
Amonte, C., Asensio-Ramos, M. et al. (2021) Hydrogeochemical temporal variations related to changes of seismic activity at Tenerife, Canary Islands. Bulletin of Volcanology, 83:24. https://doi.org/10.1007/s00445-021-01445-4
D'Auria, L., Barrancos, J. et al. (2019). The 2016 Tenerife (Canary Islands) long‐period seismic swarm. Journal of Geophysical Research: Solid Earth, 124, 8739–8752. https://doi.org/10.1029/2019JB017871
How to cite: Cartaya Arteaga, S., Melián, G. V., Asensio-Ramos, M., Hernández, P. A., Lodoso, E., Fuentes, P., Méndez, C., Perdomo, Ó., Padrón, E., and Pérez, N. M.: Hydrogeochemical monitoring of groundwater as a tool for volcanic surveillance in Tenerife, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10385, 2026.
Tenerife, the largest and most populated island of the Canary Islands, hosts a complex volcanic system characterized by rift-related activity, long-lived magma reservoirs, and an active hydrothermal system. Although historically characterised by relatively sporadic eruptive activity, the island’s volcanic system remains active, as evidenced by historical eruptions, such as those of Siete Fuentes (1704) and Chinyero (1909), as well as the 2004-2005 unrest. After more than a decade of relative quiescence, the Instituto Geográfico Nacional (IGN) began detecting seismic and geochemical anomalies in 2016 and a continuous slow deformation in 2023, which has persisted to the present.
Since 2015, numerous groundwater samples have been taken by the IGN Volcano Monitoring Group in distinct locations on the island, in order to determine total dissolved gas composition. Sampling points were chosen from among the existing hundreds of water mining galleries based on its proximity to Las Cañadas caldera, the presence of volcanic dissolved gas in the water and its physico-chemical properties such as pH, electric conductivity and temperature. Since 2022, additional sampling points were incorporated, resulting in eight-sampling point surveillance network of dissolved gases: QT61, QT62, QT63, QT65, QT66, QT72, QT73 and QT77, sampled approximately every three months. Groundwater samples were taken using the method described by Capasso and Inguaggiato (1998) and analyses were carried out at Istituto Nazionale di Geofisica e Volcanologia (INGV) laboratories in Palermo (Italy) following the methodology described by Paonita et al. (2012).
In this work, we present CO2 and H2 dissolved concentrations in the above-mentioned sampling sites, pointing out the apparent relationship between some of the observed gas changes and the evolution of seismicity and ground deformation recorded in Tenerife during the last ten years.
Regarding dissolved CO2, a wide range of concentrations have been measured in the different sampling points. The location with the maximum dissolved CO2 concentration detected was QT77 with a value of 61.67 %. Analysis of the temporal evolution highlights two key observations. On the one hand, an increase in the CO2 concentration base level in QT61, QT62, QT63 has been detected since mid 2024. On the other hand, a pronounced peak in one of the sampling sites (QT61) was recorded in September 2024, reaching 49.37% compared with the baseline mean of 24.06%.
In contrast the temporal evolution of dissolved H2 concentration is distinct from that observed for CO2. Time series are characterized by an almost absence of dissolved H2 (values below the detection limit) sporadically interrupted by significant peaks reaching variable concentrations over time. This behaviour may be associated with micro fracturing induced by increased stress in the island due to seismicity and/or ground deformation. There is a particularly interesting period covering a span of six months from December 2022 to June 2023 when almost simultaneous H2 peaks in QT61, QT62, QT72 and QT77 occurred.
How to cite: Luengo Oroz, N., Torres González, P., Alonso Cótchico, M., Rechcygier, V. P., Suárez, E., García Cañada, L., and Burgos Delgado, V.: Long-term volcanic unrest in Tenerife (Canary Islands): Anomalies in dissolved gases. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18961, 2026.
Tenerife, the largest and most populated island of the Canary Islands, hosts a complex volcanic system characterized by rift-related activity, long-lived magma reservoirs, and an active hydrothermal system. Although historically characterized by relatively sporadic eruptive activity, the island’s volcanic system remains active, as evidenced by historical eruptions, such as those of Siete Fuentes (1704) and Chinyero (1909), as well as the 2004-2005 unrest. After more than a decade of relative quiescence, the Instituto Geográfico Nacional (IGN) began detecting seismic and geochemical anomalies in 2016 and a continuous slow deformation in 2023, which has persisted to the present.
In this contribution, we analyze the temporal and spatial evolution of seismicity recorded by the IGN seismic network between 2016 and 2025. During this period, at least six seismic swarms have been identified, dominated by deep long-period and hybrid earthquakes. These swarms exhibit significant variability in their frequency content, duration, recurrence, and temporal evolution, indicating changes in the underlying physical processes driving the seismicity. In addition to these swarms, several seismic clusters have been detected, characterized by variations in seismic rate, depth distribution, and migration patterns, and showing a strong spatial correlation with major geological and structural features of the volcanic edifice, as high- and low-density bodies in the island.
The observed seismic patterns show temporal and spatial correlations with independently detected geochemical anomalies (e.g., diffuse gas emissions) and geodetic signals derived from GNSS and InSAR observations. This multi-parameter coherence suggests episodic pressurization processes occurring at different crustal levels beneath the island, likely involving both magmatic and hydrothermal components. The progressive increase in the frequency and persistence of these signals over the last decade indicates an acceleration of the unrest processes, pointing to a dynamically evolving volcanic system rather than isolated or transient perturbations.
The combined seismic, geochemical, and geodetic observations are consistent with the emplacement and accommodation of magmatic intrusions at multiple crustal depths, inducing stress transfer, fluid migration, and sustained seismicity. These results highlight the complex interplay between magma, fluids, and tectonic structures in controlling long-term unrest at intraplate ocean-island volcanoes.
Our findings emphasize the critical role of continuous, high-resolution, multi-parameter monitoring for the early detection and interpretation of subtle changes in Tenerife’s volcanic state. This study contributes to improving the conceptual models of prolonged volcanic unrest and provides valuable insights for hazard assessment and operational volcanic surveillance in similar volcanic settings.
How to cite: D. Suárez, E., Dominguez Cerdeña, I., del Fresno, C., Villaseñor, A., Torres Gonzalez, P., Luengo-Oroz, N., Alonso Cótchico, M., García-Cañada, L., Gonzalez Alonso, E., Meletlidis, S., Sainz-Maza Aparicio, S., Gomez Liste, B., Perez Frias, F. M., Martin Silvan, A., Alonso Saenz de Ugarte, E., Barco De La Torre, J., and Manzanedo Vallejo, M. V.: Long-term volcanic unrest in Tenerife (Canary Islands): Seismovolcanic signals , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18026, 2026.
Tenerife (2,034 km2), the largest of the Canary Islands, is characterized by a complex volcanic structure controlled by a volcano-tectonic rift system with dominant NW, NE and NS trends. The intersection of these rifts hosts the Teide-Pico Viejo volcanic complex, which culminates at 3,718 m a.s.l. The Teide volcano last erupted in 1798 through an adventive vent of the Teide-Pico Viejo system. The summit area of Teide volcano is affected by persistent visible and diffuse activity, with diffuse degassing representing the main pathway for gas release to the atmosphere.
Since the late 1990s and until 2025, a long-term monitoring programme has been carried out at the summit crater of Teide volcano, based on repeated diffuse gas emission surveys (more than 250). These surveys were designed to characterise the spatial and temporal variability of diffuse degassing within the summit crater area, providing a robust and consistent dataset for the assessment of changes in the volcanic-hydrothermal system over time.
Diffuse CO2 and H2S emission rates were directly estimated from field measurements obtained using the accumulation chamber method. Spatial distribution maps were generated by averaging the results of 100 sequential Gaussian simulations, allowing the estimation of total emission rates and their spatial variability.
During the study period, diffuse CO2 emissions ranged between 2 and 1257 t·d-1, while H2S emissions ranged between 0 and 31 kg·d-1. From 2007 until around 2016, diffuse CO2 emissions remained low and relatively stable, with an average of approximately 20 t·d-1. From late 2016 onwards, emissions show a sustained increase, a trend that continues to the present. Since 2021, low emission values are no longer observed, and in September 2023 the maximum value of the series was recorded (1257 t·d-1). H2S shows a nearly synchronous behaviour with CO2. Along with the observed increase in gas emissions, an increase in seismicity has also been recorded, particularly since 2016, suggesting a relationship between seismic activity and the release of diffuse volcanic gases.
Temporal variations in diffuse CO2 and H2S emissions provide valuable insights into changes in the activity of the Teide volcanic system and represent an effective tool for tracking unrest processes. Continuous monitoring of diffuse degassing at Teide volcano has proven essential for improving the understanding of volcanic behaviour and contributes significantly to volcanic risk assessment and mitigation on Tenerife.
How to cite: Asensio-Ramos, M., Melián, G. V., Di Nardo, D., Padilla, G. D., Méndez-Pérez, C., Cartaya-Arteaga, S., Hernández, P. A., Padrón, E., and Pérez, N. M.: Long-term monitoring of anomalous diffuse CO2 and H2S emissions at Teide Crater, Tenerife, Canary Islands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6518, 2026.
Tenerife is the largest island in the Canary archipelago and hosts El Teide volcano, a 3715 m.a.s.l. stratovolcano characterised by low-temperature fumaroles in its summit crater. Since 2016, changes in volcanic activity have been recorded, resulting in the occurrence of several seismic swarms, variations in geochemical parameters, and slight ground deformation since 2023.
The Instituto Geográfico Nacional (IGN), the Spanish institution responsible for volcano monitoring, has deployed a multiparameter monitoring network in Tenerife comprising seismic, ground deformation and geochemical networks. During 2024 and 2025, two actions were taken to enhance the latter one in order to detect subtle changes in the fumaroles and the aquifer. These changes could serve as early warning signals of a future volcanic eruption.
Multi-gas stations are typically used to monitor plumes from active volcanoes. However, as there has been a clear increase in the volcanic activity in Tenerife since 2016, we have decided to deploy a Multi-Gas station inside El Teide's crater since September 2024, despite not showing an active plume. This station measures SO2, H2S, CO₂, CO and H2 concentrations in the air at 30 cm above the ground every six hours with a measurement window of 30-minute length at a sampling frequency of 1 Hz. Alongside this, meteorological data is recorded. All data is stored locally and transmitted in near real time to the server.
Until mid 2025, the dissolved CO₂ concentration was determined by sampling every three months at eight sampling points in Tenerife. To dramatically improve the sampling frequency, three Mini-CO₂ instruments from Pro-Oceanus have been installed at the three most interesting sampling sites. This device uses infrared detection to measure the partial pressure of CO₂ gas dissolved in water. The instrument also measures Total Dissolved Gas Pressure (TDGP), CO₂ concentration, and water temperature.
At each site, a Mini-CO₂ was installed alongside a meteorological station. Data from the Mini-CO₂ is acquired every 15 minutes, while data from the meteorological station every 10 minutes. All data is stored locally and transmitted in real time to the server.
In this contribution, the first records and results from both improvements in the geochemical monitoring network in Tenerife are shown.
How to cite: Torres-González, P. A., Luengo-Oroz, N., Medina, G., Carrasco, J. M., Alonso-Cótchico, M., and Burgos, V.: Improvements in the Geochemical Monitoring Network in Tenerife: Multi-Gas and Continuous Dissolved CO2 stations. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18951, 2026.
Hydrogen (H2) is one of the most abundant trace gases in volcano-hydrothermal systems and plays a key role in redox reactions within hydrothermal reservoirs. Although H2 can be biologically produced in soils by nitrogen-fixing and fertilizing bacteria, soils are currently regarded as net sinks of molecular hydrogen. Due to its physical and chemical properties, H₂ generated in the crust migrates rapidly and easily escapes into the atmosphere, making it a highly sensitive geochemical tracer of deep magmatic and geothermal processes. Since 2001, systematic surface geochemical studies have been conducted along the Cumbre Vieja volcano (La Palma, Canary Islands) to monitor diffuse hydrogen emissions. The lack of visible surface manifestations of volcanic degassing at Cumbre Vieja, such as fumaroles or hot springs, highlights the importance of diffuse gas studies as a fundamental tool for continuous volcanic monitoring. Soil H2 concentrations were measured using a gas microchromatograph (Agilent 490 micro-GC) in samples collected at approximately 40 cm depth at around 600 points during each study. The soil H2 concentration data were used to estimate the H2 flux at each point. Spatial distribution maps were generated using sequential Gaussian simulation (sGs) to quantify the diffuse H₂ emissions across the volcanic edifice. The analysis of the H2 emission time series reveals significant increases coinciding with seismic swarms recorded between 2017 and 2021, with a peak flux of 36 kg·d-1 observed in June 2017, approximately four months before the beginning of seismic activity. During the eruptive phase, sharp peaks in H2 emissions (up to 30 kg·d-1) closely followed increases in volcanic tremor. In contrast, estimations obtained in the post eruptive period (Jan 2022-Dec 2025) show H2 emissions values ranging from 1 to 19 kg·d-1. This work summarizes the continuous effort to characterize the hydrogen degassing behavior within an active volcanic system and has provided valuable insights into volcanic dynamics and potential precursory signals relevant for hazard assessment and risk mitigation.
How to cite: Méndez-Pérez, C., Melián, G. V., Herrera-Rodríguez, D., Ramírez-Fragiel, J. D., Cartaya-Arteaga, S., Asensio-Ramos, M., Padrón, E., Di Nardo, D., Padilla, G. D., Hernández, P. A., and Pérez, N. M.: Soil H2 degassing studies: a useful geochemical tool for monitoring Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13750, 2026.
The measurement of geochemical parameters such as He and CO2 concentrations are important and useful for the study of characterization of volcanic systems and seismically active areas. Furthermore, the He/CO2 ratio gives useful information on the depth of the outgassing origin. Finally, extensive parameters such as He and CO2 flux are even more binding in the interpretation and modeling of these systems in question.
In an ambitious move to volcanic risk mitigation, INFICON GmbH—a global leader in measurement and sensor technology—has partnered with premier scientific institutions (INGV_Italy) to monitor active volcanic centers on Italy’s Vulcano and Stromboli islands.
The research focuses on the characterization of natural volcanic emissions at Stromboli and Vulcano (Aeolian Archipelago, Italy), where an advanced geochemical monitoring network for deep-seated fluids is currently operational. A key development in this study involves the deployment of a high-resolution instrument for the continuous measurement of helium (He) concentrations. This device was strategically located with an existing station monitoring soil CO2 flux to investigate the temporal correlation between different volatile species. The 'He-Man' sensor is a cutting-edge helium detector designed for field deployment. It employs a selective helium-permeable membrane to isolate the analyte from the atmospheric matrix, followed by a Penning ionization process to quantify the gas. This setup allows for the detection of trace levels of helium, providing a high-fidelity proxy for the arrival of primitive, mantle-derived fluids within the volcanic plumbing system.
Two 'He-Man' instruments were successfully deployed across the Aeolian Archipelago to monitor high-frequency helium variations. The first unit was installed at Vulcano Island, positioned in a target area characterized by anomalous diffuse soil degassing. The second unit was deployed on Stromboli Island, integrated within a thermal well monitoring system. In the latter configuration, the sensor is coupled with a specialized sampling interface designed for the real-time analysis of dissolved gases in the hydrothermal aquifer. These dual installations enable a comparative study of helium behavior in both sub-aerial and sub-aqueous volcanic environments.
Soils anomalous degassing:
By coupling the 'He-Man' instrument with a high-precision infrared CO2 detector, we are able to determine the He/CO2 concentration ratio within a sub-surface probe (sampling pipe) installed at the Palizzi site. This monitoring point is strategically located adjacent to the Palizzi station, which provides continuous measurements of diffuse CO2 soil fluxes. Utilizing this integrated setup, the helium soil flux (JHe) is indirectly quantified by scaling the measured He/CO2 ratio against the absolute CO2 flux (JCO2) according to the relation: JHe = ([He]/[CO2])*J(CO2)
Dissolved CO2 in natural waters:
By integrating this helium concentration sensor with an automated system for monitoring dissolved CO2 in a thermal well at Stromboli, we have successfully characterized the He/CO2 ratio within the hydrothermal environment. This setup targets the specific aquifer situated between the degassing magma body and the anomalous diffuse degassing areas of Scari. This integrated monitoring approach provides critical insights into the geochemical evolution of fluids as they migrate from the magmatic source through the island's groundwater system toward the surface.
How to cite: Vita, F., inguaggiato, S., Diaz, A., Grenz, J., Ay, D., Schiera, G., Passafiume, G., and Calderone, L.: High-Resolution Continuous Helium Measurement: A New Frontier in Volcanic and Seismic Monitoring Technology., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10350, 2026.
In closed-conduit volcanoes dominated by long-lived hydrothermal activity, both the escalation toward unrest and return to background conditions are non-linear processes. Post-unrest recovery phases are often characterised by intermittent fluctuations and reversals, complicating the definition of a stable baseline and the likely return to the pre-unrest state. Due to the low intensity of this kind of volcanic activity with respect to those involving magma bodies directly, anomalous patterns can often be hidden by external factors (e.g. meteorological and solar heating effects). For this reason, a multiparametric monitoring is essential to discriminate between background variability and actual changes leading to phases of potential concern. After the major hydrothermal unrest of 2021-2022 at La Fossa Cone (Vulcano Island, Italy), the system gradually evolved into a recovery phase, although intermittent periods of instability marked by notable change in the geophysical and geochemical parameters occurred. This study analyses the transient episodes occurring in Summer 2025 by integrating geochemical, seismic, and thermal datasets. In late July, the bulk crater SO2 flux increased, indicating a further contribution of magmatic volatiles from the shallow feeding system to the hydrothermal one. In early August, this new input of hot magmatic fluids was followed by a sharp peak in the volcano-seismic signals, reflecting a pressurization of the hydrothermal system. Ground temperatures, measured continuously by four permanent stations located at the summit and inner crater area, recorded a significant increase in temperature. Initially this increase occurred in the most permeable areas, near the fumarole field, and then rapidly expanded laterally, affecting a wide area of the crater. Although the episode was short-lived (late July to late September 2025), it was characterised by a significant release of heat and fluids. Remarkably, despite the rapid temporal evolution, soil temperatures reached peak values comparable to those observed during the main unrest phases of 2021–2022, highlighting the system's capacity to quickly restore critical conditions potentially suitable for phreatic/phreatomagmatic explosions. Interpreted as a late-stage fluctuation of the 2021-2022 crisis, the August 2025 episode underscores the need to continuously monitor the La Fossa Cone, in order to define robust baselines to correctly assess volcanic hazard.
How to cite: Indovina, E., Pailot-Bonnetat, S., Spampinato, L., Sciotto, M., Harris, A., Cannata, A., Salerno, G., and Pagano, M.: Tracking Post-unrest Instability in Long-Lived Hydrothermal Systems: A Multiparametric Analysis of the August 2025 reactivation of La Fossa Cone (Vulcano, Italy)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12179, 2026.
Anomalous gaseous emissions from tectonically active fault zones during pre-seismic, co-seismic, and post-seismic phases have been extensively documented in the literature and quantitatively characterized through in situ terrestrial measurements and remote sensing methodologies. The prevailing paradigm posits that seismotectonic activity induces the mobilization of soil gases through multifaceted geomechanical, geophysical, and hydrogeological processes. In volcanic environments, magmatic volatiles undergo exsolution during ascent as a consequence of progressive decompression and are subsequently discharged through hydrothermal systems and structurally-controlled conduit networks. Despite significant advances in understanding these phenomena, critical knowledge gaps persist regarding the high-resolution temporal characterization of subsurface gas transport dynamics. This investigation addresses these limitations through the following research objectives:
(i) Development of a novel, cost-effective instrumentation system for quantifying pressure fluctuations in subsurface gas transport. The apparatus was designed based on theoretical frameworks governing spherical gas flux propagation within the pedosphere, enabling continuous high-resolution measurements at 0.2-second temporal intervals (5 Hz sampling frequency).
(ii) Validation experiments under controlled laboratory conditions and field deployments to assess instrumental performance. The system demonstrated exceptional sensitivity to pressure variations (on the order of pascals) and micro-cyclical fluctuations. Analysis of the datasets indicates that this instrumentation substantially enhances the spatiotemporal characterization of degassing dynamics in seismogenic and volcanic regimes, as well as associated geophysical and atmospheric processes.
(iii) Investigation and mathematical modeling of physical and geophysical mechanisms governing subsurface gas transport. This approach facilitated the delineation of boundary conditions and parameterization schemes that accurately represent the natural system.
Preliminary results yielded the following findings:
- Exceptional sensitivity in detecting subsurface gaseous pressure fluctuations, with temporal resolution superior to conventional monitoring systems.
- Operational efficacy in low-permeability conditions.
- Discriminatory capability for resolving pressure oscillation cycles across multiple temporal scales, ranging from sub-second to diurnal periodicities.
- Corroboration that high-frequency temporal sampling is essential for detecting transient degassing processes and discriminating endogenous geophysical signals from exogenous atmospheric phenomena.
The results demonstrate promises for advancing continuous monitoring in seismically and volcanically active regions. This instrumentation has potential applications in geophysical fluid dynamics, particularly for characterizing natural degassing phenomena and their coupling with seismotectonic and volcanic processes. Comprehensive interpretation requires integration of pressure measurements with complementary geochemical, seismological, geodetic, and meteorological datasets to elucidate mechanisms governing subsurface degassing and their utility as precursory indicators. The high-frequency sampling enables resolution of micro-cyclical events and transient pressure anomalies undetectable through conventional monitoring, thereby establishing new avenues for investigating coupled Earth system processes.
How to cite: Spoto, S. E., Di Martino, R. M. R., Schifano, R., Giammanco, S., and Parello, F.: Continuous Monitoring of Soil-Gas Pressure Fluctuations in Active Seismogenic and Volcanic Environments: Design and Validation of a Novel Experimental Apparatus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6303, 2026.
Between 16 February and 1 April 2021, the Southeast Crater (SEC) of Mt Etna produced a spectacular sequence of 17 lava fountain paroxysms, separated by 2.5 days on average, which generated ≥ 10 km high eruptive columns and heavy tephra fallout over populated surroundings. We examine the magmatic processes responsible for these events based on pre- and syn-eruptive data for the mass flux and chemistry of Etna gas emissions, surveyed both from the ground (scanning DOAS, OP-FTIR spectroscopy) and from space (TROPOMI, SEVIRI), and comparing with the seismic tremor. Bulk plume SO2 emission rates determined from the ground and from space are consistent with one another. We show that after several months of background summit activity, sustained since June 2020 by open-system degassing of ~ 29 × 106 m3 (DRE) of magma through the central volcano conduits, an influx of deeply derived primitive magma led to a pressure build-up phase from early December 2020 to 13 February 2021, marked by a rapid increase in the SO2 flux and tremor (the former interpreted to represent an ~ 3 times higher magma degassing rate) and decreasing SO2/HCl plume ratio. A series of 17 lava fountains began immediately after a shallow seismic cluster and a sharp drop in the SO2 emission rate from the summit craters, reflecting the lateral transfer of pressurized primitive magma to beneath the SEC. The fountain paroxysms were characterized by sharp increases in tremor amplitude, intense SO2 release, and higher volcanic gas SO2/HCl ratios. The magnitude of SO2 emission rate correlates with the proportion of primitive magma in co-erupted products during the first half of the sequence. The estimated total gas discharge, compared to the co-erupted tephra mass, suggests a large excess gas release for most events, which is proportional to the length of the repose interval. Combining these observations with models of S and Cl degassing from Etna trachybasalt, we infer that the February–April 2021 lava fountain series resulted from the recurrent accumulation of H2O-CO2-rich bubble foams at ~ 2–3 km depth beneath SEC, whose periodic collapse promoted fast magma ascent and fragmentation associated with essentially syn-eruptive degassing of S and Cl. Our study thus provides further insight into the complexity of magmatic processes determining lava fountain paroxysms at Mt Etna and, possibly, other basaltic volcanoes.
How to cite: Salerno, G., La Spina, A., Allard, P., Guerrieri, L., Corradini, S., Di Grazia, G., Merucci, L., Bonfanti, P., Stelitano, D., Maugeri, R., Murè, F., and Principato, P.: The February–April 2021 sequence of lava fountain paroxysms on MtEtna: source mechanism deciphered from ground‑based and satellitesurvey of volcanic gas emissions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12920, 2026.
In remote areas, ground-based measurements are often scarce or non-existent. Therefore, accurate global spatial coverage is necessary for effective volcanic surveillance, making satellite measurements using Remote Sensing (RS) systems crucial resources for real-time monitoring of volcanoes and for the analysis of their activity. This work presents the development of an automatic procedure for the retrieval of sulphur dioxide (SO₂) fluxes, exploiting Near Real-Time (NRT) Level 2 (L2) products from the TROPOspheric Monitoring Instrument (TROPOMI), an imaging spectrometer on board the Sentinel-5P polar satellite. The core processing, implemented in Python, involves the vertical interpolation of SO₂ Vertical Column (VC) products (provided at 1, 7 and 15 km), based on the mean plume altitude, extracted from the TROPOMI L2 layer height data product. The raw satellite data are resampled in a uniform grid, and georeferenced using the Universal Transverse Mercator (UTM) projection, to correct for spatial distortions. The SO₂ flux is then computed by integrating the VCs with the wind speed profiles acquired from the nearest available radiosonde station on the day of the event. This modified version of the standard traverse method uses concentric circular transects to ensure independence from the wind direction. The developed procedure is applied to three different 2025 test-case eruptions: Etna (Italy), Nyamulagira (Democratic Republic of the Congo) and Hayli Gubbi (Ethiopia), with the aim of reconstructing the time series of their emission. The method is validated by comparing, for Etna, the satellite-derived fluxes to the ground-based measurements acquired by the FLux Automatic MEasurement (FLAME) network, a series of Ultraviolet (UV) ground-based scanning spectrometers installed around the volcano. The results confirm the validity of the approach and demonstrate the tool capability to perform a quick and automatic assessment of volcanic activity around the world, providing reliable information that can be used to mitigate the impact of these natural phenomena.
How to cite: Rosella, E., Corradini, S., Naranjo, C., Guerrieri, L., Merucci, L., Stelitano, D., Renga, A., Salerno, G., and Balagizi, C.: An Automatic Procedure for Volcanic SO2 Flux Retrieval using TROPOMI L2 Products, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20315, 2026.
Volcanoes can experience periods of change in the baseline monitoring parameters, known as unrest episodes. Detecting an unrest is important since it can sometimes end with an eruption. Among the monitoring parameters there is the surface temperature (Ts) that can be measured also from remote sensing data. Here we used the Ts derived from Landsat and ASTER satellites to monitor and detect the thermal unrest in four different volcanoes that have not erupted recently: Campi Flegeri and Vulcano (Italy), Domuyo volcano (Argentina) and Fentale (Ethiopia). Results highlighted that all these volcanoes experienced periods of unrest characterized by an increase of Ts above the background level. The detected thermal unrest episodes are related to changes in other monitoring parameters (e.g., ground deformation, seismicity and degassing), although the onset-end time of the thermal unrest is not always consistent with onset-end time of the unrest detected from the other monitoring parameters. These preliminary results highlight the importance of using also the Ts from remote sensing data to monitor volcanoes.
Acknowledgment: the Space It Up project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0 - CUP n. I53D24000060005.
How to cite: Silvestri, M., Galetto, F., and Buongiorno, M. F.: Thermal unrest in not recently erupting volcanoes detected with remote sensing thermal data (ASTER and Landsat), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6314, 2026.
During 2025, volcanic activity continued within the Svartsengi volcanic system on Reykjanes Peninsula, Iceland, with diking events and eruptions on 1 April and 16 July 2025. The dike intrusion on the 1 April 2025 was the second largest thus far, with a estimated length of ~20 km and intruded volume of about 100 million cubic meters. The concurrent volume drop within the magma domain was ~35 million cubic meters. The eruption itself however was short lived, lasting only 7 hours and producing a very small lava field (0.3 million cubic meters). It is proposed that the eruption ended because less energy was required for the magma to intrude laterally within the crust than to erupt, because of 'un-released tectonic stress' stored in the crust, despite 9 earlier diking events in the area. The April dike continued propagating for at least 10 hours, based on continuing deformation and seismicity, propagating laterally both to the SW (beneath the town of Grindavík, as occurred previously during November 2023 and in January 2024) and the NE. The dike propagation on 16 July was a smaller intrusion, with a median length of 3.5 km and volume change of ~16 million cubic meters. The volume drop within the magma domain was ~12 million cubic meters. The eruption continued until the 5 August and produced a lava field of ~31 million cubic meters.
Between November 2023 and July 2025 there have been 11 dike intrusions and 9 eruptions within the Sundhnúkur crater row and its extension. Despite the wealth of data and high frequency of events, eruption forecasting remains challenging. Since 16 March 2024, observations indicate that the volume required to trigger a new diking event/eruption has changed compared to previous events. For the last five events, the modelled volume recharged to the reservoir has been between 17-23 million cubic meters.
This presentation will provide an overview of the diking events and eruptions to date within the Svartsengi volcanic system and an update on the forecasting methodologies used thus far for medium-term eruption forecasting and future implications.
How to cite: Parks, M., Drouin, V., Lanzi, C., Sigmundsson, F., Ófeigsson, B., Geirsson, H., Fridriksdóttir, H. M., Barsotti, S., Vogfjörd, K., Pedersen, G., Gunnarson, S., and Belart, J.: 2025 diking events and eruptions within the Svartsengi volcanic system, Iceland., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6017, 2026.
Petrological monitoring of active volcanoes is an often underutilised tool for eruption forecasting due to the high cost and long lead times of petrological analyses, even though these analyses can provide vital context to interpret geophysical monitoring signals1. Ash componentry specifically is the process of classifying ash particles by grain type (e.g. juvenile, accidental, etc.), and is extremely useful for understanding the state and driving processes of the volcanic conduit and shallow hydrothermal system2, potentially helping to anticipate transitions into intensified explosive activity3. However, componentry analysis is time-consuming, and classification of particles can be subject to various classification schemes and interpretations depending on the observer. To overcome these problems, we adopted a machine learning (ML) approach to classify particles in an automatic and consistent manner.
In this work, we describe the development of a ML model, coupled with a tailored classification scheme, to classify ash from a collection of 30 samples between 1999–2016 from Tungurahua volcano, Ecuador. We analysed 180 grains in-depth to develop a systematic classification scheme for optical images of grains based on diagnostic optical features (e.g., colour, lustre, degree of alteration, and edge-angularity) and tested the robustness of the classification using evidence of the grains’ petrogenesis acquired via high-resolution surface imaging on a Quanta-SEM and automated minerology maps on a TIMA. We then imaged ~10,000 grains across the samples using a HIROX HRX-01 digital microscope at the Natural History Museum, London. The images were segmented using FastSAM4 and labelled according to our classification scheme. To set up our model, we split the dataset into training and test sets, and we followed the steps described in Benet et al.5 to obtain the Volcanic Ash Database (VolcAshDB) classifier. The model classifies relatively accurately, and performance should improve as we collect more particle images and re-train the model. We find that the obtained component proportions as time-series are instrumental to interpret the evolution of the volcanic conduit and shallow storage system throughout the studied period by linking these proportions to concurrent monitoring data such as seismicity or SO2 flux. This work is carried out in collaboration with the Ecuadorian monitoring authority (IG-EPN), and we aim to create a model that can be operational for near-real-time petrological monitoring of any future activity at Tungurahua volcano, as well as to set out a methodology that can be used to re-train the model for other volcanic systems.
1. Re et al. 2021, JVGR, https://doi.org/10.1016/j.jvolgeores.2021.107365.
2. Gaunt et al. 2016, JVGR, https://doi.org/10.1016/j.jvolgeores.2016.10.013.
3. Cashman & Hoblitt. 2004, Geology 32, https://doi.org/10.1130/G20078.1.
4. Zhao et al. 2023, Preprint, arXiv. https://doi.org/10.48550/arXiv.2306.12156.
5. Benet et al. 2024, GGG, https://doi.org/10.1029/2023GC011224.
How to cite: Adler Cancino, G., Benet, D., Petrone, C. M., Gaunt, H. E., Steele, A. L., and Bernard, B.: Development of a Machine Learning Classifier to retrieve Time-Series of Ash Componentry at Tungurahua Volcano, Ecuador, 1999-2016, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18595, 2026.
Distinguishing volcanic from tectonic seismicity remains a critical challenge for volcano monitoring and hazard assessment. Traditional approaches often rely on spectral or amplitude-based criteria, which can be ambiguous during seismic swarm activity. Here, we explore the potential of Shannon entropy as a robust discriminator of seismic signal complexity, focusing on its ability to identify seismo-volcanic signals and, specifically, the onset of volcanic tremor.
We apply Shannon entropy to band-pass filtered seismic data (1–16 Hz) using 10-minute sliding windows. This metric captures the degree of predictability in the signal: low entropy indicates a more coherent, structured waveform, while high entropy reflects greater randomness. By tracking these changes over time, entropy provides a dynamic measure of signal organization. Three case studies illustrate the method: the 2011 submarine eruption of Tagoro volcano (El Hierro, Canary Islands), the 2021 subaerial Tajogaite eruption (La Palma, Canary Islands), and the 2025 magmatic unrest at Santorini (Greece).
In all these cases, entropy exhibits a decay coinciding with the onset of seismo-volcanic activity. Remarkably, a precursor pattern emerges: a gradual decrease in entropy preceding the main drop, suggesting early changes in seismic dynamics preceding the onset of genuine volcanic tremor.
Our findings highlight Shannon entropy as a simple yet powerful tool for real-time monitoring. By capturing changes in complexity in seismic signals, this metric provides an additional layer of information that complements conventional spectral analyses. The detection of precursor entropy decay could enhance early-warning capabilities, reducing uncertainty in distinguishing volcanic from tectonic processes during swarm activity.
How to cite: Álvarez Hernández, A., D'Auria, L., García-Hernández, R., Ibánez, J., Benítez, C., Cabrera-Pérez, I., Ortega Ramos, V., Martínez Van Dorth, D., Rodríguez Rodríguez, Ó., De Armas Rillo, S., López Díaz, P., Calderón Delgado, M., and Pérez, N.: Volcanic or tectonic swarms? How Shannon Entropy could solve the riddle , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5231, 2026.
Saba and St. Eustatius are the northernmost islands of the Lesser Antilles Volcanic Arc and host the active but quiescent volcanoes Mt. Scenery and The Quill. KNMI operates a multi-sensor geophysical monitoring network on these islands to monitor potential volcanic unrest and regional tectonic processes. Continuous GNSS networks form a key component of volcano deformation monitoring but are typically sparsely distributed and may not capture all local signals. For this reason, continuous GNSS networks are commonly complemented by campaign GNSS measurements.
On Saba and St. Eustatius, campaign GNSS points were installed and surveyed by other research institutes between 1998 and 2009. Because many of these points were deteriorated, in 2023, KNMI implemented new campaign GNSS points on both islands. Where possible these were placed in close proximity to historical points, but we also installed points at additional locations to fill monitoring gaps. Links between old and new markers were established by means of short baseline analysis if feasible.
Rather than installing permanent marker pins that require tripod setups, we developed a campaign setup based on a female threaded metal anchor glued into the ground. GNSS antennas are mounted on a removable pole which is screwed into the anchor, providing a stable and repeatable setup. This design reduces setup time and minimizes the risk of unintended antenna movement. We present the layout of the new GNSS campaign network on both islands and show positioning results from the baseline analysis as well as the 2023-2025 campaign measurements.
How to cite: Krietemeyer, A. and van Dalfsen, E.: A New GNSS Campaign Network for Volcano Monitoring on Saba and St. Eustatius: Design, Initial Results, and Linking to Historical Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18882, 2026.
Between late 2025 and early 2026, Mt. Etna exhibited highly diversified eruptive activity characterized by shifting eruptive styles. These phases were precisely captured by high-resolution signals from borehole strainmeters and tiltmeters. Starting on December 24th, borehole data highlighted an acceleration of the recharge phase marking an inflation, which culminated on December 26th in an attempt of summit intrusion, well-constrained by tilt signals from high-altitude stations.
In the early hours of December 27th, an effusive vent opened on the upper eastern flank of the Voragine (VOR) crater. Later, during the same day, two lava fountains occurred at the Northeast Crater (NEC), which had not generated paroxysms in the last 28 years. The strain and tilt networks detected distinct signals associated with these paroxysmal events, providing precise timing and first constraints on the underlying magmatic sources.
From December 29th through January 7th, 2026, strain and tilt signals recorded near-continuous decompression/deflation, accompanying effusive activity from vents located within the upper Valle del Bove depression at approximately 2.100 m a.s.l. In the last days of this phase, the signals indicated a waning of the decompression trend. These findings reaffirm the exceptional sensitivity of borehole strain and tilt monitoring in capturing diverse eruptive dynamics and providing critical real-time insights into volcanic processes.
How to cite: Bonaccorso, A., Aloisi, M., Cannavò, F., Carleo, L., Currenti, G., Ferro, A., Gambino, S., Laudani, G., and Sicali, A.: Multiple eruptive events of Etna volcano in a short-time (Dec 2025 – Jan 2026) captured by high-precision borehole strain and tilt, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10563, 2026.
Seismological methods are the most widely used for monitoring active volcanoes. While conventional methods focusing on noticeable events (e.g., event counting, classification, and integrating powers) are frequently useful and are being advanced with modern analysis techniques, there are cases of eruptions where no apparent precursors are observed as events. Recently, seismic background level (SBL) analyses were proposed for detecting subtle continuous vibrations and for monitoring years of volcanic activity (Ichihara et al., 2023). The SBL successfully revealed slowly developing long-term eruption precursors for the 2011 and 2017-2018 eruptions of Shinmoe-dake, Kirishima, Japan.
In this presentation, we compare the SBL and continuous tremor analyses carried out for multiple volcanoes. The cases are Shinmoe-dake and Iwo-yama of the Kirishima Volcanic Group (Ichihara et al., 2023), including the 2025 eruption of Shinmoe-dake, Hakone (Kurihara, 2023), Kusatsu-Shirane (Kobayashi et al., 2026), Whakaari, New Zealand (Ardid et al., 2025; Behr et al., 2025), and Northern Group of Volcanoes in Kamchatka (Galina et al., 2026). The relationships between the SBL variation and other parameters, such as eruptive activity, gas emission, and ground deformation, are compared, even though the available parameters and seismic observation sensitivity depend on the dataset. We demonstrate that the SBL is an efficient tool to assess the volcano’s activity condition and is particularly effective for inferring the end of an eruptive period.
How to cite: Ichihara, M., Yukutake, Y., Kobayashi, T., Galina, N., Ohminato, T., Kurihara, R., and Matsumoto, S.: Seismic Background Level (SBL) for Monitoring Active Volcanoes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8773, 2026.
Volcanic lightning and the electrification of ash plumes have the potential to significantly impact volcanic ash-induced hazards and the fluid dynamics of the eruption column. Despite being well-known phenomena, there is still a lack of systematic quantitative observations relating electrical variations to plume dynamics, and specifically tailored sensors for the electrical monitoring of volcanoes remain scarce (Cimarelli & Genareau, 2022). Regionally deployed Very Low Frequency (VLF) antennas are designed for long-range thunderstorm detection and often prove inadequate for detecting lower-intensity volcanic discharges near the vent (Vossen et al., 2021). While Very High Frequency (VHF) antennas are more efficient in volcanic lightning detection (Behnke et al., 2014), particularly when deployed as an array, they are typically custom-designed and expensive.
We present a newly developed low-cost, so-called slow antenna system designed to detect and quantify electric field changes associated with volcanic activity. The instrument utilizes a flat metal plate antenna coupled with a charge amplifier circuit that converts electrostatic induction into a proportional voltage. The signal is then digitized and logged via a Raspberry Pi equipped with a 32-bit analog-to-digital (AD) converter. The system currently achieves a sampling rate of 19.200 Hz, enabling the detection of electrical processes that exceed the resolution of conventional monitoring systems. Our design prioritizes portability, scalability and cost-efficiency to facilitate deployment at remote volcanoes.
To validate our system, we are preparing a two-week field campaign at Sakurajima volcano, characterized by persistent explosive activity and frequent generation of volcanic lightning. Our data processing workflow involves: (1) event recording; (2) data storage and retrieval; (3) de-drooping corrections to reconstruct true changes of the electrical field; and (4) instrumental response calibration to convert voltage measurements into absolute electric field values. Additionally, we are benchmarking our antenna against the commercially available Previstorm system.
Preliminary results demonstrate the instrument's capability to capture rapid (0.1 ms) electric field transients associated with explosive events. This work establishes a foundation for the broader deployment of cost-effective electric field monitoring. Specifically, deployment as an array would enable the temporal reconstruction of discharges within the eruption column (Behnke et al., 2014), providing a crucial complementary dataset for early warning systems and plume dynamics studies. Future work will focus on correlating electric field signatures with multiparametric monitoring data to better constrain eruption mechanisms and enhance hazard assessment.
Behnke, S. A., Thomas, R. J., Edens, H. E., Krehbiel, P. R., & Rison, W. (2014). The 2010 eruption of Eyjafjallajökull: Lightning and plume charge structure. Journal of Geophysical Research: Atmospheres, 119(2), 833–859.
Cimarelli, C., & Genareau, K. (2022). A review of volcanic electrification of the atmosphere and volcanic lightning. Journal of Volcanology and Geothermal Research, 422, 107449.
Vossen, C., Cimarelli, C., Bennet, A., Giesler, A., Gaudin, D., Miki, I., Iguchi, M., & Dingwell, D. B. D. (2021). Long-term observation of electrical discharges during persistent Vulcanian activity. Earth and Planetary Science Letters, 570, 117084.
How to cite: Ischebeck, L., Weißgräber, L., Peppel, D., and Hort, M.: Portable Antenna System for Electric Field Monitoring During Volcanic Eruptions: First Results from Sakurajima Volcano, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10887, 2026.
When physical and data sciences are not sufficient to support models and/or decisions, expert judgment is a recognized approach to quantify the uncertainties around specific issues. Among different expert judgment methods, Structured Expert Judgment (SEJ) employs a formalized, documented procedure for obtaining probabilistic belief statements from a group of experts about unknown quantities or parameters. This provides an attractive approach for performing assessments at volcanoes characterized by large knowledge gaps by integrating diverse kinds of information. Uncertainties are likely to be large in these cases, and SEJ can quantify these uncertainties to provide scientists and decision-makers with indications of the reliability of the assessments. The final goal of this approach is to obtain the group’s synthesized uncertainty distribution (representing a new “virtual expert” often called Decision Maker - DM) around specific items (or “target questions”), that result from combining elicited judgments of all the experts.
More specifically, performance-based expert elicitation relies on validating expert probability assessments through an impartial empirical trial. Thus, in a performance-based elicitation, experts are tasked with providing their estimations of probability distributions for a set of known quantities, often referred to as “seed items,” which, jointly, serve as calibration benchmarks for expert performance. Experts’ responses provide the basis for performance scoring using the Classical Model algorithm (Cooke, 1991), determined empirically on the individual expert’s attainment, jointly in terms of two separate metrics: “statistical accuracy” and “informativeness”, which are evaluated on the set of seed items overall.
Traditionally, the management of a performance-based expert elicitation is time consuming and involves the collection of tens of questionnaires, often manually copied from hard-copies of the responses or email attachments. The performance-calibration algorithms and the production of standard outputs, including statistical samples of the DM responses, are necessary steps every time an elicitation is conducted, but relied on different scripts and independent pieces of software.
In this study we present the latest version of the recently released software ELICIPY (de’Michieli Vitturi et al. 2024), which allows organizing and managing performance-based expert elicitation sessions in a partially automated way, resulting in a significantly enhanced efficiency. This new version includes, among other improvements, an “agreement index” to quantify the level of agreement among experts, a continuous version of the Classical Model to compute expert weights, the possibility to import weights from an external file, new plot options, an interactive dashboard for results exploration.
ELICIPY enables the smooth conduction of elicitations with a relatively large number of questions and/or experts. Moreover, the management of multiple elicitation sessions, with questionnaire modifications and response updates are made easier. Some of these improvements are demonstrated on the case study of a hazard and risk assessment for the active Kolumbo submarine Volcano (Aegean Sea, Greece), which was made of 20 Seed Items and 64 Target Items in total, the latter structured into 17 subject matter groups (Bevilacqua et al., 2025).
How to cite: Tadini, A., Bevilacqua, A., de' Michieli Vitturi, M., and Neri, A.: Software-driven structured expert judgment: modern tools to efficiently synthesize scientific knowledge for uncertainty quantification in volcanic hazard assessment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10037, 2026.
ARISTOTLE-ENHSP (All Risk Integrated System TOwards Transboundary hoListic Early Warning European Natural Hazard Scientific Partnership) is a European scientific consortium that provides rapid, authoritative scientific advice on major natural hazards to support EU Civil Protection and Emergency Management (ERCC). It delivers 24/7 multi-hazard near–real-time scientific assessments to support decision-makers during major events, including Earthquake, Tsunami, Volcanoes, Severe weather, Forest fire and Flooding. Within the consortium the volcano hazards group provides assessments for all Pan-European volcanoes, delivering scientific advice through routine monitoring and emergency report during episodes of volcanic unrest or eruption. The group, consisting of INGV, IGN, IMO, IVAR/CIVISA, and KNMI, each with a specific role and area of expertise, forms the European Volcanic Observatories Network (EVON). Routinely 3-times per week, the group scans the European volcanoes within each area of competence, raising awareness in the case of significant changes in unrest and/or an ongoing volcanic activity. Assessments are made based on volcano activity levels and potential impact. Volcanoes showing activity above background with a yellow alert status or higher on the decision matrix are included in the weekly multi-hazard monitoring report, contributing to the provision of a transboundary assessment and to the development of an early-warning system at European level.
How to cite: Paratore, M., Salerno, G., Forlenza, G., Barsotti, S., Michelini, A., Carmo, R., De Laat, J., Domínguez Cerdeña, I., Felpeto, A., Ferreira, T., Guðmundsdóttir, L., Óladóttir, B., and Pacheco, J.: Volcanic hazard monitoring and assessment in Europe within the ARISTOTLE-ENHSP framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6832, 2026.
