The recent evolution (last 700 years) of La Fossa cone (Vulcano island) has long intrigued scientists and sparked debates regarding the origin and timing of products belonging to its various eruptive units. Although very recent, the stratigraphy of these products, the timing of the main eruptions and their characters, and the identification of the source area(s) still remain partly unclear. In the present work, we aim (i) to reconstruct in detail the stratigraphy of Pietre Cotte pyroclastic succession, representing the result of the activities from the XIV century up to the latest AD 1888-90 eruptive cycle, (ii) to define the processes that control the opening phases of explosive eruptions in intermediate–sialic systems characterized by closed conduits and intense interaction with active hydrothermal systems, and (iii) to understand the mechanisms responsible for variations in eruptive style during the eruptions. Stratigraphic fieldwork, lithofacies analysis and volcanological interpretation have been carried out, together with laboratory analyses of representative sample components, volcanic-glass geochemistry, thin-section petrography, and morphoscopic SEM analyses. EPMA glass analyses define two distinct compositional domains (trachytic and rhyolitic), with the gap bridged by the products of the 1888–90 eruptive cycle, indicating effective mixing/mingling processes within the shallow magmatic system. Juvenile fragment morphologies are consistent with phreatomagmatic fragmentation and magmatic degassing, with localized hydrothermal alteration. These studies have led to the definition of an updated volcanic succession result of recurring hydromagmatic to magmatic eruptions, with vent-opening phreatic phases, that produced multiple depositional units from fallout and pyroclastic density currents. The Pietre Cotte succession includes distinctive pumice-fallout layers and the well-known rhyolitic lava flow, reflecting a complex eruptive evolution. Based on our stratigraphic data and the re-interpretation of the available historical reports, combined with the available paleomagnetic ages, the rhyolitic lava flow is most likely dated to AD 1739, whereas the pumice fallout layers were likely emitted slightly after in AD 1771. Constraining the precise timing of the main explosive and effusive events is crucial to better understand the dynamics of La Fossa’s shallow magmatic–hydrothermal system and the evolution of its most recent eruptive activity, thus providing key insights for volcanic hazard assessment on Vulcano Island.

Long-term investigations at numerous active volcanic systems worldwide have demonstrated that environmental radionuclide measurements in volcanic plumes provide valuable insights into degassing processes, yielding important constraints on magmatic activity timescales and the depth of magmatic reservoirs. In this study, we introduce a novel methodological framework for the environmental characterization of airborne radioactivity, aimed at quantifying the coupled atmospheric transport of radionuclides and gas species (e.g., CO2 and H2S) in active volcanic environments. The approach integrates in situ gamma-ray spectroscopy with geochemical measurements of air concentrations, enabling a direct comparison between radiometric signals and volcanic gas transport. The method was applied to two distinct active volcanic sites: the Pisciarelli fumarolic field (Campi Flegrei caldera, Italy), characterized by a sustained gas flux, and the Stephanos crater (Nisyros Island, Greece) where passive gas emissions are comparatively low. Gamma-ray detection acquired at multiple heights above ground (ranging from 40 to 180 cm) allowed the assessment of vertical variations in radioactivity levels and volcanic gas concentrations from both diffuse and fumarolic sources, even under very low-emission conditions. Our results show a clear coupling between CO2 concentration and gamma radiation, demonstrating that volcanic gases act as carriers of radon and its progeny, significantly modifying the vertical distribution of radioactivity. These findings provide the first direct field evidence of height-dependent radionuclide transport driven by gas fluxes and establishes a new framework for real-time environmental radioactivity monitoring in volcanic areas.

The interdisciplinary study of volcanic processes, which extend across all timescales and lengths, requires a multitude of approaches, ranging from analogue and numerical modelling to observations and fieldwork and extending to mathematics. A conference was held at the East African Institute for Fundamental Research, affiliated with the University of Rwanda, a country which, along with the Democratic Republic of Congo, presents a unique geodynamic context. Located along the East African Rift, an active seismic region, Rwanda is close to two of Africa's most active volcanoes, including Nyiragongo, which overlooks Lake Kivu, a deep volcanic lake rich in dissolved carbon dioxide and methane, the latter of which is used for electricity generation. In this context, the conference addressed many “classic” volcanological topics and their modern advances, such as multiphase lava flows, subsurface magma propagation, seismic and deformation signals from a volcano, modelling of volcanic emission dispersion, and volcanic lakes. Yet, it broadened the discussion to the volcanic particle-water interface and its impact on soils, volcanoes and climate change, and volcanoes and health. This article aims to highlight and share the richness of the integration and interconnectedness of the various questions related to a volcanic environment, as well as their impact on society. Ultimately, this conference also demonstrated the importance of promoting science in Africa and developing countries so that the next generation of African researchers is equipped to address the challenges facing their nations.

Geophysical granular flows, such as landslides, rock avalanches and pyroclastic flows, remain difficult to model due to their unexpectedly high mobility. Several mechanisms have been proposed to interpret this low dissipative behavior, including the flow-substrate interaction. This study addresses this issue through dedicated, well-controlled experiments on steady granular avalanches of idealized and natural flowing materials (i.e., glass beads, sand, volcanic material) along a wide variety of inclined surfaces. Our observations reveal that the basal surface condition significantly influences the propagation and deposition dynamics of granular avalanches. In particular, we identify two main types of effective basal condition-smooth and rough-based on a single dimensionless parameter: the roughness-to-grain size ratio A/d with a critical transition at A/d approximate to 10-1. The dynamic modeling of granular avalanches on smooth and rough inclines is then established based on initial flow conditions, material properties, and surface characteristics. We propose a unified flow rule governed by distinct functional relationships of the inflow Froude number, depending on the repose angle and grain size of flowing material, and the basal friction angle. These results highlight the importance of accurately constraining material and basal properties in order to improve field prediction of geophysical granular avalanches.

This study investigates the mechanisms underlying phreatic explosions within the geothermal system of eastern Milos Island. Field, laboratory and historical data suggest that a long-standing hydrothermal system, characterized by silica-rich crusts over altered rhyolitic lava domes and volcaniclastics, experienced multiple explosive events leading to its eventual disruption. The explosions, occurring at depths of 3-20 m, were likely triggered by rapid depressurization, possibly induced by seismic activity. Intermediate to large-magnitude local earthquakes or large-magnitude regional earthquakes, such as the AD 365 Crete event, could have generated dynamic stress sufficient to destabilize the system, leading to cavitation-driven explosions. Overlapping craters and deposits indicate repeated explosive activity over years, ultimately resulting in the exhaustion of the hydrothermal system. Archaeological evidence, including Roman-age pottery beneath phreatic deposits, suggests that the explosions were sudden and unanticipated. The concurrent decline in settlement activity on Milos during the fourth century AD may be linked to these disruptions, in combination with broader regional seismic and socio-economic factors. This study highlights the sensitivity of hydrothermal systems to external stressors and the potential role of seismic events in triggering phreatic explosions.

Laboratory experiments on granular flows using natural material were carried out under different conditions in order to investigate the behavior of fine to coarse-grained, channelized and non-channelized granular flows passing over a break in slope. Morphometric parameters of channelized and non-channelized experiments are compared for both fine-grained and coarse-grained grain size distributions. After normalization, morphometric data provide empirical relationships that highlight the major influence of grain size vs. channelization of the experimental flows. Normalized velocity data of the flow front show third-order polynomial fit for both coarse-grained and fine-grained experiments, as well as for non-channelized and channelized ones. This highlights similar complex behavior of the different experimental flows, which differs only for different partition of inertial and frictional forces at changing grain size of experimental mixtures. The runout of coarse-grained granular flows is always longer than that of fine-grained granular flows, irrespective if they are channelized or non-channelized. Finally, we discuss the applicability of the experimental results to natural granular flows, highlighting the change in physical behavior of fine-rich pyroclastic density currents and volcaniclastic flows depending on the effectiveness of fluidization processes in fine-grained natural materials.

The persistent unrest at Campi Flegrei highlights the importance of accurate and continuous surveillance of volcanic gas emissions to support scientific interpretation and civil protection efforts. Suitable sensors capable of fast, real-time tracking of trace gas components within CO2-H2O -dominated fumarolic plumes are still missing. In this work, a compact Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) sensor was used for real-time and in situ detection of the hydrogen sulfide (H2S) emitted from the Pisciarelli fumarolic field at the Campi Flegrei caldera. The 1 s response time of the sensor allows the capture of the fast emission dynamics of the plume and accurate reconstruction of H2S emission peaks up to 60 part-per-million (ppm). By combining the QEPAS measurements with a commercial non-dispersive infrared spectroscopy CO2 sensor, a characteristic CO2/H2S ratio of 208 ± 4 was estimated for the Pisciarelli fumarolic field.

Volcanic risk management frequently encounters a significant gap between Probabilistic Volcanic Hazard Assessment and subjective risk perception. This study addresses this issue by comparing communities exposed to tephra fallout from two contrasting volcanoes in Southern Italy: the persistently active Etna and the quiescent Vesuvius. A survey of residents in proximal (high exposure: Catania, Nola) and distal (lower exposure: Siracusa, Pisticci) zones assessed hazard knowledge, multidimensional risk perception, institutional trust, and preparedness. The results identify distinct socio-cognitive paradigms. In the Etna proximal zone, chronic exposure results in hazard normalization. Residents perceive a high probability of tephra fallout but dissociate this from personal threat, relying on individual coping strategies and disengaging from institutional preparedness. In the Vesuvius proximal and Etna distal zones, a preparedness paradox emerges: High theoretical awareness and willingness to adopt protective actions coexist with low practical readiness due to insufficient hazard-specific training. Geographical distance further differentiates perception. The Etna distal area maintains realistic awareness due to frequent volcanic activity, whereas the Vesuvius distal area (Pisticci) exhibits a distal shadow effect, where distance significantly reduces risk salience despite objective transboundary threats. Although trust in scientists and the Civil Protection Agency remains consistently high, sources of hazard knowledge vary considerably across communities. These results suggest that Disaster Risk Reduction strategies should move beyond uniform approaches. Risk communication should be context-specific, aiming to disrupt habituation in chronically exposed communities and to transform abstract concern into actionable preparedness in quiescent and distal regions.

We present fourteen new Ar-40/Ar-39 ages, based on 287 single crystals analyzed from proximal and semi-proximal pyroclastic deposits, that significantly refine the chronology of Monte Vulture's initial volcanic activity (Foggianello synthem). The earliest identified eruption is the Fara d'Olivo A ignimbrite, dated at 784.7 +/- 4.7 ka (2 sigma), closely followed by the Fara d'Olivo B unit at 774.7 +/- 0.9 ka (2 sigma), which encompasses at least four distinct eruptions. We also recognize a new explosive phase at 740.0 +/- 1.6 ka (2 sigma) that we named Rapolla and that preceded the effusive Spinoritola phase (731.5 +/- 2.0 ka (2 sigma)). The youngest activity belonging to the Foggianello synthem, named "Campanile phase", is composed of pyroclastic deposits dated between 708.4 +/- 2.0 ka (2 sigma) and 700.2 +/- 1.2 ka (2 sigma). According to our results, the duration of the Foggianello system spans approximately similar to 85 ka, much longer than previously proposed. Geochemical analyses of fresh glass shards indicate a dominating phonolitic magma composition during this interval. However, a progressive change of the magmatic source, probably controlled by crustal contamination, has been observed. Furthermore, our results establish a precise correlation of Fara d'Olivo B Ignimbrite with distal tephra layers from Montalbano Jonico (V4) and Lake Ohrid (OH-DP-2869), showing that this eruption represents a robust regional stratigraphic marker of the Brunhes-Matuyama reversal. Finally, the recognition of inherited sanidines up to similar to 934 ka potentially pushes back the onset of magmatism at Monte Vulture into the Early Pleistocene, substantially earlier than previously inferred. Our results thus have implications also for the geodynamic evolution of the Apulian slab, suggesting an earlier onset of extensional tectonics and mantle upwelling.

The interaction of magmas with host-rocks is a common process in magmatic systems. Interaction with carbonate-bearing lithologies is of major interest since the thermometamorphic reactions during magma-carbonate interaction, may release CO2 affecting eruptive behaviour. The Somma-Vesuvius volcanic system is built on a km-thick Mesozoic carbonate platform, with evidence of intense interaction in the form of carbonate-xenoliths in juvenile pumices and as skarns. Nevertheless, the timescales and mechanisms of magma-carbonate interactions remain poorly constrained. Here we present an experimental study on the interaction of a dry Vesuvius' phonolite melt with a high-Ca limestone and a dolomitic limestone. We conducted the experiments in a piston cylinder apparatus at 600 MPa, temperatures of 950 degrees C and 1200 degrees C and interaction times of 0-60 min. Bubble nucleation (CO2 release) has been observed in all experiments. The dolomitic limestone is assimilated via an AFC-process, creating a skarn-like assemblage of periclase-bearing dolomite, forsterite, clinopyroxene and a Ca + Mg-enriched melt. The high-Ca limestone exhibits a partial melting texture, that includes the formation of a Na-K-Ca chloride carbonate melt due to direct diffusive transport of alkalis and chlorine from the dry phonolite melt into the limestone. The melting of limestones at crustal conditions may affect magma differentiation trends in Campanian magmas, especially the Na2O/K2O ratio. The reported assimilation timescales of 30-60 min at 1200 degrees C for both limestones are however maximum estimates, as a dry phonolitic melt was used at pressures exceeding those to be expected in the Vesuvius plumbing system (<200 MPa). The presence of water would greatly accelerate limestone assimilation.

Dense volcanic granular flows are polydisperse in terms of grain size and density, and their flow characteristics are mainly governed by particle-particle collisions and frictional forces acting at the boundaries. The parameter measuring the energy dissipation during the collisions is the coefficient of restitution (e $e$), which is proportional to the fraction of the original energy stored in the colliding particles that is restored to the same ones after the collision. e $e$ is fundamental in computational fluid dynamics (CFD) numerical models to simulate multiphase granular flows because it is required to solve the particles motion and the particle-particle momentum exchange. The calculation of e $e$ for irregular volcanic particles is an unsolved challenging problem, which is here addressed by colliding particles through a pendulum-type instrumental apparatus. e $e$ was calculated for volcanic particles with different density (rho $\rho $), diameter (d $d$) and particles size ratio (dratio ${d}_{\text{ratio}}$), and the data were used to obtain linear relationships between e $e$ and the investigated parameters. Afterward, a multicollinearity analysis and a multiple regression were applied to all data to adequately predict the value of e $e$ knowing the values of rho $\rho $, d $d$, and dratio ${d}_{\text{ratio}}$. The empirical law was finally validated against some large-scale experiments by using the multiphase CFD simulation tool Multiphase Flow with Interphase eXchanges. The CFD simulations inserting the predicted e $e$ showed a better agreement between simulated and experimental flow velocities, with an increase of the simulation accuracy up to 20%. Hence, the current paper proposes a simple instrumental apparatus to calculate e $e$, demonstrating its importance in simulations of multiphase granular flows.

Volcaniclastic debris flows are highly concentrated flows of rock debris, mud and water in which the sediment is of volcanic origin. These phenomena can be syneruptive, posteruptive, or unrelated to an eruption. To be generated, the coexistence of steep slopes, unconsolidated sediments and an adequate amount of water is necessary. The aim of this project is to investigate the role of water circulation in the initiation processes of debris flows to enhance our ability to anticipate potential new debris flows in the Campanian Volcanism area, focusing on the Sarno area. Sarno is a small municipality located in the Vesuvius Volcanism area (western side of the Campanian Apennines) that is sadly infamous for the major debris flow events that, on the 6th of May 1998, destroyed the town and killed around 150 people. The study area exhibits a convergence of geomorphological and lithostratigraphic settings that contribute to enhancing its exposure to hazards: i) the presence of a calcareous bedrock with very steep slopes (30-45°) mantled by ii) an alternation of colluvium and pyroclastic deposits, and iii) natural scarps and man-made cuts that further worsen the stability conditions. This research employs a multimethodological approach including i) geotechnical and rheological analyses of the sediments; ii) X-ray Diffraction for the mineralogical characterisation, particularly of the clay fraction; iii) large-scale experiments to investigate the role of water circulation in the sediments during simulated rainfall in the triggering of volcaniclastic debris flows; iv) in situ Time-Domain Reflectometry measurements at Pizzo D’Alvano for soil moisture vertical distribution and v) simultaneously acquisition-surveys by using a drone-mounted passive radiometer for spatial soil moisture distribution. Integrating these methods aims to achieve understanding of the water content distribution in the debris flow initiation process that could be potentially used in the rainfall-triggered landslide early-warning systems.

The hazard of pyroclastic density currents (PDCs) at Vesuvius is investigated based on past eruptions. The analysis is extended to all eruptions that left substantial deposits on the ground.The currents are bipartite, with a basal highly-concentrated part, which was fed from the impact of the eruptive fountain on the ground, and an overlying part generated by the squeezing of the collapsed material that fed a dilute and turbulent shear flow.Dynamic pressure, particle volumetric concentration, temperature and flow duration are hazardous characteristics of PDCs that can impact buildings and populations and are defined here as impact parameters. They have been calculated through an implementation of the PYFLOW code, which uses the deposit particle characteristics as input. The software searches for the probability density function of impact parameters. The 84th percentile has been chosen as a safety value of the expected impact at long term (50 years). Maps have been constructed by interpolation of the safety values calculated at various points over the dispersal area, and show how impact parameters change as a function of distance from the volcano. The maps are compared with the red zone, which is the area that the National Department of the Italian Civil Protection has declared to be evacuated in the impending of an eruption. The damaging capacity of currents over buildings and population is discussed both for the highly concentrated part and the diluted one.

Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting on population and infrastructures. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma-Vesuvius and Campi Flegrei volcanoes, as well as the nearby Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. Our recent studies focus on the analysis of the pyroclastic fall and flow deposits, and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius, 472 CE (Pollena) and 1631. Historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database. Stratigraphic, sedimentological, and archaeological analyses were carried out, in addition to rock magnetic investigations and impact parameter estimations. The field data analyses show that in both eruptions the dispersal area of the primary pyroclastic deposits is wider than previously known. Such distribution of the deposits directly affects the one of the lahar deposits, even because a significant remobilization took place during and after the studied eruptions, involving the distal phreatomagmatic ash. From these analyses, it was possible to constrain the timing of the deposition, and to estimate the thicknesses, velocities and dynamic pressures (impact parameters) of the lahars. A new shallow layer model based on depth-averaged variables, named IMEX-SfloW2D, was developed for the simulation of lahar dynamics. A thorough sensitivity analysis was carried out to identify the critical processes (erosion and deposition) and parameters (numerical and physical) controlling lahar runout, using both synthetic and real cases topographies. Effects of erosion and deposition were investigated by comparing field data with the output of simulations including vs. excluding these processes. By comparing observed and simulated flow thickness and area covered by the flows, and their evolution over time, it can be shown that the inclusion of erosion and deposition is important to properly simulate the impact parameters of lahars, particularly on uneven terrain. Lastly, a novel workflow for Probabilistic Volcanic Hazard Assessment (PVHA) for lahars was developed and applied to the Vesuvius case study. Such a workflow explores the effect of uncertainty of the flow initial conditions on the impact parameters of lahars on the target area, by sampling coherent sets of values for the input model parameters and running thousand simulations. The simulation outputs were processed to produce hazard curves, hazard maps, and probability maps for the maximum flow thickness, and hazard surface and probability maps for joint thresholds in flow thickness and dynamic pressure. It is believed that the latter hazard products represent a novel product in PVHA for lahars around Vesuvius volcano and can be applied worldwide. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas, even at distances of several to tens of km from active volcanoes like Vesuvius.

Rain-triggered lahars represent a frequent phenomenon at Volcán de Colima, Mexico. Hurricane Jova, on October 12th, 2011, was an anomalously rainfall event resulting in more than 240 mm of rainfall in 24 hours. This event triggered several lahars in the main ravines and induced multiple landslides on the valley sides. Based on data recorded at a seismic monitoring station along the Montegrande ravine, we were able to evaluate the lahar and obtain physical parameters of the flow and associated deposits. The lahar started around 7:20 a.m. (GTM) and lasted for approximately three hours. Five main flow pulses were detected. The first three pulses were closely spaced, and the final two occurred after one hour and 30 minutes, respectively. The event is classified here as a multi-pulse lahar, falling within the hyperconcentrated to debris flow regime. Three main depositional units were recognized along the ravine. The two lower units are up to 50 cm thick, massive, and mostly composed of sand and gravel. The upper unit is up to 1.5 m thick, massive with clasts embedded in a sandy matrix. The deep erosion observed along Montegrande ravine is related to the large magnitude (flow depth and velocity) of these flows, and to their long duration, with three hours of continuous scouring along the ravine. Immediately after the Jova event, dozens of landslides occurred along the ravine, some of which dammed the river and affected the flows during the 2012 lahar season. These landslides both initially trapped lahars and later provided debris for subsequent flow events, even during periods of low rainfall accumulation. The event here described is a clear example of large magnitude lahars at Volcán de Colima during tropical rainfall associated to hurricanes hitting the Mexican Pacific coast, as more recently occurred in 2015 with the transit of Hurricane Patricia. The findings of this study contribute to a better assessment of hazard scenarios in the case of extreme hydrometeorological events at Volcán de Colima and to understanding how their impact can drastically alter the hydrological balance of the volcano.

The hazard of pyroclastic density currents (PDCs) at Vesuvius is investigated by analysing deposits from past eruptions. No specific eruption was chosen as representative of the hazard of PDCs, and the analysis is extended to all the eruptions that left substantial deposits on the ground. Based on the stratigraphic evidence, we assume that at Vesuvius the currents are bipartite, with a highly concentrated basal part, which was fed from the collapse of the eruptive fountain on the ground, and an overlying part generated by the expulsion of gas and fine particulate matter that fed a dilute and turbulent shear flow. Dynamic pressure, particle volumetric concentration, temperature, and flow duration are hazardous characteristics of PDCs that can impact buildings and population and are defined here as impact parameters. They have been calculated by means of an implementation of the PYFLOW code, which uses the deposit particle characteristics as input. The software searches for the probability density function of impact parameters. The 84th percentile has been chosen as a safety value of the expected impact in the long term (50 years). There is no correlation between eruption size and impact parameters. Maps have been constructed by interpolation of the safety values calculated at various points over the dispersal area, and they show how impact parameters change as a function of distance from the volcano. The maps are compared with the red zone, which is the area that the National Department of the Italian Civil Protection has declared to be evacuated under conditions of an impending eruption. The capacity of currents to damage buildings and population is discussed for both the highly concentrated part and the diluted one.