Coastal regions of the Mediterranean basin are increasingly experiencing the impacts of climate change. Among these, sea-level rise (SLR), combined with land subsidence and storm surges, represents a major hazard for coastal environments, affecting urban areas, transport systems, ports, and other critical infrastructures. Low-lying coastal zones are particularly vulnerable to accelerating SLR, which enhances the exposure of coastal communities to flooding, shoreline retreat, and erosion. Rising sea level can also amplify the impacts of extreme events such as storm surges and tsunami. In this context, the Northern Adriatic Sea represents one of the most vulnerable sectors of the Mediterranean due to the combined effects of global SLR and significant vertical land motion (VLM), with prevailing subsidence. This study investigates future relative sea-level rise (RSLR) scenarios along the Emilia-Romagna coast (Italy) up to 2150, with particular attention to the role of differential subsidence and its implications for coastal infrastructures. The analysis integrates multiple datasets: (i) InSAR data from the Copernicus European Ground Motion Service and GNSS geodetic data from local networks to quantify the subsidence rates in the investigated area; (ii) Airborne LiDAR data provided by the Italian Ministry of the Environment to generate high-resolution digital elevation models (DEMs) for projecting potential flooding extents; and (iii) SLR projections from the IPCC AR6 under different SSP climate scenarios for the Mediterranean basin, revised for current rates of VLM. Finally, we provide a classification of the different areas according to their exposure and risks to the combined effects of VLM, SLR and storm surges, producing heterogeneous patterns of coastal vulnerability and identifying critical coastal infrastructures at risk of inundation. Our findings provide new insights into the combined effects of climate-driven SLR and land subsidence in the Northern Adriatic, support the development of adaptation strategies and coastal risk mitigation measures also for other vulnerable Mediterranean coastal systems.

IntroductionVulcano Island, in the Aeolian Archipelago (Italy), is affected by recurrent degassing crises during which elevated volcanic gas emissions may pose hazards to residents, visitors, and personnel operating in the active crater area. This study presents a scenario-based probabilistic assessment of outdoor CO2 and SO2 dispersion hazards at Vulcano.MethodsThe assessment integrates long-term meteorological variability, geochemical monitoring data and numerical dispersion modelling. Three representative degassing scenarios were considered: (i) background activity, based on long-term monitoring data; (ii) unrest conditions, representative of the enhanced degassing observed during the 2021–2022 crisis; and (iii) an escalation scenario exploring the effects of a further increase in gas emissions. Atmospheric variability was represented by randomly sampling 1,000 days from 30 years of ERA5 reanalysis data, complemented by local meteorological observations. Hazard and persistence maps were generated using the VIGIL workflow, which couples passive and gravity-driven dispersion models.ResultsThe simulations indicate that SO2 represents the main outdoor gas-dispersion hazard across the investigated scenarios. Under background conditions, hazardous SO2 concentrations remain largely confined to the La Fossa crater area, whereas under unrest and escalation scenarios the affected area expands along the crater flanks and, under specific meteorological conditions, toward sectors frequented by visitors or located near inhabited areas. In contrast, modelled outdoor CO2 concentrations at 2 m above ground level remain below hazardous thresholds under background and unrest conditions, while elevated concentrations are predicted in the escalation scenario, particularly within the crater area.Discussion and ConclusionsComparison with available monitoring data highlights the importance of poorly constrained local fumarolic and diffuse CO2 sources, particularly near Vulcano Porto and Levante Beach. Overall, the proposed probabilistic framework provides a quantitative basis for identifying areas where hazardous gas concentrations may occur or persist under variable atmospheric conditions, supporting future monitoring strategies and preparedness planning during degassing crises.

Stromboli, one of the most active volcanoes in Italy, is characterized by an ordinary eruptive activity consisting of persistent and mild explosions, occasionally interrupted by lava flows and by significant eruptions named major explosions and paroxysms. During such explosive activity, abundant loose pyroclastic material is emplaced on the upper steep slopes of the volcano. Due to intense or prolonged rainfall, this material can be remobilized, thereby generating volcanoclastic flows of different typologies that invade the lower slopes and, in several cases, reach the inhabited coastal areas causing huge damage to infrastructures. The most recent flows occurred on October 18‑20, 2024 and May 15, 2025, when Stromboli island was hit by very intense rainfall concentrated in a few tens of minutes. Consequently, loose tephra deposits were rapidly remobilized, triggering lahars that reached the villages of Stromboli and Ginostra, as well as the access routes to the volcano summit. In this work, for the first time, the grain‑size characterization of these lahar deposits is presented. Based on the sedimentological characteristics and grain‑size distributions the deposits have been classified as hyperconcentrated stream flows and proves to be dominated by coarse to fine ash. Moreover, using high‑resolution Pleiades optical satellite data, one of the depositional fans sampled during fieldwork was characterized. The results of this study provide the first quantitative grain‑size dataset for Stromboli lahars, representing a key constraint for the reconstruction and numerical modeling of these processes in volcanic hazard assessment at Stromboli.

During the years 2021-2022 Vulcano island was affected by a volcanic crisis characterized by a remarkable increase in fumarolic activity, intensified seismicity and ground deformations. With the aim of reproducing with high detail the island surface after this crisis, an Airborne Lidar survey was carried out on 4th August 2023. More than 200 × 106 3D Lidar points were processed to create a new Digital Surface Model at a very high spatial resolution (50 cm). This model reproduces the elevation surface of all natural and anthropic elements constituting the island. The model was validated through a set of Ground Control Points and a vertical accuracy of 8 cm was obtained. This level of accuracy, combined with the spatial resolution of 50 cm, makes the model particularly suitable for detailed geomorphological investigations. In addition, associated with the derived coastline, it provides the most up-to-date and accurate 3D topography for the assessment of natural hazards, such as changes in the volcanic activity state, earthquakes and mass movements triggered by extreme rainfalls.

The persistent mild-explosive activity of Stromboli volcano (Aeolian Archipelago, Southern Italy) is episodically interrupted by much more energetic and dangerous episodes called paroxysms. The Istituto Nazionale di Geofisica e Vulcanologia (Italy) set up the interdisciplinary UNO Project (UNderstanding the Ordinary to forecast the extraordinary), aimed at understanding when the Stromboli volcano is about to switch from the ordinary to the extraordinary (dangerous) activity. The UNO Project includes an outstanding variety of research activities, including the collection of new data within the timeframe of the Project (2019–2025). Key to the success of the Project is the collection of integrated high spatial and temporal resolution data and their joint analyses in a shared relational geo-spatial database. Here, we present the development of this database, focusing on the preparatory work and the design of the logical model. Several hints and examples are provided to bridge the gap between the standard perspective of field volcanologists and the technical issues and caveats governing the domain of relational geo-spatial databases.

Active volcanic areas with intense explosive activity are often affected by secondary hazardous phenomena, such as wildfires triggered by incandescent ballistic material that hits vegetated zones. A testimony of this was the wildfire induced by the 3rd of July 2019 paroxysm at Stromboli Island (Aeolian Archipelago, Italy). This wildfire involved significant portions of territory and caused the loss of a human life. In order to produce an accurate mapping and quantification of the burnt areas during the 2019 summer, the spectral indexes NDVI and NBR were derived from Landsat-8, Sentinel-2 and Pléiades data. The maps of difference in NDVI and NBR, between pre- and post- paroxysm of 3 July, were compared with the burnt areas map obtained by a very high spatial resolution drone imagery. Sentinel-2 dNDVI map results the most accurate and identifies 3.60 km2 of burnt areas covering 29.5

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.

Digital surface models reproduce the 3D topography of a territory at different spatial resolutions depending on the acquisition technique of source data. In active and densely populated volcanic areas, updated digital topographies are fundamental for mapping and quantifying the morphological changes generated by the eruptive events and play a key role in modelling volcanic phenomena and related hazards. This work presents the high-resolution Digital Surface Model of Stromboli Island, Italy, updated to 4th August 2023. The model, obtained by elaborating more than 109 × 106 Airborne Lidar points (x,y,z), reconstructs the volcano’s surface through an elevation matrix at a spatial resolution of 50 cm, reproducing both natural and anthropic elements. The model has been validated by using Ground Control Points and the vertical accuracy results in 8 cm. Nowadays, this model represents the most updated and accurate digital 3D topography of the entire island and, for this reason, can be considered a relevant data not only for multi-temporal morphological and volcanological analyses but also for hazard assessment studies.

Sea level change along the coast is caused by vertical land movements (VLM), changes in the ocean volume and additional factors. Space based observations from Synthetic Aperture Radar (SAR) satellites, combined with ground observations from GNSS data, are crucial to estimate the current rates of VLM and, in combination with climatic data, relative sea level rise projections (RSLR) along the coasts. Here we focus on the Mediterranean basin and especially on the Italian coasts, which are affected by spatially variable VLM, to estimate the RSLR projections and flooding scenarios up to 2150 AD. For the Italian region, we estimated the current and expected RSLR trend at $\mathbf{2 0 3 0}-\mathbf{2 0 5 0}-\mathbf{2 1 0 0}$ and $\mathbf{2 1 5 0}$ for $\mathbf{3 9}$ main coastal plains which are yet exposed to coastal hazard. Geodetic data consist in about 27 years of continuous GNSS observations at selected stations located within 5 km from the coast and InSAR data from the Copernicus European Ground Motion Service (https://egms.land.copernicus.eu/). The latter were integrated with additional InSAR data sets to extend to past years the data time series at specific sites, such as for the Venice lagoon. Finally, we provide revised sea level rise projections for the selected coastal plains of the Italian region by including VLM in the analysis. Scenarios are based on the IPCC-AR6 Report for different Shared Socio-economic Pathways (SSP) and global warming levels (www.ipcc.ch). In the analysis, we also considered the SL data recorded at the operational tidal networks managed by the PSMSL (https://psmsl.org) and ISPRA (https://www.mareografico.it/). Our analysis show that IPCC often underestimate the projected SLR since the current VLM rates are neglected or not adequately considered. Finally, detailed maps of the expected flooding scenarios for 39 Italian coastal plains projected on high resolution DEM obtained by the analysis of LiDAR data or low elevated aerial photogrammetry surveys by UAVs, are provided. In addition, more 65 exposed coastal zones in the Mediterranean were identified through a geoprocessing analysis, highlighting about $10,000\ \text{km}^{2}$ of the Italian coasts yet exposed to multiple hazard and about $38,500\ \text{km}^{2}$ in the Mediterranean. Based on these scenarios, adaptation measures to face the ongoing RSLR, are required.

Colli Albani Hills, a volcanic complex located 20 km SE of Roma (Italy), represents a long-dormant caldera system and its last eruption is dated back 20 ky. It is subjected to seismic swarms, gaseous emissions and ground deformations. The whole volcanic complex is affected by landslides of different typologies and in the past the most frequent were debris flows. In this study, for the first time, the debris flows susceptibility of the complex is mapped through a heuristic approach that combines parameters recognized in literature as the main predisposing factors to slope instability. Such parameters are morphometry elements, lithology and land cover. The resulting map, validated through historical landslides, classifies the entire complex according to five degrees of susceptibility, identifying Tuscolano-Artemisio caldera edge, Mt. Faete, and steep slopes of Nemi and Albano lakes at high and very high susceptibility. The instability of the entire complex is further investigated measuring the ground deformations observed by using InSAR data in the period 2016–2023. InSAR results, validated through GNSS data, show the overall stability of the complex, except a few areas. In detail, an ongoing uplift of about 1.5 mm/yr is recorded in Genzano di Roma municipality. The InSAR results combined with the debris flows susceptibility map and historical landslides highlight the steep slopes of Albano and Nemi lakes and Giulianello locality, outside the caldera, as the areas potentially most predisposed to trigger debris flows as classified at very high susceptibility and affected by both ground deformations and historical debris flows.

Campi Flegrei is an active volcanic area located in the Campanian region (southern Italy). It is characterized by a caldera structure including a subaerial portion densely populated and a submarine area represented by the Gulf of Pozzuoli. Altimetry data acquired by Airborne Laser Scanning and seafloor depth data coming from several bathymetry surveys were used to show a Digital Elevation Model with a spatial resolution of 1 m for the topography of Campi Flegrei. This model, for the first time, reconstructs a topographic continuum from land to seafloor for a total extent of 138.32 km2. Thanks to the high spatial resolution, the model allowed to map and measure seafloor features such as landslides and terraces as well as Roman-epoch artefacts. Our results provide accurate reference topography for a more complete mapping and modelling of natural hazards that affect, directly or indirectly, the entire area of the Campi Flegrei caldera.

Ischia island represents the westernmost portion of the Phlegraean Volcanic District (Campania Region, Italy) and is characterized by the presence of Mt. Epomeo, a giant centrally located resurgent volcanic horst. This horst is controlled by fault systems and magmatic dynamics able to generate recurrent seismicity. Such seismicity, associated with the presence of volcanic terrains with different degrees of erodibility, makes Ischia highly subjected to several ground instability phenomena such as landslides. This multidisciplinary study aimed to map the seismically induced landslide susceptibility of the island, taking into account the Md 4.0 earthquake that occurred on August 21, 2017, as a reference seismic event. Eight parameters were isolated as relevant predisposing factors for landslide occurrence and combined, through GIS elaborations, to compute a numerical index (SNAP index) that quantified the seismically induced landslide susceptibility for each 5 × 5 m area. The resulting map, through five classes of susceptibility, highlights that the highest exposed areas are mainly localized along the N–NW flanks of Mt. Epomeo, involving mainly the municipality of Casamicciola Terme. Moreover, the map is discussed considering the spatial distribution of historical and recent seismically induced ground effects, an ERT field survey carried out on significant test sites, and the displacement map obtained by 2015–2022 InSAR data.

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 the population and infrastructure. 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, along with the Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. This study focuses on the analysis of pyroclastic fall and flow deposits and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius in 472 CE (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory), and archeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are also referenced to the finding of ash beds in more distal areas, which were included in new isopach maps for the two sub-Plinian eruptions. The results show that for both eruptions the distribution of the primary deposits is wider than previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such a distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions, which involved distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), and it was possible to calculate the velocities and dynamic pressures of the lahars and ultimately infer the lahar transport and emplacement mechanisms. 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 kilometers from active volcanoes. This especially applies to large parts of the densely populated areas around Somma–Vesuvius up to the nearby Apennine valleys.

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

A detailed mapping of volcanic ballistic projectiles emplaced in a defined area, represents the starting point to derive preparatory data in hazard and risk studies of ballistics phenomena. Considering as case study the 3rd July 2019 paroxysmal eruption occurred at Stromboli volcano, we map and analyse at very high spatial resolution (8 cm) the distribution of the ballistic spatter clasts emplaced on the E flank of the volcano. The resulting map identifies and reproduces as geospatial polygon elements 152,228 spatter clasts with areal dimensions from 0.03 to 4.23 m 2 . Dispersed on 0.407 km 2 , the spatters cover an area of 29,000 m 2 corresponding to an erupted products volume from 2.3 to 7.0 × 10 3 m 3 , calculated here for the first time. Spatial analyses indicate that the area mostly affected by the clasts emplacement is between N67.5 and N135 directions, identifying a preferential deposition between N112.50 and N123.75 directions. The clasts size distribution rapidly decreases with the size increase, highlighting a nearly constant ratio small/large clasts regardless the distance from the vent. Finally, additional investigations reveal that clasts dispersion parameters decrease progressively with the distance from the vent only along one direction (N67.5), highlighting how the morphology influences the deposition and remobilisation of mapped ballistics.

The fallout of lapilli and incandescent bombs during the 3 rd July 2019 paroxysm had triggered wildfires in Stromboli island, destroying the endemic vegetation and cultures. Data acquired by Landsat 8 OLI/TIRS, Sentinel 2A and Pleiades 1A-B satellites were processed in order to obtain the spectral indexes for the burned areas detection: NBR (Normalized Burn Ratio), NDVI (Normalized Difference Vegetation Index) and IFIRE (Index Fire). The spectral indexes produced burnt vegetation resulting maps. Thanks to a drone imagery at spatial resolution of 8 cm, acquired within a few days after the paroxysm, it was possible to validate the results in the area of Ginostra village and identify the best satellite data useful for mapping the wildfires. This study provides elements to identify and quantify the areas affected by wildfires triggered by volcanic ballistic projectiles, providing elements for the volcanic hazard management or mitigation.

<p>Stromboli is one of the most visited volcanoes in the world due to its persistent activity consisting in mild strombolian explosions with a frequency up to 25-30 events per hour. This activity is punctuated by more energetic explosions named major explosions, paroxysms and lava flow. These types of eruption can change drastically the morphology of the affected areas and cause volcanic phenomena highly impacting for the island, including heavy fallout of blocks and bombs on the flanks of the volcano, pyroclastic flows and tsunami waves. Paroxysms are highly dangerous phenomena for the tourists that climb the volcano and can cause serious problems also to the local people living on the two villages on the coast of the island. In order to map the areas affected by morphological changes, the thickness of deposits and the associate volume estimation of erupted products, we propose a study based on two techniques of remote sensing. First, we reconstruct the Stromboli topography, before and after an event, elaborating stereo pairs of Pleiades satellite and using as base an airborne LiDAR data at spatial resolution of 50 cm. Then we map the morphological changes giving an estimation of the relative areas and volumes. These results, discussed and compared with available field data, can help to better understand the impact of the event and provide indications useful in a territory planning aimed to mitigate the effects of such calamitous events.</p>

Abstract. 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, along with the Apennine reliefs are mantled by pyroclastic deposits that can be easily remobilised, especially after intense and/or prolonged rainfall. This study focuses 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 AD (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory) and archaeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are mainly referred to the finding of ash beds in more distal areas, which was included into new isopach maps for the two sub-Plinian eruptions. The results show that for both the eruptions the distribution of the primary deposits is wider than the one previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions which involved the distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), as well as was possible to calculate the velocities and dynamic pressures of the lahars, and ultimately infer the lahar transport and emplacement mechanisms. 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. This especially applies to large parts of the densely populated areas around Somma-Vesuvius up to the nearby Apennine valleys.

Despite their protracted periods of inactivity, long-dormant volcanoes may be highly hazardous, as their reactivation can be characterized by violent explosive eruptions. An example of such volcanoes is the Colli Albani caldera, onto which deposits Rome Capital City is built, Italy. Its last volcanic activity was characterized by voluminous maar-forming phreatomagmatic eruptions dated between 36 and 25ka, but the volcano has produced several maar lake overflows during the Holocene till historical times. Presently, Colli Albani is affected by recurrent seismic events, anomalous heat flow, ground uplifts, hydrothermal circulation and gas emissions. For these reasons, the Italian Civil Protection has recently listed Colli Albani among the ten active volcanoes of Italy, but products for the evaluation of its volcanic hazards lacking. This work presents the first study on vent opening susceptibility mapping at Colli Albani. We explore the potential of an available geological dataset for building, through geographic information system analysis, an index that classifies areas at different vents opening susceptibility (low, moderate and high). Such result highlights as a solid geological mapping is a prerequisite for the volcanic hazard assessment, especially in remote or poorly studied long-dormant volcanoes such as caldera systems where the location of new vents could occur in different volcano sectors.

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