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Major explosions and paroxysms, respectively, have been the most powerful explosive phenomena at Stromboli in recent centuries. These two categories of explosions, although not sharply separable in terms of eruptive mechanisms and hazards, can produce ballistic projectiles affecting trails and observation sites in the summit area (both major explosions and paroxysms) as well as lower elevation areas of the volcano, down to the coast (paroxysms only). Time series analysis of reconstructed activity since the end of the XIXth Century highlights that such unordinary explosions are strongly non-homogeneous in time and often show notable temporal clustering. We perform a critical review of the volcanic catalogs produced by the Italian volcanological observatories in the last ~40 years. In this review, we evaluate the effect of uncertainties on the characterization of such major explosions, in contrast to intense ‘ordinary’ Strombolian explosions that do not eject large ballistic projectiles outside the Craters Terrace and the upper portion of Sciara del Fuoco. Where sufficient information is available for major explosions, we devise an analytical summary and explore comparative mapping of field data related to the dispersal areas of ballistic projectiles, taking into account relevant uncertainties. Using Monte Carlo simulations, we propose preliminary probabilistic hazard maps for areas potentially exposed to future events of this kind, varying the radius and angle-size of the circular sectors affected. We also evaluate lateral hazard modulation in terms of the density variability of ballistic projectiles per square meter of ground, based on literature review and spatial statistics of newly collected UAV data from the ballistic deposits of the 3rd July 2019 paroxysm on the slopes above Ginostra village. These new hazard maps, once combined with vulnerability and exposure data, allow preliminary quantitative estimates of individual risk exposure levels for guides, volcanologists, and tourists spending time in areas exposed to these unordinary events. Through a retrospective counterfactual analysis of the July 2019 eruption, we demonstrate how, in a future Strombolian paroxysm at another time of day, these risk rates might result in major casualty numbers.

Active volcanoes are complex, poorly predictable systems that can pose a threat to humans and their infrastructures. As such, it is important to improve as much as possible the understanding of their behavior. The Stromboli volcano, in Italy, is one of the most active volcanoes in the world, and its almost persistent activity is documented since centuries. The persistent background activity is sometimes interrupted by much more energetic, dangerous episodes. The Istituto Nazionale di Geofisica e Vulcanologia (Italy) set up the interdisciplinary “UNO” project, aimed to understand when the Stromboli volcano is about to switch from the ordinary to the extraordinary activity. The UNO project includes an outstanding variety of research activities, such as sampling in the field, the modeling of Stromboli topography from ALS technique and satellite data, the 3D numerical simulations of ballistic trajectories, or the set up of an ultrasonic microphones system. 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 database. We present here the simplified logical model of such database, focusing on the identification of entities and their relationships.

This study presents an application based on UAS optical data for mapping at very high spatial resolution the ballistic projectiles erupted during an explosive volcanic eruption. The novelty consists in the development of a GIS-based automate procedure that, elaborating high spatial resolution UAV optical imagery (RGB) acquired within few days from the explosive event, is able to reproduce the boundary of each ballistic projectile as georeferenced polygon feature. This procedure, applied for the first time at Stromboli volcano (Aeolian Archipelago, Italy), has reconstructed in 2D digital format the shape of the ballistic spatter clasts emplaced on the East flank of the volcano during the paroxysm of the 3rd July, 2019. The dimensions of the clasts, reproduced as polygon features stored in WGS 84 UTM 33 metric coordinates, range from 0.03 m2 (16 cm x 16 cm) to 4.23 m2 (~2 m x 2 m). Respect to the classic field survey, the application here presented is able to generate, in efficient and rapid way, a large amount of data and information on ballistic deposits, covering also the areas inaccessible and/or dangerous as particularly affected by ballistic fallout. Such application allowed to better understand the dynamic of ballistics emplacement, providing a useful contribution to volcanic hazard mitigation.

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.

Ground deformation at volcanic areas is mainly driven by the interaction between lithology, morphology, seismology and volcanism. In the latest decades, radar interferometry has contributed to understand the volcanic dynamics through the measurement of ground deformations. This work focuses on the displacement analysis at Ischia, an active volcanic island located at the north-western end of the Gulf of Naples and characterized by a long eruptive and seismic history. The central portion of the island is dominated by Mt. Epomeo, a volcano-tectonic horst formed by caldera resurgence, tilted southward and bordered by a system of faults and fractures which represent the preferred degassing pathway of the hydrothermal system beneath the island. Seismicity is mainly concentrated in the northern area and the most recent and severe seismic sequence started with the Mw 3.9 earthquake on August 21st 2017 producing several damages and also victims. In this study, the investigation of surface displacement was carried out over a continuous time interval of about 17 years by using Synthetic Aperture Radar (SAR) dataset with different temporal and spatial resolutions. The Small Baseline Subset interferometric technique was applied to the dataset allowing the identification of the areas more potentially prone to trigger slope instability phenomena. The resulting ground displacement maps identified the highest deformations along the north-western, western and southern slopes of Mt. Epomeo and were validated by using GPS data acquired by local geodetic network. Mean velocity maps obtained from C-band Envisat and Sentinel-1 and X-band COSMO-SkyMed SAR data will be presented together with the ground deformation effects caused by the 2017 seismic swarm.

In the two last decades the eastern flank of Mt. Etna volcano was frequently affected by unexpected, violent and dangerous flooding phenomena. The municipalities most strongly involved are Giarre, Riposto and Acireale, where the floods caused heavy damage to the territory and human causalities. In particular, the most remarkable event is dated March 13, 1995 and caused the death of several people,whereas the most recent events occurred in 2014 and 2015 and, fortunately, generated only damages to infrastructures. With the aim to provide a starting point for studying the flooding hazard in the eastern flank of Mt. Etna, we have organized and elaborated on a GIS platform the relevant data from rainfall, topography lithology and land use. The data were combined to produce, for the first time, arun-off predisposition map that can represent a useful base for future studies aimed at flooding hazard mapping along the eastern flank of Mt. Etna volcano.

Synthetic Aperture RADAR data acquired during several space missions (Envisat, COSMO-SkyMed and Sentinel-1) were treated in order to obtain the ground displacement of the Ischia island (Naples, Italy) and to retrieve the deformation evolution during the investigated time period. The results, validated with available GPS measurements, were found by applying the Small Baseline Subset (SBAS) technique [1], one of the main algorithms proposed in the context of multitemporal methods of Differential SAR Interferometry. This technique permitted to identify and monitor areas affected by slope instability phenomena in a quite continuous time period, from 2002 to the end of 2019. The presented results constitute the basic information for the future application of a GIS-based interdisciplinary approach aimed at the prevention of natural disasters in correspondence with the Ischia island.

Co-auteur étranger ; This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.; International audience; The eruptive activity of a volcano modifies its surface topography through morphological changes generated by the deposition of emitted volcanic material and resulting gravity-driven processes, which can form accumulation of material in addition to the most common erosional phenomena. Mapping and quantifying such morphological changes allow to derive new data useful to better describe and understand the eruptive history of the volcano itself. Nowadays, one of the mostly used method to identify such morphological changes consists of comparing Digital Elevation Models (DEM) of the volcanic area before and after an eruptive event. If the eruptive event is referred to periods prior to 1980's, the only method to reproduce DEMs consists of elaborating the historical cartography that is often available only in paper format. In this work we aim to prove the reliability of this approach, presenting a study on the morphological changes (from 1876 to 1944) of the summit caldera of the Somma–Vesuvio volcano (Italy). For the first time, we compare DEMs derived from historical maps (1876, 1906 and 1929) and a DEM dated 2012 obtained by remote sensing. The four models of the caldera, digitally reproduced at the same spatial resolution, are morphologically investigated through specific maps derived from the DEMs and a set of height profiles. In addition, further morphometric analyses and accurate quantifications in volume and surface are presented and discussed for a portion of the Somma-Vesuvio summit caldera, represented by the Gran Cono edifice. Considering the different typology of the source data used in this study, it is also provided a discussion on the respective accuracies that, especially for the historical maps, represent a crucial point for obtaining DEMs able to reproduce topographies more realistic as possible. For this reason, despite data source were processed following rigours criteria, the calculations of volume, surface and distance related to the morphological changes of the volcano are associated to an accurate quantification of the error. Following this, the main results obtained in this study are: i) the identification of several past volcanic deposits and the estimation of the related thicknesses, both in good agreement with published literature; ii) the quantification of the morphological changes of the Gran Cono from 1876 to 1944 resulting in a volume and surface growth of 133 × 106 m3 (±5%) and ~0.14 km2, respectively; iii) the identification of a possible migration path of the centroid of the Gran Cono crater along the SW-NE preferential direction during the investigated period.

This paper presents a contribution to Volcanoclastic Flows hazard assessment in very densely populated volcanic areas by using a multidisciplinary study applied to the Torre del Greco area, a municipality close to the active Somma-Vesuvius volcano, in Italy. This study integrates and combines in a GIS environment several types of data: i) information on Volcanoclastic Flows recorded during the years 1906–2010, derived from historical chronicles and local reports; ii) rainfall data relative to the investigated period; iii) summary of the recent activity of Somma-Vesuvius (AD 1631–AD 1944) deriving from the scientific literature; iv) morphological and morphometric analyses derived from a very high resolution Digital Elevation Model developed in the years 2009–2012. The historical analysis of the spatial and temporal distribution of the Volcanoclastic Flows recorded in the Vesuvian area during the last 104 years indicates that the zone mostly affected by such phenomena is the south-western sector of Somma-Vesuvius, and in particular the Torre del Greco municipality, for which a specific database on paths and directions of the historical Volcanoclastic Flows was implemented. The analysis and comparison of all available data allowed us to: i) recognize that the source zone of Volcanoclastic Flows occurred in Torre del Greco was a funnel-shaped area located immediately SW of the Somma-Vesuvius caldera boundary and just above the most urbanized area of the town; ii) individuate the key morphometric parameters (slope and curvature) necessary for the potential triggering of Volcanoclastic Flows; and iii) investigate possible relationships between the fallout deposits of the Somma-Vesuvius main recent eruptions and the historical Volcanoclastic Flows of Torre del Greco. Although this approach represents only a starting point for studies aimed at the assessment and mitigation of Volcanoclastic Flows hazard, it can be applied in other volcanic zones having similar characteristics to the Somma-Vesuvius area. Moreover, it can be used not only during a period of volcanic quiescence when heavy and/or persistent rains are able to remobilize loose pyroclastic deposits, but also in syn-eruptive conditions.

Volcanic islands are often affected by ground displacement such as slope instability, due to their peculiar morphology. This is the case of Ischia Island (Naples, Italy) dominated by the Mt. Epomeo (787 m a.s.l.), a volcano-tectonic horst located in the central portion of the island. This study aims to follow a long temporal evolution of ground deformations on the island through the interferometric analysis of satellite SAR data. Different datasets, acquired during Envisat, COSMO-SkyMed and Sentinel-1 satellite missions, are for the first time processed in order to obtain the island ground deformations during a time interval spanning 17 years, from November 2002 to December 2019. In detail, the multitemporal differential interferometry technique, named small baseline subset, is applied to produce the ground displacement maps and the associated displacement time series. The results, validated through the analysis and the comparison with a set of GPS measurements, show that the northwestern side of Mt. Epomeo is the sector of the island characterized by the highest subsidence movements (maximum vertical displacement of 218 mm) with velocities ranging from 10 to 20 mm/yr. Finally, the displacement time series allow us to correlate the measured ground deformations with the seismic swarm started with the Mw 3.9 earthquake that occurred on 21 August 2017. Such correlations highlight an acceleration of the ground, following the mainshock, characterized by a subsidence displacement rate of 0.12 mm/day that returned to pre-earthquake levels (0.03 mm/day) after 6 months from the event.

The topography of Mt. Etna, Italy, is subjected to continuous modifications depending on intensity and magnitude of eruptions that frequently occur at the volcano summit and flanks. In order to make high-resolution maps of morphological changes and accurately calculate the overall volume of the erupted products (e.g., lava flows, tephra fall out, scoriae cones) in ten years, we have compared the altimetry models of Mt. Etna derived from 2005 Airborne Laser Scanning data and 2015 Pleiades stereo satellite imagery. Both models cover a common area of 400 km2 with spatial resolution of 2 m and comparable vertical accuracy (RMSE

In this study, we combine reconstructions of volcanological data sets and inputs from a structured expert judgment to produce a first long-term probability map for vent opening location for the next Plinian or sub-Plinian eruption of Somma-Vesuvio. In the past, the volcano has exhibited significant spatial variability in vent location; this can exert a significant control on where hazards materialize (particularly of pyroclastic density currents). The new vent opening probability mapping has been performed through (i) development of spatial probability density maps with Gaussian kernel functions for different data sets and (ii) weighted linear combination of these spatial density maps. The epistemic uncertainties affecting these data sets were quantified explicitly with expert judgments and implemented following a doubly stochastic approach. Various elicitation pooling metrics and subgroupings of experts and target questions were tested to evaluate the robustness of outcomes. Our findings indicate that (a) Somma-Vesuvio vent opening probabilities are distributed inside the whole caldera, with a peak corresponding to the area of the present crater, but with more than 50% probability that the next vent could open elsewhere within the caldera; (b) there is a mean probability of about 30% that the next vent will open west of the present edifice; (c) there is a mean probability of about 9.5% that the next medium-large eruption will enlarge the present Somma-Vesuvio caldera, and (d) there is a nonnegligible probability (mean value of 6–10%) that the next Plinian or sub-Plinian eruption will have its initial vent opening outside the present Somma-Vesuvio caldera.

This study presents new and revised data sets about the spatial distribution of past volcanic vents, eruptive fissures, and regional/local structures of the Somma-Vesuvio volcanic system (Italy). The innovative features of the study are the identification and quantification of important sources of uncertainty affecting interpretations of the data sets. In this regard, the spatial uncertainty of each feature is modeled by an uncertainty area, i.e., a geometric element typically represented by a polygon drawn around points or lines. The new data sets have been assembled as an updatable geodatabase that integrates and complements existing databases for Somma-Vesuvio. The data are organized into 4 data sets and stored as 11 feature classes (points and lines for feature locations and polygons for the associated uncertainty areas), totaling more than 1700 elements. More specifically, volcanic vent and eruptive fissure elements are subdivided into feature classes according to their associated eruptive styles: (i) Plinian and sub-Plinian eruptions (i.e., large- or medium-scale explosive activity); (ii) violent Strombolian and continuous ash emission eruptions (i.e., small-scale explosive activity); and (iii) effusive eruptions (including eruptions from both parasitic vents and eruptive fissures). Regional and local structures (i.e., deep faults) are represented as linear feature classes. To support interpretation of the eruption data, additional data sets are provided for Somma-Vesuvio geological units and caldera morphological features. In the companion paper, the data presented here, and the associated uncertainties, are used to develop a first vent opening probability map for the Somma-Vesuvio caldera, with specific attention focused on large or medium explosive events.

The eruptive history of a volcano can be investigated by analyzing the changes of its topography through time. This type of analysis can be a useful support to improve studies aimed at volcanic hazard assessment for very densely populated active or quiescent volcanic zones as the Somma-Vesuvio (SV) area. For the first time, in this work the morphological evolution of the SV volcanic edifice from 1876 to nowadays is presented through the reconstruction of topographies obtained from IGM (Italian Geographic Military Institute) historical maps (1876, 1906 and 1929) and remote sensing techniques (e.g. LiDAR). In detail, the multi-temporal morphological analysis has been focused on the Gran Cono area. The main working environment has been the ESRI platform (ArcGIS 10®), but other specific software have been involved to manage the geo-referencing procedures and conversion data (TN-Sharc, IGM-Traspunto/Cartlab). Morphological analyses and volume changes quantification related to the summit portion of the SV edifice from 1876 to nowadays are presented. The morphometric analyses were obtained by using height profiles along the four main direction (N-S, W-E, NW-SE and NE-SW), the changes in volume were estimated elaborating each Digital Elevation Model (DEM) in the area of interest.

The Sorrentina Peninsula is a densely populated area with high touristic impact. It is located in a morphologically complex zone of Southern Italy frequently affected by dangerous and calamitous la...

Volcanic islands pose several major types of natural hazards, often interconnected and concentrated in relatively small areas. The quantification of these hazards must be framed from a multi-hazard perspective whilst building on existing single-hazard analyses. Ischia is a densely inhabited volcanic island with a long eruptive history lasting more than 150 ka (last in 1302 AD) characterized by the significant asymmetric resurgence of a caldera block. Here, we review the state-of-art of the natural hazards of Ischia, aiming at building a solid base for future holistic multi-hazard quantifications. We frame our analysis in three steps: i) review of geological, historical and current activity; ii) review of available hazard models and analyses; iii) development of an interpretative framework for the interdependent hazards. The results highlight that volcanic activity has been quite intense and many volcano-related hazardous phenomena have affected the island including in very recent times, both for eruptive (phreatic or magmatic eruptions) and non-eruptive (earthquakes, landslides, and tsunamis) phenomena. The effects of some of them (e.g. tsunamis, tephra) are also relevant beyond the island territory. Quantitative hazard assessments are almost absent and should be developed in the future considering the evident interconnections between hazards. To this end, we propose a conceptual interpretative multi-hazard framework that highlights the fundamental role played by the resurgent block in controlling and connecting the different hazards, in terms of both spatial distribution of the sources and temporal clustering.

We present here a simple web application, PeakLocator 1.0 (hereafter referred to as PL1.0), for the analysis of gridded geo-located maps. In the present version of the code, the maps can contain up to 10 different variables with different units, not necessarily measured at the same locations, as well as the same variable recurrently measured in the time. The aim of PL1.0 is to identify regions where values lie out- side the standard deviation from average values. The degree of spatial correspondence between these regions is reflected in the “fitting in- dex” associated to the overlapping area. Here we demonstrate some possible applications of PL1.0 using published datasets, although its potential applicability extends to wide range of topics where the common demand is the comparison of two or more variables mapped over a common area or over areas partially overlapping. PL1.0 is freely accessible through a web interface and runs on any platform.

We present the results of a meso-scale systematic structural analysis of fractures, faults and dykes exposed at the Somma-Vesuvius volcano (southern Italy). Observed fractures include: (i) radial and tangential (with respect the caldera axis), sub-metric to metric joints associated with the edifice load and volcano-tectonic activity (i.e. inflation, deflation and caldera collapse stages) and (ii) decameter-scale fractures related to volcano flank instabilities. For the Somma-Vesuvius volcano, preexisting radial joints were commonly reactivated as transfer faults during the caldera formation, allowing different blocks to move toward the center of the collapsing area. Dykes occur with different geometries, including en-echelon structures bounding structural depressions. The orientation analysis of all structures indicates that they are preferentially oriented. Furthermore, we provide a morphological lineament analysis using high-resolution Digital Terrain Models of Somma-Vesuvius. Azimuth and spatial distribution of dykes and morphological lineaments were analyzed for comparison with the old Somma Crater and Gran Cono axes, respectively. Results highlight the overprinting of radial and clustered strain patterns recorded in different volcano-tectonic evolution stages. We suggest a possible deformation evolution model in which structures develop along either radial or preferential trends, highlighting different volcanic conditions: (i) where radial patterns occur, the structures developed during volcanic inflation cycles with a closed magmatic conduit condition whereas (ii) clustered patterns are probably associated with a regional strain field that overcomes the local deformation field, a situation typical in the case of open-conduit activity.

Campi Flegrei is an active volcanic area situated in the Campanian Plain (Italy) and dominated by a resurgent caldera. The great majority of past eruptions have been explosive, variable in magnitude, intensity, and in their vent locations. In this hazard assessment study we present a probabilistic analysis using a variety of volcanological data sets to map the background spatial probability of vent opening conditional on the occurrence of an event in the foreseeable future. The analysis focuses on the reconstruction of the location of past eruptive vents in the last 15 ka, including the distribution of faults and surface fractures as being representative of areas of crustal weakness. One of our key objectives was to incorporate some of the main sources of epistemic uncertainty about the volcanic system through a structured expert elicitation, thereby quantifying uncertainties for certain important model parameters and allowing outcomes from different expert weighting models to be evaluated. Results indicate that past vent locations are the most informative factors governing the probabilities of vent opening, followed by the locations of faults and then fractures. Our vent opening probability maps highlight the presence of a sizeable region in the central eastern part of the caldera where the likelihood of new vent opening per kilometer squared is about 6 times higher than the baseline value for the whole caldera. While these probability values have substantial uncertainties associated with them, our findings provide a rational basis for hazard mapping of the next eruption at Campi Flegrei caldera.

Campi Flegrei (CF) is an example of an active caldera containing densely populated settlements at very high risk of pyroclastic density currents (PDCs). We present here an innovative method for assessing background spatial PDC hazard in a caldera setting with probabilistic invasion maps conditional on the occurrence of an explosive event. The method encompasses the probabilistic assessment of potential vent opening positions, derived in the companion paper, combined with inferences about the spatial density distribution of PDC invasion areas from a simplified flow model, informed by reconstruction of deposits from eruptions in the last 15 ka. The flow model describes the PDC kinematics and accounts for main effects of topography on flow propagation. Structured expert elicitation is used to incorporate certain sources of epistemic uncertainty, and a Monte Carlo approach is adopted to produce a set of probabilistic hazard maps for the whole CF area. Our findings show that, in case of eruption, almost the entire caldera is exposed to invasion with a mean probability of at least 5%, with peaks greater than 50% in some central areas. Some areas outside the caldera are also exposed to this danger, with mean probabilities of invasion of the order of 5–10%. Our analysis suggests that these probability estimates have location-specific uncertainties which can be substantial. The results prove to be robust with respect to alternative elicitation models and allow the influence on hazard mapping of different sources of uncertainty, and of theoretical and numerical assumptions, to be quantified.

This study presents a new method for producing long-term hazard maps for pyroclastic density currents (PDC) originating at Campi Flegrei caldera. Such method is based on a doubly stochastic approach and is able to combine the uncertainty assessments on the spatial location of the volcanic vent, the size of the flow and the expected time of such an event. The results are obtained by using a Monte Carlo approach and adopting a simplified invasion model based on the box model integral approximation. Temporal assessments are modelled through a Cox-type process including self-excitement effects, based on the eruptive record of the last 15 kyr. Mean and percentile maps of PDC invasion probability are produced, exploring their sensitivity to some sources of uncertainty and to the effects of the dependence between PDC scales and the caldera sector where they originated. Conditional maps representative of PDC originating inside limited zones of the caldera, or of PDC with a limited range of scales are also produced. Finally, the effect of assuming different time windows for the hazard estimates is explored, also including the potential occurrence of a sequence of multiple events. Assuming that the last eruption of Monte Nuovo (A.D. 1538) marked the beginning of a new epoch of activity similar to the previous ones, results of the statistical analysis indicate a mean probability of PDC invasion above 5% in the next 50 years on almost the entire caldera (with a probability peak of ~25% in the central part of the caldera). In contrast, probability values reduce by a factor of about 3 if the entire eruptive record is considered over the last 15 kyr, i.e. including both eruptive epochs and quiescent periods.

The Seismic lines Offshore Mount Etna (SOME) database is presented. It consists of multichannel high-resolution seismic data acquired in 2005 off-shore Mount Etna (eastern Sicily). We describe first the acquisition of seismic lines and then the architecture of the data base. Finally we describe a very basic interpretation of some seismic lines to provide clear example of the potentiality of the seismic data sets in addressing relevant issues such as the occurrence of slope instabilities and the deformation style of the continental margin off shore mount Etna.

Steep slopes mantled by pyroclastic deposits are favorable areas prone to generate hazardous volcaniclastic flows. In Italy, such a setting is well represented in the Campania Region, where pyroclastic deposits from the explosive activity of the Neapolitan volcanoes (Ischia, Campi Flegrei, and Somma-Vesuvius) cover the Apennine range bordering the Campanian Plain. In order to provide a useful contribution to the mitigation and prevention of these calamitous natural events, this work presents a multidisciplinary approach to improve the understanding of the volcaniclastic flow hazard zonation in an Apennine area of 340 km 2 surrounding the Somma-Vesuvius volcano. The disruption proneness index (DPI) was calculated in order to identify the drainage basins potentially prone to generate volcaniclastic flows. This index is obtained by combining satellite and morphometric data in a geographic information system (GIS) environment. It is calculated for 1100 drainage basins, considering the main parameters influencing the slope stability (slope angle, basin shape factor, curvature, relative relief, aspect, and land cover). The land cover mapping is obtained from Landsat data and airborne high-resolution images, while the morphometric parameters are derived from a digital elevation model (DEM) with a cell size of 10 m. The result is a zonation map that classifies the drainage basins according to different degrees of proneness to generate volcaniclastic flows (low, moderate, high, and very high). The drainage basins falling within high and very high classes are 66%, while 28% fall in the moderate class, and the remaining 6% fall in the low proneness class.

The areas characterized by dynamic and rapid morphological changes need accurate topography information with frequent updates, especially if these are populated and involve infrastructures. This is particularly true in active volcanic areas such as Mount (Mt.) Etna, located in the northeastern portion of Sicily, Italy. The Mt. Etna volcano is periodically characterized by explosive and effusive eruptions and represents a potential hazard for several thousands of local people and hundreds of tourists present on the volcano itself. In this work, a high-resolution, high vertical accuracy digital surface model (DSM) of Mt. Etna was derived from Pleiades satellite data using the National Aeronautics and Space Administration (NASA) Ames Stereo Pipeline (ASP) tool set. We believe that this is the first time that the ASP using Pleiades imagery has been applied to Mt. Etna with sub-meter vertical root mean square error (RMSE) results. The model covers an area of about 400 km2 with a spatial resolution of 2 m and centers on the summit portion of the volcano. The model was validated by using a set of reference ground control points (GCP) obtaining a vertical RMSE of 0.78 m. The described procedure provides an avenue to obtain DSMs at high spatial resolution and elevation accuracy in a relatively short amount of processing time, making the procedure itself suitable to reproduce topographies often indispensable during the emergency management case of volcanic eruptions.

Naples is a large city located between two active volcanic areas: Campi Flegrei to the W and Vesuvius to the SE. The Solfatara crater, inside the caldera of the Campi Flegrei and nearest to the western quarters of the city, is a prodigious source of natural CO 2 with a mean emission rate of 1067 ton/d, i.e. seven times higher than that of Vesuvius (151 ton/d). This study shows that the area around the Solfatara and part of the urban area of Naples are affected by the volcanic plume when atmospheric circulatory patterns are dominated by the locally frequent sea breezes. Under these conditions the CO 2 content in the air increases above normal values, reaching more than 1000 ppm in proximity to the Solfatara crater to a few tens of ppm several kilometres from the source. Although these values do not indicate a health risk even under the most unfavourable atmospheric conditions, the volcanic source contributes to the total CO 2 burden from all urban emissions and hence to overall air quality. An emission rate ten times higher than the present one would lead to an air CO 2 concentration in excess of recommended health protection thresholds.

Despite the clear evidence of active flank dynamics that is affecting the eastern side of Mount Etna, the contribution of tectonic processes has not been yet understood. So far, the various models proposed to explain the observed flank deformation have been based on onshore structural data, coming from the volcanic edifice. The Ionian offshore of Mount Etna has been only recently investigated using multichannel seismic profiles, and offers the opportunity to image the structural features of the substrate of the unstable flank of the volcano. This contribution aims at describing the deformation located offshore Mount Etna using multichannel seismic profiles recently acquired during three seismic surveys. The onshore flank deformation of Mount Etna appears to be laterally confined by two tectonic guidelines, trending roughly E–W, located to the north and south of the deforming flank; the northern guideline, in particular, takes the surface expression of a sharp fault (Pernicana Fault). Though often assumed that these boundary structures continue offshore as linear features, connected to a frontal thrust ramp, the occurrence of this simple offshore structural system has not been imaged. In fact, seismic data show a remarkable degree of structural complexity offshore Mount Etna. The Pernicana Fault, for instance, is not continuing offshore as a sharp feature; rather, the deformation is expressed as ENE–WSW folds located very close to the coastline. It is possible that these tectonic structures might have affected the offshore of Mount Etna before the Pernicana Fault system was developed, less than 15 ka ago. The southern guideline of the collapsing eastern flank of the volcano is poorly expressed onshore, and does not show up offshore; in fact, seismic data indicate that the Catania canyon, a remarkable E–W-trending feature, does not reflect a tectonic control. Seismic interpretation also shows the occurrence of a structural high located just offshore the edifice of Mount Etna. Whereas a complex deformation affects the boundary of this offshore bulge, it shows only limited internal deformation. Part of the topography of the offshore bulge pre-existed the constructional phase of Mount Etna, being an extension of the Hyblean Plateau. Only in the northern part, the bulge is a recent tectonic feature, being composed by Plio-Quaternary strata that were folded before and during the building of Mount Etna. The offshore bulge is bounded by a thrust fault that can be related to the intrusion of the large-scale magmatic body below Mount Etna.

This article presents a multidisciplinary study implemented in Geographic Information System (GIS) environment to investigate the palaeo-hydrography in a sector of the Magra River alluvial plain (north-western Italy) where the famous ruins of the Roman colony of Luna (now Luni) are located. The approach proposed here combines the results obtained by different remote sensing images (satellite and airborne photos) with the data derived from historical cartography and recent field surveys. The traces are mapped and organised in two vector databases organised in linear or polygonal features consistent with fluvial elements (e.g. palaeo-channels, abandoned streams, etc.) and marshy/swamp areas, respectively. This database represents a useful starting point that can be implemented by further more detailed studies aimed to better understand the evolution of the landscape and the possible relationship with the story of the archaeological site of Luna about which many questions are still unresolved.

LiDAR (Light Detection and Ranging) is a novel and very useful active remote sensing system which can be used to directly identify geomorphological features as well as the properties of materials on the ground surface. In this work, LiDAR data were applied to the study of the Stromboli volcano in Italy. LiDAR data points, collected during a survey in October 2005, were used to generate a Digital Elevation Model (DEM) and a calibrated intensity map of the ground surface. The DEM, derived maps and topographic cross-sections were used to complete a geomorphological analysis of Stromboli, which led to the identification of four main geomorphological domains linked to major volcanic cycles. Moreover, we investigated and documented the potential of LiDAR intensity data for distinguishing and characterizing different volcanic products, such as fallout deposits, epiclastic sediments and lava flows.

Destructive volcaniclastic flows are among the most recurrent and dangerous natural phenomena in volcanic areas. They can originate not only during or shortly after an eruption (syn-eruptive) but also during a period of volcanic quiescence (inter-eruptive), when heavy and/or persistent rains remobilize loose pyroclastic deposits. The area in Italy most prone to such flows is that of the Apennine Mountains bordering the southern Campania Plain. These steep slopes are covered by pyroclastic material of variable thickness (a few cm to several m) derived from the explosive activity of the Somma-Vesuvius and Campi Flegrei volcanoes a few tens of kilometers to the west. The largest and most recent devastating event occurred on May 5, 1998, causing the death of more than 150 people and considerable damage to villages at the foot of the Apennine Mountains. This tragic event was only the most recent of a number of volcaniclastic flows affecting the area in both historical and prehistoric times. Historical accounts report that more than 500 events have occurred in the last five centuries and that more than half of these occurred in the last 100 years, causing hundreds of deaths. In order to improve volcaniclastic flow hazard zonation and risk mitigation in the study area, we produced a zonation map that identifies the drainage basins potentially prone to disruption. This map was obtained by combining morphological characteristics (concavity and basin shape factor) and the mean slope distribution of drainage basins derived from a digital elevation model with a 10-m resolution. These parameters allowed for the classification of 1,069 drainage basins, which have been grouped into four different classes of proneness to disruption: low, moderate, high and very high. The map compiled in a GIS environment, as well as the linked database, can be rapidly queried.

Images from the Landsat 7 spacecraft have been widely used in various environmental applications because they are comparatively inexpensive with respect to other satellite data, in addition the panchromatic sensor provides high resolution with a wide coverage area. We present here a orthorectification procedure of Landsat images using the SITOGEO-GIS tool for the GCPs acquisition. Appling this method eighty-five Landsat 7 ETM+ images, cover ing the entire region of Italy, were orthorectified to the UTM-WGS 84 Geodetic Reference System and organized into a searchable database. Our Landsat images were then compared with the data downloadable from Global Land Cover Facility (GLCF) showing a planimetric discrepancies less than 2 pixels. Moreover this work shows that the best target for GCPs collection is the human-made structures.