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Eruptive activity at Turrialba volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here, we use high frequency gas monitoring to track the behavior of the volcano between 2014 and 2015, and to decipher magmatic vs. hydrothermal contributions to the eruptions. Pulses of deeply-derived CO2-rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to two weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8-10 km deep, whereas the shallow magmatic gas source is at ~3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over two orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases whereas the second did not. Massive degassing ( >3000 T/day SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2

Data on individual risk factors for chronic diseases (smoking, physical activity, body mass) are collected by company physicians in heterogeneous ways. This makes comparisons, researches and evaluations difficult.The aim of the study was to find a consensus on evaluation tools for chronic diseases risk factors and for health promotion programs in workplaces that could be performed by company physicians during their clinical activity.A first set of tools, proposed by a working group of occupational physicians in Bergamo, was submitted through the Delphi technique to a national expert panel of 22 persons including recognized national experts in specific fields and occupational physicians skilled in health promotion.In three Delphi rounds, the panel selected a set of tools to monitor the main individual risk factors for chronic diseases (smoking, alcohol, physical activity, nutrition, stress and mental health) as well as general data related to the worker and his job.The use of these specific tools, collected in a homogeneous format, should be recommended to all Italian company physicians, in particular those who work in WHP-programs, in order to allow analysis, comparison and evaluation of health promotion programs effectiveness at a national level.

Volcanic monitoring has as main goal the identification of typical phenomena of impending-eruption precursors. Therefore, recording a large amount of data of volcanic gases composition, during the quiescence period, is fundamental in order to identify baseline values to be distinguished from any anomalous geochemical signal. The gases emitted by most of the volcanoes are difficult to be sampled especially when the volcano is restless. Volcanic gases have traditionally been monitored by means of direct in situ sampling of fumaroles, followed by laboratory analysis [e.g., Symonds et al., 1994]. However, since direct sampling is often impractical and hazardous, particularly during eruptions, or of too low temporal resolution, efforts have been made (since the 1970s) to improve volcanological applications of optical remote sensing techniques [Pedone et al., 2014; and references therein]. Soil-gas surveys of hydrothermal volcanoes in a quiescent condition have also quantified diffuse CO2 emissions, but much less information has been obtained on fumarolic CO2 emissions. Because of these difficulties, the volcanic CO2 flux (the most reliable gas precursor to an eruption, [Aiuppa et al., 2015]) inventory remains sparse and incomplete for most of the active volcanoes on Earth [Burton et al., 2013]. Collection of fumarole gases is – depending on the state of volcanic activity, for logistics and other practical reasons – mostly performed discontinuously with time intervals ranging from days, weeks or even months between consecutive sample collections [Pecoraino and Giammanco, 2005]. Conventional sampling requires that operators collect fluid samples directly from the fumarolic vent in different kind of flasks directly on site. By this way any short-term variation in gasgeochemical parameters may be missed.

We present an improved density model and a new structural map of the Neapolitan Yellow Tuff caldera, the active portion of the nested Campi Flegrei caldera. The model was built using a new 3-D inversion of the available high-precision gravity data, and a new digital terrain and marine model. The inversion procedure, based on a variable-depth lumped assembling of the subsurface gravity distribution via cell aggregation, gives better defined insights into the internal caldera architecture, that well agree with the available geological, geophysical, and geochemical data. The adopted 3-D gravity method is highly efficient for characterizing the shallow caldera structure (down to 3 km depth) and defining features related to regional or volcano tectonic lineaments and dynamics. In particular, the resulting density distribution highlights a pronounced density low in correspondence of the central portion of the caldera with a detail not available till now. The joint interpretation of the available data suggests a subsurface structural setting that supports a piecemeal collapse of the caldera, and allows the identification of its headwall. Positive gravity anomalies localize dense intrusions (presently covered by late volcanic deposits) along the caldera marginal faults, and the main structural lineaments both bordering the resurgent block and cutting the caldera floor. These results allow us to both refine the current geological-structural framework and propose a new structural map that highlights the caldera boundary and its internal setting. This map is useful to interpret the phenomena occurring during unrest, and to improve both short-term and long-term volcanic hazards assessment.

The stability of steep ( > 40) slopes in loose or poorly cemented pyroclastic materials mantling some of the Italian. mountain areas is guaranteed by the positive effects of matrix suction on shear strength until an increase in saturation. (and hence a decrease in suction) occurs. Therefore, unsaturated cohesionless or slightly-bonded pyroclastic. steep deposits are relatively stable. Slope instability, initiated by wetting, can occur through different processes,. such as vapor condensation and, most typically, rainfall infiltration. The main effect is the decrease in suction up. to possible development of positive pore pressures. Here, we examine the peculiar case of a landslide on the flank. of the pyroclastic cone of La Fossa volcanic edifice in Vulcano Island (Aeolian Archipelago, Southern Italy). Its. initiation is believed to have been influenced by a sharp increase in condensed vapor produced by the degassing of. the active volcano. In active volcanoes hydraulic conditions are affected not only by infiltrating rainwater but also. by volcanic activity, which produces complex changes in the state variables of pore fluids (i.e. pore fluid pressure).. In particular, volcanic activity can modify pore fluid pressure as far as to induce slope instability.. At La Fossa crater the phenomenon was evidenced by in situ monitoring of soil suction and soil temperature. In. situ observations and measurements indicate that seepage of condensed vapor is appreciable. Simple models based. on the geotechnical characterization of pyroclastic materials suggest the hypothesis that variations in suction can. be significant to stability of volcano slopes when these are very close to limit conditions and if material hydraulic. anisotropy is considered. Noteworthy, at La Fossa at Vulcano Island steam condensation increased and variations. of chemical ratios at fumaloles occurred while large slope movements developed on the NE flank of the cone during. the most intense well documented volcanic unrest.. The validation of this hypothesis requires further monitoring data during periods of intense unrest and more comprehensive. models that account for non-isothermal multiphase pore fluid pressure and groundwater circulation,. influencing the state of stress and hence stability. Our in-progress approach points toward a correlation between. degassing activity of the hydrothermal-magmatic system and slope movements, that may bear significant implications. for the definition of the scenarios of joint volcanic-hydrogeological hazard and for the development of. monitoring techniques in the frame of volcanic surveillance. However, much more efforts are needed to establish. phenomenological relationships with the budgets of volcanic steam condensation. This should include extensive. field measurement of CO2 and thermal fluxes from the soil, as well as electrical measurements.

Raman spectroscopy can measure water concentrations of hydrous silicate glasses with several advantages such as: (1) high-spatial resolution of 1–2 μm2; (2) non-destructive character; and (3) easy access, without any specific sample preparation or mounting techniques. The latter reasons render Raman highly suitable for studying natural products, such as volcanic pumice and scoriae fragments. Two spectral regions can be distinguished in Raman spectra of hydrated silicate glasses: a low-wavenumber region (15–1500 cm−1), which corresponds to vibrations of the silicate network, and a high-wavenumber region (3100–3750 cm−1), corresponding to the OH stretching vibrations of H2O molecules and OH groups. Behrens et al. (2006) have published empirical equations relating the area ratio between these two regions and the water content. However, the proposed internal calibrations depend on chemical composition of the glasses. In this paper, we reinvestigated the previous procedures to improve the background subtraction. Our results allow us to present a more general and linear calibration. Water concentrations up to 13 wt% can be measured for a broad range of natural silicate melts, from basalts to rhyolite (40 up to 80 wt% SiO2), using a single calibration curve with an absolute error of 0.2 wt%.

Melt inclusions in phenocrysts from some shoshonite to latite eruptive products of Ischia Island (Southern Italy) provide a window on the deep magmatic feeding system. Together with similar products from the other Neapolitan volcanoes (Procida, Campi Flegrei and Somma-Vesuvius), they probe the deep physico-chemical conditions of magmas generated in a mantle contaminated by slab derived fluids/melts largely dominated by CO2. The analyzed melt inclusions bear clear evidence for CO2 dominated gas fluxing and consequent dehydration of magma portions stagnating at major crustal discontinuities. In general, magma differentiation at Ischia takes place under very oxidized conditions determined by an unusual, nearly equimolar, proportion of divalent and trivalent iron in the melt. Budgets of magma degassing show that at Ischia there is much less magma than that needed to directly supply the amount of magmatic fluids released at surface, thus constraining the role of CO2 rich deep fluids in originating the volcanism and generating caldera resurgence. The acquired data, together with those from the other Neapolitan volcanoes, show that, despite the compositional and eruptive style differences within the poorly extended Neapolitan Volcanic area, the different kinds of volcanism are linked by supercritical CO2 fluids produced by devolatilization of subducted terrigenous-carbonatic metasediment, that infiltrate the mantle wedge, generate magmas and control their ascent up to eruption. In particular, fluid upraise and accumulation at crustal levels beneath Neapolitan volcanoes occurs with different flow-rates that depend on the major geological structures, particularly NW-SE normal and NE-SW transfer regional fault systems

In silicate melts it is almost impossible to readily distinguish solute and solvent like in aqueous solutions. The anionic framework of silicate melts, in fact, makes solute and solvents so intimately related that one cannot identify a solvation shell and identify directly, from structural studies, the complexes needed to define acid-base reactions. Therefore, the distinction between solute and solvent becomes blurred in systems such as silicate melts, because speciation is not only complex but changes with the marked depolymerization of the silicate framework that obtains from pure SiO2 to metal-oxide rich compositions. These features do not allow proper understanding of the actual physico-chemical role of many species detected by conventional techniques, a fact which can lead to confusing notation. However, these may not be serious limits to account correctly for the acid-base reactions that take place in every kind of magmatic setting, provided a ‘syntax’ describing the effective interactions among significative cationic and anionic entities. In particular, the syntax for acid-base exchanges is needed such that constituting oxides (i.e. chemical components) can be treated independently of (but not necessarily extraneous to) structural features in defining such entities. So-called ionic-polymeric models highlight the mutual correspondence between polymerization and acid-base properties of dissolved oxides through the Lux-Flood formalism for molten oxides. They thus provide the syntax to write chemical exchanges, but have no pretension to structural description. In fact the concept of melt polymerization is used to identify basic anions and cations that can be used, along with their formal charge, to describe effectively acid-base interactions taking place in melts. In this respect, an example is given by the description of the amphoteric behavior of water dissolved on melts, hence water autoprotolysis. Although it exerts a profound influence on properties of magmas, this autoprotolysis reaction has been hitherto neglected for water dissolved in silicate melts. By mixing cations and anions on distinct sublattices and quantifying the disproportionation of water dissolved in silicate melts into its ionic products, H+ and OH-, we reconcile conflicting spectroscopic determinations of water speciation, and explain the contrasting rheology of hydrous basaltic and rhyolitic melts. In fact basalts show much less depression of viscosity by water addition because of a relative predominance of OH-, such that water increase tends immediately to limit depolymerization rather than enhance it. This opens new perspectives to the understanding of the chemical control leading to either effusive or explosive eruptions.

Ischia, a volcano island offshore Naples, is a densely populated active caldera as testified by the last eruption in 1302 AD, seismicity, fumaroles, and thermal springs. Ischia magmas record strong evidences for CO2-dominated gas fluxing, under very oxidized conditions. Volatile concentrations within Melt Inclusions require gas-melt equilibria between 3 and 18 km depth. Budgets of magma degassing show that at Ischia there is much less magma than that needed to justify the amount of released magmatic fluids, compatible with a deep CO2 degassing plume. Comparison with nearby volcanoes highlights the role of deep fluids in originating the Neapolitan volcanism. In fact, despite compositional and eruptive style differences, and variable occurrence of differentiation processes, the different kinds of volcanism are linked by supercritical CO2 fluids produced by the devolatilization of subducted terrigenous-carbonatic metasediments. The generation of supercritical fluids due to deep CO2-release represents thus a leitmotiv at Neapolitan volcanoes, within which, Ischia is a natural borehole probing the relatively most undisturbed supercritical CO2, and the deep physico-chemical conditions of magmas generated in a slab-contaminated mantle. Understanding the common volatile source for Neapolitan volcanism means understanding how magmas are produced at large depths and then transferred at shallow levels where they evolve, differentiate and mix/mingle in magma chambers supersaturated of volatiles.

The Campi Flegrei caldera collapsed 39 ka in the Neapolitan area (southern Italy) after the Campanian Ignimbrite eruption. This eruption, recognized as the largest and the most cataclysmic volcanic event in the Mediterranean area over the past 200 ka, extruded not less than 300 km3 of trachytic magma. Controversy exists over the timescales required to assemble a such large volume of silicic melt and thus whether large magmatic reservoirs can actually persist below active volcanic systems over prolonged periods of time. Uranium-series analyses have been performed on Campanian Ignimbrite whole-rocks, glass matrixes and separated minerals. The compositionally most evolved sample which is most radiogenic with respect to Sr isotopes records a reference age of 71 ka. By contrast, U-Th internal isochrones of the three compositionally least evolved samples give identical initial Th isotope ratios and yield consistent ages predating the eruption by up to 6.4 ka. Therefore the time preceding this large caldera-forming eruption during which the large volume of Campanian Ignimbrite magma assembled and mixed is 6.4 ± 2.1 ka. The highest Pb and Nd isotopic ratios and 230Th/232Th activity ratios together with the oldest reference age of the most evolved samples suggest the existence of a resident magma body possibly related to a magmatic system that is known to have fed earlier magmatic activity in the Campi Flegrei area. Conversely, the younger age of the least evolved and least radiogenic magma dates the crystallization/differentiation event of a chemically and isotopically new magma batch entering the reservoir of the resident magma some few thousand years before the cataclysmic eruption. The progress of crystallization yielded high-water contents (up to 6-7 wt%), thus producing an overpressurized gas cap. The onset of the eruption tapped this cap, with consequent depressurization and fast volume decrease that facilitated or even drove the caldera collapse, and allowed the water-rich magma to be discharged during the pyroclastic current phase.

In addition to temperature, pressure and main chemical components, volatiles exert a strong influence on the physical properties of magmas. In particular, water plays a fundamental role in the dynamics and evolution of magmas in the deep interior and during volcano eruptions. However, water speciation in silicate melts is not fully understood. Infrared and NMR spectroscopy had provided some valuable informations about the H2O/OH- speciation. Nevertheless, some issues still remain unsolved about the OH-/H2O linkage to the silicate network. Raman spectroscopy already allows quantifying the proportion of water dissolved in an aluminosilicate melt. Raman spectra are composed of i) a low wave number region that corresponds to vibrations of the silicate network (0-1500 cm-1), and ii) a high wave-number region, which corresponds to the OH- stretching vibrations and H2O molecular vibrations (3100-3750 cm-1). We have performed a first set of in situ experiments using a micro-furnace at ambient atmosphere. An evolution of the high wave-number region in function of the time and temperature is observed. New Raman peaks can be distinguished, particularly near 3650-3700 cm-1. In this communication, we will present and discuss these observations between water and the silicate network in melts. Raman spectroscopy provides valuable informations to build a general model of water speciation, distinguishing the OH bonds between tetrahedral species and network modifiers for example. Results from this new model confirmed the amphoteric behavior of the water previously reported from polymeric modelling for instance, and opens new ways to study water in melts.

The late Pleistocene trachytic Campanian Ignimbrite (CI; 300 km3 DRE) covers the Campanian Plain near Naples, and is found behind ridges more than 1,000 m high at 80 km from source, the Campi Flegrei caldera (CFc). Distal ignimbrite deposits reveal downhill and/or downvalley flow directions prior to deposition, whereas in the absence of significant topography, deposition came from a flow moving in a roughly radial direction. These features point to very dilute currents, that together with the huge amount of discharged magmatic material, suggest a magma reservoir highly enriched in volatiles, rather than fluid entrainment from hydrothermal bodies or seawater. Petrologic and geochemical modelling of erupted products and their chemical and textural zoning, together with MI-based studies of gas-melt saturation, corroborate this view and show that the CI huge volume differentiated and mixed at shallow depth (6-3 km). With respect to compositionally similar but also smaller CFc eruptions (e.g. Agnano-Monte Spina, A-MS), the large amount of volatiles discharged by IC was likely due to fractional crystallization and longer residence times of volatiles sourced by the subducting Appennininc slab. This yielded high-water contents (up to 6-7 wt%), as well as high void fractions (~70-80% for IC, ~45% for A-MS) and also produced an overpressurized CO2-dominated gas cap (about 150 km3), uniformly distributed at the top of the magma chamber. The onset of the eruption tapped this cap, with consequent depressurization and fast volume decrease that facilitated or even drove the caldera collapse, and allowed the water-rich magma to be discharged during the pyroclastic current phase. The gas saturation-based estimates of the tapped foamy magma are compatible with the extent of magma chamber roof collapse, strong expansion revealed by textural data and transport and deposition mechanisms, reflecting depressurization and magma inflation within the collapsed and laterally confined caldera.

The late Pleistocene trachytic Campanian Ignimbrite (CI; 300 km3 DRE) covers the Campanian Plain near Naples, and is found behind ridges more than 1,000 m high at 80 km from source, the Campi Flegrei caldera. Distal ignimbrite deposits reveal downhill and/or downvalley flow directions prior to deposition, whereas in the absence of significant topography, deposition came from a flow moving in a roughly radial direction. These features point to very dilute currents, that together with the huge amount of discharged magmatic material, suggest a magma reservoir highly enriched in volatiles, rather than fluid entrainment from hydrothermal bodies or seawater. Petrologic and geochemical modelling of erupted products and their chemical and textural zoning, together with MI-based studies of gas-melt saturation, corroborate this view and show that the CI huge volume differentiated and mixed at shallow depth (6-3 km). The progress of crystallization yielded high-water contents (up to 6-7 wt%), thus producing an overpressurized CO2-dominated gas cap (about 150 km3), uniformly distributed at the top of the magma chamber. The onset of the eruption tapped this cap, with consequent depressurization and fast volume decrease that facilitated or even drove the caldera collapse, and allowed the water-rich magma to be discharged during the pyroclastic current phase. The gas saturation-based estimates of the tapped foamy magma are compatible with the extent of magma chamber roof collapse, strong expansion revealed by textural data and transport and deposition mechanisms, reflecting depressurization and magma inflation within the collapsed and laterally confined caldera.

Chapter 14, by Marini et al. (2011, this volume), reviews how the stable isotopes of sulfur serve as an important geochemical tool for the study of processes occurring in magma-related, hydrothermal systems, melts, and magmas. Sulfur has four stable isotopes with natural abundances of 95.02% (32S), 0.75% (33S), 4.21% (34S), and 0.02% (36S). Importantly, small variations in the ratios of these isotopes can be induced by kinetic and thermodynamic effects, and these variations or fractionations are exacerbated given the multiple oxidation states of sulfur. The fractionation of sulfur isotopes between co-existing phases is particularly large when the oxidation state of sulfur differs in both phases and when the phases have different aggregate physical states (i.e., gas phases vs. condensed phases). This chapter summarizes how sulfur isotopes have been measured in volcanic gases as well as in samples from magmatic rocks and or magmatic ore deposits. These data are compared with theoretical models of degassing and the crystallization and physical separation of sulfides and anhydrite from melt to gain insights into the processes occurring in magma chambers and during the ascent of the magma to the surface. In particular, this chapter addresses sulfur isotope characteristics for magmas and eruptive products of Mt. Vesuvius, Mt. Mazama, and Mt. Etna.

Ischia, a volcano island located 18 miles NW offshore Naples (Southern Italy), is a densely populated active caldera (last eruption 1302 A.D.). Melt inclusions (MIs) in phenocrysts of the Vateliero and Cava Nocelle shoshonite-latite eruptive products (VI-IV century B.C.) constrain structure and nature of the Ischia deep magmatic feeding system. The volcanic rocks of Ischia bear clear evidence for CO2 dominated gas fluxing, under very oxidized conditions, and consequent dehydration of magma portions stagnating at major crustal discontinuities. The geochemical features of the studied products make Ischia a natural borehole probing the deep physico-chemical conditions of magmas generated in a mantle contaminated by slab derived fluids largely dominated by CO2.Volatile concentrations in MIs require gas-melt equilibria between 3 and 18 km depth. MI-based evidence for CO2 fluxing is further supported by selective enrichment of K and related trace elements during magma differentiation. Accordingly, the budgets of magma degassing show that at Ischia there is much less magma than that needed to directly supply the amount of released magmatic fluids, thus constraining the role of CO2 rich deep fluids in originating the volcanism and generating caldera resurgence. The acquired data, together with those from the other Neapolitan volcanoes (Procida, Campi Flegrei –CF-, and Somma-Vesuvius –SV- ) show that, despite the compositional and eruptive style differences within the poorly extended Neapolitan Volcanic area, the different kinds of volcanism are mostly linked by supercritical CO2 fluids produced by devolatilization of subducted terrigenous-carbonatic metasediment, that infiltrate the mantle wedge, generate magmas and control their ascent up to eruption. Geochemical features of Ischia and the other volcanoes reveal that the ,extent of fluid contamination of the pre- subduction asthenospheric-mantle was similar at Ischia, Procida, CF and SV. However, the different isotopic composition (more enriched in radiogenic Sr at Ischia, CF, SV with respect to Procida) and water amount in the source (almost double at Ischia, CFc and SV than at Procida), reflect the different flow-rate of deep slab-derived fluids through the mantle wedge that, in turns, controls the amount of magma generation. The high bulk permeability below Ischia, CFc and SV, determined by the intersection of regional NW-SE normal and NE-SW transfer fault systems, favours fluid upraise and accumulation at crustal levels, with consequent magma production and storage larger than at Procida, that is located along the NE-SW system.

In the present work, trials were carried out to verify the range of application of a neural network, designed to formulate fats from 3 raw materials from soybean. For evaluation, 17 randomly selected commercial products, originally formulated with unknown raw materials, were used. Apart from the commercial products, 3 different table margarines were formulated using conventional methods and the neural network, and produced in pilot-plant scale. According to the results obtained, the neural network presented a success index of 64.7% in the formulation of commercial products. With respect to the products formulated and produced in pilot-plant scale, the results obtained using the network were similar to those obtained using the conventional formulation methods.En el presente trabajo se realizaron pruebas para verificar la amplitud de aplicación de una red neuronal, construida para formular grasas a partir de 3 materias-primas derivadas de soja. Para la evaluación se utilizaron 17 productos comerciales seleccionados aleatoriamente y formulados originalmente con materias- primas desconocidas. Además de los productos comerciales, se formularon y se produjeron a escala piloto, otras tres margarinas de mesa por métodos convencionales y con la red neuronal. De acuerdo con los resultados obtenidos, la red neuronal presentó un índice de éxito de 64,7% en la formulación de productos comerciales. Con relación a los productos formulados y producidos a escala piloto, los resultados obtenidos por la red fueron similares a los obtenidos por los métodos convencionales de formulación.

Assessment of time and space relationships among magmatism, volcanism, and resurgence of mediumsize calderas is a necessary tool to formulate a general model for their dynamics which also permits to forecast their evolution. To define a general hypothesis for the Campi Flegrei caldera, in a persistent state of unrest, the Ischia and Pantelleria medium-size resurgent structures, in variable stages of evolution, have also been investigated. In particular some parameters such as the structural and volcanological evolution, with emphasis on resurgence dynamics and coeval volcanism, and the evolution, present state and role of the magmatic system in resurgence, have been defined. For the Campi Flegrei caldera, the data collected during unrest episodes have also been taken into account, together with those from past eruptions. They corroborate the hypothesis that the unrest episodes are transient short-term events within the long-term deformation related to caldera resurgence. The geometry of the short-term deformation is strictly related to the structural setting of the caldera. The sub-surface processes have been dominated by joint degassing of two magmatic bodies, at 3-4 and 8 (or more) km depth, with the shallower formed by magma ascending from the deeper body. Both bodies contribute to the hydrothermal system, but the shallow magma is fluxed by the continuous upstream of CO2-richer gas released by the deep body. The two-layer degassing magma allows explaining geochemical and petrological features of unrest and volcanism. The joined interpretation of geological, geodetic, and geochemical data on the three calderas is an innovative approach that adds a time-perspective on how resurgent calderas behave. The proposed general hypothesis will help in long- and short-term volcanic hazards assessment and will support Civil Defence Authorities in elaborating actions devoted to volcanic risk reduction.

Volcanic calderas are affected by unrest episodes usually dominated by hybrid magmatic-hydrothermal system dynamics. Unrest episodes can evolve to eruptions of variable intensity, up to Plinian. Campi Flegrei caldera (CFc) is a type-location for this kind of activity escalation. CFc offers unique opportunity to join volcanological information to a long record of geochemical parameters. This allows understanding the role that magmatic system plays on variations displayed by the hydrothermal system. We model uneruptive unrest episodes as driven by i) the shallow emplacement (~4 km depth) of one volatile-rich magma batch ascending from a deep (≥ 8 km) magmatic body of regional extent, ii) subsequent gas separation with degassing driven by crystallization and iii) fluxing from the deep magmatic body. Our model matches three decades of geochemical constraints from fumarole discharges, as well as data from melt inclusions of past CFc eruptions. Besides, magma physical properties demanded for modeled degassing conditions are in good agreement with existing geophysical data. Our results open new perspectives to the definition of unrest scenarios at highly-populated CFc, as well as other resurgent calderas (e.g., Orsi et al., This Assembly).

A better understanding of degassing processes at open-vent basaltic volcanoes requires collection of new datasets of H2O–CO2–SO2 volcanic gas plume compositions, which acquisition has long been hampered by technical limitations. Here, we use the MultiGAS technique to provide the best-documented record of gas plume discharges from Stromboli volcano to date. We show that Stromboli's gases are dominated by H2O (48–98 mol%; mean, 80%), and by CO2 (2–50 mol%; mean, 17%) and SO2 (0.2–14 mol%; mean, 3%). The significant temporal variability in our dataset reflects the dynamic nature of degassing process during Strombolian activity; which we explore by interpreting our gas measurements in tandem with the melt inclusion record of pre-eruptive dissolved volatile abundances, and with the results of an equilibrium saturation model. Comparison between natural (volcanic gas and melt inclusion) and modelled compositions is used to propose a degassing mechanism for Stromboli volcano, which suggests surface gas discharges are mixtures of CO2-rich gas bubbles supplied from the deep (N4 km) plumbing system, and gases released from degassing of dissolved volatiles in the magma filling the upper conduits. The proposed mixing mechanism offers a viable and general model to account for composition of gas discharges at all volcanoes for which petrologic evidence of CO2 fluxing exists. A combined volcanic gas-melt inclusion-modelling approach, as used in this paper, provides key constraints on degassing processes, and should thus be pursued further.

Many basaltic volcanoes are characterized by large amounts of volatiles, most often reflecting fluid release from subducting slabs and consequent injection in the above mantle wedge. Because of this, basaltic volcanoes can experience a wide spectrum of activity, up to Plinian. At Mt. Etna, high-energy Plinian eruptions took place in the past (e.g., 122 BC), and still represent the major volcanic threat for the town of Catania and its surroundings. Joint melt inclusion-based investigation of sulfur release and bulk rock S-isotope study from classic Strombolian or lava-fountain based activity to Plinian eruptions may provide useful indications to discriminate the evolution to either high or low-energy eruptions. We show here that different Etna magmas follow different paths of sulfur elimination. Depending on initial water contents and oxidation states, Etnean magmas can soon reach the limit of sulfide saturation or get rid of sulfur on degassing only. Melt inclusion data indicate that the magma involved in the high-energy Plinian eruption of 122 BC is richer in sulfate than other magmas. The relationship between the high sulfate contents in melts, hence system oxidation, and the energy of the eruption does not seem to be fortuitous and reflects involvement of the hydrous-rich and oxidized parental source of magma, deep seated in a fluid-contaminated mantle. Consistent with melt inclusion findings, S-isotope data support the idea that most oxidized conditions known for Etna could be considered as a proxy for the most violent explosive eruptions, such as the 122 BC Plinian event. Because the whole plumbing system is dominated by CO2 and invested by gas-fluxing, melt dehydration is a common process. Dehydrated magma portions are also more reduced than those ascending from the water-rich source. In light of this, and due to the clear role of water as oxidizing agent, we propose that the explosivity associated with oxidized Etna magmas reflects the fast ascent of deep batches from the water-rich source. Unsteady CO2 fluxing and consequent dehydration of the deep parental magma may switch Etnean activity from effusive or mild-explosive to violent highly explosive eruptions.

Melt inclusions (MIs) represent pristine melt droplets trapped in early forming phenocrysts, which record the variable physico-chemical conditions of their hosting system. Compared to whole rock studies, the MIs approach shows advantages especially because it provides information on melt composition, volatile content, pressure and temperature at well-defined pre-eruptive stage. A large amount of geochemical data is available for the magmas generated in the Phlegraean Volcanic District (PVD), which is one of the most densely populated and high-risk volcanic areas of the world, but the knowledge provided by those data on their plumbing system, ascent, degassing and extrusion is limited. We investigated the glass/melt inclusions in olivines from the Solchiaro 1 volcanics, erupted on Procida Island, which is located along main tectonic alignment of the PVD. These products represent the least evolved magma of the PVD and could testify for the presence of the “basic” and deepest reservoir from which the Phlegraean magmas upraised and differentiated through various steps. Often invoked in literature, this “primitive” reservoir is basically uncostrained. We performed microprobe and microscopy measures to determine textural and compositional features of the MIs and host-minerals. The measures by Fourier Transform InfraRed spectroscopy provided the content of dissolved H2O and CO2, hence the volatile budget of magmas and entrapment pressures (i.e. depths of crystal growth). Recalculated crystallization depths for the Solchiaro 1 olivines result to be very deep (~350 MPa) and isobars obtained for the MIs describe a degassing trend with high CO2 content, of deep origin. Taking into account the geophysical data and the MIs studies on other Phlegraean products recently published, our dataset depicts a new framework for the evolution of the PVD plumbing system up to the present time that improves both the comprehension of magma evolution and migration through various reservoirs and the volcanic hazards assessment.

The Pomici Principali Tephra (10.3 ka) is one of the two highest-magnitude eruptions of the Campi Flegrei caldera over the past 15 ka. This caldera is active and largely inhabited, consequently it is one of the most dangerous volcanic areas on Earth. Stratigraphic and stratimetric studies carried out on an area of about 1000 km2 allowed us to reconstruct both eruption sequence and dynamics. On the basis of both lithological characteristics and dominant emplacement mechanisms, the sequence has been divided in five members: A) a basal ash fallout member, produced by a phreatomagmatic opening phase; B) a second member composed of coarse fallout layers deposited by a pulsating Plinian column; C) a third member which includes an alternation of ash and coarse pumice layers, generated during a magmatic-phreatomagmatic explosion phase; D) a fourth member composed of three thick coarse fallout layers separated by ash layers and generated by a mainly magmatic phase, during which a pulsating column reached the maximum height of about 22 km; E) an upper and fifth member, composed of fine- to coarse-ash surge beds, produced by a phase dominated by phreatomagmatic explosions. During this final phase pyroclastic surges flowed both inside and outside the caldera depression. The Pomici Principali erupted products were investigated through geochemical and isotope analyses and glass inclusion studies in order to shed light on the processes operating in the plumbing system. Whole rocks and glasses, representative of the complete stratigraphyc sequence, have a fairly homogeneous chemical composition. The isotope data on whole rocks, glasses and mineral phases suggest that at least two isotopic components were extruded during the course of the eruption. One of these components, the least radiogenic one, is represented by light-green pyroxenes. The most radiogenic component is represented by glasses and the majority of the separated minerals. Glass inclusion data were collected to highlight the pre-eruptive storage conditions of the erupted magma

Volcanic calderas are affected by unrest episodes usually dominated by hybrid magmatic-hydrothermal system dynamics. Unrest episodes can evolve to eruptions of variable intensity, up to Plinian. Campi Flegrei caldera (CFc) is a type-location for this kind of activity escalation. CFc provides unique opportunity to build-up a volcanological model in which geochemical, geological and geophysical data are interpreted together to understand how degassing following magma emplacement drives the caldera resurgence. Uneruptive unrest episodes reflect i) a sudden increase of the CO2 magmatic fraction following the shallow emplacement of one single volatile-rich magma batch, ii) voluminous gas separation in a nearly single-step process, and iii), on longer times scales of 10-20 years, degassing driven by crystallization and deep gas fluxing. Our volcanological model matches three decades of geochemical constraints from fumarole discharges, as well as data from melt inclusions of past CFc eruptions. Besides, magma physical properties demanded for modeled degassing conditions are in good agreement with existing geophysical data. Our results open new perspectives to the definition of unrest scenarios at highly-populated CFc.

We present the results of a study of volcanic gases at Soufrière Hills Volcano, Montserrat, which includes the first spectroscopic measurements of the major gas species CO2 and H2S at this volcano using a Multisensor Gas Analyzer System (MultiGAS) sensor. The fluxes of CO2 and H2S were 640–2750 t/d and 84–266 t/d, respectively, during July 2008, during a prolonged eruptive pause. The flux of CO2 is similar to estimates for the entire arc from previous geochemical studies, while the measured H2S flux significantly alters our interpretation of the sulphur budget for this volcano. The fluxes of both sulphur and carbon show considerable excesses over that which can be supplied by degassing of erupted magma. We demonstrate, using thermodynamic models and published constraints on preeruptive volatile concentrations, that the gas composition and fluxes are best modeled by mixing between (1) gases derived from isobaric quenching of mafic magma against cooler andesite magma at depth and (2) gases derived from shallower rhyolitic interstitial melt within the porpyritic andesite. The escape of deep‐derived gases requires pervasive permeability or vapor advection extending to several kilometers depth in the conduit and magma storage system. These results provide more compelling evidence for both the contribution of unerupted mafic magma to the volatile budget of this andesitic arc volcano and the importance of the intruding mafic magma in sustaining the eruption. From a broader perspective, this study illustrates the importance and role of underplating mafic magmas in arc settings. These magmas play an important role in triggering and sustaining eruptions and contribute in a highly significant way to the volatile budget of arc volcanoes.