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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.

Dilute pyroclastic density currents are one major source of hazard at Vesuvius. By combining data of deposits of the explosive eruptions of the last six thousand years and interpolating data of impact parameters (Velocity, Density, particle volumetric concentration, temperature, dynamic pressure), which were calculated by modeling the currents as stratified turbulent boundary layer flows, probabilistic hazard maps were obtained. They show the decay trend of the impact as a function of distance from the vent and allow depicting the expected damage. This outcome can help civil protection authorities to more precisely-implemented mitigation measures and communicate more effectively the risk to decision-makers and the population., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The Neapolitan volcanoes are some of the most hazardous in the world because capable of large explosive eruptions releasing threatening quantities of ash in the atmosphere that would reasonably reach highly-populated urban areas, even at considerable distances from the sources. This study aims to show a long-term tephra fallout hazard evaluation posed by the Neapolitan volcanoes (Somma-Vesuvius, Campi Flegrei, Ischia) in Southern Italy, and to track future perspectives to combine a multi-hazard assessment to a more local-scale domain. Through a new HPC workflow for volcanic hazard assessment based on a Bayesian procedure, we provided the mean annual frequency with which the tephra load at the ground exceeds given critical thresholds within 50 years. By performing hazard disaggregation, we also got specific information about the prevalence of different volcanoes and eruptive style in the different target areas. Thousands of numerical simulations were run with the FALL3D model to create a large synthetic dataset of tephra ground loads on a 0.03°-resolution gridded domain and a vertical σ-coordinate system with a linear decay. Each simulation took a randomly sampled set of eruptive source parameters within the ranges established by the knowledge of each volcano and meteorological conditions extracted by the ECMWF ERA5 dataset. In particular, results show that the greater tephra load thresholds are exceeded with longer averaged return times (i.e., 100, 500, 1000 years) in the proximity of the Neapolitan area. This pushes us to do a step forward into a more detailed multi-hazard and risk-ranking quantification in the Neapolitan urban area., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Ascending magma is always interacting with its surrounding country rock, as evidenced by crustal xenoliths in volcanic products. In the case of a limestone basement this interaction, also called carbonate assimilation, may significantly affect eruption dynamics due to the limestones ability to release CO2 if heated above its crystallographic stability. Examples for such a setting include volcanic systems like Colli Albani, Etna, Merapi, Pacaya, Popocatepetl and Somma-Vesuvius.Previous carbonate assimilation studies at magma chamber conditions have already shown that this interaction might release CO2 and dissolve the ingested clast in syn-eruptive timescales. With our novel experimental procedure, we investigated the interaction of a magma with an ingested limestone at the second endmember of the volcanic feeding system (i.e., Earth’s surface and hence at atmospheric pressure). Our set-up allowed, for the first time, to discriminate between the individual processes within the carbonate assimilation (namely decarbonation and clast dissolution), their respective timescales and their controlling parameters. By comparing the results of both experimental approaches, we were able to qualitatively extrapolate the conditions and outcomes of magma carbonate interactions throughout the whole volcanic feeding system, from magma chamber to Earth’s surface. This enables a qualitative distinction of which process (decarbonation or clast dissolution) is dominant in which conditions and how the syn-eruptive interaction of magma with carbonate-bearing wall-rocks within the feeding dyke of an eruption will influence the eruptive behaviour., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)