Suchergebnisse

Abstract. The possible emplacement of pyroclastic fall and flow products from Campi Flegrei and Somma-Vesuvio represents a threat for the population living in Napoli city. For this area, the volcanic hazard was always partially investigated to define the hazard related to the Campi Flegrei or to the Somma-Vesuvio activity one at a time. A new volcanic hazard and risk assessment, at the municipality scale, as a vital tool for decision-making about territorial management and future planning, is presented here. In order to assess the hazard related to the explosive activity of both sources, we integrated the results of field studies and numerical simulations, to evaluate the future possibility for Napoli to be hit by the products of an explosive eruption. This is defined for the Somma Vesuvio central volcano through the sum of "field frequency" based on the thickness and distribution of past deposits (Lirer et al., 2001), and for the Campi Flegrei volcanic field by suitably processing simulated events based on numerical modelling (Alberico et al., 2002; Costa et al., 2009). Aiming at volcanic risk assessment, the hazard areas were joined with the exposure map, considered for our purposes as the economical value of artefacts exposed to hazard. We defined four risk classes, and argued that the medium and low-very low risk classes have the largest extent in Napoli municipality, whereas only few zones located in the eastern part of the city and in the westernmost coastal area show a high risk, owing to the correspondence of high economical value and high hazard.

The prehistoric (< 7 ka) Zaro eruption at Ischia island (Southern Italy) produced a lava complex overlaying a pyroclastic deposit. Although being of low energy, the Zaro eruption might have caused casualties among the neolithic population that inhabited that area of Ischia, and damages to their settlements. A similar eruption at Ischia with its present-day population would turn into a disaster. Therefore, understanding the magmatic processes that triggered the Zaro eruption would be important for volcanic hazard assessment and risk mitigation, so as to improve a knowledge that can be applied to other active volcanic areas worldwide. The main Zaro lava body is trachyte and hosts abundant mafic and felsic enclaves. Here all juvenile facies have been fully characterized from petrographic, geochemical and isotopic viewpoints. The whole dataset (major and trace element contents; Sr-Nd isotopic composition) leads to rule out a genetic link by fractional crystallization among the variable facies. Thus, we suggest that the Zaro mafic enclaves could represent a deep-origin mafic magma that mingled/mixed with the main trachytic one residing in the Ischia shallow magmatic system. The intrusion of such a mafic magma into a shallow reservoir filled by partly crystallized, evolved magma could have destabilized the magmatic system presumably acting as a rapid eruption trigger. The resulting processes of convection, mixing and rejuvenation have possibly played an important role in pre- and syn-eruptive phases also in several eruptions of different sizes in the Neapolitan area and elsewhere in the world. ; The authors are grateful to Roberto de Gennaro for his precious help in obtaining SEM-EDS-WDS data. This study was carried out in the framework of the GEOPAM Research Group (AGAUR, Generalitat de Catalunya, Ref. 2017 SGR 1494). We acknowledge the technical support of M. Rejas of ICTJA-CSIC Laboratory of Geochemistry labGEOTOP, infrastructure co-funded with resources from the ERDF, European Union, (CSIC08-4E-001, and partner of Project EPOS Implementation Phase, EPOS IP, Grant Agreement no. 676564-EPOS IP Call H2020-IFRADEV-12015-1). The INGV, OV laboratories have been financially supported by the EPOS Research Infrastructure through the contribution of the Italian Ministry of University and Research (MUR). Reviews by Prof. Dr. Gerhard Franz, as well as comments and suggestions by the Editor, greatly contributed to the improvement of the original manuscript and are kindly acknowledged. Funding Open access funding provided by Università degli Studi di Napoli Federico II within the CRUI-CARE Agreement ; Peer reviewed

Active calderas are major volcanic features of the Earth's crust associated with shallow magma reservoirs, high geothermal gradients, and geodynamic unrests often documented through historical time. As large caldera-forming eruptions are also among the most catastrophic events that may affect the Earth's surface, calderas are ostensibly the sites of major interest for both the scientific community and governmental institutions worldwide. The Campi Flegrei is an active volcanic area located west of the city of Naples, largely on the continental shelf of the Eastern Tyrrhenian margin that has been characterized by dominantly explosive eruptions during the latest Quaternary. This is one among the highest volcanic risk-prone areas of the world and likely the only example in the historical record of a caldera where dramatic ground/seafloor deformation (more than 4 m of uplift between 1950 and 1984) was not followed by a volcanic eruption. This suggests some important role played by the heath and gas flow from the magma chamber and the dynamics of the shallow aquifers in the unrest episodes. Recent research offshore the Campi Flegrei has shown that a significant part of the volcaniclastic products and sedimentary processes are still largely unknown. The structure of the hydrothermal system associated with the offshore substructure of the caldera system is poorly constrained, and even the caldera-like diagnostic characters postulated for the older phase in the evolution of the Campi Flegrei, largely based on outcrop data, are somewhat questionable. Therefore, it has become clear that only drilling both the onshore and offshore parts of the caldera much deeper than conventional coring may provide a relatively complete stratigraphic record that could not be preserved on land. We propose 15 drill sites (1 deep drill site onland and 14 shallower drill sites offshore) that are necessary in order to reconstruct the Late Quaternary stratigraphy, structure, hydrothermal system and geodynamic evolution of the Campi Flegrei district as a component of the eastern Tyrrhenian margin. According with the outcomes of a MagellanPlus Workshop held in Napoli in February 2017, it was suggested the Campi Flegrei Caldera Drilling Project should be jointly submitted to IODP and ICDP as an Amphibious Drilling Proposal by the end of 2018. The Workshop participant agreed on the proposition that the IODP component of the proposal should focus on integrated stratigraphy of the caldera fill and resurgent structure, as well as on petrology and architecture of shallow structural levels (0-500 m depth), whereas the ICDP component should be designed to understand the rock-fluid properties, physical-chemical processes and the geothermal system at deeper structural levels (0-3000 m depth). Onshore drilling of a pilot hole has already been completed, enlightening many new results which shed completely new light on the volcanic history and on the extension and mechanisms of the caldera itself. The joint drilling project is hence based on solid grounds and can certainly become a key for a large step forwards in the knowledge of caldera dynamics and eruption prediction.