A time-distance reconstruction of the Campanian Ignimbrite pyroclastic current based on lithofacies architecture

S01.36 - Hazard assessment of pyroclastic density currents and lahars current capabilities and new strategies for comprehensive uncertainty quantification A time-distance reconstruction of the Campanian Ignimbrite pyroclastic current based on lithofacies architecture Claudio Scarpati, Domenico Sparice, Annamaria Perrotta Dipartimento di Scienze della Terra, dell'Ambiente e delle Risorse (DiSTAR), Università di Napoli Federico II, Italy Large ignimbrites are the product of high-temperature pyroclastic density currents (PDCs) spreading over huge regions. Understanding the behaviour of these volcanic events is critical to assess the hazard posed to millions of peoples living near volcanoes producing this type of activity. Here we present a detailed examination of the medial (from 30 to 80 km from the source area) ignimbrite sequence of the Campanian Ignimbrite eruption (Campanian Ignimbrite s.s., CI), a caldera-forming Plinian event, occurred 39 ka ago, whose PDC spread over a huge area from Campi Flegrei (Italy). Ignimbrite deposits have a mass of 1.74*1014 kg and a tephra volume of 54 km3 (25 km3 DRE). We describe CI lithofacies and their vertical and lateral variations. The eruption started with a fluctuating Plinian phase that collapsed irreversibly spreading a pyroclastic density current over a rugged region. Vertical facies variations reflect a temporal evolution of depositional mechanisms, from traction- to granular- or fluid escape-dominated, that records unsteady conditions and contrast with persistent lateral facies reflecting an overall uniform spatial behaviour of the current. Our lithofacies investigation illustrates how the CI PDC evolved in time and space and the role of internal (eruptive and transport mechanisms) and external (topography, surficial water and rain) factors in governing its behaviour. Our study may have important implications for assessing the hazards related to the reactivation of the Campi Flegrei caldera with a large ignimbrite-forming Plinian event, like the Campanian Ignimbrite eruption, on the densely populated Campania region