Reconstructing Pyroclastic Currents' Source and Flow Parameters From Deposit Characteristics and Numerical Modeling: The Pozzolane Rosse Ignimbrite Case Study (Colli Albani, Italy)

Abstract

In this study, we apply a two-dimensional, transient depth-averaged model to simulate the inertial flow dynamics of caldera-forming pyroclastic currents, using the available data about the Pozzolane Rosse ignimbrite (Colli Albani, Italy) eruption (460 ka, 63 km3 DRE). By performing an extensive set of numerical simulations, we test the effects of the initial parameters of the pyroclastic current (Richardson number, mass flow rate, initial flow density) on simulated deposit characteristics which can be compared with selected ignimbrite field observables, including the deposit dispersal along topography, the maximum distance from source, the deposit thickness, the grain size distribution at different distances, and the emplacement temperature. Results permit us to quantify the first-order dependency of the flow runout on the mass flow rate, and of the deposit thickness decay pattern on the initial mixture density. By using the results of the parametric study we reconstruct the source parameters of the Pozzolane Rosse ignimbrite constrained by the ignimbrite depositional characteristics, including the mass partition into the co-ignimbrite cloud. Despite uncertainties associated with the complex, non-linear interplay between the flow variables, the single-layer, depth-averaged model demonstrates to be suitable for simulating inertial pyroclastic currents, such as those generating large-scale caldera-forming ignimbrites, providing a tool for reconstructing the eruption source parameters from deposits characteristics, and to assess pyroclastic currents' hazard for future eruptions.