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- Title
Reconstructing Pyroclastic Currents' Source and Flow Parameters From Deposit Characteristics and Numerical Modeling: The Pozzolane Rosse Ignimbrite Case Study (Colli Albani, Italy).
- Authors
Calabrò, Laura; Esposti Ongaro, Tomaso; Giordano, Guido; de' Michieli Vitturi, Mattia
- 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. Plain Language Summary: Pyroclastic currents are hot mixtures of gas and pyroclastic particles generated during explosive eruptions, which travel along topography at moderate to very high speed (tens to hundreds of m/s) under the effect of gravity. Pyroclastic currents, generated during large volcanic eruptions (often associated with formation of calderas), can travel tens of km far from the eruptive center and are able to pass topographic obstacles up to hundreds of meters high. These characteristics make them one of the most dangerous and inaccessible natural phenomena to study. For these reasons, the use of numerical modeling is essential to provide key quantitative information about pyroclastic currents' internal dynamics. In this study, we apply a new numerical simulation model to reconstruct the eruption conditions generating the Pozzolane Rosse ignimbrite (Colli Albani, Italy, 460 thousand years ago). Simulation results permit us to explain the dependency of the observable field data (flow runout, deposit thickness, grain‐size and temperature) on the initial flow conditions (thickness, velocity, density, temperature and grain‐size distribution). Despite the uncertainties still affecting the methodology we are able to invert field characteristics of the Pozzolane Rosse ignimbrite to constrain the initial mass flow rate and density of the parent pyroclastic current. Key Points: A new depth‐averaged, equilibrium mixture model for pyroclastic currents is used to study the main features of caldera‐forming ignimbritesThe ignimbrite runout and thickness decay pattern are correlated to three main flow source parametersThe main properties of the flow that generated the Pozzolane Rosse ignimbrite are reconstructed
- Subjects
ITALY; IGNIMBRITE; PARTICLE size distribution; RICHARDSON number; VOLCANIC eruptions; TEMPERATURE distribution; BLAST effect; VOLCANOLOGY; GAS mixtures
- Publication
Journal of Geophysical Research. Solid Earth, 2022, Vol 127, Issue 5, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2021JB023637