Hazard of pyroclastic density currents at the Campi Flegrei Caldera (Southern Italy) as deduced from the combined use of facies architecture, physical modeling and statistics of the impact parameters

The particle volumetric concentration at a height of 2 m within the current is always lower than 0.01, but typically it is higher than 0.001 inside the caldera, and could have severe effects on the unsheltered population, also at locations (topographic highs) where velocity and dynamic pressures are low. In distal reaches outside the caldera the widespread fine ash originated by buoyancy from the currents, which was transported by lower atmosphere winds, is to be considered as a “fallout load” slowly accumulating on the ground surface (and building roofs) during the waning stage of the current.