The 79 AD Vesuvius eruption revisited: Plinian and post-Plinian falls

The well-exposed Plinian fall deposit of the 79 AD Vesuvius eruption is herein divided into 12 lithostratigraphic units comprised of 7 units in the white pumice deposit (A) and 5 units in the grey pumice deposit (B). These distinct units are distinguished by significant variations in grain size and the ratio of lithic to juvenile clasts, enabling us to reconstruct the highly fluctuating dynamics of the eruptive column during the Plinian phase of the 79 AD eruption with a previously undetected detail. These characteristics enable the mapping of their distributions around the vent, revealing that the plume fluctuated between 14 and 34 km in height, depositing 6.4 km3 of tephra in 17 hours. To broaden the scope of our investigation, we extended our research to encompass five lithic-rich fall layers that occurred after the Plinian phase, providing information on the dispersion and eruptive parameters of these late fallout phases. Post-Plinian sustained column pulses persisted for several tens of minutes, with the first pulse being the longest, lasting 44 minutes. This initial pulse possibly facilitated the attempts made by numerous Pompeians to flee the city following the arrival of the first two weak pyroclastic density currents.