Complex Dome Growth at Campi Flegrei Caldera (Italy) in the Last 15 ka

The Campi Flegrei caldera (Italy) is an active volcanic system characterized by significant long- and short-term ground deformation phenomena ranging the maxima values in the central sector of the caldera, where La Starza marine terrace is located. A detailed study of the La Starza provided crucial clues for understanding the resurgence of the central sector of the caldera following the 15-ka Neapolitan Yellow Tuff eruption. The doming of the caldera floor, marked by two primary episodes of uplift, began soon after the collapse of about 110 m following the eruption. The first doming (15–9.2 ka) occurred as a response to loss of lithostatic loading producing magma influx, possibly regulated by thermal magmatic convection and chaotic movement inside the magma reservoir under the caldera. The calculated ~90 m of structural uplift is the persistent displacement correlated with magma volumes intruded accompanying the contemporaneous volcanic activity. The second episode of uplift (5.5–3.8 ka) produced a ground deformation pattern similar to that measured during recent unrest crises suggesting a stable and shallow (~4-km deep) source of strain like a sill in an elastic half space. By this geometry and inversion of surface deformation, the volume of intruded material was determined. Simply varying pressure history as input, the time history of the surface deformation was reproduced by using spherical source geometry with a concentric viscoelastic shell 8-km deep. The satisfactory comparison between the two models is a useful indication for interpreting the current unrest phase at the Campi Flegrei caldera.