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.