Tracking the 2007-2023 magma-driven unrest at Campi Flegrei caldera (Italy)

Understanding and managing unrest at a volcano include i) ascertaining the magmatic distribution and migration, and ii) tracking the evolution of the shallow plumbing system. Here we use multi-technique geodetic data, mechanical models, and petrological simulations to define both aspects for the ongoing (2005-present) unrest at Campi Flegrei caldera, Italy. Results show a deformation source exhibiting progressive widening and shallowing, from 5.9 to 3.9 kilometres. Concurrently, a deeper tabular source at 8 km depth experiences limited but constant deflation. Petrological calculations explain inflation of the shallower source resulting from the rise of 0.06 to 0.22 cubic kilometres of magma from depth >= 8 kilometres. Our analysis provides strong evidence that magma ascent to depths shallower than 8 kilometres is the ultimate driver behind the ongoing unrest. This merging of geodetic and petrological approaches to track the evolution of a plumbing system better constrains magma ascent at volcanoes experiencing unrest. The unrest and surface deformation observed at Campi Flegrei caldera (Italy) between 2007 and 2023 are driven by magma ascent to depths shallower than eight kilometers, according to combined geodetic and petrologic simulations.