In the last decades, volcano monitoring capabilities have increased enormously, thanks to geochemical and geophysical airborne and surface measurements that have steadily improved their accuracy and time resolution. Such a wealth of data is routinely used to track volcanic unrest and eruption evolution, although precise causative links with underground processes are often missing. Modeling of magmatic and volcanic systems has also leaped forward, thanks to the increased availability of computer power and development of numerical models. Capturing the complexity of magmatic system evolution at all scales is nonetheless still a challenge: the crystal- and bubble-size processes need to be taken into account in order to resolve the reservoir-scale dynamics detected by the monitoring networks. We have developed a robust numerical model to solve the thermo-fluid dynamics of magmatic mixtures, that includes pressure-, temperature and melt composition-dependent, locally (space-time) defined properties and constitutive equations of multi-component magmas. The model has been applied to a variety of scenarios related to magma dynamics in underground volcanic systems, including magma arrival from depth into shallow reservoirs. Model results include the space-time evolution of density, pressure, velocity and composition within the domain, that can be used as sources of synthetic geodetic and seismic datasets, akin to those recorded by monitoring networks. The synthetic and monitoring time series can thus be compared and their similarities can be exploited to detect the underground dynamics causing well-defined time and spectral patterns: we are building a physically sound reference for the interpretation of volcanic unrest signals and their relationships with the deep magma dynamics. This approach has been successfully used to detect shallow magma arrival from strainmeter records at Campi Flegrei during the ongoing unrest phase; it is also being applied to evaluate how precise gravity surveys at Mount Etna can help in detecting any shift in the eruptive sequence.

Active magma chambers are periodically replenished upon a combination of buoyancy and pressure forces driving upward motion of initially deep magma. Such periodic replenishments concur to determine the chemical evolution of shallow magmas, they are often associated to volcanic unrests, and they are nearly ubiquitously found to shortly precede a volcanic eruption. Here we numerically simulate the dynamics of shallow magma chamber replenishment by systematically investigating the roles of buoyancy and pressure forces, from pure buoyancy to pure pressure conditions and across combinations of them. Our numerical results refer to volcanic systems that are not frequently erupting, for which magma at shallow level is isolated from the surface (â\euroœclosed conduitâ\euro? volcanoes). The results depict a variety of dynamic evolutions, with the pure buoyant end-member associated with effective convection and mixing and generation of no or negative overpressure in the shallow chamber, and the pure pressure end-member translating into effective shallow pressure increase without any dynamics of magma convection associated. Mixed conditions with variable extents of buoyancy and pressure forces illustrate dynamics initially dominated by overpressure, then, over the longer term, by buoyancy forces. Results globally suggest that many shallow magmatic systems may evolve during their lifetime under the control of buoyancy forces, likely triggered by shallow magma degassing. That naturally leads to long-term stable dynamic conditions characterized by periodic replenishments of partially degassed, heavier magma by volatile-rich fresh deep magma, similar to those reconstructed from petrology of many shallow-emplaced magmatic bodies.