A model for the magma migration beneath the multi-volcanic system: Constraints from the geophysical observations of the Santorini and Kolumbo volcanos in Greece

Although the Santorini volcano is only approximately 15 km away from the Kolumbo volcanoe in Greece, geochemical signatures of the erupted magma of the Santorini volcano are obviously different from those of the Kolumbo volcanoe. However, since January 2025, these two volcanoes have shown dynamically linked behaviors. The Santorini volcano experienced the surface uplift while the Kolumbo volcano underwent the surface subsidence, accompanied by the continuous and intense earthquakes that lasted for more than a month beneath the rift zone. Regarding to the mechanisms of magma movement,and instability in this multi-volcano system, a recent international study has utilized the high-resolution machine-learning-derived seismic catalogs and the surface deformation inversion techniques to reconstruct temporal and spatial trajectories of magmatic activities during this seismic and volcanic upheaval. The results show that epicenters of the seismic swarm occurred in that period are gradually changed to the northeastward and upward directions with the time, with a final horizontal displacement straight distance of approximately 30 km. Moreover, the positive isotropy presented by the seismic moment tensor is consistent with the compensated linear vector dipole components, strongly confirming the intruding process of magma along a dike. The surface deformation modelings have constrained the expansion of a magma chamber beneath the Santorini volcano, the contraction of a magma chamber beneath the Kolumbo volcano, and the amount of magma that intruded along the rift zone to form the dike. Especially, the volume of magma for the intruded dike (0.331 km3) was much larger than the reduced volume of the magma chamber (0.076 km3). It is worth noting that this double volcano system exhibits an ″expansion–contraction″ pattern, which is different from the multi-volcano systems that are coupled through the pressure transmission. This reveals that the tectonic stress and pre-existing crustal weak zone played a dominant role in the lateral transport of magma, presnting a new model of “the deep origin of magma - the shallow structural diversion of magma”.