The seismic activity started to stir beneath the Greek islands of Santorini, Amorgos, and Anafi in January 2025. The islands experienced tens of thousands of earthquakes – many of which were over magnitude 5.0 and could be felt.
Many tourists fled, and locals feared that the nearby underwater volcano, Kolumbo, might be about to erupt – or that this was a seismic prelude to a larger earthquake, like the devastating, magnitude 7.7 quake that struck the same region in 1956.
The scientists, who published their findings in the journal Science, created a 3D map of the Earth around Santorini. They then mapped the evolving patterns of seismic activity of each tremor and the movement and stress in the crust. This resulted in a detailed model of exactly what drove this months-long seismic swarm.
The team found that the event was driven by the horizontal movement of magma – from beneath Santorini and the Kolumbo volcano – through a 30km channel that is more than 10km beneath the seafloor.
The researchers estimated that the volume of magma that moved through the crust could have filled 200,000 Olympic-sized swimming pools. These “magma intrusions”, as they are known, smashed through layers of rock, triggering thousands of tremors.
Lead author on the study, Anthony Lomax, a research geophysicist who develops scientific software to analyse seismic activity, explained: “The tremors act as if we had instruments deep in the Earth, and they’re telling us something.
“[When we analyse] the pattern those earthquakes make in our 3D model of the Earth, it matches very, very well what we expect for magma moving horizontally.”
