Study Finds Volcanic Activity Caused Santorini Seismic Swarm

The enigma of the 30,000 earthquakes that rattled Santorini in early 2025 has finally been deciphered. What started as a puzzling phenomenon in the south Cyclades, gripped by a “seismic swarm” during late January and February of that year, turned out to be intricately linked to volcanic activity.

Seismologists recorded an astounding number of earthquakes within a span of about six weeks, concentrated in an area encompassing the islands of Amorgos, Anafi, Ios, and the renowned volcanic isle of Santorini. The scenario prompted a wave of speculation, with some drawing connections to the mythical Atlantis and submerged calderas. Nevertheless, the initial cause of this unusual seismic activity left scientists scratching their heads.

By September, a collaborative effort involving 31 researchers from six different countries shed light on the situation. Their findings, featured in the latest edition of Nature, revealed that the “seismic swarm” was triggered by volcanic actions, specifically attributed to the inter-connectedness of the two nearby volcanoes near Santorini.

The seismic unrest near Santorini kickstarted on January 27, persisting for over a month. This unprecedented event led to a mass exodus of residents from the island, prompting an extensive response from Greece’s civil protection services, encompassing the military and police forces. Subsequently, a state of emergency was declared on the popular “Instagram Island,” resulting in a two-week closure of schools.

The research titled “Volcanic crisis reveals coupled magma system at Santorini and Kolumbo,” aligns with the stance of experts who maintained that volcanic activities were at the core of the seismic disturbances. The study incorporated a comprehensive analysis of onshore and marine seismological data coupled with geodetic measurements to track the movement of magma pre and post-crisis.

Key revelations from the study suggested a progressive inflation within the Santorini caldera that commenced in mid-2024, foreshadowing the intrusion of a magma-filled dike originating from a mid-crustal reservoir beneath Kolumbo in January 2025. This strategic connection between the two volcanoes was pivotal, as approximately 0.31 km3 of magma infiltrated as a 13-kilometer-long dike, reactivating primary regional faults and stalling at 3-5 km below the sea floor.