A massive influx of magma beneath Santorini caused over 28,000 earthquakes in early 2025, according to a new study. Researchers used advanced AI and seafloor sensors to track the molten rock's movement. The findings reveal a previously unknown connection between Santorini and the nearby underwater volcano Kolumbo.
In late January 2025, the island of Santorini and surrounding areas in the Aegean Sea experienced intense seismic activity, with more than 28,000 earthquakes recorded, some exceeding magnitude 5.0. Scientists from the GFZ Helmholtz Centre for Geosciences and GEOMAR Helmholtz Centre for Ocean Research Kiel, along with international partners, detailed the cause in a study published in Nature.
The analysis shows that approximately 300 million cubic meters of magma rose from deep within the Earth's crust and stalled about four kilometers beneath the seafloor. This upward push fractured surrounding rock layers, sparking the earthquake swarm. The process began earlier, with magma accumulating in a shallow reservoir under Santorini in July 2024, causing the island to lift by a few centimeters. Seismic activity ramped up in early January 2025, and by late January, the quakes migrated northeast over 10 kilometers, with depths shifting from 18 kilometers to just 3 kilometers below the surface.
Santorini lies in the Hellenic volcanic arc, a highly active region shaped by the collision of the African and Hellenic plates. The island forms the rim of a caldera from a major eruption 3,600 years ago, and nearby Kolumbo is an active submarine volcano 7 kilometers away. As the magma moved, Santorini subsided, indicating a hydraulic link between the two volcanoes.
Dr. Marius Isken, a geophysicist at GFZ and lead author, stated: "The seismic activity was typical of magma ascending through the Earth's crust. The migrating magma breaks the rock and forms pathways, which causes intense earthquake activity. Our analysis enabled us to trace the path and dynamics of the magma ascent with a high degree of accuracy."
Dr. Jens Karstens, marine geophysicist at GEOMAR and co-lead author, added: "Through close international cooperation and the combination of various geophysical methods, we were able to follow the development of the seismic crisis in near real time and even learn something about the interaction between the two volcanoes. This will help us to improve the monitoring of both volcanoes in the future."
Key to the research was an AI-driven system for analyzing seismic data and seafloor instruments deployed at Kolumbo as part of the MULTI-MAREX project. These detected pressure changes from seabed sinking up to 30 centimeters. Monitoring continues, with data shared with Greek authorities to assess risks.
Prof. Dr. Heidrun Kopp of GEOMAR noted: "The joint findings were always shared with the Greek authorities in order to enable the fastest and most accurate assessment of the situation possible in the event of new earthquakes." Co-author Prof. Dr. Paraskevi Nomikou of the University of Athens emphasized: "Understanding the dynamics in this geologically highly active region as accurately as possible is crucial for the safety and protection of the population."
