At the dawn of 2025, the Greek island of Santorini and its surrounding marine expanses were shaken by a remarkable seismic upheaval. Tens of thousands of tremors reverberated through this iconic volcanic region over a short time span, captivating the global geoscientific community and raising alarms among local populations. Now, a groundbreaking study published in Nature by researchers from the GFZ Helmholtz Centre for Geosciences, GEOMAR Helmholtz Centre for Ocean Research Kiel, and international collaborators delivers an unprecedented geological narrative of this seismic crisis. Drawing on a suite of cutting-edge observational tools and innovative artificial intelligence (AI) techniques, the study deciphers the subterranean processes that ignited this intense earthquake swarm, revealing the dynamic interplay between magma movement and crustal stress in unparalleled detail.
Santorini, perched in the eastern Mediterranean, is a geological jewel situated along the Hellenic volcanic arc—a hotbed of tectonic and volcanic activity shaped by the ongoing convergence of the African and Hellenic Plates. This tectonic dance has fractured the region’s crust into several microplates, whose relative motions fuel volcanic expression and seismicity. The island itself forms the caldera rim of a cataclysmic eruption approximately 3,600 years old, a defining event whose vestiges continue to underpin the region’s geohazard potential. Adjacent to this terrestrial volcano lies Kolumbo, an active submarine volcano whose summit protrudes just below the sea surface seven kilometers northeast of Santorini. This geographic juxtaposition is crucial as the seismic swarm of early 2025 unfolded not on the island itself but migrated toward this enigmatic underwater volcanic system.
The geological background of the area is complex, fostered by the regional tectonic regime where the African Plate presses laboriously against the Hellenic microplates. This collision promotes subduction and melting of crustal material, generating magmatic reservoirs that supply volcanic edifices like Santorini and Kolumbo. Historically, Santorini has manifested volcanic activity over millennia, with eruptions documented into the mid-20th century, the most recent in 1950. Moreover, the southern Aegean Sea witnessed two destructive earthquakes in 1956, with magnitudes over 7, which occurred mere minutes apart between Santorini and Amorgos, accompanied by a damaging tsunami. These events underscore the region’s seismic vulnerability and the inherent risks linked to both tectonic and magmatic processes.
The seismic crisis commencing in late January 2025 stands out not only for its volume, exceeding 28,000 recorded tremors, but also for the enigmatic nature of its cause. Initial uncertainty loomed over whether the quakes stemmed from tectonic fault activity or volcanic processes beneath Santorini. The strongest earthquakes in the swarm registered magnitudes surpassing 5.0, inflicting anxiety and posing significant threat assessments for residents and authorities alike. The crisis’s protracted character and spatial migration underscored a complex subsurface phenomenon rather than a simple fault rupture.
Advanced analysis now clarifies the subterranean origins of these earthquakes as fundamentally linked to magma dynamics. The onset of this magmatic unrest traces back to mid-2024, when molten rock began accumulating in a shallow reservoir beneath Santorini. This early phase manifested subtly as a few centimeters of surface uplift, detected by precise geodetic instruments. However, seismicity intensified markedly by January 2025, coinciding with the ascent of magma from deeper levels. The focal areas of the earthquake swarm shifted northeastwards, traveling over a 10-kilometer horizontal distance. Seismic hypocenters delineated successive pulses advancing from approximately 18 kilometers depth ascending to nearly 3 kilometers beneath the seabed, painting a vivid picture of magma propagation through the brittle crust.
A major technological breakthrough enabling such high-resolution insight was the application of an artificial intelligence-driven classification and localization algorithm developed at GFZ. This method efficiently processed vast seismic datasets, automating earthquake detection and hypocenter estimation to unprecedented accuracy. Coupled with real-time seafloor monitoring stations deployed by GEOMAR at the Kolumbo crater, researchers obtained near-direct observation of seismic tremors and associated pressure variations linked to seabed subsidence, which reached up to 30 centimeters amid the magma intrusion. The synergy of AI and ocean-bottom instrumentation elevated the spatiotemporal resolution of seismic event mapping, augmenting traditional land-based networks and satellite geodesy (including InSAR and GPS).
Dr. Marius Isken from GFZ, a lead author of the study, interprets this pattern as a classical signature of magma ascent, where the intruding molten rock fractures surrounding host rock to forge conductive pathways. These fracture events not only facilitate magma migration but generate the high-frequency earthquake swarms observed. The multi-pulse style of migration suggests episodic magma influx rather than continuous flow, offering fresh perspectives on reservoir pressurization and brittle failure cycles within volcanic systems.
Intriguingly, the magmatic migration induced surface deformation beyond mere uplift, as Santorini ultimately experienced subsidence during later stages of the crisis. This counterintuitive sinking is hypothesized by the researchers to reflect a hydraulic coupling between Santorini’s magmatic system and that of Kolumbo, implying that fluid or magma transfer occurred between these volcanic centers. Such hydraulic connections challenge previous notions that treated these volcanoes as isolated entities and have profound implications for volcanic hazard modeling and eruption forecasting.
The collaboration underpinning these findings, prominently the MULTI-MAREX project, epitomizes cutting-edge geoscientific synergy. This initiative, funded under the German Marine Research Alliance (DAM), unites multidisciplinary expertise and deploys long-term oceanic sensor arrays to monitor extreme marine natural hazards in the Mediterranean. Data integration from seafloor platforms, aerial remote sensing, and terrestrial seismic stations, coalesced via AI analytics, facilitated the near real-time reconstruction and comprehensive understanding of the crisis’s unfolding.
Notably, despite a decline in seismic events following the initial swarm, scientific scrutiny remains relentless. GFZ researchers maintain repeated gas and thermal monitoring campaigns on Santorini, while GEOMAR continues operating an array of seabed sensor nodes, ensuring ongoing vigilance. Such sustained observation is critical not only for immediate hazard mitigation but also for enriching global scientific knowledge about magma-driven seismicity and volcanic plumbing systems.
Project leaders emphasize the importance of prompt data sharing with Greek governmental authorities, enhancing risk management and public safety. Prof. Heidrun Kopp from GEOMAR highlights how close international scientific cooperation has facilitated timely assessments and improved situational awareness during the crisis. Co-author Prof. Paraskevi Nomikou from the University of Athens underscores the indispensable nature of this collaboration, which intertwines German technological innovation with local geological expertise to safeguard populations in a geologically active, high-risk environment.
This episode at Santorini and Kolumbo advances planetary geoscience by revealing the intricate physical coupling between adjacent volcanic systems and detailing the magmatic mechanisms generating intense seismic swarms. The successful integration of AI methodologies with traditional observational tools sets a new standard for earthquake analysis and volcanic monitoring worldwide. Furthermore, the insights gleaned from this Mediterranean case will resonate in analogous subduction-related volcanism globally, guiding future efforts to predict, understand, and ultimately mitigate volcanic risk.
Subject of Research: Geological analysis of the 2025 seismic crisis at Santorini and Kolumbo volcanoes
Article Title: Volcanic crisis reveals coupled magma system at Santorini and Kolumbo
News Publication Date: 24-Sep-2025
Web References: DOI: 10.1038/s41586-025-09525-7
Keywords: Earthquakes, Earth tremors, Seismology, Seismic tomography, Natural disasters, Magma, Volcanic processes, Volcanoes, Volcanology
