Volcanic crisis reveals coupled magma system at Santorini and Kolumbo
- Oct 2
- 3 min read
Seismic activity around Santorini: origins and evolution of the recent earthquake swarm
At the beginning of the year, the Greek island of Santorini and its surroundings experienced tens of thousands of earthquakes. A team of researchers from the GFZ German Research Centre for Geosciences and GEOMAR Helmholtz Centre for Ocean Research Kiel, in collaboration with international partners, has now presented a detailed geological study of this seismic crisis in Nature. The investigation combined data from land-based seismic stations with measurements from ocean-bottom instruments placed near the Kolumbo submarine volcano, located about 7 km northeast of Santorini. Using an innovative AI-supported technique for earthquake localization, the scientists were able to reconstruct subsurface processes with unprecedented precision. Their analysis indicates that approximately 300 million cubic metres of magma ascended from the deep crust and accumulated at a depth of around four kilometres beneath the seabed. This upward migration of magma through the crust generated the large number of earthquakes and tremors observed during the crisis.
Geological setting – a seismically active region
Santorini lies within the eastern Mediterranean on the Hellenic volcanic arc, one of the most active tectonic zones in Europe. The island itself forms the rim of a caldera produced by a major eruption about 3,600 years ago. Nearby, the Kolumbo submarine volcano remains active. The area is intersected by major faults linked to the northward movement of the African Plate beneath the Hellenic Plate, where fragmented microplates generate both tectonic and volcanic activity.
Santorini has a long record of eruptions, the last in 1950. Large earthquakes in 1956 between Santorini and Amorgos (M 7.4 and M 7.2) triggered a destructive tsunami. In early 2025, more than 28,000 earthquakes occurred in the same region, some exceeding magnitude 5.0. The swarm caused public concern, as the origin—tectonic or volcanic—was initially unclear.
Magma movement – results of the new study
Recent analyses show that the crisis was driven by magma intrusion. The process started in mid-2024, when magma accumulated beneath Santorini, causing a subtle uplift. By January 2025, seismicity intensified, and magma rose in pulses from ~18 km depth to ~3 km below the seafloor, shifting northeast toward Kolumbo. This pattern, confirmed by seismic data, InSAR, GPS, and ocean-bottom instruments, traced the upward migration of magma and revealed a hydraulic link between Santorini and Kolumbo.
Methods and implications
Key advances included an AI-based algorithm for earthquake localization and seafloor sensors installed by the MULTI-MAREX project. These measured both seismic signals and pressure changes, capturing subsidence of up to 30 cm above the magma reservoir. Ongoing monitoring combines gas and temperature measurements on Santorini with seabed sensor arrays at Kolumbo.
Close collaboration between GFZ, GEOMAR, the University of Athens, and international partners allowed near real-time tracking of the crisis and rapid communication with Greek authorities. The findings improve understanding of the coupled volcanic system and strengthen the scientific basis for hazard assessment in this geologically active region.
About: MULTI-MAREX
MULTI-MAREX is one of four projects in the research mission ‘Paths to improved risk management in the area of marine extreme events and natural hazards’ (mareXtreme), which is being implemented by the German Marine Research Alliance (DAM). It brings together ten partner institutions from six universities and the two Helmholtz Centres GFZ and GEOMAR in Germany. The aim is to develop a real-world laboratory for investigating geomarine extreme events such as earthquakes, volcanism and tsunamis in the central Mediterranean region.
Isken, M., Karstens, J. et al. (2025). Volcanic crisis reveals coupled magma system at Santorini and Kolumbo. Nature. https://doi.org/10.1038/s41586-025-09525-7
National Geographic: https://www.nationalgeographic.com/science/article/santorini-earthquake-swarm-volcano-magma
Science Journal: https://www.science.org/content/article/thousands-quakes-struck-major-greek-volcano-mapping-plumbing-beneath-it
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