Topic: Earth Science

Scientists have discovered what caused a massive earthquake swarm in Santorini. Roughly 300 million cubic meters of magma rose from deep within the crust and stalled beneath the seafloor, triggering thousands of earthquakes.

Santorini, an island in the eastern Mediterranean, was hit by over 28,000 earthquakes in early 2025. The intense shaking began in late January and lasted for several weeks. Scientists have now figured out what caused this seismic crisis. A team of researchers from Germany's GFZ Helmholtz Centre for Geosciences and GEOMAR Helmholtz Centre for Ocean Research Kiel, along with international partners, conducted a detailed study to understand the events that led to the earthquakes.

Their analysis shows that magma rose from deep within the Earth's crust and stalled about four kilometers beneath the seafloor. As this molten rock pushed upward, it fractured surrounding rock layers, triggering thousands of earthquakes and tremors. The team used data from land-based seismic stations and ocean floor instruments installed at the underwater volcano Kolumbo to reconstruct what was happening deep below the surface.

The researchers also applied a newly developed artificial intelligence method to pinpoint earthquake locations with far greater precision. Their findings point to magma rising from depth as the driving force behind the swarm. The process actually began months earlier, in July 2024, when magma started accumulating in a shallow reservoir beneath Santorini, causing the island to lift slightly by a few centimeters.

The scientists combined detailed earthquake mapping with satellite radar measurements (InSAR), GPS stations, and seafloor sensors to model the sequence of events. Dr. Marius Isken, a geophysicist at GFZ and one of the two lead authors, explains: '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.'

Why It Matters

This study helps us understand how volcanic systems work and can provide insights into predicting earthquakes in similar regions.

Key Facts

• Over 28,000 earthquakes were recorded in Santorini in early 2025.
• The earthquakes were caused by magma rising from deep within the Earth's crust and stalling beneath the seafloor.
• The process began months earlier, in July 2024, when magma started accumulating in a shallow reservoir beneath Santorini.

Key Terms

Magma

molten rock that rises from deep within the Earth's crust

Implications

This study helps us understand how volcanic systems work and can provide insights into predicting earthquakes in similar regions.