The volcano at Santorini, one of Greece’s most iconic islands, is showing new signs of activity. A study led by Marius P. Isken, and published in Nature, has revealed that the Santorini and Kolumbo volcanoes, only 7 kilometers (4.34 miles) apart, may share a deep underground magma system.
The findings shed light on the events of early 2025, when a powerful seismic crisis shook the region, forcing Greek authorities to declare a state of emergency.
Signs of unrest emerged months before
Researchers began detecting changes beneath Santorini in mid-2024. Instruments recorded a gradual uplift of the caldera floor, signaling magma movement underground. Gas emissions from the island’s central vents also rose.
Then, on January 27, 2025, an earthquake swarm erupted northeast of Santorini. Tremors lasted for more than a month, spreading toward Kolumbo and the surrounding islands.
The University of Athens in Greece have reported 15,300+ earthquakes on Santorini in just the past 15 days, something that has never happened in the history of the planet! #Santorini #Amorgos #Greece #Cyclades #Earthquake #Earthquakes pic.twitter.com/gMjSXd1w1C
— LeanneSpurs (@LeanneSpurs) February 16, 2025
The crisis was severe enough that the Greek government declared a state of emergency in Santorini and also closed schools. For an island that draws millions of tourists each year, the emergency measures struck at the heart of Greece’s economy.
By the end of February, the surface displacement of Santorini exceeded 10 cm (almost 4 inches), while Kolumbo’s seafloor had sunk by as much as 32 centimeters (just over 1 foot). Such deformation suggested that large volumes of magma were moving.
Evidence points to a shared magma system
The study combined data from land-based seismic stations, ocean-bottom sensors, GPS measurements, and satellite radar. Researchers reconstructed the magma shift beneath the two volcanoes. They found that Santorini’s inflation preceded the intrusion of a massive magma-filled dike—an underground sheetlike body—that originated from Kolumbo.
About 0.31 cubic kilometers (74 billion gallons) of magma intruded into a 13-kilometer (about 8 miles) long fracture, reactivating faults in the crust before halting just a few kilometers below the seafloor.
The simultaneous inflation at Santorini and deflation at Kolumbo suggest the two volcanoes may be hydraulically linked. Magma appears to migrate between their reservoirs, showing they are not independent systems as once thought.
Historic eruptions loom large in Greece’s memory
Santorini and Kolumbo belong to the same volcanic field and both have a record of explosive eruptions that shaped Greek history.
The Minoan eruption of Santorini around 1600 BCE devastated Aegean civilizations and remains one of the largest eruptions in the last 10,000 years. Kolumbo erupted in 1650 CE, killing people on Santorini and nearby islands and generating a tsunami that struck the Aegean coast.
The new study suggests the 2025 unrest is part of a long cycle of rejuvenation. It also confirms earlier hints that the two volcanoes can influence each other. Historical accounts even describe simultaneous activity at both sites. For Greece, these findings reinforce the urgent need for long-term hazard planning across the Aegean.
Outlook for hazards and monitoring in Greece
Analysis of more than 30,000 events revealed that the dike intrusion expanded in bursts. Each surge coincided with larger quakes and rapid surface deformation. Between surges, smaller quakes indicated gradual magma pressurization.
The model also shows that magma flowed from a mid-crustal reservoir beneath Kolumbo into the dike, while Santorini’s shallow chamber inflated. This pattern suggests a complex, multi-storage system where reservoirs interact and sometimes compete for magma supply.
Although no eruption followed the crisis, scientists warn that the interplay between Santorini and Kolumbo increases the risk of future activity.
The dike stopped before reaching the surface, but its shallow path—through crust only a few kilometers thick and in waters less than 200 meters (656 feet) deep—raises concern. Such conditions could make any future eruption more explosive and potentially disruptive for Greece.
Need for monitoring and preparedness in Greece
The study highlights the importance of high-resolution monitoring. Greek institutions, including the National Observatory of Athens and Aristotle University of Thessaloniki, already play a central role in tracking seismic and volcanic activity. However, as the 2025 crisis showed, even with clear warning signs, predicting the exact course of events remains difficult. Continuous observation and preparedness are essential to safeguard Greece’s people, heritage, and future.
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