In February 2025, more than 2,000 earthquakes rocked Santorini and its region, causing massive evacuations on the Greek island. Unlike expectations, no eruption has occurred, and known volcanoes remained silent. This situation forced scientists to review their hypotheses on the origin of tremors. A series of studies by the University of Oregon, published in the journal Geochemistry, Geophysics, Geosystems, reveals that the magma can circulate laterally in the earthly crust, well outside of traditional volcanic buildings.
A seismic swarm unrelated to visible volcanoes
Between the end of January and mid-February 2025, an unusual seismic activity struck the Santorini archipelago. More than 2,000 earthquakes, some reaching a magnitude of 5.3, were recorded in just three weeks. On several occasions, the tremors have followed a few minutes apart. They created a situation of extreme tension for the inhabitants and the authorities. About 10,000 people were forced to temporarily leave the island as a precaution. However, no imminent volcanic eruption signal was detected on the surface.
This discrepancy between the intensity of the phenomenon and the absence of visible volcanic activity first confused scientists. But for Emilie Hooft, geophysicist at the University of Oregon, these earthquakes were part of an already expected diagram. For a decade, his team has scanned the depths of the Caldera de Santorini thanks to a high -precision seismic imaging technique. Using compressed air cannons, researchers emit acoustic waves through the earth's crust to analyze the structure.
© © Emilie Hooft / University of Oregon
On these images, researchers are preparing to deploy an underwater seismometer in the Santorini caldera. © Emilie Hooft / University of Oregon
Their model had already identified an anomaly: a magmatic concentration area several kilometers deep, not aligned with surface volcanoes. This reservoir, moved laterally compared to known eruptive centers, offered a credible explanation to the seismic crisis. A hypothesis that the events of 2025 came to confirm brutally.
Magmatic plumbing much more complex than imagined
In fact, the recent geophysical analyzes led by Emilie Hooft and her team reveal a much more complex underground architecture than we thought under Santorini. The two scientific publications highlighted a partial merger zone located approximately 11 to 13 kilometers below the surface, precisely under the Horst of Anhydros. Unlike expectations, this tank is not located under an active volcano. But it is in a tectonically distorted area, far from the visible eruptive centers.
What the researchers have discovered is that the magma does not always go up directly to a volcano. It can also move laterally, following the natural flaws present in the earth's crust. These flaws act as underground channels, guiding the molten rock for several kilometers before it reaches a magmatic chamber or causes seismic activity.
© © RS HUFSTETLER et al., 2025
Drawing of the interpreted structure of magmatic plumbing under the Caldeira de Santorini and the underwater volcano of Kolumbo.
This complex circulation of magma modifies the way scientists monitor volcanoes. Internal movements are not necessarily centered under volcanic buildings. They can occur at a distance, where geological tensions open ways. This means that volcanic activity can start well outside the areas identified as dangerous until then. This observation calls into question the simplified models. It obliges to widen surveillance on a regional scale, taking into account the interactions between magma, faults and deep structure of the crust.
Two volcanoes, two underground systems
The results of the team made it possible to establish a three -dimensional volcanic plumbing model. This shows a clear separation between the Santorini and Kolumbo systems, despite their geographic proximity. These two circuits are each linked to their own source of magma in depth.
Under Kolumbo, an active submarine volcano located northeast of Santorini, the magma goes up from an intermediate reservoir located between 11 and 13 kilometers deep. This tank is under a tectonic area called the Horst of anhydros. This is where the dyke left at the origin of the earthquakes recorded in early 2025. This magma is chemically distinct. This indicates that it comes from a different section from the earthly mantle, that is to say the layer located under the crust.
In Santorini, the situation is different. Although the volcano has experienced several major eruptions, including the famous Minoan eruption around 1600 BC. AD, the researchers do not detect, for the moment, a reservoir equivalent to that of Kolumbo in the deep seismic images. However, historical data show that its upper tank, located between 3 and 6 kilometers deep, is quickly recharged before large eruptions. Researchers hypothesize the existence of another magmatic food system. He would be buried more deeply and therefore still difficult to imagine.
Towards a new understanding of volcanic risks
The data acquired in Santorini oblige to rethink in depth how scientists identify and monitor volcanic risk areas. Traditionally, surveillance efforts are concentrated around active craters. However, this approach could no longer suffice. Decentrate, invisible, but active reservoirs, can press, crack the crust and trigger seismic crises far from identified volcanoes. In a region as densely populated and touristy as cyclades, this reassessment of priorities becomes urgent.
“” The behavior of a volcano depends on a whole geological system in interaction “Recalls Emilie Hooft. Fails, fractures, composition of the crust, speed of ascent of the magma: so many parameters to integrate into the risk analysis. This paradigm shift does not mean that we know everything, but that it becomes necessary to look differently. “” It is no longer enough to monitor the top of a volcano, you have to understand everything that happens below and around ». This implies extending surveillance to the whole region, integrating the mapping of deep structures and geophysical anomalies.
Better understanding these processes is also better anticipating. Because under the peaceful landscapes of the Aegean Islands, geological forces continue to act. And if we want to protect the populations, we will have to continue to listen to what the earth whispers … before it shouts. The episode of 2025 will have at least had a merit: recall that the volcanoes are not isolated or predictable to the naked eye. In the future, it is in the depths, and sometimes away from the volcanic cones, that alerts could arise.
With an unwavering passion for local news, Christopher leads our editorial team with integrity and dedication. With over 20 years’ experience, he is the backbone of Wouldsayso, ensuring that we stay true to our mission to inform.
