Earlier this year, the iconic Greek island of Santorini was rocked by an unusual and persistent series of small earthquakes that left residents and scientists puzzled. The tremors, some occurring every few minutes, lasted over a month, reached magnitudes as high as 5.3, and forced more than 10,000 people to evacuate the area. But new research from a University of Oregon geophysicist suggests the answer lies not in tectonic shifts, but in deep volcanic unrest hidden beneath the island’s surface.
Just days before the seismic swarm began, Dr. Emilie Hooft and her team submitted a study offering new insights into the volcanic plumbing system under Santorini. Their findings now appear to shed light on the true cause of the earthquakes: magma shifting 6 to 9 miles beneath the surface — not directly under the volcano, but offset in a way that had previously gone undetected.
New Discoveries in the Volcanic Plumbing
Using sound waves to probe deep into the Earth’s crust, Hooft and her doctoral students conducted one of the most comprehensive seismic imaging projects ever performed on a volcano. Their research, recently published in Geochemistry, Geophysics, Geosystems, revealed a deep-seated magma reservoir located far from the main volcanic cone and nearby active seamount.
“We discovered magma stored in a region of the crust offset from known volcanic centers,” Hooft said. “This deep magma reservoir was the very site where the earthquake swarm began evidence of magma moving sideways through cracks in the crust.”
Two Ph.D. students contributed significantly to the study: Beck Hufstetler mapped the melt content in the magma system using sound wave analysis, while Kaisa Autumn used a different seismic method to image the deeper crust, aligning perfectly with the recent seismic swarm’s origin point.
Magma Doesn’t Always Sit Beneath the Volcano
Because the quakes didn’t originate directly under any known volcanic structure, many scientists initially attributed them to tectonic faults in the region. But Hooft’s findings suggest that magma often travels through complex underground routes guided by fault lines and cracks far from the visible volcanic peaks.
“Volcanic unrest shouldn’t be seen as an isolated phenomenon under a single mountain,” she explained. “Instead, it’s part of a much broader and evolving system involving magma, faults, and the crust. This is a key shift in how we assess future volcanic hazards.”
A Long-Term Effort to Understand Santorini’s Underworld
Hooft’s work builds on nearly a decade of research. In 2015, she launched an international expedition to carry out extensive seismic imaging around Santorini. Over a month, her team operated 24/7, sending bursts of compressed air into the ocean to create sound waves that penetrated the volcanic system. These waves acted like an ultrasound, bouncing back from different layers of rock, magma, and water to form a detailed map of the crust.
Their research successfully imaged the crust to unprecedented depths well beyond the 3 to 4 miles typically reached in earlier studies. In fact, their data extended nearly 9 miles deep, revealing how magma interacts with crustal faults and opens underground channels that can eventually lead to surface activity.
Implications for Early Warning and Volcanic Hazard Detection
The findings have wide-reaching implications, not just for Santorini, but for other volcanic regions where magma may be moving in hidden ways. With increasing global populations living near active or dormant volcanoes, the need for better early warning systems is urgent.
“Understanding how and when magma moves is critical for improving volcanic hazard forecasting,” Hooft said. “These deep crustal insights are helping us spot the signs of volcanic activity before it erupts literally and figuratively.”
As Santorini returns to calm, researchers like Hooft hope to continue building on this work to anticipate future unrest. The seismic swarm that shook the island may now serve as a landmark case in redefining how scientists detect and interpret hidden volcanic behavior.