When the Greek island of Santorini was rocked by thousands of small earthquakes earlier this year, most were left puzzled by the swarm’s cause. Over 10,000 people were evacuated as tremors struck every few minutes for over a month. The largest quake reached a magnitude of 5.3, but the origin wasn’t immediately clear until groundbreaking new research shed light on a hidden force deep beneath the Earth surface.
University of Oregon geophysicist Emilie Hooft, however, wasn’t mystified. Just days before the seismic swarm began, her lab had submitted research that turned out to hold the key to understanding the quakes: the activity wasn’t tectonic but volcanic driven by magma movements buried deep below the surface.
A Hidden Magma Reservoir Off the Volcanic Center
Hooft team discovered that magma was moving 6 to 9 miles beneath the crust, not directly under the volcanoes, but offset near the exact location of the earthquake swarm. Using powerful sound-wave imaging, her team identified a deep magma reservoir that previously went undetected because it wasn’t aligned with Santorini’s well-known volcanic features.
Two doctoral students in her lab Beck Hufstetler and Kaisa Autumn led key parts of this research. Hufstetler mapped melt content using sound waves, while Autumn used reflected seismic waves to detect the deeper magma reservoir, aligning precisely with where the earthquakes were felt.
Rethinking Volcanic Activity
This new data challenges long-standing assumptions. Because the earthquakes didn’t line up with visible volcanic cones, many initially believed the cause was tectonic. But Hooft’s team showed that magma can travel sideways through fault lines, far from the volcanic surface features we typically associate with eruptions.
This finding is part of a growing shift in volcanic science, recognizing that magma reservoirs and pathways are more complex and further reaching than previously thought.
Mapping the Deepest Parts of Earth’s Volcanic Plumbing
Hooft has studied Santorini’s volcanic system since 2015 and led one of the largest seismic imaging projects ever conducted at a volcano. Her team sent sound waves from air canisters through the ocean crust like an ultrasound of the Earth to detect different materials, including rock, lava, and magma.
Earlier efforts had only probed 3 to 4 miles into the crust. But using more advanced techniques, Hooft’s team successfully imaged all the way down to the lower crust, which is typically up to 15 miles thick.
They found that magma travels through fault cracks, sometimes laterally, creating “plumbing” networks that could spark earthquakes or even eruptions far from known volcanic centers.
Preparing for Future Hazards
Hooft hopes this research will help develop early warning systems and better hazard assessments, especially in geologically active areas like the southern Aegean.
The findings were published in two studies in the journal Geochemistry, Geophysics, Geosystems, offering some of the most detailed views to date of how magma interacts with Earth’s crust.
As Santorini continues to simmer beneath the surface, this research is a powerful reminder that volcanic systems can extend well beyond what we see and understanding their hidden complexity is key to staying ahead of the next eruption.