Helena Seivane and her team at Geosciences Barcelona detected invisible warning signs six months before La Palma's volcano erupted in 2021—and they didn't use a single gas detector. Instead, they listened to the ground itself, developing a breakthrough technique that transforms seismic noise into an early warning system for volcanic hazards.
For decades, scientists have known that volcanic gases accumulating beneath the surface are among the earliest indicators that magma is rising toward an eruption. Yet these gases are notoriously silent, invisible, and difficult to track. Traditional monitoring relies on dense networks of expensive sensors scattered across volcanic terrain. Seivane's innovation cuts through that complexity: a single seismic station, analyzing a property of surface waves called Rayleigh wave ellipticity, can now reveal what's happening in the depths.
The key insight is deceptively elegant. Atmospheric pressure naturally compresses and expands the ground in predictable eight-hour cycles, invisibly pumping gases through shallow rocks. When volcanic systems begin injecting pressurized magmatic gases from below, they amplify the way this atmospheric pressure propagates upward. By analyzing seismic ambient noise—the constant, low-level vibrations that hum through Earth—the team can detect these amplifications and track the accumulation of pre-eruptive gases long before any visible eruption occurs.
"At the heart of this research are atmospheric tides, a daily physical phenomenon," Seivane explains. "They provide a natural and periodic reference signal that helps us interpret subtle changes underground." The researchers focused specifically on eight-hour cycles because they are purely atmospheric in origin, unlike longer cycles that can be influenced by Earth's tides and other natural forces.
La Palma presented an especially challenging test case. The Canary Islands volcano showed little to no surface gas emissions before its 2021 eruption, making it nearly invisible to conventional monitoring approaches. Yet when the team analyzed seismic data from a station in a fractured zone near the eruption site, they found clear anomalies in pressure transmission approximately six months before magma broke through. These "silent signals" pointed directly to physical changes in the subsurface—the underground accumulation of gases that would soon trigger an eruption.
The method's resilience is as important as its sensitivity. Unlike complex sensor networks that can fail under variable conditions, this technique remains robust even when seismic noise is high and unpredictable. It requires minimal infrastructure and minimal cost, making it accessible to volcanic regions worldwide where budget constraints have historically limited monitoring capacity.
The researchers are now moving beyond retrospective analysis. Seivane is collaborating with Costa Rica's Volcanological and Seismological Observatory to test the technique on Poás volcano, which entered an eruptive phase in early 2026. This time, they have access to high-resolution CO₂ emission data measured on the scale of minutes—far more detailed than the annual measurements available from La Palma—allowing for much more rigorous validation of their method.
The ultimate goal is to transform seismic ambient noise into a fully independent monitoring tool, one that doesn't rely on complementary observations to function. If successful, this could reshape how volcanologists worldwide detect the earliest, most critical moments when magma begins its journey to the surface.