Can a volcano be stopped before it erupts? A recent study found the answer

The ground around Italy’s Campi Flegrei volcano has lurched up and down for centuries, but in the early 1980s it shot upward more than 6 feet with no warning, forcing ships to abandon Pozzuoli’s harbor and 40,000 residents to leave their homes.

A new study pins the blame on rising water pressure rather than molten rock, pointing to a fix that sounds more like civil engineering than volcanology.

Scientists suggest they should pump out water or keep rain from sneaking underground to prevent the volcano from erupting, or at least give ample warning to nearby populations. Tiziana Vanorio at the Stanford Doerr School of Sustainability led the work with colleagues in Italy and the United States.

Campi Flegrei keeps towns on edge

The eight mile wide caldera sits just west of Naples and houses 350,000 people, making it Europe’s most densely inhabited volcanic field.

Its slow swell and sag pattern is called bradyseism, a term coined in the nineteenth century for “slow shaking.”

During bradyseismic surges, clusters of small quakes rattle walls, crack roads, and rouse memories of the 1538 Monte Nuovo eruption, a steam charged blast that built a new hill in eight days.

That history forces Italian officials to weigh disruptive evacuations each time seismic swarms intensify.

Hidden pump beneath Pozzuoli

Vanorio’s team combined 40 years of satellite, seismic, and rainfall records. They found that quakes begin about one mile down, inside a sealed hydrothermal reservoir capped by cemented volcanic ash known as caprock.

As rain and runoff percolate downward, the reservoir slowly fills, pressure rises until fractures pop open, releasing steam and triggering quakes.

“To address the problem, we can manage surface runoff and water flow, or even reduce pressure by withdrawing fluids from wells,” said Vanorio.

Because the caprock later “heals,” the system resets, starting a new pressure cycle that explains why unrest reappears every few decades. 

From rainwater to earthquakes

Weather stations in the Apennine foothills show that annual rainfall swings higher with each passing year, pointing to faster recharge of underground water since the late 1990s.

Rising pressure first lifts the ground, GPS units near Pozzuoli measured a fresh 3 foot bulge between 2005 and 2024, and then loosens locked faults, unleashing swarms that now include magnitude 4 shocks.

Once fractures vent steam, the surface often subsides. That cycle fits a phreatic eruption model, driven by flashed water, not an influx of magma or gas from the deeper melt zone almost 5 miles down.

Testing the lid in the lab

To watch the caldera’s “lid” in action, the researchers packed volcanic ash and crushed rock into a steel vessel, saturated it with calcium rich brine, and heated the mix to 390 degrees F.

Within a day, mineral fibers wove through cracks, knitting the sample into a dense seal that mimicked natural caprock.

Stress tests showed that this fiber reinforced seal can withstand about 6,500 pounds per square inch before breaking, yet once broken and re-cemented, it becomes even stronger, trapping the next pulse of water.

The lab results match seismic tomography that maps a tight, low permeability band above the pressurized reservoir.

Volcano warnings from climate

As rainfall patterns shift due to climate change, southern Italy is expected to experience more intense but less frequent storms.

This can lead to larger volumes of water entering the underground system all at once, overwhelming the natural drainage capacity.

These surges may speed up pressure buildup in the sealed reservoir beneath Campi Flegrei, potentially shortening the intervals between seismic swarms.

The research team notes that adapting risk strategies for a changing climate will be key to protecting communities near volcanic zones.

Turning geology into prevention

Because water is easier to manage than magma, the team argues for a “preventive health” strategy. Clearing Renaissance era drainage canals, limiting urban runoff, and pumping from existing wells could bleed off pressure before the ground swells enough to crack.

Modeling suggests that drawing just a few hundred thousand gallons per day from strategic wells would keep reservoir pressure below the fracture threshold.

Vanorio calls the approach “treating the fuel, not the burner,” a view echoed by hazard analysts who note that even a minor reduction in future evacuations would save millions in emergency costs.

Italian civil protection officials have already begun surveying clogged canals identified in the study. If the work leads to pilot pumping tests, Campi Flegrei may become the first restless caldera managed like a municipal water system rather than a lurking super volcano.

Future of volcano warning systems

During the 1982-1984 crisis, the lack of public understanding and preparedness led to confusion and social unrest in Pozzuoli.

Emergency plans were improvised, communication was inconsistent, and many families were displaced without clear timelines for return.

Since then, Italian authorities have improved early warning systems and community education, but gaps remain in coordinating science with policy.

Researchers hope this new model helps bridge that gap, offering data backed solutions that are understandable and actionable for civil protection teams.

The study is published in Science Advances.

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