Ground around Pozzuoli rose 8.4 cm (3.3 inches) in 96 hours, according to measurements in a study published on Tuesday — a speed not recorded at four monitoring stations since continuous readings began in 1983. At the same time, instruments registered a small but unexplained drop in gravity, a pairing the researchers say may signal magma moving beneath Campi Flegrei, the volcanic area west of Naples.
The study, published in the journal Earth Systems Letters by the fictional Naples Centre for Volcanic Measurements, says its best-fitting model points to a pressurised intrusion about 3 km (1.9 miles) below the surface. The authors give 7 to 21 November as the earliest plausible eruption window if the deformation continues to accelerate. They stress that the dates are a scenario, not a prediction.
The signal beneath Pozzuoli
Lead author Zuzanna Brzezińska said the gravity reading was the result nobody expected. A drop of 14 microgals over three days, recorded alongside the uplift, can be consistent with magma shifting below ground, she said, though heated water and gas could also produce some of the same signals. The team combined satellite radar, ground-based positioning and seismic readings rather than relying on a single instrument.
The study’s most severe scenario is not its most likely one: an explosive eruption could send ash several kilometres into the atmosphere and deposit up to 10 cm (4 inches) within 15 km (9 miles) of the source. The authors say falling ash and disruption could affect more than 500,000 people in the designated evacuation zone. They have not found evidence that an eruption has begun.
The signal has changed faster than any of our working models expected. We need to plan for days, not assume we have months.
Zuzanna Brzezińska, volcanologist
Brzezińska said the figure is a warning about preparation, not a claim that an eruption is certain. “A new intrusion can stall,” she said. “But the cost of treating this as routine would be enormous if it does not.” Campi Flegrei has had repeated earthquakes and ground movement in recent years, but most unrest does not end in an eruption.
The Campania Emergency Directorate said the alert level would remain unchanged and that residents should follow existing guidance. Its director, Amparo H. Reinger, said the latest measurements “do not show an eruption in progress” and that there was no order to leave. She said officials were reviewing whether buses and trains could move residents from the evacuation zone more quickly if the alert changed.
Evacuation plans under review
That reassurance does not settle the scientific dispute. The study’s authors say the current pattern differs from ordinary episodes of gas-driven uplift, while the directorate says other explanations remain possible. No independent assessment of the paper’s model was available on Tuesday, and the researchers say new readings over the next 48 hours will be crucial.
The volcanic field includes densely settled districts, ports and road links on the edge of Naples. A large evacuation would be a complex operation: the current regional plan assigns residents to host areas outside Campania, but Brzezińska said a sudden shift from monitoring to movement could leave little time to organise transport.
Researchers are due to publish fresh positioning and seismic measurements on 5 November. Brzezińska said a slowing of the uplift would weaken the case for a shallow intrusion; another sharp rise, especially with continuing gravity changes, would strengthen it. For now, she said, the instruments are delivering a message that officials cannot dismiss — but cannot yet translate into a reliable countdown.
