A restless supervolcano near Naples keeps rising and shaking

Campi Flegrei, a broad volcanic caldera immediately west of Naples, has been lifting and producing frequent earthquakes during a long episode of unrest. The movement reflects pressure changes beneath a densely populated landscape that includes Pozzuoli and parts of metropolitan Naples. Scientists monitor the system continuously, but unrest does not by itself mean that an eruption is imminent.

Campi Flegrei is a caldera, not a single cone

The volcanic field spans a wide depression dotted with craters, fumaroles and hot springs. Its Italian name means the Phlegraean Fields, or burning fields. Unlike nearby Vesuvius, the system does not present one dominant summit. Past eruptions have opened vents at different places across the caldera, complicating both monitoring and hazard planning.

Italy’s National Institute of Geophysics and Volcanology describes Campi Flegrei as an active caldera showing ground uplift, shallow local earthquakes and increased fumarolic gas flow since the second half of 2005. The agency says the process intensified markedly from 2023, particularly between Pozzuoli and Bagnoli.

Bradyseism raises and lowers the ground

The slow vertical motion is called bradyseism. Pressure changes in the crust can deform rock and push the surface upward; later relaxation can allow subsidence. Campi Flegrei has experienced repeated uplift and sinking over centuries, leaving evidence on buildings and ancient shoreline features around Pozzuoli.

Modern instruments measure the process with satellite radar, ground-based positioning stations and precise leveling. INGV research links changes within the volcanic system with the deformation and seismic activity measured at the surface. The connection is expected because deforming rock accumulates stress and can break along small faults.

Earthquake swarms map stressed rock

Many Campi Flegrei earthquakes are shallow and small, but shallow events can be felt sharply near their epicenters. Swarms occur when many earthquakes cluster in time. Scientists examine their depth, location, magnitude and fault orientation to determine how stress is moving through the caldera.

Earthquakes are not a direct countdown to eruption. Fluids, gas and heated groundwater can change pressure without magma reaching the surface. Magma may also contribute heat and gas from greater depth. Separating those processes requires several data streams rather than one dramatic quake or a short burst of uplift.

Gas chemistry offers another view underground

Fumaroles at Solfatara and Pisciarelli release steam and volcanic gases. Changes in temperature, gas ratios and flow can reveal shifts in the hydrothermal system. The shallow network of hot water, steam and fractured rock may amplify pressure changes, so scientists compare gas observations with deformation and earthquake patterns.

No instrument can see a simple open chamber beneath the caldera. Interpretation depends on seismic imaging, geochemistry and physical models. Different mechanisms can create similar surface signals, and uncertainty remains part of any forecast. That is why official assessments use probability and alert levels instead of declaring a certain outcome from one measurement.

Unrest is not a prediction of imminent eruption

Campi Flegrei’s large past eruptions inspired the popular label supervolcano, but the term can distort the present risk. A future eruption, if one occurred, would not automatically match the system’s largest ancient events. Vent location, magma volume, warning time and interaction with groundwater would all shape the consequences.

INGV stressed in a 2026 clarification that a preliminary study did not provide a deterministic prediction of an imminent earthquake or eruption. The institute said monitoring continues around the clock and directed the public to official institute and civil-protection communications.

Dense development turns geology into a planning problem

Hundreds of thousands of people live within or near the caldera. Even unrest without eruption can damage older masonry, close buildings and strain public confidence. Evacuation planning must account for narrow roads, coastal geography and the possibility that the location of a new vent could remain uncertain until late in a crisis.

Continuous unrest therefore deserves serious attention without fatalism. Rising ground and earthquake swarms are real evidence that the system is changing. Their greatest value is as part of an integrated monitoring record that helps authorities update hazards, strengthen structures and prepare routes before a volcanic emergency.

Civil-protection planning separates several possible hazards. Strong shallow earthquakes can damage vulnerable buildings before any eruption. Hydrothermal explosions may affect a limited area around fumaroles. An eruption could produce ash, ballistic fragments, pyroclastic currents or lava, with the mix depending on vent location and magma-water interaction. Maps and exercises must account for those different footprints instead of treating every episode of unrest as one all-or-nothing scenario.

The caldera also provides a lesson in communicating uncertain risk. Reassurance without evidence can leave residents unprepared, while claims of certain catastrophe can erode trust and disrupt daily life. Measurements, alert levels and dated official explanations create a more useful middle course. They show that Campi Flegrei is active and worthy of sustained preparation, while preserving the scientific distinction between detected unrest and a reliable eruption forecast.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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