Roughly half a million people live inside the Campi Flegrei caldera, a restless volcanic system pressed against the western edge of Naples. Ground beneath the town of Pozzuoli has risen about 118 cm since 2005, earthquake counts have climbed in a super-exponential pattern over two decades, and satellite radar has identified a pressurized source sitting just three to four kilometers below the surface. On 30 October 2025, Italy’s Civil Protection Department responded by issuing Decreto n. 3236, approving new alert levels tied to the 2023 bradyseism emergency law. The question facing scientists and civil authorities is whether these converging signals point toward a larger volcanic event or a prolonged period of unrest that stops short of eruption.
Why accelerating uplift and seismicity at Campi Flegrei demand attention now
The caldera’s current unrest phase is not new, but its pace is changing. A peer-reviewed synthesis published in Communications Earth and Environment found that uplift followed a parabolic increase from 2000 through 2023, reaching roughly 118 cm by December 2023. Earthquake counts and seismic energy release over the same period rose in a super-exponential curve, meaning the rate of increase itself kept growing. That trajectory separates the current episode from earlier bradyseism crises in the 1970s and 1980s, which produced dramatic uplift but eventually subsided.
The hypothesis that a penny-shaped magmatic source at 3.8 km depth beneath Pozzuoli is migrating laterally along a newly forming fault is plausible but not yet confirmed by direct observation. If magma supply continued at the pace recorded between 2018 and 2020, such lateral movement could shift the center of the deformation anomaly within roughly 18 months, producing a measurable change in the uplift pattern. That shift has not been documented so far. What has been documented is a localized geodetic anomaly that interrupted the caldera’s typical bell-shaped uplift pattern between 2021 and 2023, suggesting the subsurface pressure system is not behaving as a simple, static point source.
Satellite radar and seismic data reveal a shallow, evolving pressure source
Three independent lines of peer-reviewed evidence build the case that magma or magmatic fluids are accumulating at shallow depth. First, a geodetic inversion study using multi-platform InSAR data spanning 2011 to 2022 resolved an inflating source at roughly three to four kilometers depth. The same analysis identified a possible new pulse of activity around 2018 to 2020, consistent with fresh material entering the shallow reservoir. The authors used ascending and descending satellite tracks to constrain the geometry of the source, helping to distinguish between a vertically elongated body and a flatter, lens-shaped intrusion.
Second, a separate InSAR and GNSS study detected a localized deformation anomaly beneath Pozzuoli during 2021 to 2023. That anomaly produced an uplift deficit of about 9 cm relative to what the standard bell-shaped pattern would predict. Inverting the satellite data pointed to a penny-shaped source at 3.8 km depth with a radius of about 1.2 km. The deficit suggests that part of the caldera floor is responding differently to the pressure below, possibly because local rock properties or fluid pathways have changed. Instead of acting as a rigid lid over a single inflating chamber, the crust appears to be partitioning stress and deformation into smaller, evolving blocks.
Third, a study published in Communications Earth and Environment traced how earthquake clustering evolved since roughly 2023 into an organized plane consistent with an emerging fault structure. Seismic events that were once scattered throughout the shallow crust began to align along a dipping surface, with focal mechanisms indicating a mix of shear and opening motion. If that fault acts as a conduit for rising fluids or magma, it could connect the deeper pressure source to shallower layers more efficiently than the surrounding rock. The combination of an identified shallow source, a deformation anomaly that breaks the expected pattern, and a fault that may channel material upward is what gives the current unrest its distinctive character.
These findings do not guarantee that an eruption is imminent. Many calderas experience prolonged unrest, including uplift and intense seismicity, without progressing to surface activity. However, the super-exponential growth in earthquake rates, the sustained ground deformation, and the evidence of structural reorganization at depth all point to a system that is changing in ways that are not yet fully understood. For civil protection planners, the uncertainty itself is a hazard: it complicates decisions about when to trigger evacuations, how to communicate risk, and where to invest in infrastructure reinforcement.
Italy’s updated alert framework and the gaps that remain
The Italian government’s response arrived on 30 October 2025, when the Civil Protection Department issued a new decree establishing updated alert levels and operational phases for the caldera. The decree ties directly to the 2023 bradyseism emergency law and references discussions by the Major Risks Commission, the scientific advisory body that evaluates volcanic hazard for the Italian government. By formalizing new thresholds, the decree acknowledges that the caldera’s behavior has moved beyond the parameters that earlier frameworks were designed to handle.
The updated framework defines color-coded alert states linked to specific combinations of seismicity, deformation, and gas emissions. Each state corresponds to a set of operational measures, from enhanced monitoring and public information campaigns at lower levels to possible evacuations and transport restrictions at higher ones. The intent is to create a transparent, pre-agreed ladder of responses that can be activated as conditions change, reducing the scope for ad hoc decisions under pressure.
Yet several gaps in the public evidence base remain open. No publicly available primary dataset of daily or weekly CO2 flux measurements from the monitoring network after 2023 has been cited in the published studies, even though gas emissions are a key indicator of magmatic activity. Without consistent, high-resolution gas data, it is difficult for independent researchers to test whether the inferred shallow source is dominated by magma, superheated fluids, or a mixture of both. The full seismic catalogs with precise hypocenter locations and moment tensors used to identify the emerging fault plane remain behind journal paywalls or in internal archives, limiting external scrutiny of the fault interpretation.
Similarly, the geodetic inversions that underpin the shallow source model rely on assumptions about rock elasticity and source geometry that are not trivial to verify. While the multi-platform InSAR analysis provides strong constraints, modest changes in those assumptions can shift the inferred depth or volume change of the source. More open sharing of inversion codes, model priors, and uncertainty estimates would allow a wider community to explore alternative scenarios, including models with multiple interacting sources or time-varying material properties.
On the policy side, Decreto n. 3236 clarifies how national and regional authorities should coordinate during escalating unrest, but it does not fully resolve how to manage long-duration crises that may last for years. Residents of Pozzuoli and surrounding neighborhoods have already endured repeated swarms of shallow earthquakes, building damage from ground shaking, and the psychological strain of living atop a restless volcano. Frequent shifts in alert level, if not carefully explained, risk eroding public trust or prompting “warning fatigue,” in which people begin to discount official messages.
Living with uncertainty on the edge of a restless caldera
For the roughly half a million people inside the Campi Flegrei caldera, the emerging scientific picture is double-edged. On one hand, satellite radar, ground-based instruments, and advanced seismic analysis now provide a far more detailed view of subsurface processes than was available during the crises of the 1970s and 1980s. On the other, that detail reveals a system that is complex, evolving, and only partially constrained by data. The shallow source, localized uplift deficit, and organized fault plane are all real signals, but their ultimate implications for eruption probability and style remain uncertain.
In this context, the most realistic strategy is not to wait for perfect forecasts, but to reduce vulnerability in advance. That means enforcing building codes that account for both strong shaking and potential ash loads, planning evacuation routes that can be activated in stages, and maintaining clear, two-way communication channels between scientists, officials, and communities. It also means investing in open data practices so that independent groups can stress-test official interpretations and help identify blind spots.
Campi Flegrei is unlikely to offer a simple, binary choice between “safe” and “erupting.” Instead, it will probably continue to move through shades of unrest, with periods of relative calm punctuated by swarms, deformation pulses, and shifts in gas emissions. The challenge for Italy’s civil protection system is to translate that fluctuating reality into a set of practical, proportionate actions that protect lives without paralyzing daily life in one of Europe’s most densely populated volcanic regions.
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*This article was researched with the help of AI, with human editors creating the final content.
