Campi Flegrei, a massive volcanic crater beneath Naples, Italy, has started shaking with increasing intensity. In June 2025, a powerful magnitude 4.6 earthquake struck the region, rattling buildings across the entire area. Scientists confirm this quake represents the latest jolt in an accelerating seismic pattern that residents can no longer ignore.

The ground beneath this region has been rising steadily for two decades. Since 2005, GPS equipment around Pozzuoli measured more than 3.3 feet of uplift, with recent data suggesting the total now reaches closer to 4.6 feet. Each time the Earth rises, it triggers swarms of smaller earthquakes, signaling the mounting pressure building beneath the crater. This unrest phase began around 2005 and accelerated sharply after 2012.

The situation mirrors a crisis in the early 1980s, when ground movement forced authorities to evacuate tens of thousands of people from Pozzuoli’s historic Rione Terra neighborhood. Streets cracked, buildings warped, and entire blocks saw permanent abandonment. This time, unrest persists far longer than the 1980s crisis, creating ongoing anxiety among residents living in the red zone today.

An Ancient Underworld Awakens in Modern Times

Ancient Romans viewed this volcanic landscape as a literal gateway to hell. Lake Avernus, a crater lake within Campi Flegrei, was described by ancient writers as Hades’ entrance, with toxic fumes supposedly deadly to birds flying overhead. Nearby, the Solfatara vents sulfurous steam from its boiling crater, and visitors are currently unable to access the area.

Modern scientists invoke this ancient mythology regularly, referring to Campi Flegrei as the “gateway to the underworld” as unrest surges once again. When Campi Flegrei last underwent a catastrophic transformation, it produced a massive eruption that blanketed much of Europe in ash, changing the landscape.

Geologic studies place the Neapolitan Yellow Tuff eruption at approximately 14,000–15,000 years ago—one of two enormous collapses that carved the 8-mile-wide crater visible today. This contrasts sharply with the much smaller 1538 Monte Nuovo eruption that occurred centuries later as a minor event. Roughly 500,000 people now inhabit the restless ground within Italy’s official Campi Flegrei red zone.

This high-risk area includes Pozzuoli, Bacoli, Monte di Procida, Quarto, and western Naples neighborhoods—all located within or above the caldera itself. For these residents, home literally sits inside a supervolcano. Civil Protection evacuation plans assume that authorities could relocate all residents within approximately 72 hours should alert levels reach the highest designation, although such an operation would face enormous logistical challenges.

Living with Uncertainty and Growing Risk

Italy’s National Institute of Geophysics and Volcanology monitors Campi Flegrei with unprecedented intensity, deploying seismic stations, GPS receivers, tiltmeters, and gas sensors across the entire caldera. These instruments transmit real-time data to the Vesuvius Observatory in Naples, where officials track every tremor and ground movement.

A significant 2025 study applied artificial intelligence to three years of seismic data and made a remarkable discovery: machine-learning models identified over 54,000 earthquakes compared to roughly 12,000 manually detected events using traditional methods. Although many earthquakes remained small and barely noticeable, they revealed dense, shallow fracturing throughout the crust, indicating a far more stressed system than experts had realized.

One Nature commentary called the risk “non-negligible but still low,” urging monitoring and preparation over unnecessary panic. Yet scientists warn that smaller eruptions beneath this densely populated region could cause widespread devastation. Officials face a difficult task: warn residents adequately without triggering mass evacuations. Civil Protection maintains Campi Flegrei at yellow alert rather than orange or red, despite strong recent quakes.

Residents choose to stay because economic ties, cultural heritage, and family bonds anchor them firmly to their homes. Scientists refine models; officials update emergency plans. The risk never reaches zero. Naples confronts an unanswered question: how long can so many people safely inhabit an awakening volcanic crater?

Sources
NPR, 25 Nov 2025
Popular Mechanics, 6 Jul 2023
Nature “Weighing the risk at Campi Flegrei”, 2023
Geographical, 19 Dec 2023
Phlegraean Fields Red Zone documentation, 6 Oct 2023
INGV bulletins, 2012–2024