Half a million people live inside Europe's largest active caldera. The ground has risen 140 cm since 2005 and isn't stopping. In February 2026, INGV recorded 70 earthquakes in a single week. And a peer-reviewed analysis projects the system could hit a critical mechanical threshold by 2033.
By VolcanoDB Research Team. Data: Smithsonian GVP, INGV Osservatorio Vesuviano, Italian Civil Protection.
Campi Flegrei in 2026: The Ground Won't Stop Rising
The Phlegraean Fields (Campi Flegrei in Italian, meaning "burning fields") have been in a state of accelerating unrest since 2005. The numbers from INGV's Vesuvian Observatory tell the story: between February 23 and March 1, 2026, seismographs recorded approximately 70 earthquakes in a single week, with magnitudes up to M3.5, concentrated beneath Pozzuoli and the Agnano area.
By the following week (March 2–8), the count dropped to 47 — still elevated, but a relief after the February spike. The instruments continue to detect ground uplift averaging 10 mm per month. That might sound trivial, but it's been sustained for over a year now, and the cumulative effect is massive: roughly 140 cm of total uplift since 2005. Buildings in Pozzuoli have cracked. Streets buckle. The harbor requires periodic dredging because the seafloor keeps rising.
The largest recent earthquake — M4.6 on June 30, 2025 — was felt across Naples and caused minor structural damage. It was the strongest event at Campi Flegrei in decades, and it rattled a population that was already on edge.
Current Unrest Status — May 2026
Ground uplift: ~10 mm/month (140+ cm total since 2005). Seismicity: 47–70 events/week in Feb–Mar 2026, declining but above background. SO2 and CO2 fumarole emissions elevated. INGV classifies the system as in a phase of "accelerating unrest."
No eruption is imminent. Italian Civil Protection maintains a yellow alert (attention) for the Campi Flegrei area. The red zone evacuation plan covers ~500,000 people.
What Is Campi Flegrei? A City Built Inside a Supervolcano
Campi Flegrei is a 12 × 15 km caldera located 20 km west of Mount Vesuvius, stretching from the western suburbs of Naples to the coastline around Pozzuoli and Bacoli. Unlike a single volcanic mountain, Campi Flegrei is a depression — a vast sunken area created by two catastrophic caldera-forming eruptions (39,850 BP and ~15,000 BP) — dotted with at least 24 craters, cones, and vents.
More than 500,000 people live inside the caldera itself. The greater Naples metropolitan area — over 3 million people — sits within potential pyroclastic flow range of a large eruption. It is, by population exposure, the most dangerous supervolcano caldera on Earth.
The name "Phlegraean Fields" comes from the Greek phlegra, meaning "to burn." Ancient Romans knew it as a volcanic area — they placed the entrance to the underworld at Lake Avernus, one of the caldera's crater lakes. The Sybil of Cumae, the most famous oracle of antiquity, had her cave here. The mythological associations weren't accidental: the ground steamed, sulfurous gases rose from fumaroles, and hot springs dotted the landscape.
Bradyseism: The Ground That Breathes
Bradyseism — from the Greek for "slow movement" — is Campi Flegrei's signature behavior. The caldera floor rises and falls over years to decades, driven by pressure changes in the hydrothermal and magmatic systems beneath. No other populated volcanic area on Earth experiences this so dramatically.
The most striking evidence stands in Pozzuoli's waterfront: the Temple of Serapis (actually a Roman macellum, or market). Three marble columns bear distinct bands of marine borings from Lithodomus mollusks — proof that the ground sank below sea level for centuries, then rose back above it. Those borings are the single most famous geological evidence of volcanic ground deformation in the world.
Period
Uplift
Earthquakes
Key Event
1968–1972
170 cm
~600
First modern crisis. 40,000 evacuated from Pozzuoli.
1982–1984
180 cm
~16,000
M4.0 event. 40,000 permanently relocated. Pozzuoli old town partially abandoned.
2005–present
140+ cm
Accelerating
Ongoing, accelerating. M4.6 record (June 2025). Research projects critical threshold ~2033.
The 1982–84 crisis was traumatic for Pozzuoli. Over 16,000 earthquakes in two years, with some events strong enough to crack buildings. The Italian government permanently relocated 40,000 residents to a new town (Monteruscello) on higher ground. Parts of Pozzuoli's historic center were abandoned and have never been fully repopulated. Now, four decades later, the ground is rising again — and this time, geochemical data suggests the driving force is deeper and more magmatic than before.
Eruption History: Two Caldera-Forming Events and 488 Years of Quiet
Our database records 28 eruptions for Campi Flegrei spanning nearly 10,000 years. Two of those eruptions were civilization-scale events. The rest were relatively small. And then — nothing since 1538.
1
~39,850 BP
VEI 7
The Campanian Ignimbrite eruption — the largest explosive eruption in European history. Between 179 and 243 km³ of magma ejected. The eruption column punched into the stratosphere. Pyroclastic flows covered 30,000 km² — an area the size of Belgium. The resulting caldera collapse created the basic outline of the Phlegraean Fields visible today. Some researchers believe this eruption contributed to the decline of Neanderthal populations in Europe, already under pressure from modern humans.
2
~15,000 BP
VEI 6
The Neapolitan Yellow Tuff eruption — Campi Flegrei's second caldera-forming event. Roughly 40 km³ of material erupted. This event created the inner caldera structure and deposited the yellow tuff rock that gives Naples' historic center its characteristic building material. The city was literally built from its own volcanic destruction.
3
~4,600 BP
VEI 5
The Agnano-Monte Spina eruption — the largest eruption in the last 5,000 years at Campi Flegrei. VEI 5, with pyroclastic flows extending several km. This event is a benchmark for modern hazard planning because it represents a realistic 'worst plausible scenario' for the next eruption.
4
1538 AD
VEI 2
The Monte Nuovo eruption — the only eruption in recorded history. Over 8 days (September 29 to October 6), a new mountain grew 133 meters high from flat ground near Pozzuoli. It was the first new land formed on mainland Italy in recorded history. Around 24 people died. Precursory ground uplift of several meters over the preceding decades had been observed — but nobody understood what it meant. Monte Nuovo is still visible today as a wooded hill near the coast.
The 488-year gap since Monte Nuovo is unusual — it's the longest repose period in Campi Flegrei's recent geological history. Volcanologists debate whether this means the system is "winding down" or "building up." The accelerating unrest since 2005 — with geochemical signatures pointing to increasing magmatic input — supports the latter interpretation.
The 2033 Warning: What the Research Actually Says
In April 2026, a paper on arxiv titled "Accelerating unrest at Campi Flegrei signals a critical transition within the next decade" made headlines. The research analyzed decades of seismic and geodetic data and found that the acceleration of deformation and seismicity is better described by a "finite-time singularity" than by exponential growth — meaning the trend converges on a specific window rather than growing indefinitely.
Independent analyses of different datasets (uplift rates, earthquake frequency, CO2 flux) all converge on a critical time between 2030 and 2034, with ground uplift projected to reach approximately 4 meters by the early 2030s.
But here's what the headlines miss: a "critical transition" doesn't mean eruption. The authors are explicit: the system appears to be approaching "a critical mechanical threshold whose outcome remains uncertain." That threshold could mean:
New fractures opening in the caldera floor
Increased fumarole activity and gas emissions
Localized ground failure or subsidence
A phreatic (steam-driven) eruption — small but disruptive
Or, in the worst case, a magmatic eruption
The driving mechanism, according to geochemical and statistical evidence, is deep magmatic volatile injection — gases from a deeper magma body progressively pressurizing the shallow crust. Rising CO2 fluxes, changing sulfur speciation, and isotopic signatures all point to a deepening magmatic source. This is concerning because it means the unrest isn't just hydrothermal (hot water) — there's magma involved.
A separate 2025 paper in Nature Communications ("Scenario-based forecast of the evolution of 75 years of unrest at Campi Flegrei") modeled multiple scenarios and found that seismic risk mitigation — especially retrofitting buildings — is the most effective immediate strategy, regardless of whether an eruption occurs.
Campi Flegrei vs. Yellowstone: Supervolcano Comparison
The question everyone asks: is Campi Flegrei more dangerous than Yellowstone? The answer depends on what you mean by "dangerous."
Yellowstone's caldera is physically much larger (45 × 85 km vs 12 × 15 km) and its largest eruptions were VEI 8 — one full order of magnitude above Campi Flegrei's VEI 7. But Yellowstone is in a sparsely populated part of Wyoming with its last eruption 70,000 years ago. Campi Flegrei has 3 million people within range and is actively accelerating.
In terms of immediate risk to human life, Campi Flegrei is objectively more dangerous. A VEI 4–5 eruption — well below its maximum potential — could generate pyroclastic flows that reach the outskirts of Naples within minutes.
Visiting Naples and the Phlegraean Fields
Despite the geological drama, the Campi Flegrei area is a fascinating place to visit. The volcanic geology is visible everywhere — in the building stone, the thermal springs, the fumaroles, and the landscape itself.
Solfatara craterwas the most popular volcanic attraction — a shallow crater with hissing fumaroles, boiling mud pots, and sulfurous gases. It's been partially closed since a 2017 accident (a family fell through thin crust), but guided tours of the surrounding area are available.
Pozzuoli's Macellum(Temple of Serapis) is a must-see for geology enthusiasts. The Roman columns with their marine borings are visible proof of bradyseism — a geological textbook in stone. Pozzuoli's Flavian Amphitheater (third largest in the Roman world) sits on volcanic ground.
Monte Nuovo, the hill created by the 1538 eruption, is a nature reserve you can hike in 30 minutes. Standing on a mountain that didn't exist 500 years ago is a visceral reminder of what this caldera is capable of.
For a broader Italian volcano itinerary, combine Campi Flegrei with a Vesuvius summit hike (€10, 30 min) and Pompeii — all within day-trip range of Naples. The entire Naples volcanic region is covered in our Italy volcano guide.
Explore Campi Flegrei in Our Database
Full eruption history, coordinates, VEI data, and geological classification for Campi Flegrei
Nobody can say with certainty. What scientists do know: the system has been in accelerating unrest since 2005, with ground uplift of 140+ cm, increasing seismicity (M4.6 record in June 2025), and rising magmatic gas emissions. A 2026 arxiv paper projects the current acceleration could reach a 'critical mechanical threshold' between 2030 and 2034 — but the authors are clear that this doesn't necessarily mean eruption. It could mean a regime change: new fractures, increased fumarole activity, or localized ground failure. INGV monitors the caldera with one of the densest geophysical networks in the world.
Is Naples safe to visit in 2026?
Yes. Naples and the Campi Flegrei area are safe to visit in 2026. The seismic events are small (mostly M1–3, with occasional M4+ events) and the ground uplift is gradual — 10 mm/month as of early 2026. Millions of people live and work in the area daily. The Italian Civil Protection department has evacuation plans in place for the 'red zone' (immediate caldera area), and INGV provides continuous monitoring. The risk is real but not imminent. Visit Pozzuoli's Serapeo temple columns, the Solfatara crater area, and Naples itself with normal precautions.
What is bradyseism?
Bradyseism ('slow movement' in Greek) is the gradual uplift or subsidence of ground in a volcanic caldera. At Campi Flegrei, the ground physically rises and falls over months to years, driven by pressure changes in the hydrothermal system beneath the caldera. The most visible evidence is the Temple of Serapis (Macellum) in Pozzuoli, where marine borings on the Roman columns prove the ground has moved up and down by meters since antiquity — submerged below sea level, then raised back above it. Since 2005, Pozzuoli has risen ~140 cm, causing structural damage to buildings and occasional evacuations.
How big was the Campanian Ignimbrite eruption?
The Campanian Ignimbrite eruption roughly 39,850 years ago was the largest volcanic eruption in Europe in the past 200,000 years. It's classified VEI 7 — the same scale as the 1815 Tambora eruption that caused the 'Year Without Summer.' Between 179 and 243 km³ of magma was ejected, creating pyroclastic flows that covered 30,000 km². The eruption formed the basic caldera structure of the Phlegraean Fields. Some researchers believe it contributed to Neanderthal decline in Europe, though this remains debated.
What's the difference between Campi Flegrei and Vesuvius?
They're neighbors — Campi Flegrei is 20 km west of Vesuvius — but geologically distinct. Vesuvius is a stratovolcano (a single cone) that last erupted in 1944. Campi Flegrei is a caldera system (a massive collapsed crater) with at least 24 vents spread across 150 km². Campi Flegrei is capable of much larger eruptions: the Campanian Ignimbrite was VEI 7, while Vesuvius's famous 79 AD eruption (which destroyed Pompeii) was VEI 5 — roughly 100 times smaller. Both are monitored by INGV's Vesuvian Observatory.