Campi Flegrei: the ground rises and falls

The ground at Pozzuoli rose by up to around 3.5 meters during the bradyseismic crises of 1970 to 1972 and 1982 to 1984, and it has been rising steadily again since 2005.

Up to 3.5 meters, twice, in living memory

Bradyseism is the slow vertical movement of the ground, and at Pozzuoli it reached up to around 3.5 meters across the 2 crises of the 20th century.

Two crises did most of the recorded work: 1970 to 1972, then 1982 to 1984. Together they lifted Pozzuoli by up to around 3.5 meters. Harbor steps, doorways and quaysides in the town record it directly, because the sea moved away from them.

A new uplift has been under way since 2005, and the Civil Protection Department puts the caldera's rise since then at over 150 cm¹.

A caldera 110,000 years old, quiet since 1538

The Campi Flegrei have been an active caldera for more than 110,000¹ years, and the last eruption was in 1538¹, when Monte Nuovo was formed.

More than 27 eruptions are counted in the last 5,500¹ years. That is the timescale the monitoring is built on, and it is the reason a moving ground surface is treated as normal behavior for this system rather than as an event.

Ground deformation is not an automatic precursor of an eruption. It is the thing the instruments watch, which is a different statement.

Yellow is the second of 4 levels

The alert level is yellow with the operational phase set to attention, fixed by a decree of October 30, 2025 and confirmed by the Civil Protection Department on November 4, 2025 after the volcanic section of the Commissione Grandi Rischi met.

The 4 levels run base, attention, pre-alarm, alarm. Yellow means a medium disequilibrium of the volcano and sits at the second step. It has been in force since 2012 and was redefined in 2025 within an update agreed with INGV and the Campania Region.

What phase 2 requires is administrative: reinforced monitoring, verification of civil protection measures, and non-structural prevention through training, information and exercises. None of those is a signal about the next month.

The zones are planning maps, not forecasts

The national plan puts around 500,000³ residents inside the red zone, the area of preventive evacuation, and over 800,000³ inside the yellow zone exposed to ash fall.

The red zone takes in Pozzuoli, Bacoli, Monte di Procida and Quarto in full, part of Giugliano in Campania and Marano di Napoli, and several Naples districts including Soccavo, Pianura, Bagnoli and Fuorigrotta. The yellow zone adds Villaricca, Calvizzano, Mugnano di Napoli, Melito di Napoli and Casavatore, plus 24 Naples districts.

Those boundaries describe a civil protection scenario. They are drawn so that an evacuation could be organized, and they say nothing about probability. Reading a zone map as a risk map is the single most common mistake made with this material.

Where the current number lives

Monitoring is run by INGV Osservatorio Vesuviano, which publishes 4 kinds of product: a monthly surveillance bulletin, a weekly bulletin dedicated to Campi Flegrei, web bulletins, and VONA notices for aviation, all at ov.ingv.it.

That is the correct way to check this subject: the current INGV bulletin for the measurements, and the Civil Protection Department for the alert level. Any page, this one included, is a snapshot of the day it was written.

Pozzuoli and Bacoli are ordinary places to visit under a yellow alert, and have been since the level was set in 2012. Ask locally about access to individual sites, which changes for reasons of maintenance and safety that have nothing to do with the alert level, and take the bulletin rather than the news cycle as your reference.

One last note on language, because it decides how the whole subject reads. An uplift of 150 cm¹ since 2005 is a measurement. Yellow is an administrative state with 3 defined duties attached to it. Around 500,000³ residents in the red zone is a planning figure. None of the three is a prediction, and no institution in Italy publishes one for this volcano. For the region, see Campania.

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