Campi Flegrei
The restless caldera on the western edge of Naples, where the ground has risen more than 1.5 meters since 2005
On the western edge of Naples, about half a million people live inside an active volcanic caldera. Campi Flegrei, the Phlegraean Fields, is a broad depression of craters, hot springs and steaming fumaroles that has been rising and shaking in a slow process Italians call bradisismo, or bradyseism. Since 2005 the ground at the port town of Pozzuoli has risen more than 1.5 meters, and earthquakes have grown more frequent and stronger, culminating in a magnitude 4.7 shock on July 31, 2026, the strongest recorded there with instruments. Italy's National Institute of Geophysics and Volcanology (INGV) watches the area around the clock and has reported no signs pointing to a significant short-term evolution toward eruption.
The caldera is about 12 to 15 kilometers across and partly submerged beneath the Gulf of Pozzuoli, with some two dozen craters and volcanic edifices on land, including the steaming Solfatara crater and the cone of Monte Nuovo. Its highest point reaches about 458 meters. The towns of Pozzuoli, Bacoli, Monte di Procida and Quarto, and western districts of Naples such as Bagnoli and Fuorigrotta, lie within or beside it. Uplift is centered on Pozzuoli, where the columns of the Roman market known as the Temple of Serapis have recorded centuries of rise and fall. In 2025 and 2026 INGV measured uplift of about 1 to 1.5 centimeters a month, with about 30 centimeters at the Rione Terra station between January 2025 and mid-2026. Most earthquakes are only 1 to 3 kilometers deep, so even moderate shocks are strongly felt.
Campi Flegrei produced the largest eruption in Europe of the past 200,000 years, the Campanian Ignimbrite about 39,000 to 40,000 years ago, and the Neapolitan Yellow Tuff eruption about 15,000 years ago. Its only historical eruption, in 1538, built Monte Nuovo. Uplift crises in 1969–72 and 1982–84 raised Pozzuoli by about 3.5 meters in total, and in 1983–84 about 40,000 residents were moved out. The current unrest has produced quakes of magnitude 4.4 in May 2024, 4.6 in March and June 2025 and 4.7 in July 2026, which damaged buildings and left several hundred people in Pozzuoli displaced. The alert level has been yellow, the second of four, since 2012 and was kept there after the July 2026 quake. Civil Protection plans would evacuate the red zone's roughly 500,000 residents within 72 hours at the highest alert level.