The most dangerous volcanic threat in Italy right now: Campi Fiegrei: experts fear that the volcano could be reawakening after generations at rest.

‘Be prepared for all outcomes’: Inside the saga of a supervolcano that’s waking up 

Barbie Nadeau, CNN

Forget Italy’s most famous active volcano, Mt. Vesuvius, which destroyed Pompei in 79 AD.

The most dangerous volcanic threat in Italy right now is one you’ve probably never heard of: Campi Flegrei, or the Phlegraean Fields.

This unassuming plain, which stretches 200 kilometers (125 miles) under the bay of Naples and the islands of Capri and Ischia to the outskirts of the city of Naples, is a giant caldera, or depression, left by a supervolcano some 2 million years ago.

It is now the site of multiple volcanoes that have been active for 39,000 years, many of which lie underwater. It’s also populated with villas, small villages and shopping malls and home to 800,000 people and a hospital under construction. More than 500,000 of the locals live in what Italy’s civil protection agency has deemed a “red zone,” an area encompassing 18 towns that’s at highest risk in the event of an eruption. An additional 3 million residents of Naples live immediately outside the eastern edge of the caldera, according to the civil protection agency.

The last major eruption of Campi Flegrei was in 1538, and it created a new mountain in the bay. Seismic activity in the area has been intensifying since December of 2022, according to Italy’s National Institute of Geophysics and Volcanology (INGV), and experts fear that the volcano could be reawakening after generations at rest.

The densely populated region, which is less than 50 kilometers (31 miles) from Vesuvius, is prone to a seismic phenomenon known as bradyseism, defined by cycles of uplift and gradual lowering of the ground. The last time the region saw such activity was 1984, when the ground rose 3.5 meters (11.5 feet) before it began a slow descent accompanied by seismic activity similar to what is happening in the area now.

Currently in a state of positive bradyseism, when the ground moves upward, the entire volcanic zone is also experiencing a surge in earthquakes that has rattled nerves and sent residents seeking safety out into the streets. In September, the strongest earthquake in 40 years struck the region, and that 4.2 magnitude quake was followed by one of a similar strength just days later.

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