Italy’s Campi Flegrei volcano may be waking up, scientists warn

It’s as loud and stifling as a ship’s engine room. Roberto Isaia, an Italian geologist, is taking photographs of a grey pool of bubbling mud. The wind changes, and he disappears briefly in a column of sulphurous steam rising from the ground and reeking of rotten eggs.
Here in Pisciarelli, between Naples and the seaport of Pozzuoli, there’s a palpable sense that something gigantic is slumbering underground. It lies in the Campi Flegrei, “burning fields” in Italian, an approximately 150-square-kilometre area of high volcanic activity also known as the Phlegraean Fields.
Unlike Mount Vesuvius on the Gulf of Naples to the east, a “classic” volcano with a crater-topped cone, the Campi Flegrei are a large caldera, a depression created when a volcano partially collapses after releasing most of its magma chamber in an eruption.
Much of it lies beneath the Gulf of Pozzuoli, and the part on land is comparatively flat and doesn’t seem threatening. But satellite images show its numerous volcanic craters.
Scientists are now more worried about the volcano here than the better-known and still-active Vesuvius, which looms over Naples, population 3 million, and buried the Roman settlements of Pompeii and Herculaneum in volcanic ash, mud and pumice in AD 79.
Vesuvius disgorged about four cubic kilometres of rock and lava then. When the Campi Flegrei volcano erupted some 39,400 years ago, it ejected about 350 cubic kilometres of material.
Though commonly called a “supervolcano,” strictly speaking, it’s not: Its Volcanic Explosivity Index is 7, compared with 8 for a supervolcano. The eruption was enormous nonetheless – the largest in Europe in the last 100,000 years. Ash was distributed over the entire eastern Mediterranean and as far as what now is central Russia.
The Campi Flegrei volcano has drawn increased attention since a recent study concluded that it’s “evolving towards conditions more favourable to eruption.”
Published in the London-based journal Nature Communications, the study was conducted by scientists from University College London (UCL) and the Vesuvius Observatory of Italy’s National Institute of Geophysics and Volcanology (INGV), which constantly monitors Vesuvius, Campi Flegrei and the volcanic island of Ischia in the Gulf of Naples.
Electronic visual displays at INGV show graphs with information on the volcanic systems, for example ground temperature, amount of ground uplift or subsidence, and the composition of gases emitted from ground vents known as fumaroles.
The ground of the Campi Flegrei has been rising and falling significantly in recent decades, accompanied by thousands of micro-earthquakes. Authorities raised the alert level from green to yellow in 2012. In the early 1970s, the uplift was about 1.5 metres, followed by another major uplift in the early 1980s.
“The last occasion of such behaviour occurred during the century before the caldera’s only historical eruption in 1538,” the UCL and INGV scientists write.
“The signs are alarming,” says Thomas Walter, head of the volcano hazards work group at the German Research Centre for Geosciences. “But there have been major uplifts without eruptions, as in 1983, when the ground rose by more than two metres. At the moment, we’re very far from an uplift like that.”
Isaia has worked at INGV since 1999. “Every volcanic system is different,” he says, “and there’s a world of difference between Vesuvius and the Campi Flegrei.”
Magma in the latter can erupt at any of a number of places. Some scientists think the most likely spot is at the edge of the caldera, while others point to the middle.
The reason for the recent uplifts is also a matter of dispute.
“One faction says the build-up of new magma underground is the reason,” Walter says. “Another says there’s no evidence of magma, and sees the cause in hydrothermal gases released in front of the magma chamber that then collect in underground reservoirs.”
People in the danger zone take a dim view of a deep drilling project that would take measuring instruments up to three kilometres below ground and perhaps solve the mystery. They’re afraid of awakening the slumbering giant.
If an eruption appears imminent, most of the some 80,000 inhabitants of Pozzuoli, west of Naples and regarded as the centre of the Campi Flegrei, would have to be evacuated.
The so-called red zone includes three municipalities, as well as parts of others, and extends to Naples. The yellow zone includes six municipalities and 24 districts of Naples, where it borders on the red zone for Vesuvius, statistically more likely to erupt.
During the scare in the early 1980s, about 20,000 people were evacuated as a precaution.
A Pozzuoli fisherman named Mario, aged about 70, says the uplift then was so great that fishing boats ran aground before reaching the pier. Cars now park in front of the old bollards, high and dry today.
And three standing marble columns from an ancient Roman market building – part of an archaeological site – have bands of boreholes made by molluscs after the land dropped below sea level before rising again.
“We’re travelling in the middle of a volcano right now. Can you believe it?” says Isaia as he drives his car through heavy Naples traffic. “We’re in a fix – the biggest one on Earth!” — dpa