Italian supervolcano might only need a small shake to erupt

Campi Flegrei, an Italian supervolcano, is structurally much weaker than experts thought.

But that doesn’t mean a catastrophic eruption is imminent, even though researchers from the Vesuvius Observatory suggest an eruption remains a “realistic possibility”.

Campi Flegrei is a 12km wide caldera – the leftovers of a collapsed volcano cone – which spans from the region just west of Naples and the notorious Mount Vesuvius into the nearby gulf.

In the wake of 70 years of tectonic activity in the region, which has elevated the entire Pozzuoli village built on it by four metres, researchers now believe the caldera has pushed closer to breaking apart. That’s thanks to recent analyses of Campi Flegrei’s activity, using a model based on the physics of rock breakage.

It’s the first time these methods have been applied to study an active volcano in real-time, says lead researcher Professor Christopher Kilburn from University College London.

“Campi Flegrei is moving closer to rupture,” Kilburn says.

“However, this does not mean an eruption is guaranteed. The rupture may open a crack through the crust, but the magma still needs to be pushing up at the right location for an eruption to occur. We will now have to adjust our procedures for estimating the chances of new routes being opened for magma or gas to reach the surface.

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“The study is the first of its kind to forecast rupture at an active volcano. It marks a step change in our goal to improve forecasts of eruptions worldwide.”

A steady increase in seismic activity has been registered in the Campi Flegrei region over the last few years to a level not seen since the 1980s. More than 600 mini earthquakes were registered at this site in April alone.

This ongoing activity is the cause of the substantial weakening detected in the volcano’s structure.

“This means that it might break even though the stresses pulling it apart are smaller than they were during the last crisis 40 years ago,” says Dr Nicola Alessandro Pino, a senior researcher at the Vesuvius Observatory.

Campi Flegrei last erupted in 1538, and since then there have been several periods of heightened tectonic activity, particularly in the past 70 years. This has given rise to concerns about a potential follow-up event.

40,000 people were evacuated from the region from 1982 to 1984. Today, hundreds of thousands of people reside in communities built atop the caldera.

The study conducted by Kilburn, Pino and their colleagues detected increased movement of fluids below the surface of Campi Flegrei. These fluids could be magma or volcanic gases bleeding into the solid rock above it, which can lead to these small earthquakes.

The concern held by volcanologists is that even such small earthquakes could be covertly weakening the volcano’s structure and, one day, see an eruption preceded by a somewhat minor tremor.  

“We can’t yet say for sure what will happen,” says Dr Stefano Carlino from the Vesuvius Observatory.

“The important point is to be prepared for all outcomes.”