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A ‘super volcano’ in a densely populated part of Italy could be on the verge of its first eruption since 1538, researchers warn.
The Campi Flegrei volcano near Naples, southern Italy, has become weaker and more prone to rupturing, making an eruption more likely, the experts say.
Located about nine miles (14.5 km) west of Naples, it is one of the few active supervolcanoes in the world.
About 360,000 people live on Campi Flegrei and may need to be evacuated if experts believe there is imminent danger of an eruption, though scientists say there’s no guarantee one will happen anytime soon.
When the volcano finally erupts, it will probably be comparable in size to the eruption of Mount Vesuvius that destroyed the cities of Pompeii and Herculaneum in AD 79.
Southern Italy’s Campi Flegrei volcano has become weaker and more prone to rupturing, making an eruption more likely, experts say. Pictured is Solfatara, a shallow volcanic crater that is part of Campi Flegrei. Note the yellow rocks created by sulfur gases
Campi Flegrei is located about 14.5 km west of Naples and is one of the few active supervolcanoes in the world
The study was carried out by experts from Italy’s National Research Institute for Geophysics and Volcanology (INGV) and University College London (UCL).
Lead author Professor Christopher Kilburn of UCL’s Department of Earth Sciences said Campi Flegrei is more susceptible to a ‘fracture’ – a breach or fracture through the rock that makes up the volcano’s body.
“It’s a natural result when the volcano is stretched as pressure builds underground,” Professor Kilburn told MailOnline.
“Once a rupture has occurred, volcanic fluids will be able to escape more easily.
“This doesn’t mean they will escape, just that it will be easier to do so than before.”
A rupture could cause a crack in the Earth’s crust, though the magma still has to push up in the right place for an eruption to happen.
Campi Flegrei’s large, eight-mile-wide caldera — the basin-like depression resulting from an earlier explosion — sits beneath the western suburbs of the city of Naples.
About one-third of the caldera lies partly under Pozzuoli Bay, but the remaining two-thirds is land, home to more than 360,000 people.
Campi Flegrei (or “burning fields”) is defined as a supervolcano because it has the potential to produce a magnitude 8 eruption, capable of discharging more than 200 cubic miles of material.
Campi Flegrei is about 7 to 9 miles (12 to 15 km) wide and is the largest active caldera in Europe, extending west from the outskirts of Naples to the Tyrrhenian Sea. About a third is partially submerged under Pozzuoli Bay; the remaining two-thirds are home to more than 360,000 people. The caldera is marked by the yellow dotted line; ground movement has occurred in the central area highlighted in blue
Image from the research paper shows a cut-away view of the large, eight-mile-wide caldera of Campi Flegrei. Sustained small earthquakes have been recorded there since the mid-1980s. Red dots mark seismicity between 1982 and 1984, while green dots mark seismicity since 2005
Humans live in the area and they would be in danger if the volcano erupted again and ejected ‘pyroclastic flows’ – hot and fast-moving streams of gas and solidified lava particles.
Campi Flegrei last erupted when Henry VIII last sat on the English throne, and this event followed an interval of about 3,000 years.
But the researchers warn that large calderas of this type often go through decades of turmoil before erupting.
Campi Flegrei has been restless since the mid-20th century, which is of particular concern to scientists.
It has experienced several two-year periods of unrest in the 1950s, 1970s, and 1980s, causing small, localized earthquakes and ground uplift due to movement of magma below the surface.
Campi Flegrei’s current tensile strength — the maximum stress a material can withstand before breaking when stretched — is probably about a third of what it was in 1984, the researchers said.
In addition, the soil under Pozzuoli has been creeping upwards at about four centimeters per year for the past decade, as gas increases the pressure in the magma, causing the ground surface to bulge and deform.
The new study used a volcano rupture model developed at UCL to interpret the patterns of earthquakes and ground uplift, and concluded that parts of the volcano had stretched almost to the point of rupture.
According to the London researchers, about 360,000 people live on Campi Flegrei (photo).
“This is the first time we’ve applied our model, which is based on the physics of how rocks break up, to a volcano in real time,” said Professor Kilburn.
‘Our first use of the model was in 2017 and since then Campi Flegrei has behaved as we predicted, with an increasing number of small earthquakes indicating pressure from below.
“We will now have to adjust our procedures to estimate the chances of opening new routes for magma or gas to reach the surface.”
Worryingly, an eventual eruption could be preceded by relatively weak signals, such as lower levels of ground uplift and fewer earthquakes.
This was the case with the 1994 eruption of the Rabaul caldera in Papua New Guinea, which killed only five people, largely due to proper contingency planning.
The eruption was preceded by small earthquakes that were a tenth faster than during a crisis a decade earlier.
Professor Kilburn said authorities are well prepared should an emergency arise, although ‘there is no reason to believe they are needed now’.
Immediate signs that a volcano is about to erupt include cracks in the ground and dark streams of volcanic gases being emitted, although Campi Flegrei is not yet at this stage.
“The volcano shows signs of its crust weakening as it continues to stretch,” Professor Kilburn told MailOnline.
“It’s a natural process, but finally we can recognize it as it happens.
“This will help provide clearer assessments of the volcano’s future behavior.”
The team will now apply the volcano rupture model to other volcanoes that have re-emerged after a long period of time, to help “establish more reliable criteria for deciding whether an eruption is likely.”
The research has been published in the journal Communication Earth & Environment.