Europe's only active supervolcano, Campi Flegrei, has experienced two major earthquakes and dozens of tremors in the past week, sparking fears that a devastating eruption could be on the horizon.
A quake with a magnitude of 4.0 on the Richter scale rattled the city of Naples and the surrounding regions at 10pm local time (8PM BST) last night, causing damage to several buildings and spewing rubble into the streets.
That came after last week's 4.2 magnitude quake caused widespread transport cancellations and triggered a week of near-constant tremors.
The epicentre of yesterday's quake was located at a depth of nearly two miles between Naples and nearby Pozzuoli.
Located just nine miles (14.5 km) to the west of Naples, Campi Flegrei has become weaker and more prone to rupturing, making an eruption more likely, according to experts.
An area with fallen rubble is cordoned off in via Pisciarelli, the epicentre of an earthquake, on the border between the municipality of Pozzuoli and Agnano, a hamlet of Naples, Italy, 03 October 2023
A 4.0-magnitude earthquake shook Italy 's volcanic region of Campi Flegrei west of Naples yesterday as shocked residents posted videos of cars being pelted by rubble amid the worst of the tremors
A 4.0-magnitude earthquake late on Monday at the Campi Flegrei (Phlegraean Fields) has heightened concern among people living in the volcanic area near Naples about a recent wave of seismic activity
The Campi Flegrei volcano in southern Italy has become weaker and more prone to rupturing, making an eruption more likely, experts say. Pictured is Solfatara, a shallow volcanic crater that makes up part of Campi Flegrei
Around 360,000 people live in the immediate localities around Campi Flegrei and may need to evacuate if experts think it's in immediate danger of an eruption.
New research has shown there's a one in six chance of a mega-volcano eruption this century
<!- - ad: https://mads.dailymail.co.uk/v8/us/news/none/article/other/mpu_factbox.html?id=mpu_factbox_1 - ->AdvertisementNaples meanwhile, just nine miles away is home to some 3 million people.
Scientists from Italy's National Institute for Geophysics and Volcanology (INGV) planned meetings with local officials to draw up evacuation plans this week.
The supervolcano has been restless since the middle of the 20th century, which is of particular worry to scientists.
It has exhibited several two-year periods of unrest in the 1950s, 1970s and 1980s causing small, local earthquakes and ground uplift due to movement of magma beneath the surface.
When the volcano eventually blows it is likely to be comparable in size to the eruption of Mount Vesuvius that destroyed the cities of Pompeii and Herculaneum in AD 79.
Campi Flegrei is a collapsed supervolcanic caldera consisting of several craters and volcanic edifices.
A series of small scale earthquakes and tremors have steadily weakened the caldera in recent decades, causing pressure to build up beneath the surface.
The INGV say continued tremors will only cause pressure to increase, cultivating the required conditions for an eventual eruption.
Professor Christopher Kilburn at UCL's Earth Sciences department said that Campi Flegrei is more prone to a 'rupture' – a break or fracture through the rock that makes up the body of the volcano.
'It's a natural result when the volcano is stretched as pressure builds up underground,' Professor Kilburn told MailOnline.
'Once a rupture has occurred, it will be easier for volcanic fluids to escape.'
A rupture could open a crack through the Earth's crust, although the magma still needs to be pushing up at the right location for an eruption to occur.
Campi Flegrei is defined as a supervolcano because it has the potential to produce a magnitude eight eruption, capable of discharging more than 200 cubic miles of material.
It last erupted when Henry VIII was last on the English throne, and this event came following an interval of about 3,000 years.
But the researchers warn that large calderas of this sort frequently pass through several decades of unrest before they erupt.
About 7 to 9 miles (12 to 15 km) across, Campi Flegrei is the largest active caldera in Europe and extends west from the outskirts of Naples to the Tyrrhenian Sea. About a third is partially submerged beneath the Bay of Pozzuoli; the remaining two-thirds are home to more than 360,000 people. The caldera is marked by the yellow dashed line; ground movement has occurred across the central region marked in blue
About 360,000 people live at Campi Flegrei (pictured), according to the London researchers
The closed Solfatara crater in Pozzuoli, Italy, 27 September 2023
Naples is flanked by volcanoes on both sides - Campi Flegrei to the west, and Mount Vesuvius to the east
However, Campi Flegrei's current tensile strength – the maximum stress a material can bear before breaking when it is stretched – is likely to be about a third of what it was in 1984, the researchers said, due to regular tremors.
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<!- - ad: https://mads.dailymail.co.uk/v8/us/news/none/article/other/mpu_factbox.html?id=mpu_factbox_2 - ->AdvertisementWhat's more, for the past decade, the ground below Pozzuoli has been creeping upwards at about four inches per year, as gas increases pressure in the magma, causing the ground surface to bulge and deform.
A recent study used a model of volcano fracturing, developed at UCL, to interpret the patterns of earthquakes and ground uplift, and concluded that parts of the volcano had been stretched nearly to breaking point.
'This is the first time we have applied our model, which is based on the physics of how rocks break, in real-time to any volcano,' 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 for estimating the chances of new routes being opened for magma or gas to reach the surface.'
Worryingly, an eventual eruption could be preceded by relatively weak signals such as a smaller rate of ground uplift and fewer earthquakes.
This was the case for the eruption of the Rabaul caldera in Papua New Guinea in 1994, which killed only five people, largely due to good disaster planning.
The eruption was preceded by small earthquakes occurring at a tenth of the rate than had occurred during a crisis a decade earlier.
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 at this stage.
The Earth is moving under our feet: Tectonic plates move through the mantle and produce Earthquakes as they scrape against each other
Tectonic plates are composed of Earth's crust and the uppermost portion of the mantle.
Below is the asthenosphere: the warm, viscous conveyor belt of rock on which tectonic plates ride.
The Earth has fifteen tectonic plates (pictured) that together have moulded the shape of the landscape we see around us today
Earthquakes typically occur at the boundaries of tectonic plates, where one plate dips below another, thrusts another upward, or where plate edges scrape alongside each other.
Earthquakes rarely occur in the middle of plates, but they can happen when ancient faults or rifts far below the surface reactivate.
These areas are relatively weak compared to the surrounding plate, and can easily slip and cause an earthquake.
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