For palaeontologists, Lake Avernus is the broken heart of a 39,000-year-old supervolcano that left a crater eight-miles wide and may have helped to kill off the last of Europe’s Neanderthals.
For Giovanni Chiodini and his colleagues it is something more troubling. They see signs that the long-dormant forces beneath it may be stirring once again 15 miles to the west of Naples.
While the eyes of the world have been clapped on Vesuvius, 20 miles away on the other side of the Neapolitan sprawl, a caldera volcano known as the Phlegraean Fields could unleash a far more savage explosion.
A team of researchers led by Dr Chiodini of the National Institute of Geophysics and Volcanology in Bologna has shown for the first time how a build-up of heat and pressure could suddenly gather speed and erupt.
“Under the critical conditions, sizeable fractions of high-temperature magmatic steam are injected into the surrounding rocks, causing their heating,” Dr Chiodini said.
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The Phlegraean Fields caldera has been increasingly restive since the 1950s. In 1983-84 the ground rose 1.8 metres and thousands of earthquakes shook the region.
After three decades of relative calm, Dr Chiodini is concerned that there may be worse to come. The volcano’s fumaroles, fissures in the ground that belch out sulphurous smog, are releasing more carbon monoxide and boiling mud as well as giving off small tremors, the researchers wrote in the journal Nature Communications.
Italy has been hit by four earthquakes with a magnitude of at least 5.5 this year, including one that killed 298 people and injured more than 400.
The state has upgraded the situation to a yellow warning, meaning that the area must be monitored by scientists.