2023-06-09 13:08:31
Italy
Near Naples, a super volcano threatens to wake up
Half a million inhabitants under the direct threat of a super volcano: the risk of an eruption in the Phlegraean Fields, near Naples, has never been greater.
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Vesuvius is better known than the Phlegraean Fields.
AFP
Less well known than Vesuvius, which wiped Pompeii off the map almost two millennia ago, the Phlegraean Fields volcano, which last erupted in 1538, exposed hundreds of thousands of inhabitants to a deluge of lava, ashes and rocks.
“It is an extremely dangerous volcano”, explains to AFP Stefano Carlino, co-author of the study of the London university UCL and the Italian Institute of geophysics and vulcanology (INGV), published in the journal Communications Earth & Environment. “We are not saying that an eruption will occur, we are saying that the conditions for an eruption are more favorable” today, specifies Christopher Kilburn of UCL, responsible for the work.
Neanderthal extinction
The energy of the volcano is such that its eruption 30,000 years ago would have contributed to the extinction of Neanderthal man, according to certain hypotheses. A resurgence of activity in the early 1980s led to the evacuation of 40,000 inhabitants, but the volcano has not been talked about since then.
And yet: the tens of thousands of small earthquakes that occurred from the 1950s weakened the caldera – flat-bottomed volcanic depression -, of which “parts were tested until almost reaching the breaking point”, indicates the study .
“Cumulative” effects
These tremors, even more numerous since 2019, have upset the underground strata, and the town of Pozzuoli on which the volcano is located has risen by four meters over the decades. The researchers point out that the effects of the volcano’s activity are “cumulative”: it is therefore not necessary for the intensity of this activity to increase significantly to increase the probability of an eruption.
“A possible eruption could be preceded by relatively weak signals, such as a modest level of ground uplift, and a smaller number of earthquakes,” they note. They cite the example of the Rabaul caldera in Papua New Guinea, which erupted in 1994, when the tremors that preceded it were far fewer than during the eruption that occurred ten years earlier.
“Very low” probability
The probability of a mega-eruption is however “very low”, tempers Stefano Carlino. “What’s more likely are small eruptions.” Moreover, even in the event of a rupture of the crust, “the magma must rise to the right place”, underlines Christopher Kilburn.
Scientists, who are only interested in volcanoes in the awakening phase after a long period of sleep, are using an innovative method to auscultate this flat volcano, almost invisible to the naked eye, and which is under the coast in appearance peaceful of the Neapolitan basin. In the field, they measure both earthquakes and ground movements, its deformation, to draw up a behavior model of the volcano. In the laboratory, they observe the fracturing of the rock.
Then they go back in time to compare them to other episodes, other eruptions of other similar volcanoes, when more conventional approaches are content with statistical series. If “we cannot say with certainty what will happen, what matters is to be prepared for any eventuality”, also recalls Stefano Carlino.
half a million people
Half a million inhabitants live in a high-risk area, 800,000 others in a lower-risk area. In the event of an alert, the plan of the local authorities provides for the evacuation of the population by public transport. The alert level – green, yellow, orange, red – is reviewed each month.
“Currently in Pozzuoli, the alert level is yellow,” local spokeswoman Giordana Mobilio told AFP. “We have a constant channel of communication with the inhabitants of the town that we inform of tremors” of a magnitude greater than 1.5, she underlines.
(AFP)
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