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One of the longest swarm earthquakes gave the residents of the supervolcano a sleepless night. A scientist advises evacuation.
Pozzuoli – Over 160 earthquakes in 24 hours: The approximately 500,000 residents of the red zone of the supervolcano of the Phlegraean Fields in southern Italy have probably not experienced a night like this for 40 years. The series of quakes began on Monday (May 7th) at 4:21 p.m. with a magnitude 1.6 tremor. This was followed by a barrage of fire that lasted until early Tuesday afternoon, with the strongest blow reaching a magnitude of 3.2 at 1:46 a.m. Nine more tremors with a magnitude of over 1.5 followed until shortly before seven o’clock in the morning.
Then the quakes became weaker until they stopped at 2:54 p.m., only to resume again at 7:37 p.m. with a new shock of magnitude 2.7. Almost all earthquakes occurred at a shallow depth on Monte Olibano, which researchers recently identified as a new source of danger.
Researcher at online seminar on earthquakes in Italy: “I believe that magma is there”
People are probably at their wits’ end. In the middle of this situation, a video bursts in which scientists argue about the causes of the earthquakes. This is the recording of a scientific online seminar by the National Geophysical and Volcanological Institute INGV on March 11th, which dealt with the phenomenon of volcanically caused ground movements in the Phlegrean fields and has now been put online by the INGV.
Above all, the statements of volcanologist Roberto Scandone, former professor of volcano physics at the University of Roma Tre and representative of the state commission for major risks, caused unrest. When asked by INGV volcanologist Lucia Pappalardo whether an eruption would happen soon, Scandone replied: “I think there is already magma, that is my opinion.” As for the earthquakes and the uplift of the ground, he said: “I think it’s all dominated by the magma that’s there trying to deform, and as the fractures open up it’s going to come up more or less quickly.”
On a map, he points to an area of the most intense red where fractures could occur and magma, which may be contained at shallow depths, is rising. The area corresponds to the location where the recent earthquakes were most strongly felt.
The next eruption from Italy’s supervolcano could last two years and be explosive
According to Scandone, it is possible that “the rate of uplift will decrease, leading to a decrease in seismicity, and the crisis will end for now.” This was the case after the last earthquake crises in the 70s and 80s. It is also possible for the crisis to develop slowly over days, weeks or months, ending with the escape of viscous lava in a lava dome and ultimately with possible explosive activity. “No one has put forward this hypothesis yet,” Scandone explained.
He referred to the lava domes that were created during the longer period of activity between 4,800 and 3,800 years ago: the “Academy Cathedral”, Monte Olibano and Monte Spina – all three in the vicinity of the famous Solfatara crater. “Emission from a dome probably occurs at fairly slow flow times,” Scandone continued. And he gave examples of other volcanic craters in the Phlegraean Fields where such eruptions lasted two years. “This does not prevent the situation from developing into an explosive eruption within hours or days.”
At that time, eruptions with a volcanic explosiveness index of four to five occurred on the eastern side of the supervolcano’s caldera. This is somewhere between the relatively harmless eruption of Eyjafjallajökull in Iceland in 2010 or the devastating eruption of Vesuvius in 79 AD. Scandone: “When we find ourselves in a situation like the one described, the ascent of magma can occur very quickly with very short seismic precursors within a few hours and precede an explosive eruption.”
Expert advises: “If I had resources, I would evacuate the Phlegraean Fields”
The expert continues: “We are witnessing a process that has been going on for at least 60 to 70 years,” explains Scandone. “I really don’t know what point he’s at.” Monitoring of the Caldera of the Phlegraean Fields is much better than it was 40 or 50 years ago. But: “The volcano does not always behave as linearly as we would like.” His conclusion: “If I had unlimited resources, I would evacuate the Phlegraean Fields.”
Giovanni Chiodini, head of research at the INGV, said of Scandrone’s theses: “I have no certainty about this.” INGV researcher Monica Piochi said during the seminar: “I agree with the fact that there can be magma at a depth of four kilometers and that this rise is modulated depending on the properties of the magma.”
For INGV research leader Giuseppe Mastrolorenzo, what is happening in the supervolcano is not necessarily due to the presence of magma at shallow depths, but rather to fluctuations in heat flow or fluids that come from the large magma chamber, which is probably located at a depth of around eight kilometers. This involves gas and water that is fueled by magma at great depths.
The supervolcano remained silent for 3,300 years – until 1538
This model has been confirmed by most researchers in recent decades. In fact, the Phlegraean Fields have subsided over the past 3,800 years without an eruption – with the exception of Monte Nuovo in 1539 near Pozzuoli, which was relatively harmless.
However, according to Mastrolorenzo, this is “not a thesis that protects us from eruptions”. Because: “The reality is that when the erupting magma rises, the rate of ascent to the surface is generally very fast.” In all explosive eruptions of the Phlegraean fields in the past, the magma was released in very short times, between tens of minutes and several hours lay, rising from the magma chamber about eight kilometers away. Mastrolorenzo had recently warned against building a stadium in the Phlegraean Fields and criticized the evacuation plans as inadequate.
Giuseppe De Natale, INGV’s first research manager, said: “I believe that there is no evidence for the presence of magma in the Phlegraean fields.” However, he had to admit that an eruption could occur if there is none at a more superficial level Magma would be present.
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