The Italian supervolcano is active again, like it hasn't been for months. An earthquake raises concerns about an eruption in the sea - with a devastating mega-tsunami.
Pozzuoli - For months, the approximately 500,000 residents of the red zone around the supervolcano of the Phlegraean Fields have been terrorized by incessant earthquakes. On Thursday afternoon alone (April 11th), over 60 shocks were reported within 24 hours in the Bay of Pozzuoli in southern Italy. Experts have been warning of an impending outbreak for months.
Earthquakes are increasing in the middle of the bay in front of Pozzuoli
It is noteworthy that the two earthquakes are concentrated in two areas: One is the immediate area around the port city of Pozzuoli, where the Solfatara crater is also located. And then there is a cluster in an area in the middle of Pozzuoli Bay, which is also part of the huge caldera that a mega-eruption of the Phlegraean Fields blasted into the bay around 39,500 years ago.
Volcanologist Aldo Piombino is concerned about the earthquakes in the bay. Above all, a small earthquake in the bay at a depth of six kilometers makes people sit up and take notice. Piombino published a map on Facebook in which he marked the two zones. “Green is the area where earthquake activity is directly linked to ground uplift,” he writes. The area around Pozzuoli has risen by 1.25 meters since 2005. Researchers believe this uplift is caused by hot water fueled by a lava chamber in the earth.
Is lava seeping into the ground beneath the bay?
Piombino continues: “Red is the seismicity of the Gulf, which is caused by a fault that is present in the Gulf and where there are also hydrothermal vents.” A fault is something like a crack in the earth's crust, hydrothermal vents are something like that like mini volcanoes from which hot water emerges. Piombino explains: "These are two areas of different seismicity: in the area of the hydrothermal system there cannot be deep earthquakes because they cannot actually occur in the hydrothermal system, while deeper earthquakes can occur along the fault in the Gulf."
The earthquakes in the Phlegraean Fields usually occur at relatively shallow depths of a maximum of three and a half kilometers - the researchers interpret them as eruptions of hot water in the worn-out subsoil. Deep earthquakes, on the other hand, are interpreted as signs of rising magma. “The deeper the tremor, the more you have to worry about magma ejection”; worries one user. Piombino tries to reassure: “The magma chamber is still very far away.” However, magma prefers to penetrate upwards into fracture zones in the earth's crust, which end here under water.
An underwater volcano triggers devastating tsunamis when it erupts
An eruption of the supervolcano would be devastating even on land, as a look at previous eruptions shows. An eruption in the Gulf of Pozzuoli would also result in devastating tsunamis. In a study published in
the Journal of Volcanology and Geothermal Research
in 2019, Martina Ulvrova from the Institute of Geophysics at the Swiss Federal Institute of Technology in Zurich and her colleagues created models that show the potential tsunamis that arise from eruptions of different sizes in different locations in the Bay of Pozzuoli would.
A video simulation from the Auckland Museum in New Zealand, which recreates the course of a relatively small eruption near an inhabited coast, shows how devastating volcanic eruptions can be.
Ulvrova's findings suggest that "there is a significant tsunami risk in many areas of the Bay of Naples," with the risk being greatest in the Bay of Pozzuoli. Most of the outbreak scenarios involved tsunamis that struck populated areas. Most regions would only be affected by relatively small waves - less than ten meters high, most likely around one and a half meters high.
Waves 30 meters high could hit Naples and Sorrento
In the worst case, however, waves 30 meters high could hit the coast. Ulvrova: “This would particularly affect densely populated coastal areas in the Bay of Pozzuoli, which have dense infrastructure such as houses, railway network, restaurants, historical buildings, etc..” Much of the population in the Gulf, inhabited by over three million people of Naples is located on the coast, also the hotels of Sorrento, Capri, Ischia and the Amalfi Coast.
The waves would take about 15 minutes to cross the Gulf of Naples. There isn't much time for an evacuation. The eruption of Hunga Tonga-Hunga Ha'apai in the Pacific island state of Tonga in January 2022 proved that the models are not exaggerated. Directly at the volcano, the wave generated by it was estimated to be 85 meters high; when it arrived at the uninhabited island of Tofua, 90 kilometers away, it was probably a maximum of 45 meters high.
The fact that there were only four deaths in the sparsely populated island world was due to the fact that the region's hotels were closed due to Corona. According to Ulvrova, the tsunami risk should therefore definitely be included in the national emergency plan for the Phlegraean fields.