The area of the Italian city of Naples was shaken this Wednesday by the largest earthquake in four decades. An earthquake that has occurred due to bradyism, the phenomenon that has been deforming the volcanic caldera that is located 9 kilometers from the city for years.

The earthquake has not caused damage but the director of the Vesuvius Observatory, Mauro Antonio Di Vito, has explained that it was the biggest shock in the last 40 years and that it belongs to a seismic swarm unleashed this Tuesday at 5:00 p.m. (3:00 p.m. peninsular time ) that has preceded 84 other earthquakes: almost all “very small” and only two above magnitude 3.

Thus, the “fiery” Phlegraean Fields, as the Greeks called them, are a vast volcanic area located in the northern part of the Gulf of Naples in municipalities such as Bacoli or Pozzuoli.. Many of its craters are under the sea and it has been an active area for more than 80,000 years. The last major eruption was in 1538, which generated Monte Nuovo, but in recent times its activity is being closely monitored because something is moving in the bowels of this land.

As Di Vito explained to Efe, the tremors in this area are normal because bradyism is continually brewing beneath its subsoil.. It is a phenomenon of rise and depression of the terrain related to the void or filling, of lava or gas, of the magmatic chamber of its subsoil.. If it fills, like a breath, the ground rises; if it empties, it goes down. And now the trend is upward.

So much so that the ground level in the Phlegraean Fields increases by about 15 millimeters per month and in the historic center of Pozzuoli it has risen 118 centimeters since 2006, which represents an obvious risk for buildings and other infrastructure.

It could be the prelude to an eruption

Di Vito has also explained that bradyism has preceded a volcanic eruption at other times but that right now “there is no evidence” that it will occur. “Right now we rule out an eruption but we are monitoring the situation with great attention,” he noted.

The Phlegraean Fields caldera has around twenty known craters, most of them underwater, but in the event of an explosion it is unknown which mouth could open to expel the magma or gas.

“We don't know which volcano could open because this is a very large caldera. We can only predict it based on the data that surveillance will give us.. But the eruption is currently not a hypothesis that we consider,” he added.

For this reason, in the neighborhoods most exposed to the Campos, such as Pozzuoli, Bacoli, Monte di Procida and Quarto, where nearly half a million people live, the Civil Protection has already drawn up a National Plan for an evacuation of the area in in case this occurs. At this time, the alert status is the “yellow” of said plan, the second on a four-level severity scale.

It should be noted that the history of the Gulf of Naples has always been closely linked to volcanoes and earthquakes, as demonstrated by the tragic fate of Pompeii and Herculaneum or the remains of the city of Baia, currently visible under the sea due to the depression of the land.