AAt first glance they look inconspicuous. The Phlegraean Fields, an area in southern Italy with high volcanic activity, are comparatively flat and hardly threatening. But beneath the surface of the earth on the Gulf of Naples there is a huge volcano – a super volcano, even.

Italy is known for its volcanoes. The most well-known – Etna in Sicily and Mount Vesuvius not far from Naples – are already keeping the Mediterranean country busy. But researchers are currently worried about the Phlegraean Fields (Italian: Campi Flegrei) and the magma below. Because the earth’s crust over the volcanic giant is getting weaker and weaker.

At least since a new study by researchers from University College London (UCL) and the Italian National Institute for Geophysics and Volcanology (INGV) the “burning fields” and the possible effects of an eruption of the super volcano are in focus. Because according to the results of the volcanologists, the earth’s surface in the fields is becoming weaker and more prone to cracks. Supervolcanoes are characterized by a particularly large magma chamber.

Unlike regular volcanoes, they don’t just erupt, they actually explode. Instead of a volcanic cone, i.e. a mountain, they leave behind a huge crater after an eruption. This is called the caldera.

According to the researchers, the caldera of the Phlegraean Fields is currently going through the transition from an “elastic” to an “inelastic” phase. The experts have identified movements at depth that indicate rising gas. This manifests itself in uplift and subsidence, which can lead to fractures in the crust.

Volcanoes that wake up after a long period of dormancy first have to break up the thick crust that has grown over the years in order to be able to eject the magma. Such a rupture is preceded by these same repeated ups and downs and volcanic tremors. According to the researchers, this is exactly what is currently happening under the Phlegraean Fields. Such a break would lead to the eruption.

The approximately 150 square kilometer area near Naples and on the Mediterranean coast has been causing researchers more or less concern for some time now. The Phlegraean Fields are quite close to their well-known neighbor – Mount Vesuvius. The fields are characterized by a volcanic area with several volcanic centers that has been active for over 80,000 years.

From the air, the numerous explosion craters are inconspicuous at first glance. Fumaroles, i.e. volcanic steam outlets, as well as thermal springs suggest that it is rumbling underground.

The concern of an outbreak is great because the effects could be devastating – and not just for the immediate area. During an eruption around 40,000 years ago, an enormous amount of ash was thrown into the atmosphere, which had a massive impact on the climate not only regionally but also worldwide. Then again 15,000 years ago. The last eruption occurred in 1538.

It has been rumbling underground again for 70 years. Tens of thousands of small earthquakes shook the area during this time. According to INGV data, there were 661 earthquakes in May of this year alone. Although weak, 633 of them with a strength below 1.0, they contribute to the instability. For eleven years now, the area has been on the yellow alert level issued by the civil defense, which calls for caution.

However, despite fears of an eruption, it is also possible that activity in the Phlegraean Fields will level off again – or even come to a complete standstill. Or there is an “aborted eruption”: In another study by the INGV, it becomes clear that there have been eruptions in the past in which a magma transfer took place between a source deep in the earth and an opening – but the magma never did reached the surface of the earth. And even with the last major eruption in 1538, only about a hundredth of the amount of magma erupted that had accumulated under the volcano in the previous centuries.

Although the Phlegraean Fields are currently more susceptible to eruptions, an eruption is therefore not guaranteed. The number of low-magnitude earthquakes has increased. However, the head of the INGV Observatory in Naples, Mauro di Vito, who was not involved in the UCL study, is reasonably relaxed: “Currently we have no signs of rising magma.”

Nevertheless, increased attention is required, he said. Because the past has shown that eruptions in the Phlegraean Fields can be powerful and explosive. “We can’t yet say for sure what will happen,” said Stefano Carlino, an author of the UCL study. “It is important that we are prepared for all developments.”

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