Phlegraean Fields


The Phlegraean Fields are a vast area of volcanic origin located north-west of the city of Naples. The area has a singular structure: it is not a volcano with the shape of a cone but a wide depressed area, of about 12x15km.

In 1538 the last eruption occurred, which, although being one of the smallest in the entire eruptive history of the Phlegraean Fields, interrupted a period of quiescence of about 3000 years and, within a few days, gave rise to the cone of Monte Nuovo, high about 130m. Since then, the activity in the Phlegraean Fields is characterized by phenomena of bradyseism, fumarolic and hydrothermal activity located in the area of the Solfatara.

The eruptive history of the Phlegraean Fields is dominated by the eruptions of Ignimbrite Campana and Tufo Giallo Napoletano. These events were so violent that the volumes of magma produced and the speed with which they were emitted caused collapses and originated calderas. For this reason, the area is shaped as a semicircle bordered by numerous volcanic cones and craters.

The word “Phlegrean”, which derives from the Greek flègo “burn”, does not refer to eruptive manifestations because in Roman times the volcano was quiescent for centuries. Rather, the name could derive from the presence of numerous fumaroles and thermal waters, known and exploited since ancient times. In fact, in the area there are several areas subject to a secondary type of volcanism, such as fumaroles and hot springs. In particular, in the area of Solfatara there are gaseous manifestations while the localities of Agnano, Pozzuoli, Lucrino are known for their thermal waters.

The phenomenon of bradyseism that characterizes the area consists in a slow movement of lifting and lowering of the ground. The lowering phases, which currently represent the normal condition, are aseismic and are characterized by low speed. The lifting phases, on the other hand, are faster than the movement of the ground and are accompanied by intense local seismic activity. The last bradyseismic crisis occurred in 1983.

On the basis of the monitoring data recorded to date and the assessments expressed by the Major Risks Commission in December 2012, then reiterated in subsequent years until today, the Department has decided to maintain the level of alert “yellow” at the Phlegraean Fields. Unlike the “green” alert level, which corresponds to the ordinary activity of the volcano, this level is in fact determined by the variation of some of the parameters monitored.


Phlegraean Fields
Corso Umberto I, 16
081 576 9111