Right from the start
The Phlegraean Fields is a vast active volcanic area with a structure called a “caldera,” that is, a lowered area with an almost circular shape that was formed by large explosive eruptions. The caldera of the Phlegraean Fields extends from Monte di Procida to Posillipo and also includes an underwater part in the Gulf of Pozzuoli. Within the caldera, more than 70 eruptions have occurred over the past 15,000 years, forming volcanic buildings, craters and volcanic lakes that are still visible, such as Astroni, Solfatara and Lake Averno. The last eruption, in 1538, was preceded by a ground uplift that reached 19 meters in two years and gave rise to the volcano Monte Nuovo. Since then, the caldera has been quiescent, “dormant,” but now shows signs of activity such as seismicity, fumaroles, and ground deformation.
In particular, the Phlegraean Fields are characterized by the phenomenon of bradyseism, that is a slow lifting and lowering of the soil. The last bradyseismic crises occurred in 1969-1972 and 1982-1984 with a considerable lifting of the ground and hundreds of earthquakes that led to the removal of the population of the Rione Terra di Pozzuoli.
Since 2006 the soil lifting reached a new phase and in 16 years rose by one meter causing many earthquakes.
Since 2012, the variations of some parameters monitored by the INGV Vesuvius observatory (seismicity,changes in the geochemical composition of the Fumarola ans soil gas and soil uplift) led to the need to raise the alert to the yellow level and the activation of the operational phase of attention.
In the past, the volcanic activity of the Phlegraean Fields has been mainly characterized by explosive eruptions. This type of eruption, and the following phenomena, could also be expected in the future:
- formation of an eruptive column of gases and shreds of incandescent lava, high up to tens of kilometres;
- falling of large volcanic material in the area closest to the eruptive mouth, and also of ash and lapilli up to ten kilometers away, along the wind direction;
- pyroclastic flows (avalanches of gas, ash and volcanic fragments) generated by the collapse of the eruptive column. These flows have high speeds and temperatures and can flow for several kilometres;
- phreatic explosions, particular explosive phenomena that occur mainly in areas with intense hydrothermal activity, such as that of Solfatara/Pisciarelli;
- flooding of depressed areas, due to abundant rainfall generated by the water steam released during the eruption and the accumulation of volcanic ash that makes the soil impermeable.
At the Phlegraean Fields there is a volcanic monitoring system of geophysical and geochemical parameters (seismicity, ground deformation, gas composition and temperature, etc.), changes in which could anticipate an eruption.
The Monitoring of these phenomena is essential for defining the volcano’s activity status and alert level, and for the implementation of measures in the Civil Protection Plan. However, current scientific knowledge does not allow us to predict with certainty when, how and, particularly for a caldera, where the next eruption will occur. Also, it is not possible to predict the duration of the eruption.
The alert system provides specific “alert levels” describing the state of activity of the volcano, based on the parameters of monitoring and any ongoing phenomena. The green alert level corresponds to the ordinary activity of the volcano while the yellow, orange and red alert levels represent increasing stages of unbalance of the volcano towards a possible eruption. The duration of each alert level can be extremely variable.
The alert levels are declared by the Department of Civil Protection, in conjunction with the regional civil protection. A possible change in level is assessed on the basis of the indications provided by the Vesuvian Observatory of the National Institute of Geophysics and Volcanology and the opinion of the National Commission for the Forecasting and Prevention of Major Risks.
Actions to be implemented by the National Civil Protection Service are defined in the operational phases (attention phase, pre-alarm and alarm) provided for in the civil protection plans. The President of the Council of Ministers declares the pre-alarm and the alarm phase.
For the red zone, the only preventive measure is to remove the population before the eruption begins. People can decide whether to find accommodation outside the risk zones or to benefit from accommodation offered by the State in the Autonomous Region or Province twinned with their Municipality.
For the yellow zone, the removal of the population will be assessed on the basis of the current event, the direction of the winds and the extent of the eruption.
The Plan for volcanic risk at the Phlegraean Fields is set at national level, therefore it must be drawn up by the entire National Service of Civil Protection starting from the Civil Protection Department, the Campania Region, the Prefecture of Naples, the Municipalities of the red zone, the Regions and twinned autonomous Provinces.
The red zone encompasses the area exposed to pyroclastic flows which, due to their high temperatures and speed, represent the most dangerous phenomenon for people. The red zone includes the municipalities of Pozzuoli, Bacoli, Monte di Procida and Quarto; part of the municipalities of Giugliano in Campania and Marano in Naples; some districts of Naples: Soccavo, Pianura, Bagnoli, Fuorigrotta and part of the districts of San Ferdinando, Posillipo, Chiaia, Arenella, Vomero, Chiaiano and Montecalvario.
The yellow area includes the area exposed to the danger of lapilli and volcanic ash fallout. The yellow zone includes the municipalities of Villaricca, Calvizzano, Marano di Napoli, Mugnano di Napoli, Melito di Napoli, Casavatore and 24 districts of the Municipality of Naples: Arenella, Avvocata, Barra, Chiaia, Chiaiano, Mercato, Miano, Montecalvario, Pendino, Piscinola, Poggioreale, Porto, San Carlo all’Arena, San Ferdinando, San Giovanni a Teduccio, San Giuseppe, San Lorenzo, San Pietro a Patierno, Scampia, Secondigliano, Stella, Vicaria, Vomero and Zona Industriale.
In the pre-alarm phase, people wishing to leave the red zone can do it independently, moving to an alternative accommodation (second home, to relatives or friends, rented house)part receiving a financial contribution from the State.
In the alarm phase, the population can decide whether to move by their own means, notifying their municipality, following the routes provided by the plan and according to the timetable established, or by means made available by the State. It is possible to decide whether to move to an alternative accommodation chosen independently, receiving a financial contribution from the State, or to benefit from the accommodation offered in the region or autonomous twinned province.
Those who decide to leave with the means made available by the State, are required to go to the waiting area identified by the Municipal Civil Protection Plan, either independently or with the shuttles organized by their municipality. From here, the transfer to the meeting area outside the red zone will take place with the buses of the Campania Region while the transfer to the Region or twinned Autonomous Province will be provided by the means of transport identified by the planning (train, bus, ship). Details regarding the transfer and reception to the population will be defined in the Plans of the individual Regions and Autonomous Provinces.