What to know - Volcanic risk and bradyseism

The caldera of the Phlegraean Fields is featured by the phenomenon of bradyseism, from the Greek bradýs (βραδύς), meaning "slow," and seismós (σεισμός), meaning "movement.": a ground deformation involving slow lowering (subsidence) phases alternating with more rapid uplift phases.

The process of bradyseism is associated with the volcanic activity of a caldera. Uplift occurs due to pressure from beneath the surface, which causes the rocks above to deform and rise. As the rocks deform, they may reach a point of breaking, resulting in earthquakes.

The seismic activity in this area can damage both structural and nonstructural elements of buildings and affect the functioning of infrastructure such as water and gas networks and port docks. The maximum expected magnitude of the earthquakes is estimated to be between 4.5 and 5.0 on the Richter scale. There were bradyseismic crises during 1969-1972 and 1982-1984, which resulted in a total ground uplift of more than three meters and thousands of earthquakes. During these crises, Pozzuoli's historic center residents were displaced and relocated to other parts of the city.

Specific studies of caldera activity indicate that bradyseismic crises do not necessarily end in an eruption, as in the 1970s and 1980s. However, these prolonged bradyseismic phenomena may precede an eruption in some cases.

The current crisis

A new uplift phase of the Phlegraean Fields caldera began in 2005. At the end of August 2024, the maximum uplift value reached in the Rione Terra in Pozzuoli (the point of maximum caldera deformation) was 132.5 cm. Specifically, the uplift recorded from January 2023 to August 2024 was 30.5 cm.

Since 2018, there has been an increase in seismic activity. In 2023, there was a higher frequency of earthquakes, most of which were of low magnitude. However, on September 27 and October 2, earthquakes with magnitudes of 4.2 and 4.0, respectively, were recorded.

The majority of earthquakes in the area occurred between Astroni, Solfatara-Pisciarelli-Agnano, Pozzuoli, and Golfo di Pozzuoli, with maximum depths of about 4 km, and most of them were concentrated in the first 2 km. In 2024, seismic activity increased starting from April, with two major events: on May 20, a magnitude 4.4 earthquake was recorded in the Solfatara area of Pozzuoli, and on July 26, a magnitude 4.0 quake occurred in the Golfo di Pozzuoli.

To check real-time seismic events in the Phlegraean area, click here.

Together with the phenomenon of bradyseism, the Phlegraean Fields area is also affected by volcanic gas emissions from the ground, particularly in the Pisciarelli and Solfatara areas. When present in high concentrations, some of these gases can pose a danger to human and animal health. Carbon dioxide (CO2) is particularly hazardous as it is odorless and colorless. As a result, access to certain areas affected by high concentrations of CO2 may be restricted by the mayor's ordinances.

Explosive eruptions have mainly characterized the volcanic activity of the Phlegraean Fields. 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 kilometers;
•  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 kilometers;
•  phreatic explosions, particular explosive phenomena that occur mainly in areas with intense hydrothermal activity, such as that of Solfatara/Pisciarelli;
•  Mudslides, formed by volcanic fragments, mainly ash and water, that can be generated either during the eruption, due to possible concurrent rainfall, or long afterward.

In the mini-documentary "Volcanic eruptions and bradyseism: The Civil Protection Response," the eruption scenario on which national volcanic risk planning is based is exemplified through a 3D animation.

A volcano's geophysical and geochemical parameters monitoring system is currently active in the Phlegraean Fields and the Gulf of Pozzuoli. By analyzing the observed variations, the scientific community can evaluate changes in the volcanic system that may indicate an upcoming eruption. The Vesuvius Observatory, part of the National Institute of Geophysics and Volcanology (INGV), is responsible for monitoring and analyzing volcanic gas characteristics, as well as collecting data on seismic activity and ground deformation. The National Research Council's Institute for Electromagnetic Sensing of the Environment (CNR-IREA) also contributes to this monitoring through satellite observations.

The warning system features four alert levels that are determined by monitoring parameters and the activity status of the volcano. A green alert indicates regular volcanic activity, while yellow, orange, and red alert levels signify increasing volcano instability, possibly leading to a potential eruption. The duration of each alert level can vary significantly. The Civil Protection Department, in collaboration with the Campania Region, is responsible for declaring these alert levels.

Changes in alert levels are determined based on assessments from INGV's Vesuvius Observatory and the advice of the National Commission for the Forecasting and Prevention of Major Risks. The National Civil Protection Service outlines the necessary actions during the operational phases of attention, pre-alarm, and alarm as part of civil protection planning. The President of the Council of Ministers is responsible for declaring the pre-alarm and alarm phases in anticipation of a potential eruption.

In 2012, the volcanic risk alert was elevated to a yellow level due to ongoing changes in various monitored geophysical and geochemical parameters, such as increased seismic activity, alterations in gas emissions, and ground uplift. This prompted the activation of the attention phase that included enhanced monitoring activities and the validation of civil protection plans.

The National Emergency Planning for volcanic risk in the Phlegraean Fields has clearly defined the red and yellow zones, which should not be confused with the expected volcano alert levels.

Red zone: includes the area exposed to the risk of pyroclastic flooding, which, due to their high temperatures and speed, represent an extremely dangerous phenomenon for people.

Municipalities of the red zone: Bacoli, Monte di Procida, Pozzuoli, Quarto and part of the municipalities of Giugliano in Campania, Marano di Napoli, and some neighborhoods of Napoli: Bagnoli, Fuorigrotta, Pianura, Soccavo and part of the neighborhoods of Arenella, Chiaia, Chiaiano, Montecalvario, Posillipo, San Ferdinando and Vomero. Residents: about 500,000.

Yellow zone: includes the area outside the red zone exposed to the danger of lapilli and volcanic ash fallout.

Municipalities of the yellow zone: 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. Residents: over 800,00.

A browsable map of volcanic risk zones is available on the Civil Protection Department website.

Bradyseism affects the whole area of the Phlegraean Fields. Still, the most affected areas are the intervention area and, in particular, the restricted intervention area (internal to the red zone), identified in the Rapid Emergency Planning for the bradyseismic phenomenon.

Intervention area: includes the area affected by earthquakes of magnitude 2 or more (recorded since 1983) and ground uplifts of 10 cm or more since 2015 (corresponding to about 20 cm since 2006). The data refer to October 2023, the month the intervention area was identified. Municipalities involved: Pozzuoli, Bacoli, and Napoli (Bagnoli district and parts of Soccavo/Pianura and Posillipo municipalities). Residents: about 85,000.

Restricted intervention area: this is the area within the intervention area affected by earthquakes of magnitude 2 or greater (recorded since 1983) and ground uplift equal to or greater than 30 cm since 2015 (corresponding to about 45 cm since 2006). The data again refer to October 2023. The greatest effects could occur in this area if bradyseism continues and/or intensifies. Municipalities involved: part of Pozzuoli and a small part of Napoli (Bagnoli district). Residents: more than 33,000.

A browsable map of the intervention area is available on the Civil Protection Department's website.

National planning for volcanic risk in the Phlegraean Fields is based on alert levels and reference scenario of a possible eruption and identifies the risk zones (red and yellow). It also describes the activities required to be organized by the Civil Protection System in the different operational phases (attention, pre-alarm, and alarm) preceding a possible eruption. The Department of Civil Protection coordinates planning in conjunction with the Campania Region, INGV Vesuvius Observatory, Prefettura-UTG of Napoli, municipalities in the red zone, twinned Regions and Autonomous Provinces, and all institutionally mandated parties.

Attention: Volcano monitoring is intensified and Civil Protection Plans are tested.

Pre-alarm: Operations begin in the red zone to relocate people in hospitals and penal institutions, move farm animals, and secure major cultural heritage.

Alarm: The entire population from the red zone must be evacuated. The maximum estimated time for this activity is three days (72 hours). Operations are coordinated by the Civil Protection Authorities.

Evacuation from the red zone: In the pre-alarm phase, individuals can voluntarily relocate to accommodations of their choice and receive financial support from the state. However, if there is an alert for a potential eruption, mandatory evacuation of the population residing in the red zone becomes necessary as the only safety measure. An IT-alert message is sent to cell phones in Campania to announce the start of operations.

People who decide to evacuate independently must inform their municipality and follow the designated road routes according to the established schedules. From these planned routes, they can access accommodations offered in the twinned region or autonomous province or any housing they have personally identified, such as a second home, the homes of relatives or friends, or a rented property. They will receive financial assistance from the state for their evacuation.

People who decide to evacuate with assistance will be accommodated in a twinned region or an autonomous province. To utilize the state's resources, individuals must reach the designated waiting areas identified by the Municipal Civil Protection Plan. This can be done either independently or by using the shuttles organized by their municipality. Transfers to the meeting areas outside the red zone will be conducted from the waiting areas using buses provided by the Campania Region. Travel to the twinned region or autonomous province will then be arranged using transportation options outlined in the plan, such as trains, buses, or ships. The specifics of population reception are detailed in the individual plans of the Regions and Autonomous Provinces.

Waiting areas, meeting areas, and first-level gates can be found on the Department of Civil Protection website.

For the yellow zone, evacuation measures will be assessed during the event based on the severity of the eruption and wind direction. This assessment will help determine which areas will likely be most affected by ash fall.

Why isn't alternative accommodation offered in less populated areas of the Campania Region?
Due to the high number of people living in the red zone, relocating them to Campania would create significant challenges in terms of organization and habitability. Small towns lack the necessary public facilities to accommodate such a large population influx. Instead, relocating to other regions or autonomous provinces would allow the citizens from the red zone to access better housing, healthcare, continuity in schooling, and essential services.

In response to the ongoing bradyseismic crisis, volcano monitoring activities have been enhanced, and, more generally, prevention actions of the Civil Protection System have been strengthened through Decree-Law No. 140 of October 12, 2023.

The measure outlines a series of actions, including analyzing the vulnerability of built-up areas, creating a Rapid Emergency Planning framework, establishing a Communication Plan, verifying the functionality of transportation infrastructure and other essential services, and enhancing the local civil protection operational response.

Updates on ongoing civil protection activities are available on the Department of Civil Protection website.

Rapid Emergency Planning

The plan, prepared by the Civil Protection Department in collaboration with the Campania Region and in consultation with the Prefecture of Napoli, as well as local authorities and administrations, outlines the strategy and operational procedures for addressing the effects of bradyseism in both the intervention area and the restricted intervention area.

Unlike volcanic risks, there are no established alert levels for bradyseism due to the unpredictable nature of seismic activity and ground deformation. Instead, the plan outlines three operational scenarios of increasing severity, focusing on the varying impacts of bradyseism on buildings and infrastructure. Following the guidelines for Rapid Planning, municipalities within the affected area are responsible for updating their Municipal Civil Protection Plans with specific measures related to bradyseism.

Is evacuation also expected for residents in the intervention area?
In the third scenario, which is the most serious, the population in the restricted intervention area may need to be temporarily evacuated and moved to other municipalities in Campania. This would occur if damage to buildings and infrastructure prevents essential services from being ensured for residents. Timely evacuations could be required at any moment.