Naples lies in the shadow of Vesuvius and next to Campi Flegrei.

Mount Vesuvius, the volcano responsible for the destruction of Pompeii and Herculaneum in 79 AD, remains one of the most dangerous volcanoes in the world.

Situated less than 10 km from the southern Italian city of Naples, a densely populated metropolitan area home to more than three million people, Vesuvius is the only active volcano in continental Europe.

The volcano is currently in a phase of “active rest”, according to the Vesuvius National Park, and it is constantly monitored to detect any significant variation in its activity.

Part of a large volcanic area that formed almost two million years ago, Vesuvius is a composite stratovolcano, meaning it has the potential for explosive, high-energy eruptions.

Unlike shield volcanoes, which produce slow-moving lava flows, stratovolcanoes like Vesuvius can generate violent explosions, launching ash, gas and molten rock into the sky.

Eruption of Mount Vesuvius

The next eruption of Vesuvius would most likely be an "explosive eruption of medium-low energy", according to Italy's civil protection department.

The most recent eruption, marked by low-energy effusive and explosive activity, was in 1944, killing 21 people dead and partially destroying the towns of San Sebastiano al Vesuvio and Massa di Somma.

While this event was significant, it was relatively minor compared to earlier eruptions - particularly the catastrophic 1631 eruption, which covered Naples in ash and led to thousands of deaths.

However, while modern technology can detect warning signs, the task of predicting the exact timing and scale of an eruption remains a challenge.

The immediate impact of a Vesuvius eruption

If Vesuvius were to erupt today, the scale of devastation would depend on several factors, including the size of the eruption, the wind direction and the response time of emergency services.

Even a moderate eruption could significantly impact Naples and its surroundings, while a large-scale eruption could have consequences reaching across Europe and beyond.

While the most likely type of explosive eruption at Vesuvius will be of medium-low energy, as a safety measure the civil protection department emergency plans refer to a medium energy eruption scenario. This includes:

• An eruptive column made of gas, burning lava clots and ash several kilometres high
• The fall of volcanic material, both large ("lava bomb" rocks) in the area nearest the volcano and smaller particles (ashes and lapilli) which are blown by the wind and can be deposited tens of kilometres away
• Pyroclastic flows, which are superheated avalanches of gas, ash and volcanic fragments that flow at high speed for several kilometres down the slopes of the volcano.
• Seismic activity may occur before the eruption and accompany its different stages, damaging buildings already hit by falling ash and lapilli.

Ashfall over Naples and beyondEven if pyroclastic flows remain limited to the immediate area, volcanic ash could spread across southern Italy and beyond, depending on the wind direction. The effects of heavy ashfall would include:

• Roof collapses and structural damage due to the weight of accumulated ash.
• Severe disruptions to air travel, with airports like Naples International Airport shutting down for days or even weeks.
• Health hazards caused by fine ash particles, which can lead to respiratory problems and eye irritation.
• Water contamination, as volcanic ash can infiltrate reservoirs and drinking water supplies.

Tsunami riskAnother dangerous possible consequence of a major eruption is a tsunami in the Bay of Naples.

This has happened in past eruptions and could threaten coastal cities and towns, including Sorrento, Amalfi and Positano, as well as maritime infrastructure, disrupting ports and sea routes in the Mediterranean.

Campi Flegrei

Vesuvius is not the only volcanic threat to Naples. Just west of the city lies Campi Flegrei, a highly seismic area with the potential for an even greater disaster.

Unlike Vesuvius, which is a single peak, Campi Flegrei is a giant volcanic system, made up of 24 craters and several active fumaroles.

Why is Campi Flegrei so dangerous?

The largest active urbanised caldera in the heart of the European continent, Campi Flegrei last erupted in 1538, creating Monte Nuovo, according to Italy’s National Institute of Geophysics and Volcanology (INGV) which monitors the caldera closely.

Experts believe the recent spike in seismic activity is linked to bradyseism, a phenomenon that involves the gradual uplift or descent of part of the earth's surface, caused by the filling or emptying of underground magma chambers or hydrothermal activity.

In response to a "sensational" documentary in 2024 that represented a doomsday scenario for Campi Flegrei, followed by "alarmist" media reports, the INGV said that, based on the scientific data available at the time, there was "no evidence of the imminence of a volcanic eruption, much less of large proportions".

The two most devastating eruptions in Campi Flegrei occurred about 40,000 years ago and about 15,000 years ago, when tens to hundreds of cubic km of magma erupted in a single event.

INGV experts stressed that none of the 70 eruptions that have occurred in the area in the last 15,000 years come "even remotely close" to such devastating events.

The INGV said that the probability that the next eruption will be of a similar force as the one 15,000 years ago is "very low" and that in order for such an large-scale eruption to occur, it would require an enormous amount of magma whose entry into the system would be detected by the monitoring system.

What would happen if Campi Flegrei erupted?

A major Campi Flegrei eruption could cover Naples and surrounding areas in ash, trigger earthquakes and landslides throughout southern Italy as well as cause widespread air pollution and acid rain.

Following the 4.4-magnitude earthquake in Campi Flegrei on 13 March 2025, Francesca Bianco, director of the Vesuvius Observatory, the Naples branch of the INGV, said: "For the moment we are at another step of intensification of the bradyseismic process, like what happened in August 2023 and May 2024, but for now no type of process that gives us a signal of imminent eruption, for this to happen magma must rise to the surface and this is not happening.”

Is Italy prepared?

Italy has emergency plans, including for the mass evacuation of people living in the areas of Vesuvius and Campi Flegrei, particularly residents in the high-risk red zones.

Italy's public warning system IT-alert broadcasts useful information to cell phones in a given geographical area in the event of imminent or ongoing serious emergencies or disasters, including an upcoming eruption at Vesuvius or Campi Flegrei.

Both Vesuvius and Campi Flegrei are monitored very closely, however Naples remains one of the most vulnerable cities in the world to volcanic disaster.