Risk description

Although less frequent and devastating than earthquakes, volcanic eruptions pose a significant risk to the densely populated areas of the Italian territory. Volcanic risk can be defined as the product of the probability of occurrence of an eruptive event and the damage that could result from it.

Risk can be translated into the equation R = H x V x E, where:

H = Hazard: it is the chance that a phenomenon of a certain intensity occurs within a specific time frame and in a given area.

V = Vulnerability: it refers to the susceptibility of an element—such as people, buildings, infrastructure, or economic activities—to experience damage when exposed to stresses from an event of a given intensity.

E = Exposure or Exposed value: it refers to the quantity or 'value' of at-risk elements—such as people, buildings, or other assets—present in a specific area.

In general, the Vulnerability of people and buildings is always high when it comes to volcanic phenomena. The risk is minimal only when the Hazard or the Exposed value is also minimal. This is the case for "extinct" volcanoes, volcanoes that show phenomena with limited danger, or volcanoes located in uninhabited areas.

The greater the probability of an eruption, the greater the risk. When the hazard level is the same, however, risk increases with the degree of urbanization around the volcano. For instance, the risk is higher for Vesuvius, where approximately 600,000 people live in the surrounding areas, compared to the volcanoes in Alaska, which are located in low-population-density areas.