Based on the state of activity, the scientific community divides volcanoes into two main categories: extinct and active. The latter can be further divided into two subgroups: quiescent and with persistent activity. The first are volcanoes whose last eruption took place over the last 10 thousand years and which, despite being in a resting phase, continue to show signs of volcanic activity. It is not possible to exclude that in the future they may return to erupt again. According to a more rigorous classification, scientists consider as dormant those volcanoes whose current resting time is less than the longest previously recorded resting period. In Italy they find themselves in this situation: Vesuvius, Campi Flegrei, Colli Albani, Lipari, Ischia, Vulcano, Pantelleria, Panarea and Isola Ferdinandea. On the other hand, those volcanoes that give continuous eruptions or separated by short periods of rest are defined as persistent activity. In Italy there are two, as also reported by the Ingv: Etna and Stromboli.
Quiescent volcanoes in Italy
Among the dormant volcanoes present in Italy, Vesuvius, Vulcano and Campi Flegrei are distinguished by a very low eruptive frequency. Furthermore, all three are in a state of blocked duct activity. The level of risk of dormant volcanoes depends on various factors, including the danger of the expected phenomena and the size of the exposed population. Another characteristic that must be taken into consideration are the secondary volcanic phenomena, such as the fumaroles, typical of the Phlegraean Fields, and the degassing from the soil.
Volcanoes with persistent activity in Italy: Etna
Etna is located along the eastern coast of Sicily and covers an area of about 1250 km². Its 3,300 meters high make it the largest volcano in Europe. It has four eruptive vents located at the top of the volcanic building, known as Bocca Nuova, Voragine, Northeast Crater and Southeast Crater. Its eruptions occur at intervals that can last from a few months to twenty years. Among the most recent episodes, that of September 2021 when an eruption was recorded, with an intense emission of lava ash.
Besides Etna, the only other persistently active volcano in Italy is Stromboli. It is distinguished by the explosions of moderate energy, with the launch of shreds of incandescent lava, lapilli and ash up to a few hundred meters high, which originate from its different mouths every 10-20 minutes. It is precisely this characteristic, known as ‘Strombolian activity’, that makes it one of the most active volcanoes in the world. One of the last episodes dates back to October 2021, with a strong explosion on the North crater.