Campi Flegrei

Gas emissions from the fumarole Pisciarelli at Campi Flegrei. Image credit: Mike Stock
Gas emissions from the fumarole Pisciarelli at Campi Flegrei. Image credit: Mike Stock

Campi Flegrei – or the Phlegrean Fields – is a large, complex caldera volcano that lies just to the west of the city of Naples, in central Italy. Vesuvius lies just 25 km away, on the other side of Naples.

Geological Setting

The Campi Flegrei caldera is a part of the ‘Roman Volcanic Province’ of central Italy. These volcanoes typically erupt quite exotic compositions of magmas, notably rich in potassium; but the reasons for this are not agreed.

Last known eruption: The last eruption within the Campi Flegrei caldera was an eruption in 1538, that led to the formation of the Monte Nuovo. This is the only major eruption known from historical times (there was a smaller eruption in 1198), and at the present day the main evidence for the volcanic nature of the caldera comes from the extensive fumaroles, and their vigorous sulphurous fumes.

Explosivity (Volcanic Explosivity Index) – 7. Although the margins of the caldera are not well exposed, Campi Flegrei has experienced some very significant explosive eruptions in the deep past – most notably the Campanian Ignimbrite eruption around 39,000 years ago; and the Neapolitan Yellow Tuff, 15,000 years ago.

Height – 458 m. Large areas of the Campi Flegrei are close to, or below, sea level.

Deadliness. 0. Although this is a large, restless volcano, the lack of recent eruptions means that it scores low on ‘deadliness’.

Wow factor – 23. This is a sprawling volcanic field that might lack the visual ‘wow’ of a classical volcanic peak, but makes up for this in smelliness.

Unpredictability – 84. Campi Flegrei is a large and restless caldera, that has a history of ‘bradyseisms’ – periods of large-scale ground uplift and earthquakes, that then sink back down, or die away. It has had large explosive eruptions in the past; and some of these may have occurred with little warning – but with only two known eruptions in the past 3000 years, there is some uncertainty about its current state. Campi Flegrei is very well monitored by volcanologists from INGV Naples, from their base in the oldest volcano observatory in the world, the Osservatorio Vesuviano.

Devastation Potential – 1000. Based on the huge scale of pre-historic eruptions from Campi Flegrei, and the large urban populations that live both within and outside the caldera, this volcano rates very high on the Top Trumps ‘devastation potential’ score.

Resources about Campi Flegrei. 

Campi Flegrei is very well studied, but much remains to be understood about its current behaviour – and how that links to the way it has behaved in the past. The lakes and craters of Campi Flegrei feature prominently in Roman stories of the underworld: the entrance to Hades was thought to be at lake Avernus. Campi Flegrei is not to be confused with the Campi Flegrei Mar di Sicilia – a cluster of shallow submarine volcanoes south of Sicily, one of which erupted to form the shortlived Graham Island in 1831.