Gases released by magmas at the Campi Flegrei caldera in Naples, Italy, may be reaching a critical pressure that may drive volcanic unrest, suggests a study published in Nature Communications this week. The Campi Flegrei caldera formed 39,000 years ago by the largest eruption in Europe in the past 200,000 years, and recently has been showing signs of reawakening. However, it must be cautioned that there is no indication that an eruption is imminent at Campi Flegrei in the near future.

Long-lived caldera systems commonly develop hydrothermal systems during periods of repose. As a volcano reawakens and magmas rise, complex interactions between the magmas and the overlying hydrothermal systems determine whether the magma will erupt. Giovanni Chiodini and colleagues use physical and volatile models to show that magmas reaching a critical degassing pressure release increasingly water-rich volatile gasses. Injection of these volatiles into overlying hydrothermal systems can lead to heating and expansion triggering an accelerating deformation, which can result in eruption.

Campi Flegrei is a resurgent caldera with signs of unrest since the 1950s. Frequent episodes of uplift and gas emissions evidence indicate that there has been a general heating of the hydrothermal system over the last 15 years. The authors apply their modelling data to Campi Flegrei and suggest that the magmas are reaching a critical degassing pressure. However, they note that the factors underlying volcanic unrest are complex, making it difficult to fully predict the evolution of any period of unrest.