A MASSIVE underground volcano in southern Italy could be heading towards a catastrophic eruption would would have disastrous consequences for the city of Naples, and the 1.5 million people who live there, a new study has shown. A team led by Francesca Forni from the Institute of Geochemistry and Petrology in Switzerland has been studying 23 previous eruptions at the Campi Flegrei caldera, concluding the magma reservoir underneath the area, which they described as “one of the most hazardous regions on Earth” may be building up in advance of a massive explosion. Their research, published in the journal Science Advances involved detailed analysis of rocks, minerals and glass samples from each of the eruptions in an effort to detect changes in magmatic temperature and water content throughout the region’s eruptive history.
The region was the scene of two huge eruptions – the Campanian Ignimbrite (CI) eruption of 39,000 years ago and the Neapolitan Yellow Tuff (NYT) eruption which happened 15,000 years ago – plus many smaller events.
The most recent was the eruption of Monte Nuovo in 1538.
Ms Forni and her colleagues concluded the Monteo Nuovo eruption was charaterised by “highly differentiated magmas” similar to those which fed the CI and NYT eruptions – suggesting a new phase was now underway.
Their report said: “Home to more than 1.5 million people, the Campi Flegrei caldera represents one of the most hazardous regions on Earth, and its magmatic history has been the focus of a number of studies
“We suggest that this eruption is an expression of a state shift in magma storage conditions, whereby substantial amounts of volatiles start to exsolve in the shallow reservoir.
“The presence of an exsolved gas phase has fundamental consequences for the physical properties of the reservoir and may indicate that a large magma body is currently accumulating underneath Campi Flegrei.
“After the Monte Nuovo eruption, the Campi Flegrei caldera has entered a new phase of quiescence accompanied by several episodes of ground deformation.
“Three major periods of unrest characterised by shallow seismicity and an increase in hydrothermal degassing have been recorded since the 1950s, thus increasing concern for a potential reawakening.
“Transfer of magmatic fluids from the main reservoir located at a depth of 7 to 8 km to the shallow hydrothermal system has been indicated as the possible cause for the recent unrest.
The high CO2 content of fumarolic gases is compatible with the typical compositions of recharge magmas at Campi Flegrei.
“We suggest that this behaviour is consistent with the presence of water-saturated conditions in the upper crustal phonolitic reservoir, which facilitates the accommodation of volatile-rich recharge magmas without leading to an eruption, promoting reservoir growth.
“Hence, we propose that the subvolcanic plumbing system at Campi Flegrei is currently entering a new build-up phase, potentially culminating, at some undetermined point in the future, in a large volume eruption.”
Ms Forni told the New York Times the presence of two calderas – CI and NYT – suggested Campi Flegrei had completed at least one cycle, adding: “We are potentially at the start of a new cycle.”
She said it was impossible to predict when another eruption would occur, explaining: “The best we can do for now is to see how the system behaved in the past.”