The crust of Campi Flegrei volcano, which last erupted in 1538, has become weaker and may lead to a volcanic eruption
by Victoria Heath
A new study has revealed that parts of the Campi Flegrei volcano in southern Italy have been stretched almost to breaking point, confirming scientists’ prediction that the structure of its crust is changing and may make the volcano more prone to eruption.
Published in Nature’s Communications Earth & Environment journal, the new study is the first to apply a volcano modelling method, created by UCL, to any volcano. The model is based on ‘the physics of how rocks break’, according to Kilburn.
‘Our new study confirms that Campi Flegrei is moving closer to rupture,’ said lead author, Professor Christopher Kilburn of UCL Earth Sciences. ‘However, this does not mean an eruption is guaranteed. The rupture may open a crack through the crust, but the magma still needs to be pushing up at the right location for an eruption to occur.’
The study of Campi Fregrei’s crust
Volcanoes which erupt after a prolonged period of inactivity must rupture the crust before magma erupts. A rupturing sequence has been developing across four episodes of ground uplift at the Campi Flegrei caldera: in 1950-1952, 1969-1972, 1982-1984 and since 2004.
The study suggests that these ruptures are caused by the movement of fluids about two miles beneath the surface, including molten rock or natural volcanic gases.
Researchers at UCL and Italy’s National Research Institute for Geophysics and Volcanology (INGV) used a model of volcano fracturing to interpret earthquake patterns and ground uplift to determine the study’s conclusion.
Campi Fregrei’s current tensile strength (the maximum stress that a stretched material can bear before it breaks) is around a third of its strength in 1984, according to researchers.
‘Our results show that parts of the volcano are becoming weaker,’ said Dr Nicola Alessandro Pino from the Vesuvius Observatory, which represents the INGV in Naples. ‘This means that it might break even though the stresses pulling it apart are smaller than they were during the last crisis 40 years ago.’
The history of Campi Flegrei
Campi Flegrei is the largest active caldera in Europe, extending from Naples to the Tyrrhenian Sea. Approximately one-third of the caldera is partially submerged under the Bay of Pozzuoli, with the other two-thirds being home to more than 360,000 people.
The volcano has been mostly restless for more than 70 years, with two-year spikes of unrest in the 1950s, 1970s and 1980s, and a slower phase of unrest throughout the last ten years.
In these periods, tens of thousands of small earthquakes occurred. Pozzuoli, a coastal town, has been lifted by nearly 4m (13ft) – roughly the height of a double-decker bus.
These earthquakes are the result of faults slipping due to the crust stretching. In the pattern of earthquakes from 2020, the rock appears to respond in an inelastic way, breaking rather than bending.
The future of UCL’s volcano modelling method
Researchers will now begin to apply the volcano modelling method developed by UCL to other volcanoes which have erupted after a period of inactivity. They will then be able to gain more reliable criteria to decide if an eruption is likely.
‘We will now have to adjust our procedures for estimating the chances of new routes being opened for magma or gas to reach the surface,’ said Kilburn. ‘The study is the first of its kind to forecast rupture at an active volcano. It marks a step change in our goal to improve forecasts of eruptions worldwide.’
