The densely inhabited area of Naples, Italy, between Campi Flegrei caldera and the Vesuvius volcano, is one of the most hazardous regions in the world-Heritage data from ESA’s ERS and Envisat missions are proving to be vital in studying possible interactions between the two volcanic landforms.

Over the past 15,000 years, several dozen eruptions occurred at Campi Flegrei, accompanied by the resurgence of its centre. After approximately three thousand years of quiescence and centuries of subsidence, the last eruption occurred in 1538, and was preceded by a period of increasing seismic activity and uplift.

Since then, Campi Flegrei has been generally subsiding but has experienced intermittent unrest since the 1950s, with four main episodes of activity occurring between 1950–1952, 1969–1972, 1982–1984, and 2005 to the present day.

Since 2012, the alert level of Campi Flegrei has been “yellow”. As for Vesuvius, the most recent Plinian eruption took place in 79 AD, and was followed by sub-Plinian eruptions in 472 and 1631. The latter was followed by semi-persistent activity that lasted until 1944. Since then, Vesuvius has been considered dormant and the alert level is “green”.

Although Campi Flegrei and Vesuvius are only about 25 km apart, their eruptive histories are different and the materials produced by their respective eruptions, such as lava or ash, have contrasting physical characteristics. Nevertheless, past erupted products are not incompatible with the possible existence of a magma accumulation layer at a depth of 8-10 km, which extends beneath the entire Neapolitan volcanic area; geophysical investigations also suggest the presence of this layer. However, whether some interaction between Campi Flegrei and Vesuvius, such as a shared source of magma, actually exists remains an open question.

The Heritage Mission programme ensures that data from missions that are no longer operational are continuing to aid in present day scientific studies, which have extensive benefits for our society and the ongoing environmental research of the planet. 

Some examples of key missions from the programme include the European Remote Sensing satellites (ERS-1 and ERS-2), and Envisat.

In particular, the SAR images produced by ERS-1/ERS-2, and Envisat are the only ones from which it is possible to obtain reliable and uninterrupted ground displacement time series in the Campi Flegrei and Vesuvius region, from the early 1990s to 2010.

A team of researchers from the Department of Physics, University of Salerno, Italy, and from the Department of Earth Sciences, University of Cambridge, UK, used ground displacement time series from ERS-1, ERS-2, and Envisat images to investigate the ground deformation history in the whole area comprising Campi Flegrei and Vesuvius from 1993 to 2010, during the transition from subsidence to uplift at Campi Flegrei; while the ground displacement time series were provided by the National Research Council of Italy.

They used a blind source separation technique called variational Bayesian independent component analysis (vbICA), with the objective of decomposing space-time displacement fields into separated statistically independent components, consisting of ground displacement spatial distributions and associated temporal evolutions. In this way, they showed that the transition from subsidence to uplift at Campi Flegrei occurred concurrently with the onset of a contraction of a deep volume below Vesuvius.

This suggests the possibility of the transfer of magma and/or magmatic fluids between the plumbing systems of the two volcanoes at a depth of 8–9 km during the investigated period, thus indicating that Campi Flegrei and Vesuvius are somewhat interacting.

The researchers from the Department of Physics at the University of Salerno also used ERS-Envisat ground displacement time series and those obtained from Copernicus Sentinel-1A imagery, to compare the ground displacement pattern at Campi Flegrei during the 1993-2000 subsidence, with the one during part of the present uplift (2015-2022). In this way, they obtained the first evidence of the deformational effects of a pressurised source at approximately 8 km depth during the Campi Flegrei uplift.

Luca Crescentini, Head Researcher at the University of Salerno, states, “The use of historical data from ESA’s Heritage Programme has proven to be a game-changer in analysing volcanic interactions across different historical periods, to better understand current ground displacement phenomena and the general behaviour of volcanic areas”.