The Campi Flegrei are an active volcanic complex surrounded by high-risk urban areas. Among the most studied in the world, their eruptive history is only well documented for the past 40,000 years. A new study reveals that 109,000 years ago, an eruption of similar magnitude to the ‘Ignimbrite Campana’ occurred, the largest eruption in the Mediterranean area.

Reconstruction of the magnitude of the eruption was carried out by an Italian team of researchers from the Institute of Environmental Geology and Geoengineering of the National Research Council (CNR-IGAG), Sapienza University of Rome, the National Institute of Geophysics and Volcanology (INGV), and the University of Bari “Aldo Moro”. The study was published in Nature's journal Communications Earth and Environment.

“In the Phlegraean Fields area, the geological evidence of the oldest activity is difficult to access because it lies deep underground, under considerable thicknesses of more recent volcanic rocks”, says Gianluca Sottili and Giada Fernandez, from Sapienza University of Rome. “Reconstructing the entire eruptive history of this volcano is nevertheless crucial to highlight some fundamental parameters for defining its hazard, such as the frequency and magnitude of eruptive events. In this respect, the ash produced by large eruptions deposited in areas remote from the volcano offers the possibility of extending the study of a volcano's eruptive history far back in time, allowing for a more complete reconstruction”.

“Just as fingerprints or DNA distinguish individuals, certain stratigraphic, chemical and chronological properties of ash levels found in marine or lake sediments, even thousands of kilometres from the volcano, can allow scientists to identify the volcanic source and, in some cases, even the single eruptive event that produced them”, adds Biagio Giaccio, of the CNR-IGAG. “More precisely, through the dating and chemical analysis of the micro-fragments of pumice, of which the volcanic material transported by the wind to distant areas is made up, it is possible to reconstruct the ash dispersion area of a specific eruptive event”.

“With the data already at our disposal and by means of volcanic ash dispersion models, we were able to reconstruct the dynamics and magnitude of the eruption”, continues INGV's Antonio Costa. “We have thus obtained estimates of some fundamental parameters such as, for example, the volume of magma erupted and the height of the column or cloud of ash and gas”.

Through this multidisciplinary approach, commonly applied to recent eruptions whose traces are clearly documented around the volcano, the researchers reconstructed the main eruptive parameters of an ancient Phlegraean eruption of 109,000 years ago, known as the ‘Maddaloni Eruption’, which is almost inaccessible in the volcano area but well documented by ash deposited in remote areas, known as ‘X-6’ and found in a wide area of the Mediterranean, from central Italy to Greece.

“Surprisingly”, continues Antonio Costa, “the modelling results provided a magnitude estimate of 7.6, i.e. slightly lower than that of the famous Campanian Ignimbrite of around 40,000 years ago, defining the eruption of Maddaloni as the second largest event in the eruptive history of the Phlegraean Fields”.

“The fact that this volcanic system has produced several large eruptions throughout its history suggests that the structure of the caldera, the volcano-tectonic depression that forms during large eruptions following the release of a large volume of magma to the surface, may be much more complex than previously assumed”, points out Jacopo Natale of the University of Bari “Aldo Moro”.

The results of the research shed new light on the recurrence of large magnitude events at the Phlegraean Fields and show how, even for an intensely studied volcano, a detailed and complete reconstruction of its history requires further investigation for a better assessment of volcanic hazard.

References: 

Giada Fernandez, Antonio Costa, Biagio Giaccio, Jacopo Natale, Danilo M. Palladino, Gianluca Sottili, “The Maddaloni/X-6 eruption stands out as one of the major events during the Late Pleistocene a Campi Flegrei”, Communications Earth & Environment, 2025, 6:27, https://doi.org/10.1038/s43247-025-01998-8

Further Information:

Gianluca Sottili

Department of Earth Sciences

gianluca.sottili@uniroma1.it

Giada Fernandez

Department of Earth Sciences

giada.fernandez@uniroma1.it