A mysterious eruption came from the Caldera de Campi Flegrei

The eruption forming a caldera of Campi Flegrei (Italy) 40,000 years ago is the largest known eruption in Europe in the last 200,000 years, but little is known about the other major eruptions that occurred on the volcano before a more recent event forming a caldera. A new Geology An article by Paul Albert and his colleagues tackles a 29,000-year-old eruption, here confirmed as coming from Campi Flegrei, which has spread a layer of volcanic ash over more than 150,000 square kilometers of the Mediterranean.

The knowledge of large explosive eruptions is mainly established from geological studies of exposed deposits discovered around the source volcano, deposits of large eruptions forming thick sequences. However, since the late 1970s, an extensive layer of volcanic ash, dated about 29,000 years ago, was commonly identified in the cores of marine and lacustrine sediments on the other side of the Mediterranean, documenting the occurrence of a large magnitude eruption. Despite this extensive distribution and its relatively young age, no clear evidence of such an event has been identified on any of the region's major active volcanoes.

In this study, the detailed chemical analysis (volcanic glass) carried out by the team of an eruption deposit discovered five kilometers northeast of the Caldera de Campi Flegrei in Naples, in Italy, corresponds quite to the distinctive composition of this layer of ashes. This, combined with a new dating of the near-source eruption site, confirms that Campi Flegrei was responsible for this widespread ash layer.

The constraints on the size of the eruption were determined by the team using an ash dispersal computer model incorporating the thicknesses of eruption fields close to the source, named here Masseria del Monte Tuff, with those of the corresponding ashfall on the Mediterranean.