Concern is mounting over the risk of an eruption on a sprawling volcanic area close to Naples after the area was struck by the strongest earthquake in 40 years. Seismic activity on Campi Flegrei, a constellation of ancient volcanic craters, has intensified over the past year and especially in recent months, with more than 80 events occurring in the early hours of Wednesday morning, the biggest being a 4.2 magnitude quake.

“Considering that seismic activity has only increased in recent months, at the moment we don’t see an end,” Carlo Doglioni, the president of Italy’s National Institute of Geophysics and Volcanology (INGV), told TGCom24. Doglioni said the best-case scenario would be that the activity ends, as it did after a long period of unrest in the early 1980s, while the worst would be an eruption akin to the last one in 1538, which created a series of small hills and craters.