A weak layer of crust deep below the floor of Italy's Campi Flegrei causes the caldera to undergo periods of earth-trembling unrest, new research has found.
According to the new study, published April 5 in the journal AGU Advances, this layer sits between 1.8 and 2.5 miles (3 to 4 kilometers) deep. It is made of a rock called tuff, which has been weakened by multiple magma intrusions over tens of thousands of years.
