This landform began to appear in the Messinian stage of the Miocene, about 7.2 to 5.3 million years ago. It went on to mature in the Pliocene. Also in this time volcanic activity associated with the faults and the weakening of the crust over the subduction created the volcanic zones of Latium and Campania, which intruded into the karst-graben, mainly on the karst side. In the Pleistocene the basins slowly filled with sediment from the weak run-off of the mountains, accelerating with the deforestation of modern times.