The digging process of the Verdon in its gorges did not meet the same conditions everywhere, hence their more or less significant narrowing. In the middle part, the extreme narrowness of the canyon is explained by the incision of the notch in a single perfectly homogeneous and hard layer of tithonic limestone. On the other hand, upstream and downstream, the erosion of the torrent has scoured by the base outcrops of less hard lower layers. Such a phenomenon caused landslides of the upper layers and gave rise to wider and not-so-high sections with fewer vertical walls.