At the end of the Eocene and the Pyrenean-Provençal compression, the formation of the large basins of Carpentras, Malaucène, and Vaison and of the collapse ditches of Aurel-Sault and Barroux individualized the Mont Ventoux. For twenty million years, it formed an island above the shallow sea that covered the Rhone Valley. The Alpine uplift of the Middle Miocene (from -16 to -2 Ma) gave the massif its current structure following the closure of the Strait of Gibraltar and the 4,921 ft (1,500 m) drop in the level of the Mediterranean Sea. During the Quaternary, the uplifting of ripples and the deepening of the hydrographic network continued. The current facies of Mont Ventoux - characterized by the development of karstification and the formation of the cryoclastic scree of its summit cap - is due to the alternation of glaciations and warmer periods.