The Mediterranean Sea evaporated almost completely 5.6 million years ago
When tectonic movement sealed the Strait of Gibraltar around 5.96 million years ago, the Mediterranean lost its Atlantic inflow and its hot, dry climate evaporated most of the basin, leaving salt deposits up to 3km thick. The crisis ended when the Atlantic broke back through in the Zanclean flood, possibly refilling the entire sea within just a couple of years.