A Sea Vanishes
The dramatic white limestone cliffs of the Calanques plunge into the Mediterranean, forming narrow and steep-walled coves. These are river canyons, not river canyons carved during one of the most extreme geological events in Earth's recent history: the Messinian Salinity Crisis.
Beginning around 5.96 million years ago, tectonic movements closed the ancient connections between the Atlantic Ocean and the Mediterranean Sea. Cut off from its primary water source, the sea began to evaporate. The basin, which loses more water to evaporation than it gains from rivers, saw its level plummet. Over several hundred thousand years, the Mediterranean nearly vanished, leaving behind immense salt deposits—in some places several kilometers thick—on the newly exposed seabed. During this period of desiccation, rivers that flowed into the basin, such as the Rhône, extended their courses across the dry plains and carved immense canyons into the landscape, including the limestone bedrock that now forms the Calanques.
The Zanclean Megaflood
The salinity crisis ended was dramatic like its beginning. Around 5.33 million years ago, the natural dam at the Strait of Gibraltar breached. This triggered the Zanclean Flood, a cataclysmic event that refilled the entire Mediterranean basin. Water from the Atlantic Ocean cascaded into the desolate, low-lying basin in what may be the largest flood known on Earth.
Estimates suggest the maximum discharge was about 100 million cubic meters per second, a flow rate roughly 1,000 times that of the modern Amazon River. At its peak, the water level in the basin may have risen by more than 10 meters per day. The entire Mediterranean Sea was likely refilled in a period estimated to be between a few months and two years. This immense influx of water submerged the deep canyons that had been carved into the coastline, creating the steep, drowned valleys known today as the Calanques.
Echoes of the Ice Age
The landscape of the Calanques reveals more recent sea-level changes as well. Hidden within the massif is the Cosquer Cave, a collection of prehistoric art. Its entrance now lies 37 meters (121 feet) below the current sea level and is only accessible via a 175-meter-long underwater tunnel.
During the last glacial period, when much of the Earth's water was locked up in ice sheets, the sea level was over 120 meters (393 feet) lower than it is today. The entrance to the cave was high on a cliff face in a grassy plain, and the coastline was miles away. Humans used this cave during two distinct periods: around 27,000 years ago and again around 19,000 years ago. They left behind hundreds of paintings and engravings, including 65 hand stencils and 177 depictions of animals. The art features common Ice Age animals like horses, bison, and ibex, but also uniquely includes marine life such as seals and great auks, showing the cave's eventual proximity to the rising sea.