The underwater geology of France’s Mediterranean coast, which stretches from Roussillon in the west to the French Riviera in the east, provides us with essential information on the climatic changes which occurred during the Quaternary period.
But first some geology
The word ‘karst ‘comes from Kras, the name of a region in Slovenia where this type of landscape is common. Karstic landscapes are unusual in that water does not run across the surface of the rock but instead filters into the subsurface. They are often called ‘causses’ after the French vernacular word for ‘plateau’. They are most common in areas where the subsurface is made up of limestone, in particular dolostone, but also chalk and marble.
Surface corrosion is the main characteristic of karsts but astonishing underground formations may also develop. Various geological terms are used in relation to these types of relief, such as doline, stalagmite and stalactite.
Karsts in the Mediterranean
The very many karsts in Provence have shaped the region’s landscape. The mountains of Sainte Victoire, Sainte Baume and Vaucluse are all karstic formations. Vaucluse is home to an underground system of cavities whose main outlet is the Fontaine de Vaucluse, one of the world’s most powerful springs. On the shores of the Mediterranean we find the Calanques massif, which drains into the powerful underwater springs of Cassis (Port Miou and Bestouan), and further to the east, the karsts of the secondary calcareous mountain chain in the hinterlands of the French Riviera.