The Causses and Gorges
Causse Méjean © MAP – Syndicat Mixte des Gorges du Tarn, de la Jonte et des Causses
The main Causses in the area are the Méjean, Noir, Sauveterre and Larzac. They are one of the largest karst groups in Western Europe and are formed from marine sediments deposited in a warm sea during the Secondary period, 150 to 200 million years ago.
During the Tertiary period, these sedimentary rocks were pushed up by the tectonic surges of the Pyrenees and Alps, creating the distinctive shapes of the limestone plateaus that we know today, split into several homogenous entities by deep gorges – the Tarn, Jonte, Dourbie and Vis.
The altitude of the Causses varies between 750 and 1,200 m, compared to around 400 m for the gorges. The limestone Causses were affected by a long period of erosion, which is still ongoing today, and has shaped these unique landscapes, with vast blockfields of ruiniform rocks, grasslands and dolines above ground, and sinkholes, chasms and caves underground.
All the buildings and roofs are made of stone, blending in with the limestone rock in the gorges and on the Causses.
Canoeing in the Tarn canyon © MAP – Syndicat Mixte des Gorges du Tarn, de la Jonte et des Causses
Another characteristic of these environments is the lack of surface water due to the karstic soil, although rainy spells are common, which forced humans to create specific and original structures to capture and store rainwater: cisterns, cistern roofs and lavognes.
These rural heritage features and the quality of the hamlets’ architecture add to the OUV (Outstanding Universal Value) of the Causses and Cévennes, as recognised by their listing as a World Heritage Site.
Agropastoral activity on the Causses has helped to encourage great biodiversity on the extensive steppe-like grasslands where the sheep graze, areas that are home to unique flora and fauna, along with occasional cultivation of the dolines. These distinctive landscapes, which are kept open and preserved by the still-thriving agricultural activity, have been listed in the World Heritage category of organically evolved cultural landscapes.
See also the other geographic areas :
