It’s original configuration is what makes the Pont du Diable Gorges so interesting: the valley, already quite steep-sided around the Jotty area, ends with a narrow fissure, deep and partly subterranean; The Dranse River in Morzine ran up against the resistance of a limestone layer, similar to that further down between La Vernaz and Pombourg, or at the Bioge canyon.
The repeated appearance of these features, which obstructed the erosion of the valley, can be explained by the local geology: cretaceous marls cover the Jurassic limestone. These stones - originally marine sediments - were subjected to the pressure of the Alps as they formed; pushed back into folds, about one kilometre wide, they reappear alternately throughout the length of the Dranse River that cut through them, in the wake of the glaciers. The valley widens where the marls are weaker; it becomes tighter when it comes up against a limestone layer, like here at the Pont du Diable.
Pour en savoir plus sur la géologie exceptionnelle de notre région, consultez le site internet du Geopak Chablais :