With the after-effects of the alpine uplift, the first Jura mountains appeared 35 million years ago. As a result, Mont d’Or, in Doubs, and Crêt Pela, in Jura, have risen to 1,463 metres and 1,495 metres respectively. However, it’s in Ain that the mountain range boasts a series of record altitudes: Crêt de Chalam at 1,545 metres, Crêt de la Goutte at 1,621 metres and Crêt de la Neige at 1,720 metres.
On either side of these peaks, karstic phenomena shape the mountain range. The limestone surface, streaked with gaps and fissures, becomes permeable, supplementing the underground water network. On the surface, there are signs of tectonic disturbances that occurred up to the end of the Tertiary period, and of the relentless pressure of underground and surface waterways. As a result, we can see combes, ripples, vaults, faults, cliff plateaux, blind valleys, chasms, folds, anticlines, peaks and gorges, which shape and form the topography of the Jura Mountains.
Visions in the Limestone
Chapeau de Gendarme in Septmoncel.
Coiserette Canyon, an impassable 1,400-metre ravine, hollowed out by the turbulent waters of the Tacon.
Marmite des Géants in Pont-de-Poitte.
The sinkholes of the Hautes-Combes, vast closed craters, characteristic of the karstic erosion system.
The blind valley of Consolation and the gushing source of the Dessoubre river.
The karstic path of Mérey-sous-Montrond… (all 25!).
The erratic crumbling rock at Pont des Pierres, which extends from Valserine to Montanges or even the ruins of the same Valserine and their rocky mazes.
The Loulle Karren, an immense limestone slab, veined and eroded near Champagnole and the Plagne dinosaur trail.