Crêt de la Neige

At 1720 m, the Crêt de la Neige is the highest mountain peak in the entire Jura. It is part of the Haute Chaîne, the easternmost and highest chain of the French Jura, and is located in the Pays de Gex (Ain department), about 17 km northwest of the city of Geneva.

The Crêt de la Neige is bordered to the east by the plain of the Pays de Gex and to the west by the valley of the Valserine. The crest of the Crêt de la Neige slopes steeply in both these directions. It rises directly from the plain of the Pays de Gex without any foothills and towers over the basin of Geneva by about 1300m. To the southwest, the Jura ridge leads directly to the Reculet, to the northeast to the Grand Crêt. A resurvey in 2003, carried out by the Institut géographique national (IGN) in Villeurbanne, attested an altitude of 1720 m to the Crêt de la Neige. Previously, the official altitude was given as 1718 m, which was obtained by rounding up the effectively measured altitude of 1717.6 m. This meant that Crêt de la Neige was only 20 cm higher than the neighbouring Reculet (1717.4 m). Even earlier, it was assumed that the Reculet was the highest mountain in the Jura.

From a structural geological point of view, the Crêt de la Neige forms an anticline of the folded Jurassic, whereby the rock layers were thrust onto the sediments lying further west at the time of the Jurassic folding in the late Miocene and Pliocene. The anticline is about five kilometres wide at the root and is oriented south-southwest-north-northeast according to the strike direction of the Jurassic chains in this mountain section. The rock material of the Crêt de la Neige originates from marine sediments of the upper Jurassic (in the ridge area mainly the dolomitic limestones of the Portlandien and the limestone beds of the Kimmeridgien and the Sequanien) and Cretaceous (mainly at the foot of the slope).

The limestone has allowed various karst phenomena to form on the crest of the Crêt de la Neige. There are numerous karst fields and sinkholes here, precipitation water seeps into the porous subsoil and usually only resurfaces at the foot of the Jura chain in karst springs. For this reason, the slopes of the Haute Chaîne show very few surface watercourses.

Unlike the other Jura peaks, the Crêt de la Neige is not predominantly grassy in the ridge area, but shows a rocky, rugged relief, partly crossed by small gorges. The mountain has a harsh climate with an annual rainfall of about 2000 mm. In deep, unsunny and wind-protected crevices, the snow can last the whole summer half-year.

Another special feature of the Crêt de la Neige is the mountain pines growing in the ridge area. This robust pine species, found at altitudes between 1800 m and 2500 m in the Alps, is found nowhere else in the Jura. The steep slopes of the Crêt de la Neige are densely forested. Below about 900 m there is mostly deciduous forest, above that up to about 1400 m there is a coniferous forest zone, which in turn is replaced by mountain pastures with subalpine vegetation. The Crêt de la Neige is part of the Haute Chaîne du Jura nature reserve.