Vercors Massif

The Vercors Massif lies in the Prealps, in the south-east France, straddling the departments of Drôme and Isère, both of which are part of the Rhône-Alpes region, about 100 kilometres (62 mi) south-east of Lyon. The massif covers 135,000 hectares (520 sq mi) with a north-south length of 60 kilometres (37 mi) and an east-west width of 40 kilometres (25 mi).

The massif is surrounded by the Chartreuse Mountains to the north, the Matheysine area of the Dauphiné Alps to the east, and the Diois Massif to the south. In the far south-east, the massif joins with the 1,457 metres (4,780 ft) col de Menée.

The massif is drained in the north-east and the north-west by the Isère, in the east by the Drac, and in the south by the Drôme. The western side overlooks the Rhône Valley.

DEM of the Vercors massif

The Vercors Massif is known as the fortress or as the French dolomites because of its geomorphology. The massif is likened to a plateau: the fall from the massif to its inner valleys is a few hundred metres, while the fall to the surrounding areas is between 800 metres (2,600 ft) and 1,200 metres (3,900 ft).

The crest of the eastern edge has several summits over 2,000 metres (6,600 ft). The interior varies between 800 metres (2,600 ft) and 1,500 metres (4,900 ft). The massif also has wide valleys including the valley of Lans-en-Vercors, the regions around Autrans, and La Chapelle-en-Vercors, and plateaus including forêt des Coulmes, forêt de Lente, and the high plateau. There are a number of deeply incised gorges, including the Bourne and Furon Gorges. These have imposing cliffs often exceeding 400 metres (1,300 ft) such as the Combe Laval and the Cirque d'Archiane.

Mont Aiguille stands apart from the rest of the massif as the result of erosion. Other parts are isolated from the rest of the massif due to its relief. For example, to reach Gresse-en-Vercors in the south, one must travel 100 kilometres (62 mi) via the col de Rousset or journey 70 kilometres (43 mi) via Saint-Nizier-du-Moucherotte in the north. The villages at the far northern end were isolated by a landslide near the Mortier tunnel. Another example is the Peuil plateau in the east. During the Ice Age, the Grésivaudan glacier reached the Peuil plateau leaving a marsh.

Topographic map with the different parts of the Vercors

The central part of the Vercors Massif is divided into several regions.[5]

The Coulmes, in the north-west, are heavily covered in forest. Folds of Urgonian limestone are rounded, making the area appear mountainous.

The four mountains area has been developed for tourism and skiing but is also known for its traditional activities such as the breeding of dairy cows and cheese making. The main villages, Autrans, Méaudre, Lans-en-Vercors, and Villard-de-Lans, are spread over two plateaus covered by wooded hills.

The Drômois Vercors is an area made up of a number of smaller plateaus. In the north of the Drômois Vercors there are several gorges which are traversed by roads cut into the cliffs. Grassy areas are used as pastures in the summer months, and the biannual migration (transhumance) of animals is a period of celebration for the people of Die.

The Haut-Plateaux (high plateaus) are the highest wilderness areas of the massif. The area is managed and the pastures are used for grazing in the summer.

At the fringes of the massif, the Vercors regional park has four geographical areas. The Royans, the north-west foothills are the location of walnuts growing. Three valleys descend to the edge of the Royans: the Gorges de la Bourne, the cirque of the Combe Laval, and the Échevis valley, including the Grands and the Petits Goulets.

The Gervanne, in the south-west, is a rugged area of hills at the foot of the plateau, with picturesque villages. It looks towards Crest.

The Diois is a part of the Drôme valley around Die. This region has a Mediterranean character, with vineyards and fields of lavender. It acts as a buffer between Gervanne and the interior of the massif.

The Trièves, in the east, is a low hilly plateau, which lies between the highest summits of the Vercors and the gorge carved out by the Drac.

Panoramic view of the main ridge of the massif, from the Moucherotte (on the left), to the Grande Moucherolle (on the right), as well as the val de Lans.

View of the Grand Veymont and Mont Aiguille from the south

From north to south:

• Le Moucherotte, 1,901 m, the summit which dominates Grenoble, most northerly of the massif
• Le Pic Saint-Michel, 1,966 m
• Roc Cornafion, 2,049 m
• Les Arêtes du Gerbier, 2,109 m
• La Grande Moucherolle, 2,284 m
• La Petite Moucherolle, 2,156 m
• La Tête des Chaudières, 2,029 m
• Les Rochers de la Balme, 2,063 m
• Le Sommet de Malaval, 2,097 m
• Le Grand Veymont, 2,341 m, highest point of the massif
• Le Mont Aiguille, 2,087 m, with its characteristic silhouette, its first ascent in 1492 was the birth of alpinism
• Le Dôme ou Pié Ferré, 2,041 m, to the east of Die, in the Glandasse uplands.

By descending altitude:

• Col du Mont Noir, 1,421 m, between Malleval-en-Vercors and Rencurel
• Col de l'Allimas, 1,352 m, between Gresse-en-Vercors and Saint-Michel-les-Portes
• Col de la Chau, 1,337 m, between Vassieux-en-Vercors and Bouvante
• Col de la Bataille, 1,313 m, between Léoncel and Bouvante
• Col de Rousset, 1,254 m (tunnel altitude), between Die and Saint-Agnan-en-Vercors
• Col de Saint-Alexis, 1,222 m, between Vassieux-en-Vercors and Saint-Agnan-en-Vercors
• Col de la Croix-Perrin, 1,218 m, between Lans-en-Vercors and Autrans - Méaudre
• Col de Carri, 1,202 m, between La Chapelle-en-Vercors and Bouvante
• Col de la Portette, 1,175 m, in Bouvante
• Col de l'Arzelier, 1,154 m, between Château-Bernard and Le Gua
• Col de Tourniol, 1,145 m, between Léoncel and Barbières
• Col de Proncel, 1,100 m, between Vassieux-en-Vercors and La Chapelle-en-Vercors
• Col des Limouches, 1,086 m, between Léoncel and Peyrus
• Col de Romeyère, 1,069 m, between Rencurel and Saint-Gervais
• Col de la Machine, 1,011 m, between Saint-Jean-en-Royans and Bouvante.

The Tunnel du Mortier links Montaud with Autrans, at an altitude of 1,391 metres (4,564 ft). It was closed on 20 April 1992 after a landslide of 20,000 m³ of rock which involved part of the slope to the north of the route. The instability of the slopes have proved an impediment for the realisation of further work below the site, particularly work on the gorges d'Engins to Sassenage road, the D531.

Entrance to Gouffre Berger, the deepest cave in the Vercors

The commune in which the cave is situated is given in italics.

• Réseau du Gouffre Berger, d'Engins en Isère, 45,118 metres (148,025 ft) long, 1,271 metres (4,170 ft) deep.
• Réseau du Trou qui souffle
  , Autrans-Méaudre en Vercors, 49,300 metres (161,700 ft) long, 670 metres (2,200 ft) deep.[4]
• Réseau du Clot d'Aspres
  , Villard-de-Lans, 42,000 metres (138,000 ft) long, 1,066 metres (3,497 ft) deep.[4]
• Réseau de Coufin-Chevaline
  , Choranche, 32,301 metres (105,974 ft) long, 425 metres (1,394 ft) deep.[4]
• Grotte de Gournier
  , Choranche, 18,000 metres (59,000 ft) long, 680 metres (2,230 ft) deep.[4]
• Antre des Damnés
  , Corrençon-en-Vercors, 5,000 metres (16,000 ft) long, 865 metres (2,838 ft) deep.[3]
• Grotte de la Luire
  , Saint-Agnan-en-Vercors, 37,563 metres (123,238 ft) long, 547 metres (1,795 ft) deep.[4]
• Réseau des Chuats, Bouvante, 48,171 metres (158,041 ft) long, 368 metres (1,207 ft) deep.

The Grotte de Bournillon, located in the commune of Châtelus, has the highest cave opening in Europe at 105 metres (344 ft).

The constituent rocks of the Vercors were formed by sedimentation about 165 million years ago, in the middle Jurassic period, at the bottom of the Piemont-Liguria Ocean. The deposition of animal material formed limestone, with detritus rocks, formed primarily from the erosion of marl from the Variscan orogeny formed the massif in a period marked by changing climatic conditions and ocean depth. At Diois and Trièves is a layer of the massif, formed in the Tithonian age. Then, about 130 million years ago, in the Cretaceous period, a rise in temperatures combined with shallow waters led to the development of coral reefs, which abounded with molluscs, particularly rudists. These were the origin of the Urgonian Limestone which forms the upper part of the massif, more prominently in the northern half. This primitive fauna left numerous fossils, some of which have been found at a site near Rencurel in the Coulmes.

In the Paleogene period, the Tethys ocean closed up and at the start of the Miocene, the raising of the Alps involved the thrusting of a nappe to the west. Sedimentary rocks were raised 2,000 metres (6,600 ft) above the current location of the Massif des Écrins and faulted and folded in the process.

Subsequent marine transgressions were responsible for secondary sedimentation in the basins. There was widening of the gorges and erosion of the cliffs from runoff, leading to the formation of the molasse in the Royans and also in the valleys of Lans, Autrans, and Rencurel. At the close of the Miocene, a new period of uplifting brought about the final receding of the sea.

Once formed, the massif underwent severe erosion, which accentuated the relief. The different synclines grew larger, eventually forming valleys including those of Autrans, Méaudre and Lans, Villard, Corrençon, the Col de Romeyère and the Col de Rousset. The water hollowed out the cirque of Archiane, the steephead valley of Bournillon, and the Combe Laval.