Réseau du Clot d'Aspres

The Réseau du Clot d'Aspres is a cave system located mainly under the valley of Clot d'Aspres, which lies within the commune of Villard-de-Lans in the north of the Vercors Massif, in Isère, France. This extensive karst system contains 42 km of passages over a height range of 1,066 meters. The highest point is upstream of the Oréade cave +74 m, and the lowest point is the siphon of the Nuits-Blanches scialet which has been dived to a depth of 34 m.



The Réseau du Clot d'Aspres is the second deepest cave in the Vercors massif, and only one of two deeper than 1000 m. The combined waters of the caves drain into a master cave and emerge at the Goule-Blanche Karst spring (°N, °W) in the Bourne Gorge, 832 m above sea level.

Geology
The cave system is developed within Urgonian Limestone, with the master cave developed at its base on the Hauterivian marls. There is major horizontal development at an intermediate level in the limestone.

Explorations


Explorations in the system began with the visit to grotte des Deux-Sœurs in 1902 by Fonne and Muller. In 1952 the Grenoble section of the CAF of Lyon including Pierre Chevalier explored the réseau des Grenoblois to a depth of -181 m. Further explorations by the Lyonnais of the Clan de la Verna in 1954 reached a siphon at -315 m.

On the plateau, from the scialet de la Nymphe-Émue, located 200 meters above this cave, a descent of 341 m was carried out in 1964 by the Clan des Tritons de Lyon, but without discovering a connection. In September 1986 a group of Drôme and the caving group Le Graoully broke through into the main system, discovering kilometres of galleries from the scialet de la Nymphe-Émue and a new entrance: the grotte de l'Oréade, located on the outer flank of the Clot, in the commune of Gua.

At the end of 1987, the Spéléo Club du Veymont (SCV) explored the scialet de la Bourrasque to where it connected with the scialet de la Nymphe-Émue at a depth of 370 m.

In 1988, the scialet des Brumes-Martinales was explored to a depth of 645 m by the SCV. In the same year, Drôme cavers, unattached to any clubs, found the scialet du Pré de l'Achard which they descended to -410 m.

In 1989, le scialet du Blizzard was explored by the SCV and found to connect to the scialet des Brumes-Matinales at a depth of 521 m. In the process, the SCV explores the scialet du Silence to -542 m.

In May 1990, the scialet des Nuits-Blanches was discovered by the Spéléo club du Veymont and connected to the master cave at a depth of −688 m.

In 1991, the Drôme cavers found a junction between the grotte des Deux-Sœurs and the scialet de la Nymphe-Émue. The upper network now includes four entrances: the Deux-Sœurs, l'Oréade, the Nymphe-Émue and the Bourrasque. In the summer of 1991, the SCV discovered galleries that connected with the scialets of the Brumes-Matinales, the Blizzard, the Silence and the Pré de l'Achard. These passages are referred to as the median network.

In May 1993 the sump of the scialet des Nuits Blanches was dived by Frédéric Poggia to -34 m.

The upstream section of the Blizzard collector was explored by the Fontaine Mountain caving group in July 1994, after climbing a 25 m waterfall. A superb river passage was ascended for 700 m until it ended in a sump. This was dived in September 1995 by Frédéric Poggia, resulting in the discovery of 800 m of further river passage with two new siphons and a boulder choke.

The downstream passages and the upstream passages and median networks were connected through the master cave, by the Grenoble Cavers of the French Alpine Club (SGCAF) in 2008, by pushing the boulder chokes, making it the second 1000 m deep system in the Vercors.

On October 26, 2015, the SGCAF discovered the entrance to a 70 m deep shaft named Jeunesse d'Automne. This scialet was integrated into the réseau du Clot d'Aspres by connecting it to the Nuits-Blanches on November 28, 2015. The junction between the two cavities is just before the terminal siphon of the Nuits-Blanches.

In 2015, 2016 and 2017, explorations were concentrated downstream. The issue is whether the grotte du Clot d'Aspres (extensions discovered by the Clan des Tritons), the scialets de la Chambre-Froide and du Candy (explored by the SGCAF) communicate with the network. A new cave, the Puits Sans Fond-Arche de Noé, located under the summit of Agathe, one of the Two Sisters, with a pitch of 200 m is potentially also part of the network, but no connection has yet been found as of 2019.