Gouffre Jean-Bernard

Gouffre Jean-Bernard or Réseau Jean Bernard, sometimes known simply as Jean Bernard, is the seventh deepest cave in the world, and the third deepest one in Europe. It is in the Alps in Samoëns, France. The first entrance to the cave was found by the French caving group Groupe Vulcain in 1963. More entrances have been found over the years since, and currently at least thirteen are known. The highest entrance, known as C37, is at 2333 m above sea level. The cave is named after Jean Dupont and Bernard Raffy, two Groupe Vulcain members who died in 1963 in an unrelated expedition in Goule de Foussoubie Cave.

Exploration
The first entrance, known as V4, was discovered in 1963 and exploration in that year took the cave to a depth of 100 m. Further explorations in the following year reached the main drain, or master cave, of the system at a depth of -210 m. This was further explored downstream in 1965 and 1966, reaching the base of a wet shaft, the Puits des Affreux, at -380 m. Explorations in 1968 reached Puits de la Rivière at -450 m. A major expedition in 1969, attended by many French cavers, reached a sump at -623 m.

In the upper part of the Vallon des Chambres, Gouffre B19 at an altitude of 2118 m, which had been discovered in 1968, was explored down to -450 m. In 1975, winter expeditions began. The -900 m elevation was exceeded on 4 January and at -938 m, the Salle des Crêpes was discovered two days later, marking the end of explorations for that year. The Gouffre B19 was connected to the network on the first of November, giving a system depth of 1208 m.

The sump at -1298 m was reached on 1 January 1976. In July 1979, exploration of Gouffre B21 at an altitude of 2237 m allowed the network to become the deepest in the world with a depth of -1358 m. It remained so until January 1998, when its depth was surpassed by Gouffre Mirolda.

In 1980, 1981, 1982 in February, three sumps were dived increasing the depth to 1494 m, progress being stopped by a fourth impenetrable sump. In August 1983, Gouffre B22 at 2194 m was explored and connected to the B21, giving access to the upstream galleries which allowed the system to exceed the -1500 m difference in height at -1535 m. At that point, further exploration was blocked by a water-filled passage.

More recent explorations have increased the depth to 1612 m, making it the seventh deepest cave known in the world.

Karst Development
The Gouffre Jean Bernard is located in a synclinal valley (Vallon des Chambres). The various entrances are located on the north-eastern flank of the syncline between 1800 m and 2300 m above sea level and are perpendicular to the master cave. The master cave flows close to the Urgonian Limestone-Hauterivian marl contact in a meander 2 m to 3 m wide. The resurgence is located at an altitude of 780 m in le Clévieux stream. The passages of 10 m to 15 m in diameter that are found in the upper part of the network are fossil passages developed before the incision of the Giffre valley.