Lac souterrain de Saint-Léonard
Origin of the name Lac souterrain de Saint-Léonard
The lake takes its name from the municipality of Saint-Léonard, beneath whose vineyard it lies, 30 to 70 m down.[4]
Founding of Lac souterrain de Saint-Léonard
The lake lies in the municipality of Saint-Léonard, beneath the vineyard. It was formed by the erosion of a bed of gypsum, a porous, water-soluble rock, wedged between black Carboniferous shales to the north and a marble, the « pierre de Saint-Léonard », to the south. Rain and snowmelt, along with underground springs, hollowed out the cavity, using cracks opened by earthquakes in the region. The lake is still growing today. Explored in 1943, it has been fitted out for visitors since 1949.[1][3][4]
History of Lac souterrain de Saint-Léonard
less than 12'000 years ago. The erosion of the gypsum is thought to have begun after the last glaciation, and the cavity to have formed in only a few thousand years.[4]
1943. Jean-Jacques Pittard explores the cave. Only 50 cm then separate the water surface from the roof.[2][3]
around 1946. Three years after the exploration, an earthquake of magnitude 5.6 drains about half of the cave's water through cracks in the floor. The authorities of Saint-Léonard then approve a plan to develop the site commercially.[2]
1949. The lake opens to the public.[2][3]
2000. A two-tonne boulder breaks loose and smashes one of the boats. As the rock is judged unstable, the cave is closed.[2]
2003. The lake is drained for consolidation work with iron anchoring rods. The 2.5 million francs needed are raised by local residents. Refilled with 1.8 million litres of water, the lake reopens to the public.[2]
Historic sites in Lac souterrain de Saint-Léonard
Underground lake. The lake is 300 m long, 20 m wide and 10 m deep. It attracts more than 100'000 visitors a year, who cross it by boat, from March to November, in about half an hour.[1][3]
Cave walls. To the north, black Carboniferous shales more than 300 million years old. To the south, the marble known as « pierre de Saint-Léonard ». In between, gypsum formed about 220 million years ago, when Valais was covered by the sea.[4]
Sources
- Dictionnaire historique de la Suisse, « Saint-Léonard » (Alain Gallay, Bernard Truffer, version du 26.06.2012)
- Dale Bechtel, « Subterranean lake comes back from the dead », swissinfo.ch, 16.06.2003
- Valais/Wallis Promotion, valais.ch, « Lac souterrain de Saint-Léonard »
- Lac souterrain de Saint-Léonard, site officiel, « History and Geology » (géologie et hydrologie)
- geo.admin.ch, recherche de lieux (coordonnées)
Other villages near Lac souterrain de Saint-Léonard
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