Grand Roc Cave - Rock formations - Dordogne
Grotte du Grand Roc
Grand Roc rock shelter is located in Manaurie, in the municipality of Les Eyzies-de-Tayac-Sireuil.
It was discovered on April 29, 1924 and open to the public 3 years later.
UNESCO listed Grand Roc as World Heritage Site in 1979, under the label Sites préhistoriques et grottes ornées de la Vallée de la Vézère.
The cave's entrance is located on a terrace located halfway up the cliff and therefore boasts prime views over the meander or cingle that skirts the village of Tayac.
Formation of the rock shelters
Grand Roc displays an amazing array of eccentric rock formations that appeared over millennia.
They had also carved and shaped the limestone plateaux of Périgord and Quercy.
They had formed the meanders of the rich alluvial plain where men later settled and developed agriculture.
Rainwater charged with carbonic acid had dissolved the sections of the limestone subsoil or enlarged the existing fissures of the rock, the future rock shelters.
All was in place!
Eccentric rock formations
The slow and constant infiltration of water rich in calcite created stalactites, as the sediments accumulated and built up from the ceiling downwards.
The same accumulation of water droplets loaded with calcite created stalagmites as they touched the floor of the gallery.
Some stalactites and stalagmites eventually met and therefore created columns.
The velocity of the dripping droplets also acted on the shape of the concretions.
They therefore created eccentric shapes, as they landed on the floor and projected the sediments randomly in all directions.
Among these are the amazing star or spike-shaped concretions that defy all laws of gravity and overcome the limits of imagination.
Some concretions are translucent, some display a wide range of colours and shades.
Those are produced by the presence and density of the sediments carried by rain water when traversing the limestone layers.
Clay therefore produces ocher concretions, iron oxide rich crimson, orange, red or brown and manganese produces black.
These sediments were obviously the same than those used to produce the outstanding wall paintings that gained the region worldwide fame.
Amazingly, the concretions are constantly building up under the action of water infiltration.
However, it takes centuries to witness the slightest change in size or shape!
Department of Dordogne - Les-Eyzies-de-Tayac
Coordinates: Lat 44.949467 - Long 0.998210
Photos via Wikimedia Commons: interior cave stalactites and stalagmites
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