The Aubrac mountains, between basaltic columns and erratic stones
The forms that nature seem to provide us here are exciting: where do these stones with extraordinary appearance we discover along our hikes come from? Basaltic columns and other erratic blocks are remnants of the plateau’s ancient volcanic activity as well as from previous ice ages.
Aubrac is a volcanic massif 5 to 9 million years old. Its highest point is the Signal de Mailhebiau (1469 meters). It is bounded by rivers: to the south the Lot river, to the north the Truyère and to the east the Colagne. The plateau is made up of different rocks. On the foothills of the plateau, near the Lot river Valley, there are many Gneiss and shale. In the centre, the basalt, reminding us of the volcanic origin of the place, is omnipresent. To the north and east of the plateau, the landscape is similar to that of the Margeride mountains, with large granite blocks arranged here and there on the plateau.
The creation of the basalt part of the plateau is the result of an effusive volcanic episode (with lava flows). Traces of this ancient volcanic activity are numerous here, and basaltic columns sometimes appear in unexpected places. Among the most impressive are waterfalls such as the Deroc and the Saltou.
On the granite and basalt parts, we find traces of the ice ages that have followed three times: erratic blocks, areas of glacial overcrement that have bequeathed us peatlands and lakes, alluvials deposits..