Aubrac is a volcanic and granitic plateau that extends over an area of 1,500 km2. The volcanic eruptions occurred between 6 and 9 million year ago and were of Hawaiian type with fluid lavas. There are therefore no individual volcanic cones. The volcanic zone occupies the west side while the other part of the plateau is formed of granite. The average altitude is about 1,200 meters with the highest point at 1,469 meters (Signal de Mailhebiau) in the south. All the region has been eroded by glaciers during three glacial periods. The Aubrac includes four glacial lakes: lac des Salhiens, lac de Saint-Andéol, lac de Souveyrols and lac de Born. In the south, the highest summits of the Aubrac dominate the Lot valley, which lies 1,000 m below.