Volcanoes appeared in Auvergne following the backlash of the formation of the Alps, which thinned the earth's crust and created vast cracks under Auvergne. The magma then rose to the surface in various places all along the cracks until forming the eighty volcanoes that constitute the Chaîne des Puys ensemble. These monogenic volcanoes were shaped by a brief, single eruption and became extinct once the eruption ended.