An immense island in the heart of southern France, the Massif Central is a very old plateau, which with Brittany and Vosges was part of the hercynian mountain chain that 500 million years ago dominated what today is France. Worn by time the summits became plateaux. These were fractured by large movements during the formation of the Alps and the Pyrenees. Large areas collapsed while others were raised. The collapsed areas are the river plains of Limagne of the Allier, Plaine d’Ambert of the Dore and Plaine Roanne in Montbrison of the Loire. The raised areas are the principal summits of the ancient massif. The most affected by the uprising are those in the east, particularly Cévennes and Forez. Also, ancient marine areas were raised by these movements which are the plateaux of the causses. 25 million years ago the valleys of the Loire and the Allier were immense lakes. Later volcanic eruptions completely changed the face of the west of Auvergne and Velay and new forms appeared. The volcanic eruptions appeared later in the Puy Chain, with the youngest less than 5000 years old. Erosion followed by digging deep gorges. The glaciers covered a large area above 1000m and created many typical U shaped valleys. The long geological history gives the mountains uniqueness due to their variety.