Cantal Mountains - tale of a volcanic giant
The Cantal Mountains are one of the earliest forms of volcanic activity in the Massif Central of France. In the southern Auvergne, the Cantal region is a beautiful, wild and rugged region, with mountain ridges and summits, culminating around 1800m. Large u-shaped valleys have been carved through the Cantal by glaciers, creating an upland area of great contrasts making it an ideal venue for our self guided and guided walking holidays.
It is only by looking at a map that the origins of the Cantal mountain range become apparent. The whole area is one gigantic ancient volcano. It's formation took place between 13 million and two million years ago and is geologically speaking very complex, giving rise to numerous theories on its formation. Below is a brief explanation as to its possible development.
The origin of the volcanoes across Auvergne in central France are thought to be linked to the convergence of the African and Eurasian plates. The collision between Italy and the continent, which continues to build the Alps created a shock further afield in the bedrock and mantel. This shock has stretched the earth's crust creating rifts such as that at Limagnes just east of Clermand Ferrand. The decompression in the earth's crust creates weaknesses which allows the magma to rise.
There are a number of major volcanic events across Auvergne with the Puy de Dome chain of perfectly preserved volcanic cones and domes being the most recent and most striking. However the Cantal volcano represents the largest volcanic event in the Auvergne. Despite its modest altitude, only 1885m, the Cantal is the widest volcano in Europe with a diameter of 70km and a surface area of 2500 sq km.
The Cantal Volcano is a stratovolcano which means that it was formed by a succession of different types and phases of activity in one general area. The activity began about 22 million years ago with a large number of Strombolian type volcanoes appearing through the granite bedrock, much as we find today in the Chaine de Puys further north in Auvergne. Little evidence remains of this early phase. About 9 million years ago a very explosive phase concentrated in the centre of the mountain range, created a first stratovolcano. These eruptions weakened the bedrock, whilst the summit of the volcano collapsed creating a huge caldera, much as you find today in Tenerife. A second explosive period about 6 million years ago created much of the central mountains you'll see on our walking holidays today, such as the summits of Puy Griou and Puy Mary
After this, hundreds of volcanic vents opened up away from the centre spewing liquid lava over a wide area. These flows created what are known as "Planèzes" - huge gently sloping plateaux which create rich grazing land.
The last major impact on the area has been the effect of glaciers creating beautiful cirques and straight u-shaped valleys. These are defined by narrow ridges which lead to pointed summits, which in turn are the remains of volcanic interiors eroded by ice.