Volcanoes - Auvergne Region - Central France
Plains of Auvergne
Volcanoes, a term which in France is automatically associated with Auvergne in the Massif Central.
This country of ancient mountains and extinct volcanoes covers 15% of France.
The northern region, though, is flat; this is indeed where the vast Limagne and Bourbonnais plains stretch from Moulin to Montluçon and Vichy.
They then narrow and end in the gorges of the Allier, farther south, near Clermont-Ferrand.
This is where the land of the volcanoes starts!
Origin of the Volcanoes of Auvergne
The Massif central formed 60-million years ago, when the African and European tectonic plates collided.
The thrust they produced triggered the formation of the Alpes Mountain ranges.
However, the European plate slipped under the African plate.
The thrust weakened it and provoked the appearance of faults lines in the area we today call Massif Central.
Some 25 million years the magma began to rise to the surface in the northern part of the Massif Central.
- The volcanoes of Cantal appeared between 13 million and 3 million years BP
- The volcanoes of Devès-Velay between 13 million and 1 million years BP
- The volcanoes of Cézallier between 6 million and 3 million years BP
- The Mont-Dore and Puy de Sancy between 3 million and 200,000 years BP
- Finally, the volcanoes of the Chaîne des of Puys appeared only 150,000 years ago!
The Massif Central remained an active volcanic area throughout the Tertiary and Quaternary epochs.
So yes, Auvergne is the Land of Volcanoes.
Volcanoes of Auvergne
There are 450 of them, spread in the Chaîne des Puys, Cantal, Monts Dore, Monts d' Artense, Monts du Cantal and Monts du Cézallier (between the Monts Dore and Cantal).
The Chaine des Puys or Monts Dôme is a set of 80 volcanoes located in a 45km long by 5km wide area.
These are the 'youngest' volcanoes of Auvergne.
Their age indeed ranges from 70,000BP to 7,600 BP, however, most were active between 45,000BP and 30,000 BP.
They have the traditional volcano shape we are used to, as they had only one very brief and recent eruption.
The Puy-de-Dôme is the highest volcano in the Chaîne des Puys (1465m); the Puy de Sancy is the highest in the Massif Central (1886m).
The volcanoes of Cantal and Monts Dore were gradually formed by the accumulation of lava and volcanic materials during the successive eruptions over a long period of time.
Prolonged glacial erosion then formed abrupt ridges and circuses in their center.
Some of these have turned into lakes.
Cantal boasts Europe's largest volcano, Plomb du Cantal, which peeks at 1858m.
The volcanoes of the Monts du Cézallier have an average altitude of 1200m to 1500m.
Most have soft and rounded reliefs, because they were formed with fluid lava that spread instead of building up.
These volcanoes are part of the Parc des Volcans d'Auvergne.
Extinct versus dormant
Now the question is: are the volcanoes of Auvergne extinct or dormant?
Vulcanologists all agree that they could wake up one day, especially as some of them were active a mere 7000 years ago.
This is indeed very recent in terms of geology!
Another reason is that “the Mohorovičić discontinuity or Moho, the boundary between the Earth's crust and upper mantle“ is only 20km thick under Auvergne (versus 35km under Paris).
They are also concerned that the coat - “an intermediate layer between the planetary core and the crust of the earth" - is at a temperature of 1300°C at 30 km of depth while the norm is 900°C.
Interestingly the hottest area is located under the ancient volcanoes of Cantal, and not underneath the 'young' Chaîne des Puys!
That said, there is no panic as the period of inactivity separating us from the last eruption is much shorter than the precedent period of inactivity, as proven by the study of geological layers.
They might wake up one day, but in a few millennia!
Volcano Natural Park and Vulcania
You can discover these volcanoes in the Parc Naturel Régional des Volcans d'Auvergne.
This regional park opened on October 25, 1977.
It spreads over 389,733 hectares over 120 km in the departments of Cantal and Puy-de-Dôme.
The largest natural park in metropolitan France, it altitude varies from 400m to 1886m.
Children will most likely enjoy Vulcania.
This educational attraction park was inaugurated in 2002 in Saint-Ours-les-Roches, in the northwestern outskirts of Clermont-Ferrand.
This park is mostly underground and one of the most popular attractions is the 4-D film The Awakening of the Auvergne Giants, a title that leaves little doubt about the topic.
Wikimedia Commons: header