The Plateau des Dômes
– 350 million years (long before the appearance of the dinosaurs)
The Plateau des Dômes is situated between the Limagne fault and the Sioule valley. Its surface lies up to 700 m above the Limagne plain, and it forms the basement for the Chaîne des Puys volcanoes.
The current relief of the plateau belies its history, as this area was originally a mountain chain which formed nearly 350 million years ago (Ma). The mountains have been worn down by several hundred million years of erosion to form the plateau we see today.
Formation of the Plateau des Dômes
The pulling apart of two continents formed an ocean, named the Massif Central Ocean. From 450 My the two continental blocks started to converge, and the ocean progressively disappeared.
By 350 My the ocean had completely disappeared, and the collision of the two continental blocks led to the growth of the mountain chain known as the Hercynian mountains. The highest peaks would have been around 5,000 m asl.
The mountain chain was gradually eroded, largely due to the effects of rain.
By the end of the Palaeozoic era (when the first reptiles appeared), around 250 My, the Hercynian mountain chain had been totally planed off by erosion to form a huge plateau on which the Chaîne des Puys were installed many millions of years later.
Did you know? Fragments of the same Hercynian mountain chain exist in the United States, for example the Appalachian Mountains in the east of the country, testifying to a time before the opening of the North Atlantic Ocean.