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How were the Ardennes formed?

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The Ardennes is an ancient plateau with a complex geological history shaped by intense tectonic activity and erosion. Its formation is primarily linked to the Hercynian (or Variscan) orogenic belt, which evolved during the Devonian and Carboniferous periods, approximately 419 to 299 million years ago.12

This mountain-building process resulted from plate-tectonic interactions, including the collision of continental plates, which caused significant crustal thickening and folding. Over millions of years, the region underwent extensive faulting, uplifts, and denudation, leading to a landscape where older rock strata were thrust over younger ones.12

The modern relief of the Ardennes is characterized by Paleozoic rocks, such as slate, quartzite, and sandstone. The current topography is the result of differential erosion acting upon these ancient formations, which created the region's signature long ridges and sinuous valleys. Today, the Ardennes serves as the western extension of the Middle Rhine Highlands.13