When did the formation of the Pyrenees begin?

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Aneto Peak, Pyrenees — Pyrenees Aneto Peak in the Pyrenees.

The formation of the Pyrenees is a complex process involving multiple geologic events rather than a single origin point. The region's foundation was established by the Variscan (or Hercynian) orogeny, which occurred between 370 million and 290 million years ago.1

Following a period of relative stability, the area became tectonically active again approximately 225 million years ago. The most recent and significant phase of mountain building, which created the present-day chain, resulted from the collision of the Iberian and European tectonic plates. This process began during the second half of the Cretaceous Period (100.5 million to 66 million years ago), with the majority of the uplift occurring during the Eocene and Oligocene epochs, spanning from 56 million to 23 million years ago.1