Arriving at Puy-en-Velay, we are so surprised by this giant coming out of the land that we want to declaim “It's a peak! It is a rock”. But who is he really?
You have to take a big leap back two million years, the Puy basin being a huge lake. Sub-lacustrine volcanic eruptions have shaped this landscape.
The lava encountered large amounts of water on reaching the surface. Numerous explosions, not very violent, fragmented the pulverized lava which immediately fell back into the water. The debris coalesced into multiple layers and coalesced and then turned into a light brown material. Thus was born the volcanic tuff. Whole panels of rock fell with each explosion in the chimney. The Rock is thus made up of large slabs close to the vertical which testify to the fragile pile-up in the deep chimney.
At the beginning of the ascent of the rock, after the Saint-Raphaël oratory, we follow with our eyes the black ribbon of basalt which rises in the rock, it indicates an old fault by which the last lava which went to the assault rose. from the crater of the Aiguilhe volcano.
The erosion of the volcanic tuff has left in place only the deep root of the old chimney. Today, geologists refer to this rock as a neck, and as a dyke the ancient fissure filled with basalt.
A climb like no other
It's hard to imagine that in the heart of the town of Le Puy-en-Velay, you can climb to the top of a volcanic chimney. You can even brag about it when you return from vacation, after climbing the 268 steps.
