It was at least 300 million years ago. Tremendous forces pushed in from the north and south and pushed the layers together. This is how the Rhenish Slate Mountains were formed in their day. And you can see it very well here on the demolition wall of the old quarry. Layers that used to lie flat on top of each other now show up as folds in the upper part of the wall.
And about 65 million years ago, the rock began to heave. Thus, the layers are broken down into individual clods. This can also be seen here. But even this is not enough, because with the uplift further processes are triggered in the earth's interior. Magma rises and the volcanoes in the region are formed.
What a rock wall like this doesn't hold!
The rock fold belongs to the German Volcano Road and is documented there as No. 39 on the West Tour.