In reply to Ramon Marin:
> But I would imagine other crags have had fires before and I wonder how come the rock hasn’t been destroyed the way it has in Oliana.
I live in New Mexico, and we have had crags completely obliterated by fires. For example, Cochiti Mesa, which in the 90s was a pretty famous place, with people like Lynn Hill climbing there. It is unclimbable now, the outer layer of the rock peeled off and all that is left is sandy blankness.
It depends on the heat of the fire, to state the obvious. One of the biggest differences between wildfires of the past and now is that they burn hotter, so destroy the soil more comprehensively. This isn't just because of climate change, it is because of fire suppression. And that in turn is because ppl are living in places where wildfires used to happen naturally and regularly. Furthermore, things like powerlines that come with the habitation become major causes of the fires.