Lord's Rake - decomposing rock layer

I'd read about it for years but I've finally been to inspect Lord's Rake on Scafell. I was amazed by how weak and fractured the rock is. Bits look like they are about to fall from the walls and some bits come off in your hand. Then there are the solid retaining walls. I haven't been able to find anything out about the geology but it is volcanic and will be part of the Scafell caldera. So my guess is going to be that we might have ash layers that have been upended and sit vertically. In one layer the ash particles are less cohesive and that accounts for the weakness. There have been earth movements before in this area - I posted about the fractured rock on Scafell Pike last time I went.