Seemed to be a very fresh and huge amount of rock debris across the floor of The Lost World in the Llanberis slate quarries last weekend. Haven't been in there before but there's no longer a pond as I expected to find and the stone hut has been pulverised. Ladders still okay and tunnel out is clear. Trees under boulders still had leaves on and there was dust on everything. It's obviously all come off the huge northern wall and the dust implies it came down after the last rain.