In reply to Tom Ripley Mountain Guide:
Cader is a giant choss-pile of doom... Hence the huge approach slope of scree. The only time I've climbed the Arete, some companions on an adjacent route managed to dislodge a fridge-sized lump. Fortunately, just as the second was topping out; he stepped onto the block, which then fell away from under him. Fortunately, he managed to just step off it onto more solid ground as it fell away.
I was belaying a bit higher up, in a gulley, and could only hear the shouts, and the terrible crash of rock. I didn't know where it was falling, so I just hunkered in and hoped for the best. Fortunately, it was all going on below me... I was more than a little bit spooked by that, and glad we were very near the top at that point.