Imagine a Rockfall in your garden
with dirt, pebbles, centipede, cat dirt etc
There is a critical mass at which point the sides collapse and sheets of dirt, pebble, cat mess etc slide down the valley edges towards the bottom. The valley becomes wider and shallower. See diagram above. Imagine that you are a rock that was once perched nicely on the side of the valley in the sunshine high up and the next minute you are at the bottom under three tens of feet of other rocks. Its impossible.,Fucking other rocks you think, on top of me, blocking the rays of the sun. Fuckers. What can you do?