Beckley Demonstration Coal Mine
...kettle bottoms. Kettle Bottoms are stumps of petrified trees that protrude from the coal layer into the rock layer above. Because of their shape and the fact that they are made from different material that doesn't bond tightly to the rocks, they drop out unexpectedly, occasionally onto the head of an unlucky miner. They can weigh upwards of a hundred pounds. You do the math...