Quotes About Rock layers

The hardest challenge of early coal mining was drainage. Rainwater flows through rills and streams into brooks and brooks into rivers, drawn always downward by gravity to the sea. About a third of any rainfall soaks into the soil and percolates downward into the earth. Eventually it encounters impermeable layers of rock. There it spreads out and flows along the rock layer until it finds cracks or permeable rock, when it continues percolating down to the next impermeable layer.

Mount Everest is about as tall as a mountain on Earth can grow before the lower rock layers succumb to their own plasticity under the mountain's weight.