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Learning About Erosion

Part 2 of 3:
Erosion Slowly Changes the Shape of a Mountain.

What causes erosion? Imagine a sandbox. If you shaped a mountain of sand and left it alone long enough, rain would wash sand from its sides. Wind would blow at your mountain, carrying off some of the sand grains. In some climates, melting snow could wash sand away. Eventually wind and water would reduce your mountain to a bump on the surface of the sand. The same thing happens to a real mountain, but because its rock is stronger than a pile of sand, it takes millions of years for wind and water to wear it down.

Our planet is about five billion years old. That is five thousand millions. If a million years were like a day, Earth has been here thirteen years' worth of those days. In all that time, mountains have been lifted and worn down and lifted again. From the point of view of human beings, who seldom live more than a hundred years, the rise and fall of mountains takes a long time.

Go to part 1.	Go to part 3.