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Mountain rivers flow at superhigh speeds because they are steep. The rivers strip away bits of rock and carry them downhill.
After thousands of years, the river strips away enough rock to form a canyon. That’s a wide, deep crack in solid rock. If water can carve a huge canyon, imagine what else it can do. People put water to work long ago. They used it to move heavy objects, to travel down rivers and across oceans, and even to keep time. Here are just a few of the water-powered machines and systems humans have built.
