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What makes waterfalls?
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A fast-flowing river erodes its bed downward. This erosion is not constant, but depends on the hardness of the rock over which the water is passing. When there is a particularly hard bed of rock in the river, it erodes so slowly that the river falls over it as a waterfall. The downstream rocks are eroded into a 'plunge pool'. Eventually the hard rock at the top of the waterfall is undermined and the river can cut back into it as a gorge. | | The plunging waters of Niagara Falls are gradually undermining the hard dolomite rock and retreating upstream. |
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Previous:
Back
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Book:
1001
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Section:
Earth
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Chapter:
Landscape
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