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It's All Downhill From Here!

Erosion is the process where rocks are broken down and moved to other areas by water, ice, waves and wind. When the broken down materials collect, they form soil.
Erosion by water:
Water is the most common cause of erosion on land. Water erosion takes place in a downhill direction. Broken down rocks are carried down from mountains by streams and rivers. Eventually, the particles collect forming soil. Erosion also occurs on roadsides and small hills. When there is a wildfire or removal of plants on a slope, the chances for erosion during a rainstorm are greatly increased.
Other causes of erosion:
Ice causes erosion by trapping rocks beneath glaciers. Then as the glacier moves, it breaks down the rocks and moves them. Ocean waves take sand out to sea and bring it back in. The wind carries dirt particles in the air, transporting it to other places. (In the desert, the wind is constantly changing the dunes by blowing the sand in different directions.)
The two pictures at the right are both examples of how erosion changes rocks and soil. 
Try it!


  • Sand
  • Water


  1. Pile up the sand as tall as you can.
  2. Slowly pour water on one side of your sand pile. Observe what happens.
  3. Increase the pouring speed of the water and see what changes.
  4. Try building a different sand pile design. Then vary how you pour the water.
  1. How did the experiment show erosion as it happens on Earth?
  2. What differences did you see when you changed the sand pile design or changed how you poured the water?

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Updated October 24, 2008 by: Glen Westbroek

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