Linda F. Malanson
(figure available in print form)
Erosion is the movement of weathered materials—rock fragments and particles of soil broken down by water, ice and temperature changes. Water, ice, wind, and gravity are the agents of erosion. They move these materials and change the shape of the land.
As rivers flow, they carve their own valleys. Where masses of moving ice called glaciers are present, they widen and deepen the valleys. Wind hurls sand against rocks, sculpturing them into different shapes. The pull of gravity and heavy rains and snow cause landslides and avalanches.
Where any slope exists, surface material is moving slowly down it. Water, wind, and ice deposit rocks and similar debris, forming deltas, dunes or piles or rocky material called moraines.
The combined actions of weathering and erosion would eventually wear the surface of the earth into a smooth, low plain if it were not for the movement of the earth’s plates. The plates are constantly shifting. building mountains and raising the land’s surface in other ways.
EXPERIMENT: EROSION
(figure available in print form)
This experiment will show you the effects of rocks, plants and contouring on the way water erodes land.
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MATERIALS NEEDED:
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1. Something to use as a container. A paint roller pan is perfect, or try a dishpan, long wallpaper pan, baby bathtub, long plastic windowsill planter or planter trays, or old lasagna pan.
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2. Piece of wood, 5 by 10 cm (2 by 4 inches) or a brick (if you are NOT using a paint roller pan)
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3. Bucket of soil or sand; sandy soil works best
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4. Trowel
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5. Plastic knife, putty knife, or a flat stick for shaping the soil
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6. Large nail
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7. 2 paper cups
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8. Water
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9. Rocks, small blocks of wood, small clumps of moss, twigs from short-needled evergreen trees, lichens, pebbles, model railroad trees or any other objects that you can use to imitate plant growth
DIRECTIONS:.
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1. If you are not using a paint roller pan, place the brick or piece of wood under one end of your container so that it will have a slope and water can drain away from the landform you will build.
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2. Build a hillside at the high end of the container. Fill the entire end of the container, and build the hill at least 13 cm (5 inches) high.
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3. Use the nail to poke four or five holes in the bottom of one of the paper cups. Space the holes evenly so that the bottom of the cup looks like a watering can spout. Fill the other paper cup with water.
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4. For your first experiment, hold the holey paper cup about 30 cm (12 inches) over the hill, and put water into it from the other cup. Move your hand around so that the rain falls evenly on the hilltop. Watch to see what happens to the hill as rain falls on it. Draw a picture of the before and after.
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5. Let the water drain to the low end of the container, then carefully pour only the water out. The soil should stay at the other end of the container. Now put the container back on its brick or piece of wood, and rebuild the fill. This time, add some rocks to the hill. Create another rain shower and watch what happens to the hill. Make notes or drawings.
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6. Keep emptying water and rebuilding the hill each time you change the experiment. Try planting trees mad of moss or evergreen twigs; try contouring the hillside in different ways, much as farmers do when they plant crops on hillsides. Each time, build the hill as much as possible as it was built at first, and note what happens when it rains. Try placing some small blocks of wood (house) on the hillside in different places and watch what happens to them when it rains. What does this experiment show about the effect of plants, rocks and different kinds of contouring on erosion?