So You Want to Do a Project about Erosion!
To determine erosion by water.
- 1/2 cup (12S mL) soil
- Four 12-ounce (360-mL) Styrofoam cups
- Tap water
- Cookie sheet
- 2-cup (500-mL) measuring cup
- Adult helper
- Pour the soil into one of the cups; dampen the soil with enough water to make thick mud, and stir.
- With your hands, mold the mud into 8 equal size balls.
- Place the mud balls on the cookie sheet.
- Ask your adult helper to bake the mud balls in an oven at 275°F (135°C) for 1 hour or until they are dry.
- Prepare the remaining three cups, to be called cups A, B, and C, as follows:
- Use the marker to label the cups "A," "B," and "C."
- Use the pencil to make 8 to 10 holes around the bottom edge of cup A. Place the mud balls in this cup.
- Use the pencil to make 12 holes in the bottom of cup B.
- Fill cup C with tap water.
- Observe the shape of the mud balls in the cup.
- Set the measuring cup on a table.
- Hold cup A in one hand above the measuring cup and hold cup B just above cup A.
- Ask a helper to pour the water from cup C into cup B.
- After the water has drained out of cup A, observe the shape of the mud balls in the cup.
- Allow the contents of the measuring cup to sit for 30 or more minutes. Then observe the amount of soil in the cup.
The mud balls change shape. Parts of the balls are dissolved in the water, and parts are broken off. The dissolved and broken parts are washed out through the holes in the bottom of cup A, into the measuring cup. After a while, the soil settles to the bottom of the measuring cup. The amount of soil washed away varies depending on the type of soil used.
The mud balls are said to have eroded. Erosion is the process by which rock and other materials of Earth's crust (thin outer layer) are broken down and carried away by natural agents, such as water, wind, ice, and gravity. The part of the erosion process that involves only the breakdown of crustal materials is called weathering. One weathering process is chemical weathering, which affects the chemical properties of substances that make up crustal materials.
This experiment demonstrates one of the main causes of chemical weathering, the dissolving action of water. One part of the erosion process is the dissolving of some of the substances to form a solution. Another part is the mixing of the substances with water to form a suspension (a mixture in which tiny solid particles are spread throughout a fluid but are not dissolved and settle out slowly). The water erodes the mud balls by first dissolving and mixing with the substances in the ball, then carrying the substances away.
The agents of erosion in this experiment are water and gravity. Gravity pulls the water down, and the water carries the dissolved materials and mixed substances down with it as it flows out of the holes in the cup. When the water stops moving, gravity pulls the undissolved materials in the water down, where they collect in the bottom of the measuring cup. Particles of rock carried away by erosion are called sediment. The buildup of sediment is called deposition. Erosion is a wearing-down process and deposition is a building-up process.