Water erosion happens when moving water carries soil, sand, and small rocks from one place to another. In this tray investigation, students build two small slopes and gently pour water over them to see what changes. One slope has bare soil, and the other has grass-covered soil.
Comparing the two sides helps show why plants are important for keeping land in place.
Key Facts
- Erosion is the movement of soil or rock by water, wind, ice, or gravity.
- Runoff is water that flows over the ground instead of soaking in.
- More slope usually means faster water flow and more erosion.
- Plants reduce erosion because roots hold soil particles together.
- A fair test changes only one main variable, such as bare soil vs grass-covered soil.
- Soil lost = starting soil amount - ending soil amount
Vocabulary
- Erosion
- Erosion is the process of moving soil, sand, or rock from one place to another.
- Runoff
- Runoff is water that flows across the surface of the ground.
- Slope
- A slope is a surface that is higher at one end and lower at the other.
- Roots
- Roots are the parts of plants that grow underground and help hold soil in place.
- Fair Test
- A fair test is an experiment where only one important thing is changed so the results can be compared.
Common Mistakes to Avoid
- Changing the amount of water on each side, which is wrong because the bare soil and grass side must get the same water to make a fair comparison.
- Tilting one side more than the other, which is wrong because a steeper slope can cause more erosion even if the soil covering is the same.
- Pouring water too fast, which is wrong because a heavy splash can knock soil loose instead of showing gentle runoff erosion.
- Judging only by how muddy the water looks, which is wrong because students should also observe soil movement, small channels, and how much soil collects at the bottom.
Practice Questions
- 1 A class pours 200 mL of water on the bare soil slope and collects 35 g of washed-away soil. How many grams of soil were eroded?
- 2 The grass-covered slope loses 8 g of soil, and the bare soil slope loses 32 g of soil. How many more grams of soil did the bare slope lose?
- 3 If the grass-covered slope loses less soil than the bare slope, explain how the roots helped protect the soil.