Age: 3rd-6th grade
Objectives: Students will learn what soil erosion is, how it is caused, and what effect it can have on land.
Ask your students the following questions. Then explain the answers and talk about how you are going to demonstrate these concepts in the activity.
What is soil erosion? It is when rain and wind wash away the fertile topsoil and leave infertile land exposed. Crops and native plants can no longer grow there. This leaves the land even more exposed to weather. Eventually, the land will become drier (more arid) and this leads to desertification. Desertification is where continued exposure to the elements causes all the nutrients to be washed from the soil until the land is so barren it cannot support its native plants. It had become a desert.
How does soil erosion start? Areas that once had fertile soil can be exposed to erosion in many ways. Over-grazing by livestock can cause the soil to be exposed to the elements and begin the erosion cycle. Clear cutting forest for timber harvest can expose soil to erosion. Forest fires or blow downs uncover fragile soil.
This is a simple demonstration of how erosion works.
Materials: 4 dish pans, potting soil or sand, rocks, leaves, sticks, grass, water, watering can
1. Divide class into 4 groups.
2. Talk to them about the concept of erosion.
3. Tell them they will each build a mountain in different ecosystems. Then they will see how erosion effects soil in their ecosystem.
4. Have each group make a "mountain" (small mound in dishpan) using rocks, sand and soil. Pat it down firmly.
5. Have one group keep their mountain as is to represent a desert. Have 2nd group sprinkle a bit of grass onto their mountain to represent an overgrazed area (don’t cover the soil much). Have 3rd group sprinkle lots of grass until soil is well covered to represent a healthy grassland. Have 4th group lay sticks and leaves over their mountain until the soil is fully covered to represent forest.
6. Each group should make a label to tell what ecosystems their display represents. Make sure they pat their mountain down firmly.
7. Each ecosystem should then be exposed to the elements. Fill the watering can with about a quart of water. Start with the forest and sprinkle the water over the mountain. It must fall with enough force to show how the leaves and sticks protect the mountain. Next use the same amount of water and pouring force on the grassland, then the overgrazed grassland, then the desert.
9. Have the students observe how the water affected the different ecosystems. Can they explain why some mountains wash away more than others? Compare this to real ecosystems.
Grade 3 - 3-ESS3 Earth and Human Activity
Disciplinary Core Ideas
ESS3.B: Natural Hazards
• A variety of natural hazards result from natural processes. Humans cannot eliminate natural hazards but can take steps to reduce their impacts. (3-ESS3-1)
Performance Expectations Students who demonstrate understanding can:
3-ESS3-1. Make a claim about the merit of a design solution that reduces the impacts of a weather-related hazard. [Clarification Statement: Examples of design solutions to weather-related hazards could include barriers to prevent flooding, wind resistant roofs, and lightning rods.