Duration: 40 to 60 minutes
Setting: Outside – General
Vocabulary: erosion, landscape, weathering, prevention
Summary: Students learn about the process of erosion and look for places in their area where erosion is occurring. They then plant grass seed to try to stop the process.
Objectives: Students gain an understanding of the process of erosion and that the shape of a landscape changes over time due to the forces of wind, water, gravity, and human activity.
Materials: grass seed, straw, watering cans
Erosion is defined as the process of weathering and transport of solids (sediment, rocks, etc.) in the environment from one place to another. It can be a natural or human-made process. Natural forces of erosion include wind, sun, and water.
Wind kicks up dirt and sand and can rub away at rocks and other materials. The sun heats up rocks and soil, causing it to expand, crack, and break down easily. Water is an especially powerful force of erosion. Water can dissolve materials and move particles around. Think of a river after a large storm—it is usually brown, murky, and full of debris. This is because the fast-moving water picks up the soil and carries it around.
Trees and plants are an important part of erosion prevention because their roots hold on to the soil. Additionally, when it rains, water falling through the trees and into forests with a lot of plant debris on the ground is slowed down, and has less of an impact on the soil below.
Earthworms and insects can also have an effect on the erosion process. The more earthworms and other insects churn up the soil, the easier it is for water to seep into the ground. Water seeping into the ground quickly means less water moving over the surface and eroding the soil.
Erosion is a natural process but at times human actions can impact the surroundings and cause erosion. If we cut down too many trees or remove too much grass in certain areas, soil can get into streams and make it dirty. Erosion can be dangerous for many reasons—if we lose the soil, there will be none left for us to grow food on or live on! It is also bad for fish and other aquatic organisms, as soil in the water can clog their gills and take up oxygen.
Warm Up: Show students pictures of erosion and videos of flooding areas. What do they notice? What is happening to the soil? Ask them if there is something the areas that are eroding have in common. Help them realize that what they have in common is the lack of vegetation on the area.
Take students out on a walk around the schoolyard and look for signs of erosion. Look for places where there is exposed soil and it looks like the dirt will easily wash away. There might be more places along the edges of parking lots or undercutting hilltops. Keep track of where you see each spot.
After you walk around the grounds, choose a few areas to improve upon. Plant grass seed with students and then lay down straw on top. Water the seeds gently with watering cans.
Revisit the area over time to see how the grass is growing.
Ask students to define erosion and explain what causes it. What are some natural causes and what are some human-made causes? Why is reducing erosion important?
If possible, take students outside right after a heavy rain to see how the water moves and where it is going. This will help show areas where erosion is prevalent.