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Science - 4th Grade
Standard 3 Objective 2
These classroom activities will help students understand erosion.
When sediments are formed, they are often carried away by the action of water, wind, or people and machinery. Wind erosion is most obvious in dry, desert places. In regions where there is no sheltering vegetation, the wind can strip off dry soils. The abrasive action of wind often wears away softer layers of rock, leaving the harder ones sticking out. Utah's Goblin Valley State Park is a great example of wind-created rock sculptures.
The wind carries only fine particles, but the force of flowing water can move much larger fragments. The faster the water flows, the larger the fragments it can carry. Water from rainfall or melting snow runs downhill, taking particles of rock and soil with it. Rocks carried along by water are gradually reduced in size and become smooth and rounded as they bounce along a riverbed or against each other.
Most of the power of wind, water, and ice that strip away rocks comes from the abrasive effect of the rock fragments they carry. In deserts, windblown sand scours rock surfaces into fantastic honeycomb shapes. Rocks carried by a river current widen the river by knocking out more material along the way. Along shorelines, the tides grind sand and pebbles against rock surfaces.
Natural erosion tends to happen very slowly. Humans speed up the process tremendously by altering the environment. When forests are cut down leaving exposed soil, erosion may be devastating. Overgrazing by animal herds and unsound farming practices also accelerate the process of erosion.
1. Use a Science Process and Thinking Skills
Pre-Assessment/Invitation to Learn
Invite the students to think of times when it has been so windy that the air has been filled with dust. Where did that dust come from? Where does it go? Ask if they have walked along the Jordan River. Have they noticed what the water does to the bank? Where does the soil go that falls into the water?
Activity 1 - Modeling erosion
Use a syringe to pull out the water and measure.
Activity 2 - Discovering erosion
Homework & Family Connections
Find examples of erosion around the yard. Make a plan outlining how to stop the erosion (put in plants, arrange rocks, etc.).
View the segment from "Dirt: Secrets in the Soil" video that shows the dust bowls in Utah. (Contact USU Extension to order the video and binder of activities.)
Journal entry: How did the dust bowls in Utah affect the economy? Can that kind of erosion be prevented? Explain.