The Causes of Soil Erosion. human activities

NOTES ON GRASE 11 CAUSES OF SOIL EROSION

1. The Causes of Soil Erosion Understanding How Topsoil Disappears Lesson Objectives Identify and explain four causes of soil erosion: human, animal, physical, past/present Observe and describe physical erosion through a water-and-soil experiment 2025-09-30 Environmental Science

2. Lesson Objectives 1 Identify and Explain Four Causes Human activities (deforestation, improper farming) Animal impacts (overgrazing, trampling) Physical forces (water and wind erosion) Past and present actions 2 Observe and Describe Physical erosion through a water-and-soil experiment: Setting up the experiment Observing water movement Comparing soil erosion with/without plants

3. What is Soil Erosion? Definition: Soil erosion is when the top layer of soil (topsoil) is moved from one place to another. This happens naturally, mainly by forces like wind and water . It's Like... The soil is being washed away by water The soil is being blown away by wind Example of soil erosion - cracked and dry land The Erosion Process Healthy Soil Wind Water Erosion

4. Human Causes of Soil Erosion Deforestation Cutting down trees removes the protective canopy and root systems that hold soil in place, making it vulnerable to wind and water erosion. Improper Farming Methods Plowing up and down hills creates channels for water to flow rapidly Monoculture depletes soil nutrients and structure Over-tilling breaks down soil aggregates and increases wind erosion Construction and Urbanization Building roads, houses, and infrastructure often involves clearing vegetation and disturbing large areas of soil, leaving it exposed and easily eroded. Mining Surface mining operations remove topsoil and vegetation, creating vast areas of exposed and unstable land prone to erosion. Deforestation removes protective vegetation Human activities significantly accelerate soil erosion through various practices

5. Animal Causes of Soil Erosion Overgrazed pasture showing soil erosion Overgrazing When too many animals (like cattle, sheep, or goats) graze on a small area, they eat plants down to the roots. This: Removes the protective plant cover Compacts the soil with their hooves Reduces water infiltration Increases surface runoff and erosion Trampling Repeated movement of livestock on soil: Compacts the soil, reducing its porosity Makes it harder for water to penetrate Creates pathways for water to flow rapidly Increases surface runoff and erosion Burrowing Animals that dig burrows (e.g., rabbits, prairie dogs): Loosen soil, making it more susceptible to erosion Creates tunnels that can carry away soil during rain Is especially problematic on slopes

6. Physical Causes of Soil Erosion Natural forces that move soil from one place to another Water Erosion Rainfall Impact Raindrops hit bare soil, dislodging soil particles that can be carried away Sheet Erosion A thin layer of topsoil removed across wide areas by flowing water Rill Erosion Small channels form from concentrated water flow, carrying away soil Gully Erosion Rills deepen into large channels, removing significant amounts of soil Wind Erosion Deflation Wind carries fine soil particles away Abrasión Particles impact and wear away other particles Saltation Particles bounce along the ground surface Suspension Fine particles carried high into atmosphere Gully erosion: Water erosion has created deep channels in this landscape

7. Past and Present Causes How history and current actions work together Past Causes Early deforestation Poor farming Present Causes Urbanization Climate change Cumulative Effect Past and present causes create a feedback loop that makes soil more vulnerable.

8. Physical Erosion Experiment Water Erosion Demonstration This experiment shows how water moves soil and how plants can protect against erosion. What You'll Observe: Water moving soil on bare land Water moving more slowly with plants Less soil erosion with plant cover "Plants act like a shield, protecting soil from water erosion." Plant Protection Without Plants More erosion With Plants Less erosion

9. Experiment Materials and Steps Materials Needed Two shallow trays or containers E.g., baking pans Soil Enough to fill both trays halfway Watering can or bottle With a spout Something to represent plants Grass clippings, sponge pieces, or small plant Experiment Steps 1 Prepare Trays Fill both trays with an equal amount of soil. Spread the soil evenly. 2 Add "Plants" Place or sprinkle plant material on one tray. Leave the other tray bare. 3 Set Up for Erosion Slightly tilt both trays. Place empty containers at the lower end to catch runoff. 4 Simulate Rain Pour equal amounts of water over the bare tray. Observe the soil and runoff. 5 Repeat with "Plants" Pour the same amount of water over the tray with plants. 6 Observe Compare the water runoff and soil in both trays.

10. Conclusion Today, we learned that soil erosion is when the top layer of soil (topsoil) is moved from one place to another. This happens naturally by forces like wind and water, but it's also accelerated by human activities, animals, and past decisions. Human Causes Deforestation, improper farming, construction, and mining remove soil protection. Animal Causes Overgrazing, trampling, and burrowing animals compact soil and remove plant cover. Physical Causes Water and wind erosion forces move soil particles, creating new landscapes. Past & Present Causes Historical practices and current activities both contribute to soil erosion. Why This Matters Understanding these causes helps us see why preventing soil erosion is so important for our environment. Plants act like shields, protecting soil from being washed away. When we protect soil, we protect our future.