Soil & Erosion

1. Soil & Erosion Chapter 14.3 & 14.4

2. What is soil? • A loose mixture of rock pieces and organic material that can support the growth of vegetation. • Soil results from weathering.

3. Soil Profile & Horizons

4. What’s Erosion? • EROSION- The breakup and removal of rock by moving natural agents (rivers, glaciers, wind, water)

5. Types of Erosion • Soil erosion = as rock weathers it eventually becomes very fine particles that mix with water, air, and humus to form soil. • Gullying = Plowing of furrows, or long, narrow rows. These furrows allow water to run swiftly over soil. As soil is washed away with each rainfall, a furrow becomes larger & forms a small gully. • Sheet erosion = process by which water flows over a layer of soil & removes the topsoil.

6. Soil Conservation • Erosion rates are affected not only by natural factors but also by human activities. • Certain farming & grazing techniques can also increase the rate of erosion. • Land clearing removes protective ground covering plants & accelerates topsoil erosion. • Soil conservation methods can help to prevent rapid & destructive soil erosion

7. Soil Conservation Methods • Contour plowing: soil is plowed in curved bands that follow the contour, or shape, of the land. • Strip cropping: Crops are planted in alternating bands. Alternate between one band and a band that covers the surface of the land, known as a cover crop (Ex. corn & alfalfa). This cover crops help to protect the soil by slowing runoff.

8. Terracing: Step-like ridges that follow the contours of a sloped field. • Crop rotation: farmers plant one type of crop one year and a different type of crop the next. Stops erosion in early stages.

9. Gravity & Erosion • Mass movements – Movement of a large mass of sediment or a section of land down a slope caused by gravity. • Types of fast mass movements: • Landslides - sudden movement of bedrock or loose rocks down a cliff. • Slumps – Occurs along very steep slopes; large block of soil and rock that becomes unstable and moves downhill. • Mudflow - fast movement of a large amount of mud.

10. ← Landslide ↑ Mud flow ← Slump

11. Solifluction • Solifluction = slow, down slope flow of soil saturated with water in areas surrounding glaciers at high elevations. • Creep = the slow downhill movement of weathered rock material. • Talus – piles rock fragments that accumulate at the base of a slope

12. Landforms • Three major landforms (physical features of Earth’s surface) that are shaped by weathering and erosion: • Mountains • Plains • Plateaus