Soil & Erosion Chapter 14.3 & 14.4

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

Soil Profile & Horizons

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

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.

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

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.

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.

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.

← Landslide ↑ Mud flow ← Slump

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

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