Soil Formation Soil – weathered particles of rock, minerals and organic material (from living things) 1. Residual Soil – formed from the local bedrock below. Has same color and minerals as bedrock. 2. Transported Soil – brought from somewhere else (usually by glaciers). May have different color and minerals than local bedrock.

Soil colors

Soil Horizons A-Horizon = Topsoil; usually dark and rich. Contains organic matter like leaves, twigs and dead grass. B-Horizon = Sub-soil; mostly clay-sized particles, not much organic matter. C-Horizon = Partly weathered bedrock.

Erosion Erosion – movement of weathered material. Natural Agents of Erosion 1. Water 2. Wind 3. Ice (glaciers) * All affected by gravity – eroded material moves down hill

Soil Erosion How much topsoil is needed to grow most crops? 25 Billion tons of topsoil is lost each year worldwide. Where does it go? How long does it take on average for 1” of topsoil to form?

Farming Methods to Conserve Soil Contour Farming - Planting in horizontal rows across hillsides

Strip Cropping - Planting alternating rows of crops that help anchor soil and add nutrients to soil

Terrace Farming Cutting steps into hillsides to create flat surfaces

Wind Breaks - planting a barrier of trees around the perimeter of you fields.

Dustbowl - 1935

Characteristics of Eroded Sediments: 1. Water transported sediments are smooth and rounded. 2. Wind transported sediments are small and angular (rough edges) 3. Ice (glaciers) leaves scratches called striations on rock surfaces. Also polishes the surface.

Glacial Striations