Soil AKA Dirt Development of Soil Soil loose

Soil AKA Dirt

Development of Soil • Soil - loose covering of broken rock particles and decaying organic matter, called humus, overlying the bedrock of Earth’s surface.

There is soil everywhere • Except, steep mountain slopes, and extremely cold regions. • Soils rich in nutrients are called fertile soils.

Where does soil come from? • Soil starts with the breakdown of rock by mechanical or chemical weathering.

Soil Composition • Residual soil is located above its parent material. • Transported soil has been moved from its parent bedrock.

5 Ingredients that build Soil Parent Material Climate Living organisms Topography Time

5 Ingredients that build Soil

5 Ingredients that build Soil

5 Ingredients that build Soil

5 Ingredients that build Soil

5 Ingredients that build Soil

Soil Profiles and Soil Horizons • Soil profile is a vertical sequence of soil layers. • Soil horizon is a distinct zone within a profile.

The “O” Horizon • Is the top layer. • It consists of detritus, leaf litter and other organic material lying on the surface. • This layer is dark because of the decomposition that is occurring.

The “A” Horizon • Has high concentrations of organic matter or humus. • These soils are dark in color.

The “B” Horizon • Contains subsoils that are enriched in clay minerals. • Subsoils may be red or brown in color due to iron oxides.

The “C” Horizon • Below B and above bedrock, contains weathered parent material.

The “R” Horizon • Is made up of bedrock which is unweathered rock.

The Layers

Topography’ affect on Soil The topography of a region affects the thickness of developing soil. Soil formed on slopes tend to be thin, coarse and infertile. • Soils formed in valleys are thicker and fertile.

Polar Soils • Form at high latitudes and high elevations.

Temperate Soils • Vary greatly and can support diverse environments.

Desert Soil • Low levels of precipitation.

Tropical Soils • High temperatures and heavy rainfall.

Swamp Soils • Are so water logged that organic matter does not break down due to a decrease in Oxygen.

Soil Texture Triangle Soil texture is classified according to size: Clay, which is the smallest, then Silt and Sand is the largest.