Week 6 Soil Formation PDF

Geology AECE 2210 Soil Formation  What is Soil? 2 Soil is a complex mixture of: minerals (approximately 45%) organic matter (approximately 5%) void (empty space) (approximately 50%, filled to varying degrees with air and water). The uppe...

Geology AECE 2210 Soil Formation  What is Soil? 2 Soil is a complex mixture of: minerals (approximately 45%) organic matter (approximately 5%) void (empty space) (approximately 50%, filled to varying degrees with air and water). The uppermost layer of the surface of the Earth and is formed by the processes of weathering of mountains over thousands of years.  What is Soil? 3 Soil is a product of weathering. The essential components of soil are sand, silt and clay.  Soil Formation 4 known as pedogenesis, is the process by which soil is created and developed. Soil Formation: https://www.youtube.com/watch?v=6Q3hGJNByi8  Soil Formation Factors 5 This process is influenced by factors such as:  Soil Formation Factors 6 Parent Material The mineral material from which soil forms. The mineralogical composition effect the type of soil been produced. Most soils derive from: Transported materials that have been moved many miles by wind, water, ice and gravity (erosion) – Transported soil Bedrock (underlying) - Residual soil Typical soil parent mineral materials are: Quartz, Calcite, Feldspar, Mica  Soil Formation Factors 7 Climate Temperature and precipitation affect the rate of weathering and organic matter decomposition. Variation of both will determine whether mechanical or chemical weathering will dominate. For instance: In hot and wet climate – produced chemical weathered soil. In cold and dry climate - produced mechanical weathered soil.  Soil Formation Factors 8 Topography Geological structural characteristics such surface elevation, relief and slope. It effects the amount of erosion and water content of soil. For instance: Steep land slope Erosion is high resulting in shallow and thin-layered soil. Slope is moderate resulted soil depth is moderate.  Soil Formation Factors 9 Time Thousands of years for a transformed soil to form in a natural environment. According to soil scientists, it takes hundreds of years for a layer of soil just two cm thick to form. Depends on the hardness of the parent material Soft shale rocks form soils quickly but hard igneous rocks form very slowly.  Soil Formation Factors 10 Plants and animals (organisms) Each soil has a unique combination of microbial, plant and animal. Influenced in the mineral transformations of the soil. The dead remains of animals and plants are decomposed and incorporated into the soil called as humus. Soil which is rich with organic matters usually good for vegetation but not for construction.  Soil Profile 11 Vertical section of soil that reveals its various layers, known as soil horizons. O Horizon (Organic Layer): This topmost layer is rich in organic matter, including decomposed leaves and plants. A Horizon (Topsoil): mix of organic material with minerals. It’s crucial for plant growth and is often referred to as the humus layer. E Horizon (Eluviation Layer): leaching of minerals and organic matter B Horizon (Subsoil): accumulates minerals leached from the upper layers. C Horizon (Parent Material): Weathered parent material from which the soil is formed. R Horizon (Bedrock): Unweather bedrock. It is not considered soil but provides the material from which soil develops.