Soil Formation PDF - SES4U

SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: Soil Formation By the end of this lesson, I will be able...

SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: Soil Formation By the end of this lesson, I will be able to describe the process of soil formation and identify types of soil based on their compositions. Introduction Soil is defined to be a loose covering of broken rock particles (sediments), decaying organic matter (humus) and water that overlies the bedrock of Earth’s surface. The following steps are involved in soil formation: ​ Bedrock is weathered into smaller pieces. Continued weathering breaks the bedrock down into smaller and smaller pieces. ​ Organisms take shelter within this weathered material. (bacteria, fungi, insects) ​ These organisms die and decay, adding organic matter to form humus. ​ The humus improves the soil causing more organisms to ‘move in,’ more organisms to die, and more humus to form. In this way, the soil quality improves over time. SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: The solid bedrock from which the weathered material first breaks off is called the parent rock. The soil located above its parent material is called residual soil. The parent material determines what kinds of minerals a soil contains. Transported soil is the name given to soil that has been moved to a new location away from its parent rock through erosion. Soil can be divided into layers called soil horizons. Types of Soil There are four fundamentally different soil types: ​ Polar soils form at high latitudes and high altitudes. These soils have good drainage, but no distinct horizons because they are very shallow (a few centimeters deep). Permafrost is often present under the soil. ​ Temperate soils vary greatly and can support diverse environments. ​ Desert soils often have an elevated level of accumulated salts. They have little to no organic matter and a very thin A horizon. However, they do have an abundance of nutrients. ​ Tropical soils contain little humus and very few nutrients due to the repeated leaching due to frequent precipitation. The type of soil produced depends upon the climate, types of plants and animals living (and dying) amongst the soil, topography, length of time the soil has been forming and the parent rock. Soil can be classified according to its texture. This texture is determined by the size of the soil’s sediments. These particles range from clay (the smallest) to silt, to sand (the largest). To the right is a soil textural triangle used to identify different soils. SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: Practice! 1.​ Using the soil textural triangle above, identify the name of the soil that contains 60% clay, 10% silt and 30% sand. 2.​ Using the soil textural triangle above, identify the name of the soil that contains 20% clay, 60% silt and 20% sand. 3.​ Using the soil textural triangle above, identify the name of the soil that contains 30% clay, 10% silt and 60% sand. 4.​ The regolith of the moon is not considered a true soil. Why? 5.​ Differentiate between residual soil and transported soil. 6.​ Speculate on how each of the following factors could affect soil conditions. a.​ climate b.​ topography c.​ parent rock