L2 Soil Science Soil their Components hlayiso.com

SUBJECT: SOIL SCIENCE LEVEL: 2 TOPIC: SOIL AND THEIR COMPONENTS DATE: 14/04/2020-17/04/2020 COMPILED BY: MR MAPUWA AND MR MPHUTHI SEFIKENG CAMPUS Downloaded from hlayiso.com

SOIL AND THEIR COMPONENTS SO2: Explain how soils are formed and describe the properties of the main layers. LO1: Outline, in very simple terms, the weathering of rock and the effects of living organisms on developments. Downloaded from hlayiso.com

AFTER THE LESSON STUDENTS SHOULD BE ABLE TO ANSWER/DO THE FOLLOWING: • Explain the different types of weathering which includes: physical, chemical and biological weathering. • Explain the differences between weathering and erosion. • Factors influencing soil formation. • Eluviation and illuviation explained in details. Downloaded from hlayiso.com

1. WHAT IS WEATHERING? Primary process that forms soil. Weathering breaks down the parent material, which is rock, into smaller particles. These small particles of mineral or rock combine with decomposing organic material to form soil. As a result, soil is neither completely biotic nor completely abiotic. Downloaded from hlayiso.com

1. WHAT IS WEATHERING? 1.1. THERE ARE THREE TYPES OF WEATHERING THAT CAN CONTRIBUTE TO SOIL FORMATION. Downloaded from hlayiso.com

2. EXPLAIN THE DIFFERENT TYPES OF WEATHERING WHICH INCLUDES Physical weathering Chemical weathering Biological weathering . . Physical weathering Chemical weathering Biological Weathering consists of water Or occurs when the rock is weathering caused wind separating piece reacts with surrounding by organisms such as of the rock It can also materials, such as when tree roots wedging a occur when water in a a weak acid dissolves rock apart or lichens crack in the rock part of a rock. secreting acids to freezes, wedging the dissolve a rock rock apart Downloaded from hlayiso.com

3. DIFFERENCES BETWEEN WEATHERING AND EROSION WEATHERING EROSION • Occurs in place and is when • Is the removal and transport of rocks/minerals break down due to surface materials through the actions wind, water or an other natural of wind and water. process. • Erosion occurs because of factors like • Weathering is caused by factors wind, water, ice, human activities. such as rain, heat and temperature. • Erosion is caused by the movement of • Weathering there is no movement eroding agents Downloaded from hlayiso.com

4. FACTORS INFLUENCING SOIL FORMATION CLIMATE: Temperature and humidity will influence the speed of weathering. ORGANISMS: Burrowing animals can help to mix soil and distribute organic and inorganic components. Plants can secrete acids that can help to speed chemical weathering. TOPOGRAPHY: The steeper the slope will lose soil due to soil erosion, whereas valley will accumulate large amount of soil. Wind exposure or heavy rains on one side of a hill/mountain could speed Downloaded from hlayiso.com weathering as well.

4. FACTORS INFLUENCING SOIL FORMATION (CONT…) PARENTAL MATERIAL: The chemical composition of the parent materials (basalt, limestone and granite) determines how quickly it will weather and will determine the mineral content and many other properties of the soil. TIME The more time passed, the more developed soil will become. Old soil with productive ecosystem and moderate rainfall can become very deep and fertile such as grassland. Soil with heavy rainfall maybe less fertile due to the leaching of nutrients from the soil. Downloaded from hlayiso.com

ELUVIATION AND ILLUVIATION EXPLAINED IN DETAILS ELUVIATION • The transportation of dissolved or suspended material within the soil by the movement of water when rainfall exceeds evaporation. In soil sciences eluviation is the transport of soil materials from upper layers of soil to lower levels by downward precipitation of water across soil horizons. • Is the material displace across a soil profile from one layer to another one by the action of rainwater. • Enrichment of a horizon with materials from another horizon transported by the flow of water in the soil. These materials can be silicate clays, organic matter, iron and calcium. Downloaded from hlayiso.com

ELUVIATION The loss of material such (clay particles, organic matter, oxides of iron and aluminum) from horizon whether it be in solution or suspension. A horizon in a soil profile from which materials has been removed is called ELUVIAL HORIZON. Downloaded from hlayiso.com

ACTIVITY TO BE COMPLETED 1. Explain the following terms according to understanding.(6) 1.1. Weathering 1.2. Eluviation 1.3. Illuviation 2. Mention and explain the different types of weathering rocks.(9) 3. Soil formation is influenced by certain factors: Mention those factors(5) 4. Supply the correct word for the following sentence.(4) 4.1. Temperature and humidity will influence the speed of weathering. 4.2. The steeper the slope will lose soil due to soil erosion, whereas valley will accumulate large amount of soil. Wind exposure or heavy rains on one side of a hill/mountain could speed weathering as well. Downloaded from hlayiso.com

ACTIVITY TO BE COMPLETED 5. Choose a description from COLUMN A to match an item in COLUMN B. (10) COLUMN A COLUMN B 1. Mixture of loose materials in the upper A. Altitude layer of the earth’s surface. B. Biological weathering 2. Blowing wind on bare soil. C. Organic 3. Water that is not held so strongly by the D. Inorganic material soil particles. E. Erosion 4. Height above sea level. F. Capillary 5. Living or originating from living, but now G. Soil dead. H. Latitude Downloaded from hlayiso.com

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