chapter 6 weathering and soil
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Chapter 6 Weathering and Soil . Types of Weathering. Mechanical Weathering – Breaks apart rock without changing its chemical composition Examples Plant roots grow into the cracks of rocks Animals burrowing Ice Wedging. Types of Weathering. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 6Weathering and Soil
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Types of Weathering
• Mechanical Weathering – Breaks apart rock without changing its chemical composition
• Examples– Plant roots grow into the cracks of rocks– Animals burrowing– Ice Wedging
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Types of Weathering
• Chemical Weathering – Breaks up rocks due to a change in their chemical composition. (Water and Oxygen are factors)
• Examples– Acid Rain– Rust
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Mechanical vs. Chemical
Mechanical
Chemical
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Ice Wedging
• Type of mechanical weathering
• This happens when water gets inside rocks, freezes, and then expands causing the rock to break.
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Carbonic Acid
• When water mixes with carbon dioxide in the air, carbonic acid forms.
• Type of chemical weathering
• Comes in contact with different rocks, and reacts with the minerals in them.
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Oxidation• Oxidation occurs when a material is exposed
to water and the oxygen in the air.
• This causes “rust”
• Type of chemical weathering.
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Climate and Weathering
• Cold climates – mechanical weathering breaks down rocks rapidly through ice wedging
• Chemical weathering is more rapid in warm, wet climates. (tropical areas)
• Lack of moisture and cold climates keeps chemical weathering at a minimum.
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What is Soil?
• Soil – A mixture of weathered rocks, decaying organic matter (plants & animals), mineral fragments, water, and air.
• Sediments + Organic Matter= Soil
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What is Humus?
• Humus – Dark colored organic matter found in soil; made of decayed plants and animals.
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• Soil Profile – Vertical section of the different soil layers.
• Horizon – Each layer in the soil profile. (Three Horizons: A, B, and C)
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Horizons
• Horizon A– Most evolved– Known as topsoil– More humus and smaller rock and mineral
particles than other layers.• Horizon B– Less evolved– Lighter in color– Some plant roots reach here
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Horizons Continued
• Horizon C– Bottom layer of soil profile– Contains partly weathered rock– Solid rock
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Layers of Soil
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Process of
Soil Formation
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Leaching
• Removal of soil materials dissolved in water.
• Occurs throughout all three Horizons.
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When does Desertification occur?
• When soil is dry due to lack of rain combined with poor farming practices and over – grazing.