1. Chapter 6 Weathering and Soil

2. 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

3. 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

4. Mechanical vs. Chemical

5. Ice Wedging Type of mechanical weathering
This happens when water gets inside rocks, freezes, and then expands causing the rock to break.

6. 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.

7. Oxidation
Oxidation occurs when a material is exposed to water and the oxygen in the air.
This causes “rust”
Type of chemical
weathering.

8. 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.

9. What is Soil?
Soil – A mixture of weathered rocks, decaying organic matter (plants & animals), mineral fragments, water, and air.
Sediments + Organic Matter
= Soil

10. What is Humus?
Humus – Dark colored organic matter found in soil; made of decayed plants and animals.

11. Soil Profile – Vertical section of the different soil layers.
Horizon – Each layer in the soil profile. (Three Horizons: A, B, and C)

12. Horizons Horizon A Horizon B 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

13. Horizons Continued Horizon C Bottom layer of soil profile
Contains partly weathered rock
Solid rock

14. Layers of Soil

15. Process of
Soil Formation

16. Leaching Removal of soil materials dissolved in water.
Occurs throughout all three Horizons.

17. When does Desertification occur?
When soil is dry due to lack of rain combined with poor farming practices and over – grazing.