1. Weathering

2. What Will We Learn In This Chapter?
Distinigiush between weathering and erosion
Identify variables that affect the rate of weathering
Analyze the impact of living and nonliving things on the processes of weathering and erosion.
Describe the realtionship of gravity to all agents of erosion
Describe how soil forms
Explain the relationship between the organic and inorganic components of soil
Identify Soil Characteristics
Recognize soil horizons in a soil profile

3. Development of Soil Almost found every where on earth Soil
loose covering of broken rock particles
Plus Decaying Organic Material
Results from
Chemical Weathering
Mechanical Weathering
Biological Activity

4. Development of Soil

5. Soil Composition
Soil is developed from the breakdown of the exposed bedrock
As pieces weather they rest on top of bedrock
Over time soil becomes more inhabitable
Living and Dead material plus weathered rock remain
Residual Soil
Soil located above the parent material

6. Soil Composition
Soil that is exposed to the elements can be transported.
This type of soil is called Transported Soil

7. Check for Understanding
Soil is composed of which of the following?
Weathered rock
Living organisms
Dead organisms
Moisture
Atmospheric gases
All of the above

8. Check for Understanding
Soil is composed of which of the following?
Weathered rock
Living organisms
Dead organisms
Moisture
Atmospheric gases
All of the above

9. Soil Profiles Soil Profile Soil Layers are called… Soil Horizons
Is a vertical sequence of soil layers
Soil Layers are called…
Soil Horizons
A distinct layer or zone
4 Types
O, A, B, C

10. Classification of an Soil Profile
O Horizon
Living, Organic matter
Grey to Black
A Horizon
Rich in Humus
B Horizon
Enriched with clay
C Horizon
Weathered Parent Material

11. Soil Profile of Wisconsin

12. Soil Profiles are Due to Topography
The topography of a region affects the thickness of soil
Sloped Areas: thinner layers of soil because of erosion
Lowlands/Valleys: thicker layers of soil because of increased deposition
South-Facing Areas: areas facing the south receive more sunlight  more vegetation  more soil than areas facing other directions

13. Soil Types Classified mainly based of climatic conditions of the area
4 major types
Polar Soils: very thin layers of soil covering the frozen, permafrost, ground
Temperate Soils: vary greatly; support vast array of organisms
Type of soil most of WI has
Desert Soil: receives little precipitation  little vegetation  thin A soil horizon
Tropical Soil: high temps & precipitation  intense weathering with a high degree of bacteria in soil  very little humus & few nutrients found in soil  poor growing soil

14. Soil Texture Soil Triangle
Tells us the texture of soil based on it feel
Three main types of sediments thatmake up soil
Sand
Silt
Clay
The proportion of these sediments give soil its texture

15. Weathering is the process that produces change in the surface of rocks exposed to the atmosphere and/or hydrosphere.

16. Two Types OF Weathering:
Mechanical weathering is breaking rock by force.
ex: hitting, scratching, cracking
Chemical weathering is where the rock material is changed into another substance by reacting with a chemical.

17. Frost Wedging Frost action (ice wedging)-
Water seeps into small cracks in rocks.
When the water freezes it expands creating great pressure.
The crack widens and allows water to seep deeper into the rock.

18. Root Wedging Plant action-
Tiny root hairs seek out small cracks and pits in rock.
Once the root hairs find a place they grow and expand.
The expansion causes great pressure and cracks the rock.

19. Exfoliation
Rocks formed deep in the Earth are made under high pressure.
When the pressure is released the rocks expand & crack.
May also be caused by alternate heating and cooling of rocks by weather conditions.

20. Types of Chemical Weathering
Oxidation-
Oxygen in the atmosphere chemically reacts with minerals.
ex.: rusting of a nail
Iron Silicates
Iron Sulfides

21. Types of Chemical Weathering
Hydrolysis
Minerals are dissolved in water.
ex.: Halite, calcite
Feldspars react with water to form clay plus other minerals

22. Rates of weathering will be influenced by:
Surface area exposed - weathering occurs on the surface. More surface exposed, the faster the weathering will occur.

23. A smashed piece has greatest surface area exposed
A smashed piece has greatest surface area exposed. The interior can now be attacked.
A full, solid block has the least surface area. The interior is safe from exposure.

24. Rates of Weathering will depend on:
Mineral composition- some minerals are more resistant than others.
ex.:Quartz is resistant to chemical and physical weathering.

25. Where is the rock more resistant to weathering?F A C E B D

26. Where is the rock least resistant to weathering?F A C E B D

27. You might also see it like this…

29. Rates of Weathering will depend on:
Climatic Conditions:
Cold and/or dry climates favor physical weathering.
Warm and wet climates favor chemical weathering.
Frost action works best in areas where the temperature fluctuates wildly.