1. Weathering and Soil

2. Weathering Weathering:
breaking down of rocks, soil and minerals as well as artificial materials through contact with the Earth's atmosphere, organisms and water.
Two basic types
Physical/mechanical
Chemical

3. Physical/Mechanical Frost/Ice wedging
Water seeps into open spaces and freezes.
Expansion of water wedges and cracks material
Breaks at distinct angles

4. Physical/Mechanical Exfoliation
also known as unloading, overlying materials (not necessarily rocks) are removed (by erosion, or other processes)
which causes underlying rocks to expand and fracture parallel to the surface

5. Physical/Mechanical Plant roots
seedlings sprouting in a crevice and plant roots exert physical pressure
Provide a pathway for water and chemical infiltration.
Paper beats rock 

6. Physical/Mechanical Abrasion
mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion.
moving particles dislodge loose and weak debris from the side of the rock.

7. Chemical Weathering Oxidation:
Materials react with Oxygen from atmosphere or water (H2O)
Most common Iron (Fe) “rusting”

8. Chemical Weathering Hydrolysis(water):
Materials react with water to form new material
Water dissolves rock
Chemicals in water react

9. Chemical Weathering Reactions Dissolution:
Acid dissolved in water dissolves rock
Reactions
carbon dioxide + water → carbonic acid
CO2 + H2O → H2CO3
carbonic acid + calcium carbonate → calcium bicarbonate
H2CO3 + CaCO3 → Ca(HCO3)2

10. Chemical Weathering
Plant Acids:
Some plants produce weak acids that seep into rocks and dissolve certain minerals
Examples : Lichens and Mosses

11. Question
What type of chemical weathering process produces corrosion and iron oxide?
Oxidation
Times up!
Timer

12. Factors that influence weathering
Rock Composition
Climate
Very cold( no change)
Slow weathering
Polar regions
Dry and Hot
Desert regions
Moderate (warm summer/cold winter)
Fast weathering
Temperate regions
Rocks are made of minerals
Tougher the mineral the slower the weathering
Surface area
More area exposed to weathering forces, faster the weathering

13. Surface area and speed of weathering

14. pH scale

15. Lower pH = more H+ ion (acidic)
pH concentration
“power of Hydrogen”
Lower pH = more H+ ion (acidic)
Higher pH= less H+ more OH- ion (basic or alkaline)
1 x 10 – pH =Concentration

16. Lab analysis 1 x 10 -2.5= .003 1 x 10 -6.5= .0000003 Or 6.5-2.5=4
.003/ = times more concentrated
Or =4
104 =10000

18. The dirt on dirt (soil) Bedrock: Regolith:
Solid un-weathered rock below the surface
Regolith:
layer of loose, weathered material covering solid rock.(bedrock)

19. Components of Soil Minerals Water Gases 5% organic matter:
45% weathered rock
Rocks are made of minerals
Water
25% water
Gases
25% Air
5% organic matter:
Mostly humus

20. Weathering and soil formation
Explain the relationship between weathering and soil formation.
Weathering and erosion make soil

21. Soil profile Soil profile: Cross section, shows layers top to bottom
O. Organic materials
Topsoil (organic material)
Subsoil minerals collect
Regolith
R. bedrock

22. Activity

23. Answers Tropical climate: Desert: Arctic:
Rain and High temperatures cause thick infertile soils to develop.
Desert:
Low precipitation causes thin soil
Arctic:
Slow weathering creates thin soil

24. Explain why temperate climates are ideal soil producing regions.
Explain why the study of soil is important for everyone (not just farmers).

25. Composition of soil
Sally Shoppingcart has a sample of soil. After separating the sample she has 40 grams of silt, .04 kg of sand and 20,000mg of clay. Convert all samples to the same units and find percentage of each component in the total sample.

26. Soil triangle