1. Weathering

2. Not to be confused with WEATHER!
What is weathering?
The process that breaks down rock into smaller pieces, called sediments.
Not to be confused with WEATHER!

3. There are two types of weathering:
Mechanical Weathering
(physical)
Chemical
Weathering
Rocks are physically broken into smaller pieces.
Rocks are broken down through chemical changes.
The rate of weathering is affected by climate.
Mechanical happens faster in the cold weather.
Chemical is faster in warm weather.

4. Forms of Mechanical Weathering
Ice Wedging
Exfoliation
Abrasion
Plants and animals

5. Ice Wedging (a.k.a. Frost wedging)
The cycle of water freezing and thawing in the cracks of rocks, causing the rock to break.
Click the picture for ice wedging animation!

6. Pressure causes rocks to crack and “peel’ away in slabs.
Exfoliation
Pressure causes rocks to crack and “peel’ away in slabs.

7. Abrasion
Sediments carried by wind or water rub against other rock and wear it down. Like sandpaper!

8. Plant roots grow large and break apart rock.
Plant Wedging
Plant roots grow large and break apart rock.

9. Animals burrow into the ground and loosen sediment and soil.

10. These smaller pieces will be weathered faster than a larger piece.
Surface Area of Rock
As rock is broken apart by mechanical weathering, the amount of rock surface area exposed to air and water increases.
These smaller pieces will be weathered faster than a larger piece.

11. EXIT SLIP What is weathering?
How do mechanical weathering and chemical weathering differ?
What type of weather conditions would increase the rate of chemical weathering?
The diagram shows the process of
ice wedging. Explain how this
process physically weathers rocks.
How can plants and animals
contribute to the mechanical weathering process?

12. Forms of Chemical Weathering
Oxidation Dissolution Hydrolysis Organic Acids

13. Oxidation
When materials that contain iron are exposed to oxygen and water, they become a reddish color.
Ayer’s Rock, Australia

14. Dissolution
Carbonic acid in rain dissolves rock. This can form caves and cause sinkholes.

16. Hydrolysis
Water combines with the minerals in rock and cause a chemical change. If water combines with the mineral feldspar, clay is formed.

17. Plant roots give off acids that dissolve rock.
Organic Acids
Plant roots give off acids that dissolve rock.

18. EXIT SLIP
Oxidation occurs when materials that contain iron are exposed to what two compounds?
Dissolution can form sinkholes. Explain the process of dissolution.
How do plants and animals chemically weather rocks?

19. Can you tell which mountain is older?

20. What is soil?
A mixture of weathered rock, decayed organic matters, mineral fragments, water, and air.

21. Factors Affecting Soil Formation