1. Chapter 5 Weathering, Soils, & Mass Movements

2. What do you know? What process breaks down rock into smaller pieces?
A.) cementation
B.) compaction
C.) weathering
D.) deposition
Answer –
C.) weathering

3. What do you know? Which of the following are types of weathering?
Mechanical?
Chemical?
Answer: Both are forms of weathering

4. Mechanical Weathering
physical forces break rock into smaller without changing rock’s mineral composition
Each piece has the same characteristics as the original rock

5. Mechanical Weathering
Mechanical Weathering Animation
Mechanical Weathering
How does surface area affect weathering?
increases as breakup a rock

6. Mechanical Weathering of Rocks 3 types1 2
Unloading
Frost wedging 3
Root wedging

7. 1. Unloading What is it? Large masses of igneous rock
exposed through uplifting and erosion
of overlying rocks

8. 2. Frost Wedging
1. Mechanical breakup of rock caused by expansion of freezing water in cracks and crevices
2. Sections of rock that are wedged loose and fall apart
Frost Wedging Animation
Can of coke explodes when it is frozen!

9. Frost Wedging

10. 3. Biological Activity What is it?
1. Plant roots can grow into cracks in rock and wedge rock apart as they grow
2. Burrowing animals move rocks to surface, where weathering is more rapid

11. Chemical Weathering What is it?
Chemical weathering - transformation of rock into one or more new compounds
If I gave you a piece of paper, how would you show me mechanical weathering?
How would you then show me chemical weathering?

12. Chemical Weathering Agents of Chemical Weathering
1. Water (rain)
2. Carbon Dioxide (CO2)

13. How does carbonic acid cause chemical weathering?
Rain mixes with CO2 (gas) in atmosphere
Rain + CO2 = carbonic acid
Carbonic acid dissolves and breaks down rocks

14. Chemical Weathering Examples (1) Rust
Iron on barrels coverts to rust
Iron + oxygen (from air) coverts to iron oxide (rust)

15. Chemical Weathering Examples (2) Acid Rain
Rain + sulfur + nitrogen = acid rain
Where does sulfur and nitrogen come from?
burning fossil fuels- like coal & gasoline

16. Chemical Weathering “Acid Rain”
Acid rain accelerates the chemical weathering of stone monuments and structures

17. Chemical Weathering Exposure to moisture and
oxygen turns the copper into
copper sulfate which is green
in color.

18. Chemical Weathering Examples (3) Cave formation
Rain + CO2 = carbonic acid
Carbonic acid enters soil
Areas where soil contains limestone can form caves

19. Chemical Weathering Examples (4)- Sinkholes
Rain + CO2 = carbonic acid
Carbonic acid weathers holes in limestone rock