1. Weathering

2. Weathering –breaking down and changing the rocks on Earth’s surface
2 main types

3. 1) Mechanical weathering
rocks and minerals breaking down without changing their chemical composition

4. Factors of Mechanical Weathering
A. Temperature
When water freezes it expands by 9%
If water collects in spaces in rocks and freezes it can cause them to split
This is called frost wedging

5. B. Pressure
Buried rocks have a lot of pressure on them
As rocks get closer to the surface, there is less pressure
With less pressure, rocks can expand and crack

6. 2) Chemical weathering
rocks and minerals undergo changes due to chemical reactions

7. Agents of Chemical Weathering
A. Water
Water can dissolve many minerals and rocks

8. B. Carbon Dioxide
Carbon dioxide reacts with water to form carbonic acid
Carbonic acid can dissolve rock

9. C. Oxygen
Oxygen will react with many substances
These reactions are called oxidation
Ex. Iron oxidation – rust formation

10. Caused by human activities (pollution)
D. Acid precipitation
Caused by human activities (pollution)
Sulfuric acid – burning coal
Nitric acids – car exhaust
cause other problems as well

11. What affects rates of weathering?
Climate
High chemical weathering in warm, moist climates
High mechanical in cool, dry climates

12. Rock type and composition
Igneous resist weathering
Sedimentary would be most vulnerable
Surface area
More rock above ground = more rock exposed to weathering
Topography
Level areas weather less than slopes