1. 5.1 Weathering Define Mechanical weathering
Explain chemical weathering
Identify the factors that affect the rate of weathering

2. Mechanical weathering :
physical forces break rock into smaller & smaller pieces without changing the rock’s mineral composition.

3. 3 physical process that cause mechanical weathering:
1. frost wedging
2. unloading/exfoliation
3. biological activity.

4. 1. Frost wedging: mechanical breakup of rock caused by expansion of freezing water in cracks & crevices

5. 2. Unloading/exfoliation
Reduced pressure on igneous rock causes it to expand & allows slabs of outer rock to break off in layers in a process called exfoliation.

6. 3. Biological activity
The activity of organisms, including plants, burrowing animals, and humans, can also cause mechanical weathering.

7. Chemical weathering: transformation of rock into one or more new compounds.
Examples: Acid Rain and Rust

8. Spheroidal Weathering: Corners breakdown first in chemical weathering

9. Rate of Weathering
 2 factors affecting the rate of weathering are rock characteristics and climate.
1. Rock characteristics
Mineral composition and solubility
Physical features such as joints and cracks
influence the ability of water to penetrate the rock
2. Climate
• Temperature and moisture are the most crucial factors
• Chemical weathering is most effective in areas with high temperatures and abundant moisture. (slow in deserts/arid & polar regions)