1. Weathering

2. Weathering is the breaking down of rocks and other materials on the Earth’s surface.

3. Two types of weathering

4. Mechanical / Physical Weathering
No change in the rock’s chemical composition.
Factors of mechanical weathering include:
- Temperature
- Pressure

5. Mechanical / Physical Weathering
1. Frost Wedging (freeze-thaw cycle): When liquid water goes into cracks and then freezes causing the cracks to get wider.

7. Mechanical / Physical Weathering
2. Organic activity (root-pry, burrowing animals, human activities

8. Mechanical / Physical Weathering
3.Gravity: rocks falling and colliding with other rocks

10. Mechanical / Physical Weathering
4. Abrasion: wearing away by solid particles, driven by wind

11. Mechanical / Physical Weathering
5a. Contraction: squeezing due to an increase in pressure
5b. Unloading: the expanding of high pressure rock when exposed to a lower pressure

13. Chemical Weathering
The altering of the composition of minerals within a rock that results in a reduction in size.
Types of chemical weathering include:
-1. Water: Dissolves minerals out of rocks making them weaker

14. Chemical Weathering
2. Oxygen combines with iron minerals and sulfur minerals changing the composition of the rock. Oxidation = rust
Oxidation turned these rocks in Nevada’s Valley of Fire red.

15. Chemical Weathering
3. Carbon dioxide: Combines with water to create carbonic acid. This dissolves limestone to create caverns and damages buildings and trees.

16. Type/Amount of Weathering
1. Climate:
Warm, wet climates – chemical weathering breaks down rocks rapidly
Cold climates – mechanical weathering breaks down rocks rapidly

17. Type/Amount of Weathering
2. Composition
Physical condition of the rock
Cracks, holes, crevices – increased weathering
Solid, unbroken – less weathering

18. Type/Amount of Weathering
In which shape will weathering occur faster?
Increased surface area = increased weathering

19. Type/Amount of Weathering
Topography: the position of the rock Slopes = increased weathering Flat= decreased weathering
Mechanical and chemical weathering work together
Air Pollution
Exposure time
Surface area exposed