1. Weathering
Chapter 5

2. Weathering
The breakdown and changing of Earth’s rocks through direct contact with the planet’s hydrosphere, biosphere, and atmosphere
There are two types of weathering: mechanical and chemical

3. Mechanical Weathering
or Physical Weathering occurs when rocks are cracked or broken into smaller pieces, without changing the rock’s composition
3 types of mechanical weathering are:
Frost wedging
Unloading
Biological activity

4. Frost Wedging
The mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices
Sections of rock that are wedged loose may tumble into large piles called talus, which typically form at the base of steep, rocky cliffs

6. Unloading
Pressure released on igneous rock causes it to expand and allows slabs of outer rock to break off in layers in a process called exfoliation

7. Unloading (exfoliation)

8. Biologic Activity
The activity of organisms, including plants, burrowing animals, and humans, can also cause mechanical weathering

9. Biologic Activity

10. Chemical Weathering
The transformation of rock into a different substance or new compounds
Types of chemical weathering are:
Water
Oxygen
Carbon Dioxide
Spheroidal

11. Water is the most important agent of chemical weathering
Chemical reaction of oxygen with water (oxidation)
Forms rust
Chemical reaction of carbon dioxide with water (carbonic acid)

12. Water absorbs with sulfur oxides and nitrogen oxides, that are produced from burning fossil fuels, causes acid rain
Spheroidal weathering changes the chemical composition and causes the corners and edges to
be more rounded

13. Rate of Weathering
Mechanical weathering affects the rate of chemical weathering
Physical characteristics (mineral composition) of rocks influence the rate of weathering
Climate, especially temperature and moisture, influence the rate of weathering