1. Weathering & Erosion
Weathering is the process by which natural forces break down rocks.
There are 2 types of weathering:
Mechanical weathering
Chemical weathering

2. Mechanical Weathering
Mechanical weathering is the breaking up of rocks by physical forces.
There are 4 main types:
Ice wedging
Exfoliation
Plant root growth
Abrasion

3. Ice Wedging
When water freezes, it expands. When water freezes in the cracks and pores of rocks, the force of its expansion is strong enough to split the rocks apart.

4. Exfoliation
The process in which layers or sheets of rock gradually break off due to the expansion of the rock caused by a decrease in pressure.

5. Plant Root Growth
Trees, bushes, and other plants may take root in cracks of rocks. As the roots of these plants grow, they wedge open the cracks.

6. Abrasion
The process of wearing down by friction, the rubbing of one object or surface against another.

7. Chemical Weathering
The breakdown of rocks by chemical reactions that change the rocks’ makeup, or composition.
There are 2 main types:
Dissolving
Rusting

8. Dissolving
Water is the main cause of chemical weathering.
Many more minerals dissolve in water that is slightly acidic – like lemonade.

9. Rusting
The oxygen in air is also involved in chemical weathering.
Many common minerals contain iron. When these minerals dissolve in water, oxygen in the air and the water combines to produce rust.

10. Rates of Weathering
Most weathering occurs over long periods of time – hundreds, thousands, or even millions of years.
There are 3 Influential factors:
Surface area
Rock composition
Climate

11. Surface Area
The more of a rock’s surface that is exposed to air and water, the faster the rock will break down.

12. Rock Composition
Different kinds of rock break down at different rates.

13. Climate
Chemical weathering occurs faster in hot, wet regions than it does in cold, dry regions.
Mechanical weathering caused by freezing and thawing occurs more in cold regions than in hot regions.