1. Rock is physically broken into smaller pieces
Mechanical/Physical
Rock is physically broken into smaller pieces

2. Chemical
Process in which rocks are decomposed, dissolved, or loosened by chemical processes

3. Chemical
1. Water-over many, many years, certain rocks can dissolve in water

4. Chemical
2.Oxygen- iron combines with oxygen in the presence of water in a process called oxidation. The product of oxidation is rust.

5. Chemical
3. Carbon dioxide- it dissolves in rainwater and then sinks through air pockets in the soil. The result is a weak acid called carbonic acid that can dissolve certain rock types.

6. Chemical
4. Living Organisms- plantlike organisms, such as lichens, produce weak acids that chemically weather rock.

7. Chemical
5. Acid rain- when pollutants such as sulfur, carbon, and nitrogen gas mix with water vapor, acid rain is formed in clouds.

8. Mechanical/Physical
1. Release of pressure- As erosion removes material off the surface of a rock; pressure on the rock is reduced. This release in pressure causes the outside of the rock to crack.

9. Mechanical/Physical
2. Ice wedging- the freezing and thawing of water inside the cracks of rocks expands and makes the cracks bigger.

10. Mechanical/Physical
3. Animal Actions- Animals that burrow in the ground loosen and break apart rocks in the soil.

11. Mechanical/Physical
4. Plant Growth- As the roots of trees and other plants grow, they enter the cracks in the rocks and force the cracks farther apart.

12. Mechanical/Physical
5. Abrasion- sand and other rock particles that are carried by wind, water, or ice can wear away exposed rock surfaces.