1. Stress in the Earth

2. Stress Stress is a force that changes a rocks shape or volume
Because stress is a force it adds energy to the rock

3. Stress There are three types of stress occurring in the Earth’s crust:
Shearing
Tension
Compression

4. Shearing
When rock is pushed in opposite directions and the layers slide by each other.

5. Tension
When rock layers pull apart and stretch.

6. Compression
Caused when parts of the crust squeeze together.

7. Any change in the volume or shape of the layers is called deformation
Slow deformation of the crust causes uplift and folding (mountain ranges).
Rapid deformation of the crust results from Earthquakes

8. Faults If stress builds in a rock it can break.
A fault is a break in the Earth’s crust where the rock moves.

9. Faults There are three basic types of faults: Strike-Slip (lateral)
Normal
Reverse

10. Strike-Slip Fault Caused by shearing forces
Rocks on either side slide past each other.

11. Normal Fault Caused by tension
The foot wall moves up relative to the hanging wall

12. Normal faults usually form at an angle
The block that is above the crack is called the Hanging Wall
The block that is below the crack is called the Foot Wall

13. Reverse Fault Caused by compression forces
The foot wall moves down relative to the hanging wall

14. Reverse Fault A special type of reverse fault is a thrust fault
In a thrust fault the hanging wall is pushed out over the foot wall