Stress in the Earth

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