1. NOTES
FAULTS and FOLDS

2. What is a fault?
A fault is a fracture or series of fractures in Earth’s crust that occurs when stress is applied too quickly or stress is too great.
Many faults occur along plate boundaries.
Faults can also occur anywhere in the crust where rocks are bent (folded) until they break.
Faults occur as a result of various types of stress.

3. Stress vs. Strain Stress is the force that acts on a material.
Strain is the deformation (change of shape) of a material in response to stress.

4. Most Faults Have a Hanging Wall and a Foot Wall
The Hanging Wall is the one with the slope on which you could hang. The Foot Wall is the one with the slope on which you could walk.
The type of fault is determined by the motion of the Hanging Wall.

5. Most Faults Have a Hanging Wall and a Foot Wall

6. Is this the Hanging Wall or Foot Wall?

7. Is this the Hanging Wall or Foot Wall?
The FOOT WALL is the one with the slope you would put your feet on.

8. Is this the Hanging Wall or Foot Wall?
The HANGING WALL is the one with the slope you would hang from.

9. Types of Faults
There are several different kinds of faults. These faults are named according to the type of stress that acts on the rock and by the nature of the movement of the rock blocks either side of the fault plane.

10. Types of Faults
Stresses can be compressional (push), tensional (pull) or shear (slide past each other).
The type of stress determines how the Hanging Wall moves and therefore the type of fault.

11. 3 Types of Faults Caused by 3 Different Types of Stress
Normal Fault
(Caused by Tension)
Reverse Fault
(Caused by Compression)
Transform Fault
(Caused by Shear Stress)

12. Normal Fault
Occurs when tensional stress pulls the fault apart and the Hanging Wall drops.
The fault is an example of tensional strain.

13. Reverse Fault
Occurs when compressional stress pushes the two parts of the fault together and the Hanging Wall moves up.
The fault is an example of compressional strain.

14. Transform Fault AKA “strike-slip” fault
Shear stress causes the parts of the fault to slide past one another.
This fault is an example of shear strain.

15. Examples of Faults

16. Folds
Occur when stress is applied to both ends of a section of rock or rock layers. Some rocks would break, but a fold occurs when rocks bend.

17. Folds
An anticline looks like a “rainbow”; a syncline looks like a “smile”.

18. Examples of Folds