1. Forces in Earth’s Crust Part 1

2. Stress: a force that acts on rock to change its shape or volume
Stress: a force that acts on rock to change its shape or volume *The movement of Earth’s plates creates an enormous force that squeezes or pulls the rock in the crust

3. Three different types of stress can occur in the crust:
1) Tension
2) Compression
3) Shearing

4. Types of Stress

5. Tension
*a stress force that pulls on the rock, stretching it so that it becomes thinner in the middle *occurs when two plates are moving apart

6. Compression Squeezes rock until it folds or breaks
One plate pushing against another can compress rock like a giant trash compactor

7. Shearing Stress that pushes a mass of rock in two opposite directions
Can cause rock to break and slip apart or to change shape

8. What is a Fault?
When a rock breaks as a result of stress build-up in the rock
A fault is a break in the rock of the crust where rock surfaces slip/grind past each other
Rocks on either side of a fault can move up, down, or sideways.

9. 3 Types of Faults
Normal Faults
Reverse Faults
Strike-slip Faults

10. Normal Fault

11. Normal Fault

12. Normal Fault Tension in the Earth’s crust pulls rock apart
The fault is at an angle, so one block of rock lies above the fault line while the other block lies below the fault line
Hanging Wall: The block of rock that lies above the fault line
Footwall: The block of rock that lies below the fault line

13. Normal Fault
When movement occurs along a normal fault, the hanging wall slips downward
Normal faults are found along the Rio Grande rift valley in New Mexico

14. Normal Fault

15. Normal Fault