Forces in Earth’s Crust Part 1

1. Forces in Earth’s Crust Part 1

2. 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