1. Forces in the Earth

2. What are Earthquakes?
The shaking or trembling caused by the sudden release of energy
Usually associated with faulting (breaking of rocks)
Continuing adjustment of position results in aftershocks
Aftershock: small earthquakes following a large earthquake

3. Forces in the Earth’s Crust
Stress
Force applied to the rocks eventually exceeds the strength of the rock
Bending
Stretching
Tilting
Folding
Sliding

4. Types of Stress Tension: pulls on the crust Stretching it
Causing a thinning in the middle
Divergent boundaries: 2 plates move apart

5. Types of Stress Compression: pushes on the crust Folding it
Causing a thickening in the middle
Convergent boundaries: 2 plates move together

6. Types of Stress
Shearing: pushes on the crust in 2 different directions
Slide past
Transform boundaries: 2 plates move past each other

7. What is the Elastic Rebound Theory?
Explains how energy is stored in rocks
Rocks bend until the strength of the rock is exceeded
Rupture occurs and the rocks quickly rebound to an undeformed shape
Energy is released in waves that radiate outward from the fault

8. Parts of a fault Hanging Wall
The side of the fault that is thicker at the top and thinner at the bottom
It looks like a man could “hang” from the edge
Footwall
The side of the fault that is thinner at the top and thicker at the bottom
It looks like a man could walk up the edge

9. Types of Faults: Dip-slip (vertical motion)
Normal fault
Hanging wall moves down compared to footwall
Reverse Fault
Hanging wall moves up compared to footwall

10. Types of Faults: Strike-slip (horizontal motion)
Lateral right
Motion is to the right
Lateral left
Motion is to the left

11. Changing the Shape of the Crust
Anticlines: a upward fold in a rock that forms a hill
Synclines: a downward fold in rock that forms a valley
Two plates colliding (convergent) causing folds
Examples of Folded Mountains:
Appalachian in N. America & Himalayan in Asia

12. Changing the Shape of the Crust
Fault block Mountains
When 2 plates move away
Forming 2 Normal Faults parallel to each other
Examples:
Sierra Nevada & Beaverhead Range