1. Earthquakes

2. vocabulary
Stress-
a force that acts on rock to change its shape or volume.
Adds energy to the rock.
Stores energy until rock changes shape or breaks.
Stress occurs slowly by shifting of Earth’s plates and cannot be observed

3. Types of stress
Tension
Compression
Shearing

4. tension Stretches rock so it becomes thinner in the middle
(pulling apart a warm piece of bubble gum)
Occurs when 2 plates are moving apart

5. Compression Squeezing of rock until it breaks (like a trash compactor)
Plates pushing against each other

6. Shearing Pushing of rock in opposite directions Can cause rock to:
Break
Slip apart
Change shape

7. Faults-what causes them?
Stress build up to the point the rock breaks
A fault is exactly that……a rock that breaks
Rock surfaces slip past one another
Can move up, down, or sideways

8. Faults
3 kinds
Normal
Reverse
Strike-slip

9. Normal faults Fault is at an angle “stretches” rock
Tension is force causing this
One rock lies above the fault (hanging wall), one below the fault (footwall)
Hanging wall slips downward
Occurs where plates divergent boundary

10. Reverse Fault Rock of crust is pushed together
Compression causes reverse faults to form
Same as normal fault but blocks move in opposite direction
Hanging wall slides up and over the footwall
Formed the Rocky Mountains
Convergent boundary
This Photo by Unknown Author is licensed under CC BY-SA

11. Strike-Slip Faults
Plates move past one another or “shears” one another
Move past one another sideways
Forms a transform boundary
San Andreas fault in CA is an example

12. US fault lines

13. Earth’s surface changes-Folding
There are “folds” in rock
Anticline=(arch)
A fold that bends upward into an arch (like a mountain)
Syncline=(sags)
A fold that bends downward to form a valley
Himalayas and Alps