1. Earthquakes

2. An Earthquake is…
the shaking and trembling that results from the movement of rock beneath Earth's surface
The movement of Earth's plates produces strong forces that squeeze or pull the rock in the crust

3. Stress Force that acts on rock to change its shape & volume
Adds energy to rock until it breaks or changes shape
Causes deformation
Rocks can break…creating a fault
Causes earthquakes

4. Stress
There are three different types of stress that occur on the crust, shearing, tension, and compression
These forces cause some rocks to become fragile and they snap
Some other rocks tend to bend slowly like road tar softened by the suns heat

5. Shearing
Pushes rocks in opposite directions

6. Tension
Pulls, stretching rock so it becomes thinner in the middle
2 plates move apart

7. Compression
Squeezes rocks until it folds or breaks

8. Faults
A fault is a break in the crust where slabs of crust slip past each other. The rocks on both sides of a fault can move up or down or sideways
When enough stress builds on a rock, the rock shatters, creating faults
Faults usually occur along plate boundaries, where the forces of plate motion compress, pull, or shear the crust too much so the crust smashes

9. Strike-Slip Faults Shearing creates this fault
Rocks on both sides of the fault slide past each other sideways
Forms transform boundary

10. Strike-Slip Faults

11. Normal Faults
Tension forces in Earth's crust causes these types of faults
Normal faults are at an angle, so one piece of rock is above the fault, while the other is below the fault
The above rock is called the hanging wall, and the one below is called the footwall
When movement affects along a normal fault, the hanging wall slips downward
Occurs at divergent boundaries

12. Normal Faults

13. Reverse Faults Compression forces produce this fault
Same structure as a normal fault, but blocks move in opposite directions
Hanging wall slides up over footwall
Occurs at convergent boundaries

14. Reverse Faults

15. Friction Force that opposes the motion of one surface across another
Low friction: rocks slide without sticking
Medium friction: sides of the fault jam together & then jerk-free to produce small earthquakes
High friction: rocks lock & don’t move, stress increases until it overcomes friction, produces major earthquakes

16. How Do Mountains Form?
1.) By Faulting- when two normal faults form parallel to each other, a block of rock in between them moves upward as hanging wall slips down (fault-block mountain)

17. How Do Mountains Form?
2.) Folding: when 2 plates collide, compression forces cause the rock to fold or bend

18. Anticlines and Synclines
An anticline is a fold in a rock that arcs upward
A syncline is a fold in a rock that arcs downward
These folds in rocks are found on many parts of the earths surface where compression forces have folded the crust

19. Anticline

20. Syncline

21. Plateaus
The forces that elevate mountains can also raise plateaus, a large area of flat land elevated high above sea level

22. How Earthquakes Form