Earthquakes

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 • Theforces that elevate mountains can also raise plateaus, a large area of flat land elevated high above sea level

22. How Earthquakes Form