Forces in the Earth & Earthquake Vocabulary 

Be sure you know the definitions to the following words. You will have a vocabulary quiz before your content exam on earthquakes. 

1. Stress- A force that acts on rock to change its shape or volume 

2. Tension-2 plates pulling apart. Becomes thinner in the middle

3. Compression-squeezing of rocks, I plate pushing against another. Stress force squeezes the rock until it folds or breaks

4. Shearing- Pushes 2 rocks in opposite directions. Slip past each other

5. Normal Fault- Caused by Tension, Pulling apart of 2 rocks,  Divergent Plates

6. Reverse Fault-Compression causes rock to push together resulting in blocks to move in the reverse direction of a normal fault

7. Strike and Slip fault- Sharing  forces of 2 rocks slipping past eachother sideways (lateral movement), with little up or down motion

8. Thrust Fault-Caused by major compressional forces pushing the hanging wall completely on top of the footwall

9. Hanging Wall-  sits over the footwall. When movement occurs along the fault, it slips downward

10. Footwall- moves down, The rock below the fault zone

11. Rift Valley- 2 normal faults occur in the same area

12. Fault-block mountains- When 2 reverse faults cut through a block of rock, fault movement may push up a  

13. Plateau- Large flat of flat land elevated high above sea level -

14. Mountains- Format comparison sites (convergent boundaries) when continental plates collide and fold.

15. Anticline- A fold in rock that bends upward into an arch

16. Syncline- A fold in the rock that bends downward to form a V-shape (occurs at thrust or reverse faults-folded mountains)

17. Earthquake-  is the vibration  of earth produced by the rapid release of energy; sudden movement of earth's crust 

18. Epicenter-  Location on earth's surface directly above focus 

19. Focus- (aka hypocenter) the point underground where the release of stress is located

20. Aftershock- an earthquake that occurs after a larger earthquake in the same area.

21. Liquefactication-  earthquake's violent shaking suddenly turns loose, soft soil into a liquid-like slurry.

22. Seismic waves- carry energy from an earthquake away from the focus 

23. P wave- compress and expand the ground

24. S wave- can vibrate the ground from side to side

25. L wave-  can make the ground roll like ocean waves

26. Deformation- any process that affects the shape, size, or volume of an area of the Earth's crust

27. Richter scale- Rating an earthquakes magnitude based upon the size of the earthquake seismic waves (1-10)

28. Modified Mercalli scale- Rates earthquakes according to the level of damage at a given scale

29. Moment Magnitude scale- Rate the total energy an earthquake releases seismographs and other sources 

30. Seismograph- instrument that records and measures an earthquakes seismic waves

31. Ring of fire- Many of the world’s earthquakes are of geologic activity called the 

32. Tsunami- Large bodies of water displaced by an underwater earthquake releasing energy into the water