Earthquakes: Understanding the Forces of Nature

1. Standard 8-3.8 EARTHQUAKES

2. Assessing Prior Knowledge and Relativity • What have you heard about earthquakes lately? • Why should we study earthquakes?

3. Falcon Focus • 8-1.1 The standard metric unit of length used in a science lab is… • a. Celsius • b. Gram • c. Liter • d. Meter

4. Essential Question • What causes earthquakes and where do they happen?

5. Earthquakes!

6. INTRODUCTION • http://video.nationalgeographic.com/video/player/environment/environment-natural-disasters/earthquakes/earthquake-101.html

7. Deadliest Earthquakes The earthquake that caused the most destruction in history occurred in the Shansi province of China on January 23,1556. An estimated 830,000 people were killed. The second most destructive earthquake also occurred in China--in July, 1976--and killed 255,000 people.

8. What is an Earthquake? The definition of an earthquake is… vibrationsthat causethe breaking of rocks. These vibrations move in all directions through the earth. They begin at a point along a fault.

9. Earthquakes • Forces___ and __Stresses__ (8-3.7– tension, compression, and shearing) along faults can build up as blocks of rock are pushed (compression or shearing) or pulled apart (tension). If the __pressure___ or stress becomes too great, the rock breaks at a weak point along the fault and ___energy_____ is released

10. Earthquakes • ____Earthquakes_____ are vibrations produced when rocks break along a ___fault_____. The term earthquake describes the sudden slip on a fault and includes the ground shaking and radiating _____seismic waves___ that is caused by the slip.  ___Volcanic Activity____, or other geologic processes, may cause stress changes in the earth that can also result in an earthquake.

11. How do faults form? The earth’s crust is constantly experiencing pressure from forces within and around it. This pressure builds up over time, and eventually causes the crust to break. This becomes a fault. Let’s experience it…

12. Kinds of Faults... Faults are divided into three main groups: Normal fault- when two plates are moving apart and one side of the fracture moves below the other; (caused by tension forces!) Reverse fault- when two plates collide and one side of the fracture moves on top of another; (caused by compression forces!!) Strike-slip - when two plates slide past each other. (caused by shear forces!)

13. Three Types of Faults Strike-Slip Reverse Normal

14. What is an Earthquake? An earthquake begins along a fault (a crack in the earth’s surface) at a point called the focus. Directly above the focus is a point on the earth’s surface called the epicenter.

15. Where does an earthquake begin? Epicenter Focus

16. Why is the epicenter important? Seismologists have stations all over the world that continuously collect information about earthquakes. This kind of information can help scientists figure out where larger, more destructive earthquakes may strike by mapping out the location of smaller ‘quakes. They also get a greater understanding of the changes the earth’s crust makes as the earthquakes occur. How do they do this???

17. What is an Earthquake? When the fault ruptures with a sudden movement energy is released that has built up over the years. This energy is released in the form of vibrations called 'seismic waves'… earthquakes! It is actually when these seismic waves reach the surface of the earth that most of the destruction occurs, which we associate with earthquakes.

18. Parts of the Earthquake • The energy spreads outward in all directions as vibrations called ____seismic waves_____. • The _focus____ of the earthquake is the point in the crust, or mantle, where energy is released. • The _epicenter___ is the point on Earth’s surface directly above the focus; energy that reaches the surface is greatest at this point.

19. Focus – point inside the Earth where an earthquake beginsEpicenter – point on Earth’s surface above focus

20. Focus, Epicenter, and Fault

21. WHAT CAUSES EARTHQUAKES? Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip Caused by volcanic or magmatic activity, Caused by other sudden stress changes in the earth.

22. What causes earthquakes? Tectonic plates move past each other causing stress. Stress causes the rock to deform

23. http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

24. Cause of Earthquakes What Causes an Earthquake?  Aftershocks and Foreshocks • An aftershock is a small earthquake that follows the main earthquake. • A foreshock is a small earthquake that often precedes a major earthquake.

25. What Kind of Damage Do They Do? Earthquakes can also cause landslides, sudden eruptions as in the case of a hot lava flow from a volcano or giant waves called tsunamis. Sometimes new land mass are also formed. Such earthquakes are attributed with the creation of the greatest undersea mountain range and the longest land mountain range.

26. Landslides & Tsunamis • http://video.nationalgeographic.com/video/101-videos/landslides • http://video.nationalgeographic.com/video/101-videos/tsunami-101

27. San Francisco, 1989

28. San Francisco, 1989

29. San Francisco, 1989

30. San Francisco, 1989

31. San Francisco, 1989

32. San Francisco, 1989

33. San Francisco, 1989 …And that was just a 7.2 on the Richter scale!

34. Haiti 2010

37. Focus, Epicenter, and Fault

38. Earthquake Hazard Potential Map Parkfield, CA “Earthquake Capital of the World”

39. Where Do Earthquakes Occur and How Often? ~80% of all earthquakes occur in the circum-Pacific belt • most of these result from convergent margin activity • ~15% occur in the Mediterranean-Asiatic belt • remaining 5% occur in the interiors of plates and on spreading ridge centers • more than 150,000 quakes strong enough to be felt are recorded each year

40. Review!!! • http://www.iknowthat.com/mhscience/Earthquakes/Fixed.htm • http://www.iknowthat.com/mhscience/Earthquakes/earthquake_movie.html

41. Focus and Epicenter of Earthquake

42. HOMEWORK • .

43. FALCON FOCUS • THE POINT ON EARTH’S SURFACE WHERE THE GREATEST ENERGY FROM THE EARTHQUAKE IS RELEASED IS ___________. • THE EPICENTER • THE FOCUS • THE ASTHENOSPHERE • THE FAULT

44. FALCON FOCUS • THE POINT ON EARTH’S SURFACE WHERE THE GREATEST ENERGY FROM THE EARTHQUAKE IS RELEASED IS ___________. • THE EPICENTER • THE FOCUS • THE ASTHENOSPHERE • THE FAULT

45. ESSENTIAL QUESTION • HOW WOULD YOU COMPARE AND CONSTRAST THE THREEE TYPES OF SEISMIC WAVES?

46. INTRODUCTION • IN A POP AND LOCK DANCE MOVE, STUDENTS WILL DEMONSTRATE THE 3 TYPES OF SEISMIC WAVES

47. SEISMIC WAVES • _SEISMIC WAVES___ are waves generated by an earthquake that travel through the Earth. These waves can cause the ground to moveforward, backward, up, down, and even to ripple. Seismic Waves are generated at the __SAME___ time but move in different ways, and at different speeds.

48. Seismic Waves in the Earth http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

49. 3 TYPES OF SEISMIC WAVES • PRIMARY (P) WAVES • SECONDARY (S) WAVES • SURFACE WAVES CONSIDERED AS BODY WAVES

50. Seismic Waves