Geology Chapter 8 Earthquakes and Earth S Interior

Name: ______Geology Chapter 8 – Earthquakes and Earth’s Interior

Michael Wysession Washington University Big Ideas Earthquakes are the rupture of rock within Earth. The result of the rupture is a fault. Earthquakes are important because they are significant natural hazards, with the capability of destroying cities. They are also important because the waves they create are used to investigate the structure of Earth's interior. Space and Time Earthquakes can occur anywhere near Earth's surface, but mostly occur in narrow bands that turn out to be the boundaries between pieces of lithosphere. About 200,000 earthquakes are located each year. An earthquake usually lasts for only seconds, and there may be a wait of years to hundreds of years between large earthquakes on a given fault. Despite a tremendous amount of research, efforts to predict earthquakes have been unsuccessful, and it may turn out that earthquakes cannot be predicted. Forces and Motion Earthquakes occur because bending stresses within the rock exceeds the strength of the rock. The rupture causes seismic waves to propagate through Earth (P and S waves) and along its surface (surface waves). Matter and Energy Seismic waves, as with most waves, are a propagation of energy, not matter. Seismic waves are recorded on seismographs, and the amplitudes of the waves are used to determine the magnitude of the earthquake. The biggest earthquakes release more energy than the world's entire nuclear arsenal. Earth as a System Seismic waves are used to make images of Earth's layering, which is based on density, with the light rock of the crust overlying the heavier rock of the mantle, which overlies the dense iron/nickel core. Though high pressures keep most of Earth's interior solid, the high temperatures cause some of it to be molten.

Section 1 – What is an Earthquake?

1. Each year, more than ______earthquakes occur worldwide that are strong enough to be felt.

2. Under what conditions are earthquakes one of the most destructive natural forces on Earth?

3. What is an earthquake and what are they caused by?

4. What is the focus of an earthquake?

5. What is the epicenter of an earthquake?

6. What is a faults?

7. Describe the cause of earthquakes.

8. Describe the elastic rebound hypothesis.

9. Most earthquakes are produced by the ______release of ______energy stored

in rock that has been subjected to great forces. When the strength of the rock is ______, it

suddenly breaks, causing the ______of an earthquake.

10. What is the difference between aftershocks and foreshocks? Section 2 – Measuring Earthquakes

11. What is seismology and how far back does it date?

12. What is a seismograph?

13. What is a seismogram?

14. The ______from an earthquake spreads ______as ______in all

directions from the focus.

15. Describe what surface waves are and how they move.

16. What are body waves and describe the two types?

17. A seismogram shows all three types of seismic waves - ______waves, ______

waves, and ______waves.

18. Why do the waves arrive at different times on the seismogram?

19. Which waves are fastest and which are the slowest?

20. The difference in ______of P and S waves provides a way to ______the

______.

21. Describe the two steps in determining the distance from the recording station to the earthquake.

22. How can the precise location of an earthquake be found?

23. About ______of the major earthquakes occur in a few ______zones.

24. Name two zones of earthquake activity.

25. Historically, scientists have used two different types of measurements to describe the size of an earthquake.

Name them and describe the difference between them.

26. What is the richter scale and what is it based on?

27. What type of scale does the richter scale use and what does it mean?

28. What is the moment magnitude – what is it derived from?

29. What are the factors used to calculate the moment magnitude?

30. Moment magnitude is the most ______used measurement for earthquakes because it is the

only magnitude scale that ______the ______released by earthquakes. Section 3 – Destruction from Earthquakes

31. The damage to buildings and other structures from earthquake waves depends on several factors. List them.

32. What type of building material turned out to be the most serious safety threats during earthquakes and what

type seem to be the best suited to withstand damage?

33. What is liquefaction?

34. What are tsunamis?

35. How is a tsunamis triggered?

36. How can a tsunamis go unnoticed in the ocean?

37. Describe the tsunamis warning system.

38. List three other dangers from earthquakes other than tsunamis.

39. With many earthquakes, the greatest damage to structures is from ______and ground

______, or the ______of the ground triggered by the vibrations.

40. Earthquake vibrations can also cause large sections of the ground to ______, liquefy, or

______.

41. The greatest destruction during the 1906 San Francisco earthquake was caused by ______that

started when ______and ______lines were cut. Many of the city’s

______lines had also been broken by the quake, which meant that the ______

couldn’t be stopped.

42. What do scientists measure in an attempt to make short range predictions?

43. Have short-range prediction methods been successful?

44. What do long-range forecasts do?

45. What are long-range forecasts based on?

46. What is a seismic gap?

47. Can scientists make accurate long-term predictions? Explain.

Section 4 – Earth’s Layered Structure

48. Where does most of our knowledge about Earth’s interior come from? 49. The general increase in speed of seismic waves with depth is due to what factors?

50. As a result of these factors, what happens to the waves’ paths?

51. Earth’s interior consists of three major zones defined by its chemical composition – the

______, ______, and ______.

52. Describe the crust and the two types it is divided into.

53. What percent of the Earth’s volume is contained in the mantle?

54. Describe the mantle.

55. Describe the core.

56. Earth’s interior has a gradual increase in ______, ______and

______with depth.

57. Name the layers Earth can be divided into based on physical properties.

58. What is the lithosphere?

59. Describe the asthenosphere?

60. Describe the material found in the lower mantle.

61. What is the difference between the inner and outer core?

62. What is the Moho?

63. What is the shadow zone?

64. Early seismic data and ______technology indicate that the ______crust is

mostly made of lighter, ______rocks.

65. What is the crust of the ocean floor composed of?

66. Surprisingly, ______that collide with Earth provide evidence of Earth’s inner composition.

67. What is Earth’s core thought to be made of?

68. What is the surrounding mantle believed to be made of?