1. Earthquakes & Volcanoes

2. BIG Ideas: 1. Most geologic activity occurs at the boundaries between plates. 2. Earthquakes are natural vibrations of the ground, some of which are caused by movement along fractures in Earth’s crust. 3. Volcanoes develop from magma moving upward from deep within Earth.

3. I. Forces Within Earth Faults form when the forces acting on rock exceed the rock’s strength. Faults form when the forces acting on rock exceed the rock’s strength. Fault: a break or crack in Earth’s crust along which movement has occurred. Fault: a break or crack in Earth’s crust along which movement has occurred.

4. Most active faults are located at or near plate boundaries. Most active faults are located at or near plate boundaries. Earthquakes result when movement occurs along a fault. Earthquakes result when movement occurs along a fault.

5. Locations of Earthquakes from 1980 to 1990

8. A. Stress and Strain

9. Stress: the total force acting on crustal rocks per unit area. Stress: the total force acting on crustal rocks per unit area. Strain: the deformation of materials in response to stress. Strain: the deformation of materials in response to stress. Rocks that are strained past a certain point will fracture and spring back to original shape. Rocks that are strained past a certain point will fracture and spring back to original shape.

10. a change in the shape or size of an object due to an applied force a change in the shape or size of an object due to an applied force misshapen misshapen contort, twist and press out of shape contort, twist and press out of shape Deformation:

11. Elastic Rebound Theory

13. Three Types of Stress 1. compression: decreases volume of material 2. tension: pulls material apart 3. shear: causes material to twist

16. B. Types of Faults

23. Facts: 1000 km (621 miles) long 15-20 km (9-12 miles) deep

24. Parts of an Earthquake Focus: spot within the Earth’s crust (lithosphere) where the origin of the Earthquake is located (where slippage along a fault occurs). Epicenter: spot on the surface of the Earth directly above the focus.

25. C. Earthquake Waves Seismic Waves: vibrations of the ground produced during an earthquake. Seismic Waves: vibrations of the ground produced during an earthquake. Every earthquake generates three (3) types of seismic waves… Every earthquake generates three (3) types of seismic waves…

26. Types of Seismic Waves: Types of Seismic Waves: 1. PRIMARY Waves:  P-WAVES  travel the fastest  FIRST to be recorded  travel through solid AND liquid  compressional waves that push and pull

27. Think Slinky!

28. 2. SECONDARY Waves:  S-WAVES  second to be recorded  only travel through solid material (NOT through liquid)  shear waves that move side to side (like a rope)

29. Which layer of Earth will S-Waves NOT travel through?

30. 3. SURFACE (LAND) Waves:  travel only along Earth’s surface  slowest wave (last to be recorded)  cause the surface of Earth to move sideways and up and down (like ocean waves)

31. Which waves are the most destructive?

32.  Surface Waves (also known as L-WAVES) cause the greatest damage.

33. II. Seismic Waves and Earth’s Interior A. Seismograph: instrument that detects and records seismic waves

35. Seismogram: record produced by seismograph

36. Analyzing a Seismogram:

38. B. Clues to Earth’s Interior

39. III. Measuring and Locating Earthquakes Scientists measure the strength and chart the location of earthquakes using seismic waves Scientists measure the strength and chart the location of earthquakes using seismic waves

40. A. Earthquake Measurement magnitude: measure of energy released by an earthquake

41. Richter Scale measures energy of the largest seismic waves (magnitude) produced during an earthquake measures energy of the largest seismic waves (magnitude) produced during an earthquake

45. Los Angeles

46. New York City

47. Which city would better withstand a catastrophic earthquake? WHY?

48. B. Locating Earthquakes scientists graph the arrival times of the P and S waves scientists graph the arrival times of the P and S waves the longer the S wave takes to arrive, the further away the quake the longer the S wave takes to arrive, the further away the quake THREE (3) seismic graph stations are required to locate the epicenter THREE (3) seismic graph stations are required to locate the epicenter

49. Finding the epicenter…

50. Damage Ground Rupture: Damage due to ground motion will depend on Ground Rupture: Damage due to ground motion will depend on Amplitude, Amplitude, Duration of vibrations, Duration of vibrations, Nature of material building is built on, Nature of material building is built on, Design of structure Design of structure Fire Fire Landslides Landslides Tsunamis Tsunamis tidal (harbor) wave - vertical displacement at seafloor due to earthquake causes giant "ripple" in ocean tidal (harbor) wave - vertical displacement at seafloor due to earthquake causes giant "ripple" in ocean

52. Nimitz Freeway - Oakland, 1989

53. Loma Prieta - Ground Rupture

54. Mexico City, 1985 Before After

55. Tsunamis: Giant ocean wave or a series of waves usually associated with an undersea earthquake or landslide

56. Formation of a tsunami

59. IV. Volcanoes Opening where magma erupts onto Earth’s surface. Opening where magma erupts onto Earth’s surface.

60. MAGMA: molten (liquid) rock UNDERGROUND MAGMA: molten (liquid) rock UNDERGROUND LAVA: molten rock that is ON THE SURFACE LAVA: molten rock that is ON THE SURFACE

61. VENT: opening through which lava flows VENT: opening through which lava flows VOLCANO: the build up of material around the vent VOLCANO: the build up of material around the vent

62. A. MAJOR VOLCANIC ZONES Most volcanic activity is associated with: subduction, subduction, rifting, or rifting, or seafloor spreading seafloor spreading

63. 1. Pacific Ring of Fire

65. 2. Mid-Ocean Ridges: rifting and seafloor spreading

66. 3. Hot Spots: Volcanism within plates

67. Hot Spot volcanic activity is exceptional because… Hot Spot volcanic activity is exceptional because… this activity is NOT related to plate boundaries! this activity is NOT related to plate boundaries!

69. B. TYPES OF VOLCANOES

70. 1. SHIELD: LAYERS OF LAVA WIDE AND FLAT Hawaiian Islands

71. 2. CINDER CONE: STEEP LAYERS OF PYROCLASTIC MATERIAL small, most common type of volcano

72. 3. COMPOSITE: STEEP WITH LAYERS OF ALTERNATING LAVA AND PYROCLASTIC MATERIAL Mount Saint Helens

73. SKYLIGHT – WINDOW INTO THE EARTH’S INTERIOR