1. Section 3: Earth’s Interior
Chapter 12
Section 3: Earth’s Interior

2. Basic Layers of the Earth
Crust
Mantle
Outer Core (liquid)
Inner Core (solid)

3. Earth’s Crust
Continental Crust: rock layer under continents made of mostly granite
Oceanic Crust: rock layer under oceans made mostly of basalt
Basalt is much more dense than the granite. Less dense continents ride on the denser oceanic plates.

5. The Lithosphere
The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the lithosphere.
The crust of the Earth is broken into many pieces called plates. The lithosphere makes up Earth’s plates.

6. The Asthenosphere
The asthenosphere is the part of the middle mantle that flows gently like melted plastic.
The lithosphere, or Earth’s plates, ride on top of the asthenosphere.

7. Convection Currents
The middle mantle or asthenosphere moves Earth’s plates due to convection currents.
Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again.

8. Outer Core Under the mantle lies the outer core of Earth.
The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the metals of nickel and iron.

9. Inner Core
The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together to create a solid.

10. Earth’s Magnetic Field
Don’t forget: Earth’s magnetic field is caused by the spinning of the molten iron core!

11. Chapter 12
Section 1

12. Continental Drift
In 1915, Alfred Wegner hypothesizes the continents were once part of a super-continent called Pangea. Over time, the continents drifted apart.

13. Proving Wegner Correct
Over time, there were three pieces of evidence found that supported Wegner’s idea:
Matching coastlines: South America looks like it fits with the coast of Africa
Matching fossils: The same fossils from ferns and dinosaurs are found on multiple continents.
Matching rocks and mountain ranges: When fitting continents into Pangea, it shows mountains were originally one large mountain range.

14. Matching Coastlines

15. Matching Fossils

16. Matching Mountain Ranges

17. Sea Floor Spreading
Dr. Harry Hess used sonar to map the seafloor and revived Wegner’s ideas.
Discovered a mid-ocean ridge, or MOR, wrapped around Earth.

18. MOR
Magma from the mantle is forced upward due to its low density (convection currents).
This causes the ocean crust to crack (fault) and move apart. This is sea floor spreading! New oceanic crust is created.

19. Mid-Ocean Ridge Around the Globe

20. Mountains and Rift Valleys
The MOR creates a twin mountain range along the fault.
A rift valley is also produced with the mountain range.

21. Which crust is older?

22. Theory of Plate Tectonics
Plate tectonics- The theory that pieces of the Earth’s lithosphere are in constant motion, driven by convection currents in the mantle
No plate can move without affecting the other plates surrounding it; they must bump, grind, or pass each other in order to move.
Remember, the plates of the lithosphere float on top of the asthenosphere (the top layer of the mantle)

23. Divergent Plate Boundary
Divergent Boundary: the spreading apart of two plates. Examples: MOR and in East Africa.
Features: Rift Valley, mountain range for MOR, earthquakes

24. Transform Plate Boundary
Transform Boundary: two plates that move past each other horizontally
Examples: western US called the San Andreas Fault
Features: Earthquakes

25. Convergent Plate Boundaries
Convergent Boundary: two plates that collide. There are three ways these form:
Oceanic crust collides with continental crust
Oceanic crust collides with oceanic crust
Continental crust collides with continental crust
With convergent boundaries, subduction can occur. This is when the plate with more density sinks, melts from contact with magma, and can produce volcanoes.

26. Convergent: Oceanic and Continental
Two features created: volcanic arcs and a deep sea trench, earthquakes
Examples: Cascade and Andes Mountain Ranges

27. Convergent: Oceanic and Oceanic
Two features created: deep sea trench and a volcanic island arc
Examples: Japan, Alaskan Aleutian Islands, Ring of Fire

28. Convergent: Continental and Continental
Features: Mountain range and plateaus
Examples: Himalayas in Asia, Appalacian Mountains East US

29. Chapter 12 Section 2
Earthquakes

30. What is an earthquake?
Earthquake- The shaking that results from the movement of rock beneath the Earth’s surface

31. Types of stress
Shearing- stress that pushes a rock in two separate directions
Tension- stretches rock, causing it to become thinner in the middle
Compression- pushes the two plates together until they either fold or break

32. Types of stress

33. Kinds of faults Strike Slip Faults- created by shearing
Normal Faults- Footwall rises above hanging wall
Reverse Faults- Hanging wall rises above footwall

34. Normal Fault
Reverse Fault
Strike-Slip Fault

35. Strike-slip faults

36. When there is a movement along a fault, the place where the movement starts is called the focus. The spot above where the focus is called the epicenter.
Focus- The point beneath the Earth’s surface where rock breaks under stress and causes an earthquake
Epicenter- The point on the Earth’s surface directly above an earthquake’s focus

40. 3 Types of Earthquake Waves
Primary waves- push pull type waves
Secondary waves- side to side waves
Surface waves- up and down waves

41. 1. Primary waves (P-waves) – arrive first.   (fastest of the three)

42. 2. Secondary Waves (S-waves) – arrive second after the P wave
2. Secondary Waves (S-waves) – arrive second after the P wave. (second fastest)

43.  3. Surface waves (L-waves) –  slowest moving seismic waves. Arrives last. Most destructive!

46. Seismographs
We use a seismograph to measure/ detect seismic waves

47. Modern day seismographs

50. Triangulation to find the epicenter

51. Ways we measure earthquakes
Mercalli scale- relies on eyewitness accounts
Richter scale- measures ground movement
Moment Magnitude scale- uses both eyewitness accounts and ground movement

52. How earthquakes cause damage
Loose soil
Can cause landslides or mudslides

53. Liquefaction
Soil and the water that is in it become separated
Because the soil is heavier, it sinks pushing the water to the surface

55. Mudslide and landslide

56. Earthquake damage

58. Crack in the surface

59. Faults in
California

60. Aftershocks
Movement along a fault that occurs after a larger earthquake along that same fault

61. Tsunamis
Tidal waves that can reach upwards to 115 feet
Caused by Earthquakes that happen deep under water

63. Earthquake Hazards

64. Volcanoes

65. What is a volcano?
Volcano- A weak spot in the crust where magma has come to the surface
Magma- The molten mixture of rock-forming substances, gases, and water from the mantle
Lava- Magma that reaches the surface

66. How is magma formed?
Decompression Melting and Wet Melting

67. Lava flow at Mount Etna, Sicily, Italy

68. So where might you find a volcano?
Ring of fire- volcanoes that rim the Pacific Ocean
Most volcanoes occur at convergent boundaries (subduction zones) and diverging plate boundaries (MOR)
Many volcanoes are found underwater

70. Ring of Fire from space

72. Crater on a shield volcano

73. Side vent

74. Hot spot- An area of magma from deep within the mantle melts through the crust above it
The only major hot spot is located in the middle of the Pacific Ocean on the main island of Hawaii
Another is in Yellowstone National Park

76. So why does some lava flow while others don’t?
The more silica present in the lava, the thicker it becomes.
Lava low in silica will flow like water (low viscosity); called basaltic lava. Lots of IRON AND MAGNESIUM!!!
Lava high in silica will tend to form into a moving wall of crumbly rocks (high viscosity)

77. Pyroclastic Eruptions
Pyroclasts: Volcanic fragments hurled in the air during an eruption
Watch here

78. The stages of a volcano’s life
Active volcano- volcano that is erupting or has shown signs of erupting in the near future
Dormant volcano- volcano that does not show signs of erupting in the near future
Extinct volcano- volcano that is unlikely to erupt again

79. Active Volcanoes

80. Other features of Volcanoes
Hot springs- where hot steam and water rises to the surface after being heated by magma
Where you find hot springs, you will also find geysers

81. Hot springs in New Zealand

82. Geyser in Iceland and Old Faithful (Yellowstone National Park)

83. Geothermal Energy
Pump water underground to heat it
This makes steam
We can use this as a renewable energy source!

84. There are three types of Volcanoes
Shield
Cinder Cone
Composite

85. Shield Volcano
Flat
Short
Broad (wide)
Low viscosity lava

86. Kilauea in Hawaii is a shield volcano

87. Cinder Cone Volcano
Larger crater
Homogenous (one kind of rock)
Tend to be tall, but not wide
Eruptions are like fountains; violent!

88. Izalco in El Salvador is a cinder cone

89. Composite Volcano
Has layers of alternating rocks
Layers of stone
High viscosity lavas
VERY TALL!!!
Eruption style varies

90. Mount Egmont in New Zealand is a composite volcano