1. Plate Tectonics Evolution of the Earth
Free powerpoints at

2. Interior
Inner Core
Outer Core
Lower Mantle
Upper Mantle
Crust

3. Interior
1220 km
2259 km
2851 km

4. What’s in the Earth’s Layers:
Crust: is made up of Silicates which are cooler-rigid rock
Mantle:
-made up softer weaker rock that can flow slowly.
Core:
-Outer core: liquid metal and very hot!
-Inner core: solid metal and very high pressure!

5. Volcanoes
Volcanoes are the result of hot spots within the crust or mantle of the earth.
The hot, liquid rock will break through weak spots in the surface and form volcanoes or flood basalts. These are called Effusive/Quiet Volcanoes
Many volcanoes do not release lava, instead they spit ash. These are called Explosive Volcanoes
The type of volcano is determined by the materials in it. Go to:

6. Volcanoes Fill in the following table to determine how quiet and
explosive volcanoes differ:
Dissolved Gases
Silica Content
Type of Volcano
Looks like….
Effusive or Explosive
High
Low

7. Volcanoes
Quiet
lava
flows

8. Volcanoes
Mt. St. Helen before the explosive eruption

9. Volcanoes

10. Volcanoes
Time lapse of the eruption

11. Volcanoes
Mt. St. Helen after the eruption

12. Volcanoes
Mt. St. Helens begins the rebuilding process

13. Flood basalts: When volcanic eruptions coats a thick layer of cooled magma over the surface of the earth.
This is IGNEOUS ROCK.
Igneous Rock is a type of rock that is made in the mantle

14. Volcanoes

15. Where does the energy to make a Volcano come from?

16. The earth’s core is extremely HOT
The earth’s core is extremely HOT! Magma in the mantle is always moving in the earth because of the Earth’s Core, which causes Convection: Hot materials rise and cool materials sink.

17. This causes the plates to move with the magma of the mantle to: 1) move apart
(Divergent
Boundaries) or
2) move together
(Convergent
Boundaries) and even
3) past one another (Transform Boundaries.)

18. Because Plates move they cause the magma to be released through cracks in the earth’s crust creating volcanoes.

19. Volcano locations: Why at these locations?

20. The answer is Tectonic Plates

21. The reason volcanoes occur at specific locations:
1. Plate Tectonics Move at a Convergent Zone: (together)

22. Convergent Zones: Volcanoes

23. The reason volcanoes occur at specific locations:
2. At Divergent Zones: (a part)

24. Tectonic Plates

25. Tectonic Plates Another source of evidence is based on seafloor ages
which get younger
as we approach
sea floor ridges

26. Pangea What is Pangaea? Pangaea was a super continent at one time.
Scientists use the similarity of rock types and fossil types that date to the same age to support their theory that the continents were connected to form a super continent.
The map below give just one example of areas on different continents that show the same fossils and rock types.

27. Pangea

28. Pangea

29. Pangea
The break up
of Pangea

30. The reason volcanoes occur at specific locations:
3. Magma moves to the surface of the earth near a weak spot and can activate a magma chamber
4. This can
happen over
a HOTSPOT. The
Hawaiian Islands
have formed
because a plate
moved over a
hotspot.

31. Mid-Plate Hotspots

32. What types of energy are taking place to have a volcano?
Mechanical Energy:
Magma moves from the interior earth up to a weak portion in the earth’s crust.
Magma also moves out from the volcano.
Ash and rock can also move out from a volcano like in a pyroclastic flow.
Heat Energy
The earth’s core has large amounts of heat that escape at the earth’s surface through a volcano
Draw how a volcano works by using words to describe the process such as: magma, crust, mantle, mechanical energy, heat energy

33. Earthquakes Earthquakes are a result of motion within the earth.
This only occurs where the earth is solid and therefore can only occur within about 100 miles of the surface
Earthquakes provide the best evidence regarding the interior structure of the Earth.

34. Earthquakes

35. Earthquakes

36. Earthquakes

37. Earthquakes A. Where the earthquake occurs
B. Directly above the earthquake
C. Where the land masses move past one another
D. Where the land will either drop down, jet up or change along the fault.
E. Waves that move outward causing the shaking movement of the earth.

38. Waves fall under two categories:
P-Waves: occurs when fault moves past each other horizontally, cause a compressed wave.
S-Waves: occurs when faults move vertically, causes a wavy wave.
* Both display Mechanical Energy!

39. Both Body Waves and Surface Waves will differ in both S & P Waves:

40. Seismograph: Measures movement in the earth.

41. Finding an Earthquake’s Epicenter

42. Earthquakes occur often!

43. Earthquakes occur at plate boundaries more frequently
Location of worldwide earthquakes

44. Earthquakes Earthquakes by depth.
Notice that the deep earthquakes occur only at subduction zones.

45. The bigger the magnitude of the earthquake, the more mechanical energy there is.
Go to:
Fill out the following table:
Bed rock
Low
Description of Damage
High
Fault
Land fill

46. Different Forms of Energy In the Earth
Mechanical Energy: Energy due to motion
Heat energy: energy due to heat
Potential energy: energy that is built up but not yet released
Kinetic Energy: energy that is occurring (in motion)

47. Tectonic Plates

48. Tectonic Plates Today plate boundaries are determined by examining
the location of volcanoes and earthquakes.
Volcanoes result from the friction (heat) of the plates
motion.
Earthquakes occur where plate rub against one another

49. Plate Boundaries Convergent – plates move toward one another
Divergent – plates move away from each other
Transform – plate moves sideways from each other

50. Faults occur at these Plate boundaries, where land masses move
Faults occur at these Plate boundaries, where land masses move. These faults when moved release energy in the form of an earthquake. There are 3 different faults:
1. Normal Fault: as stress is pulled away on the plates, one land mass slips down. (Divergent Plate boundary)

51. 2. Reverse Fault: as two plates come together one land mass jets up above the other making a hanging wall. (Convergent Plate Boundary)
3. Transverse Fault: occurs as two plates slide past one another. (Transform plate boundary)

52. Tectonic Plates
Volcanoes

53. Tectonic Plates

54. Tectonic Plates

55. Tectonic Plates

56. Tectonic Plates Another source of evidence is based on seafloor ages
which get younger
as we approach
sea floor ridges

57. Tectonic Plates Our final piece of evidence is the magnetic record
of the ocean floor.
This shows the
pattern of reversal
and we find a near
perfect mirror image
on opposing sides
of the ridge

58. Tectonic Plates

59. Tectonic Plates

60. Tectonic Plates

61. Composition vs. Motion We can look at the interior of the Earth based
on the composition of the rocks or based on the movement

62. Based on Composition
Crust – solid, relatively low density silicate rock
Mantle – Semi fluid, denser, mafic (iron and magnesium bearing) rocks
Core – Liquid then solid iron and nickel with traces of heavier elements

63. Plate Types Oceanic plates: basalt
Dark (black) and dense rock type composed of silicates, iron and magnesium
Continental plates – granite and andesite
Light colored (pink, white and gray) and low density rock type composed almost entirely of silicates.

64. Plate Boundaries

65. Plate Boundaries

66. Convergent Plates

67. Convergent Plates

68. Convergent Plates

69. Convergent Plates
The only subduction zone
in the Atlantic

70. Convergent Plates Black arrows show subduction zones and
the direction of plate movement

71. Convergent Plates Looking at the depth of earthquakes shows
that angle that the
plate is being subducted

72. Divergent Plates

73. Divergent Plates

74. Divergent Plates

75. Divergent Plates

76. Transform Plates

77. Mid-Plate Hotspots

78. Mid-Plate Hotspots

79. Transform Plates
San Andreas
Fault

80. Mid-Plate Hotspots

81. Mid-Plate Hotspots

82. Why do the Plates Move?

83. Why do the Plates Move?
No single idea explains everything but we can identify several forces that contribute to the movement of the plates.
Slab pull
The sinking of the cooled dense oceanic plates pulls on the rest of the plate
Ridge rises
The material deposited on the top of the ridge slides downs from the rise pushing on the plate
Convection
Movement within the mantle could be part of the driving force behind the motion of the plates.

84. The Big Picture

85. Pangea What is Pangaea? Pangaea was a super continent at one time.
Scientists use the similarity of rock types and fossil types that date to the same age to support their theory that the continents were connected to form a super continent.
The map below give just one example of areas on different continents that show the same fossils and rock types.

86. Pangea

87. Pangea

88. Pangea
The break up
of Pangea

89. Where are we going? We appear to be headed for another
super continent as North America,
South America, Asia and Australia converge in the
ever shrinking Pacific Ocean