2. Alfred Wegener came up with the idea of continental drift in He stated that there was once one large landmass called Pangaea that broke apart about 200 million years ago.
Continental drift is the idea that the continents have drifted slowly over time to their current locations.

6. Continental Drift Theory:
Evidence to support
Continental Drift Theory:
1)  puzzle-like fit of the continents
2)  fossil evidence
3)  climate clues
4)  rock clues
5) earthquake/volcano data
6) sea-floor spreading
* sonar map of sea floor
* dating of sea-floor rock samples
* paleomagnetism

7. Fossil Evidence
Similar plant and animal fossils are found around different continent shores, suggesting that they were once joined.

8. Climate Clues
Fossils have been found in Antarctica of plants that can only live in tropical climates so at one point it must have had a tropical climate. The Climate changed because the island moved!

9. Rock Evidence (Landforms)
The discovery that similar rock formations and mineral deposits match up along coastlines of different continents.
Certain rocks such as coal only formed in hot climates but were found in cold regions.
There is similar mountain building along coastline of different continents.

10. Sea-floor spreading
Scientists found a system of ridges and valleys throughout the ocean floors.
In the 1960s scientist Harry Hess suggested the idea known as sea-floor spreading.
Mid-Atlantic Ridge

11. Sea-floor spreading
1) Hot, less dense material in the mantle is forced upward to the surface at the mid-ocean ridge.
2) It then turns sideways, carrying the seafloor away in both directions.

12. Sea-floor spreading
3) Magma under the sea-floor flows up into the cracks and hardens to create a new seafloor.
4) The old seafloor gets hard and sinks to create a valley.

15. Magnetic polarity at mid-ocean ridge

16. The crust of the Earth is broken into large segments or pieces called tectonic plates.

17. What causes tectonic plates to move?
A convection current is occurring in the mantle.
* Hot, less dense liquid magma rises to the top of the mantle.
* As it cools it gets heavy and sinks back down.

18. Convection currents

19. Types of
Tectonic Plate
Boundaries

22. Divergent boundaries
* two plates are moving apart from each other
* Example- sea-floor spreading at Mid-Atlantic ridge

23. 2) Convergent boundaries
* two plates are moving toward each other; two plates collide
* Subduction zone- two plates collide and one goes under the other and melts.
* mountains are created when two plates collide

24. Subduction Zone

25. 3) Transform boundaries
* two plates slide past one another in opposite directions
* earthquakes can occur when this happens

26. VOLCANISM

27. VOLCANISM:
All processes associated with the discharge of magma, hot fluids, and gasses

28. Volcano- a mountain that forms when layers of lava and volcanic ash erupt and build up.
* most volcanoes on Earth are dormant (not active)
*There are about 600 active volcanoes on Earth.

29. Magma- molten (melted) rock that is located beneath the Earth’s surface.
The more silica magma contains the thicker it is.
Lava- magma that flows to the Earth’s surface.
lava
magma

30. What types of tectonic
activity cause
volcanoes to
occur?

31. Divergent boundaries
* When 2 plates are moving apart, it creates an opening or ridge.
* Magma flows into the ridge and is cooled by sea water.
* pillow lava
* non-explosive

32. 2) Convergent boundaries-
* Magma created in the subduction zone is forced upward because the HOT magma is less dense than cooled rock of the surrounding crust.
* example: Mount St. Helens in Washington State

33. Formation of a volcano at subduction zone

34. TWO major belts (volcanoes at convergent boundaries):
Circum-Pacific (Ring of Fire)
* Pacific plate
2) Mediterranean Belt:
* Eurasian, African, & Arabian plates 34

35. Pacific Ring
of Fire

36. Mediterranean
Belt 36

37. 3) Hot Spots-
* Some areas of the mantle are hotter than others. These areas are called hot spots.
* These hot spots melt rock which is forced upward to the Earth’s crust.

40. Yellow Stone National Park

41. * Example- Hawaiian Islands
Hot Spots- OCEANIC
* As the plates move over the hot spot, many volcanic islands may form.
* Example- Hawaiian Islands 41

42. A chain of island volcanoes can form at a hot spot.

44. Hot Spots- CONTINENTAL
* Flood basalts form when lava flows out of long cracks in the Earth’s crust called fissures.
* This lava flow results in flat plains called plateaus.
* Ex: Columbia Plateau in Washington & Oregon 44

47. Three types
of volcanoes
                                                                                                                                                                                                                                                

48. Shield volcano-
* quiet eruptions
* slow-moving, non-viscous lava flows out in flat layers (low silica content)
* creates a broad volcano with gently sloping sides

49. Shield volcano
                                                                                                                                        

50. 2) Cinder Cone Volcano-
* explosive eruptions that shoot lava high into the air (thick, viscous lava that has high silica content)
* lava then falls back down and cools
* this creates a small, steep-sided volcanic mountain (cone shape)

51. Cinder- Cone
volcano

52. 3) Composite volcano (stratovolcano)-
* both explosive and quiet eruptions
* First, an explosive period shooting up lava. Then, a quiet period of slow moving lava flows.
* large, steep-sided and symmetrical built of layers of ash and lava

53. Composite
Volcano

54. ERUPTION!
The type of eruption is determined by the composition of magma.
Temperature
Pressure
Presence of water
Amount of silica

55. AMOUNT OF SILICA high silica= high viscosity traps gasses EXPLOSIVE!!
low silica= not viscous
easy flow
QUIET & NON-EXPLOSIVE!!

56. Three Types of Magma
Basaltic
Andesitic
Rhyolitic

57. Anatomy of a Volcano
Ash cloud
Crater
Vent
Conduit
Magma Chamber

58. Anatomy of a Volcano

59. Anatomy of a Volcano

60. CRATER
Bowl-shaped depression formed around the vent, Less than 1 km in diameter
VS.
CALDERA
Larger depression, can be up to 50 km in diameter, often forms when top or sides of the volcano collapses into the magma chamber

61. Eruption of a Volcano
Terms to know:
Tephra
Pyroclastic flow
Lahar

62. Types of Lava
Aa: forms from cooler, thicker lava. Hardens into a rock with a rough, jagged surface

63. Types of Lava
Pahoehoe: formed from thin, runny lava. Hardens into a rock with a smooth, rope-like surface.

64. Pillow lava: lava formed from eruptions under water
Types of Lava
Pillow lava: lava formed from eruptions under water

65. Pillow lava: lava formed from eruptions under water
Types of Lava
Pillow lava: lava formed from eruptions under water

66. Extinct: volcano that is unlikely to erupt again
Volcanoes can be…..
Active: a volcano that is erupting or shows signs that it will erupt in the near future
Dormant: volcano that scientist expect to awake in the future and become active
Extinct: volcano that is unlikely to erupt again

67. EARTHQUAKES

68. is the force that acts on rocks to change the shape of volume
Stress-
is the force that acts on rocks to change the shape of volume

69. 3 Types
of Stress

70. Tension
> plate pulling apart (divergent boundary)
> The rock of the crust thins in the middle
> The thin rock in the middle acts like warm bubble-gum.

71. 2) Compression
> Plate converging (convergent boundary)
> Plates are pushing into each other
> Squeezes the rock until it folds or breaks

72. 3) Shearing
> Two plates at a transform boundary
> Pushes a mass of rock in opposite directions
> Rock can break and slip apart OR change shape

73. earthquake-
is the movement of the ground caused by waves from energy released as rocks move along faults

74. facts:
Most earthquakes occur along tectonic plate boundaries
80% of all earthquakes occur along the edges of the Pacific Plate.
(Pacific Ring of Fire)

75. A fault is a large crack in rocks.
The rocks not only crack but move along side each other.

76. 3 Types
of Faults

81. Normal Fault Reverse Fault (Thrust Fault) Strike-slip Fault Foot Wall
Hanging Wall
Reverse Fault
(Thrust Fault)
Strike-slip
Fault

82. Normal faults- (Divergent Boundary)
Tension
The hanging wall (fault surface) moves DOWN
This type of fault created the Sierra Nevada Mountains

83. 2) Reverse fault- (Convergent Boundary)
Compression
Hanging wall (fault surface) moves UP
This type of fault movement created the Himalaya Mountains of India.

84. 3) Strike-Slip Faults- (Transform Boundary)
Shearing
Rocks on either side of the fault surface are sliding past each other
Transform boundary
When the pressure and stress builds up as the rocks move past each other, eventually they will break resulting in an earthquake.

85. 3 types of faults
Name ________________
Date______ period _____ A
__________________
B. __________________
C. __________________ B C