1. Plate Tectonics

2. Learning Objectives
Students will understand the basic structure of the earth
The solid Earth is composed of a relatively thin crust, a dense metallic core, and a layer called the mantle between the crust and core that is very hot and partially melted. (6-8 ES2E).
The crust is composed of huge crustal plates on the scale of continents and oceans, which move centimeters per year, pushed by convection in the upper mantle, causing earthquakes, volcanoes, and mountains. (6-8 ES2F).

3. Looking at the world map, what do you notice about the shape of the continents?
Jot down your ideas on your paper…

4. The thing is…the world didn’t always look like this
The thing is…the world didn’t always look like this! It used to look like this:

5. How is this possible?!?!?
Geological Changes—3:25

6. Plate Tectonics Theory
The lithosphere is divided into a number of large and small plates and the plates are floating on the mantle

7. Lithosphere = the Earth’s crust plus the upper portion of the mantle layer

9. Earth’s Structure by Brainpop

12. Plate Boundaries Divergent boundary:
Plates are moving away from each other
Midocean ridges are created and new ocean floor plates are created

13. Plate Boundaries
Divergent boundary:

15. Leif the Lucky Bridge Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates.

16. Convergent Boundary: plates are moving toward each other and are colliding (3 types)

17. When Ocean Plates collide with Continental Plates
Create subduction zones,
Trenches
Create near coast volcanoes

18. When Ocean Plates collide with Continental Plates
Benioff shear zones (a pattern of earthquakes as an ocean plate grinds down the underneath side of a continent)

20. When ocean plates collide with other ocean plates
Island arcs are created
(a pattern of volcanic islands created from a subduction zone that is located off the coast)

23. What About Hawaii?
Do you see any plate boundaries there??
Hawaii

24. What About Hawaii? Hawaiian Volcanoes form from HOT SPOTS
(places where the mantle is hotter than others…we’re not sure why)

25. When a continental plate collides with another continental plate
Mountain ranges are created
(example: Himalayan Mountains)

26. Himalayan Mountains
Mountains 2:46

27. Transform Fault Boundary
Plates are neither moving toward nor away from each other, they are moving past one another.

28. Transform Fault Boundary
The plates may move in opposite directions or in the same directions but at different rates and frequent earthquakes are created (example: San Andreas Fault)

29. San Andreas Fault

30. Why is Earth not getting bigger or smaller?
NOTE:
Plates are destroyed as fast as they are created (2 ways)
Plates may be subducted and melted or may push be pushed upward to form mountains

31. Boundaries Between Tectonic Plates—1:23

32. How can Oreos model the plate boundaries?
Very carefully, take just the top cookie off the Oreo.
Break the top cookie into 2 equal halves.
Replace the cookie halves back on the Oreo
Using the cookie,
Demonstrate a transform fault boundary
Demonstrate a divergent plate boundary
Demonstrate a convergent plate boundary

34. Learning Objectives
Students will understand that the surface of Earth changes over millions of years.
Our understanding of Earth history is based on the assumption that processes we see today are similar to those that occurred in the past. (6-8 ES3A)
Thousands of layers of sedimentary rock provide evidence that allows us to determine the age of Earth’s changing surface and to estimate the age of fossils found in the rocks. (6-8 ES3B)
In most locations sedimentary rocks are in horizontal formations with the oldest layers on the bottom. However, in some locations, rock layers are folded, tipped, or even inverted, providing evidence of geologic events in the distant past. (6-8 ES3C)

35. So how do the continents move?

36. Ocean floors are moving like broad conveyor belts
Seafloor Spreading Theory:
Ocean floors are moving like broad conveyor belts

37. New ocean floor crust is being created at the midocean ridges

38. What causes this? Convection currents within the mantle
The up-welling leg of the current creates a divergent boundary which produces midocean ridges

40. Convection Currents

41. Convection Current Demo

42. The down-welling leg of the current creates one type of convergent boundary that results in trenches and a subduction zone

44. What evidence do we have to support this idea?
Midocean ridges are warmer than surrounding ocean floors
Active volcanoes on ridges, earthquakes on ridges
Midocean ridge rocks are younger than surrounding ocean floor rocks
Midocean ridge volcanoes are younger than volcanoes further away

45. What evidence do we have to support this idea?
Ocean floor sediments are THINNER on the ridges and get THICKER as the distance from the ridges increase
Polar reversal magnetism proves that the ocean floor is moving away from the ridges

47. Polar Reversal Magnetism
Magnetic Poles
Magnetic Field Reversals—2:54

48. Speed of Spreading Atlantic Ocean – 2-3 cm/year
South Pacific Ocean – cm/year

49. Seafloor Spreading The Seafloor is Spreading Clip—4:01
How Earth’s Structure Affects Plate Tectonics—5:43

50. Distribution of Volcanoes & Earthquakes

52. Continental Drift Theory
The continents have shifted their position over geologic time…

53. …And at one time all land masses were connected into one piece called Pangaea
Continental Drift Theory 3—2:21

54. Pangaea began to split apart 200 million years ago Diagram
North America
Laurasia Greenland
Eurasia
Pangaea
Africa
West G. S.America
Gondwanaland
Antarctica
East G. Australia
India
Pangaea—A History of the Continents: 2:23

55. USGS Plate Motions Clip

56. Continents
The continents are like packages on the seafloor conveyor belt

57. Evidence
High percentage fit of continents at the 500 fathom level

58. Evidence
Minerals, fossils, and mountains on now different continents match if the continents were together
The Mystery of Brachiosaurus (~3 min)

60. Evidence
Glaciation patterns indicate a common ice cap at the South Pole

61. Evidence
Paleomagnetism (magnetism of old rocks) indicate a common pole if the continents were all connected

62. Bill Nye’s Great 100: Plate Tectonics 2 –4:22

63. Plate Tectonics by Brainpop
What can be found underneath Earth’s plates?
2) What kind of boundary involves two plates moving toward each other?
3) What process can explain why we see fossils of the same prehistoric animals on DIFFERENT continents?

64. Pacific Ring of Fire