2. Alfred Wegener
Proposed idea (hypothesis) of “CONTINENTAL DRIFT”

4. Evidence for Wegener’s Idea
Continents fit together like puzzle pieces

6. Evidence for Wegener’s Idea
Continents fit together like puzzle pieces
Fossils found on different continents were identical…separated by thousands of miles…how’dey do dat?

7. This is a freshwater reptile called a Mesosaurus
This is a freshwater reptile called a Mesosaurus. Look at the distribution of fossils….hmmmm
Wegener compiled information about fossil discoveries from around the world. He felt this evidence was compelling.

8. Assorted Fossil Evidence

9. Evidence for Wegener’s Idea
Continents fit together like puzzle pieces
Fossils found on different continents were identical…separated by thousands of miles…how’dey do dat?
Dey ustabe neighbors

10. Evidence for Wegener’s Idea
Continents fit together like puzzle pieces
Fossils found on different continents were identical…separated by thousands of miles
Evidence from Glaciers: Marks in bedrock left behind by glaciers located on AFRICA, SOUTH AMERICA, INDIA, and AUSTRALIA indicate that portions of these continents must have been CONNECTED in polar regions far from their present positions.

11. Marks from ice
movement
striations

12. Evidence for Wegener’s Idea
Rock types on the east coast of North America MATCH EXACTLY the rocks in the British Isles, Scandinavia, and Africa

14. Continental Drift Hypothesis
The continents were all connected at one time
Supercontinent was called Pangaea
Pangaea broke apart up into two continents call Laurasia and Gondwanaland
Continents are still moving today

15. …plus, he was “only” a climatologist
Few believed Wegener…..
…because he could not explain what hidden mechanism might be responsible for the movement of an entire continent!!!
…plus, he was “only” a climatologist

16. 1930
Wegener leaves for Greenland to seek more evidence to test his hypothesis.
He is never seen again. Some speculate that he ate his own dogs before he froze to death.
The last photo him…
His hypothesis is “hotly” debated for the next 30 years

17. Cut and Paste Playtime

18. “What Wegener Wished He Knew”(animations from USGS)
Plate Tectonics
A.K.A.
“What Wegener Wished He Knew”(animations from USGS)

19. Evidence for Plate Tectonics
1. Location of earthquakes and volcanoes

20. Map of earthquake foci for the last 30 days

23. Evidence for plate tectonics
So, how would you characterize the distribution of earthquakes and volcanoes around the world?
Random?
Patterned?
Isolated?

24. Evidence for plate tectonics
Location of earthquakes and volcanoes
The distribution of earthquakes and volcanoes is not random. Earthquakes and Volcanoes occur TOGETHER in narrow bands under the oceans and along the edges of some continents.

25. Evidence for plate tectonics
…turns out…these locations are the edges of plates called “Plate Boundaries” where the plates rub against each other.

26. Volcanoes
Volcanoes are evidence of HEAT escaping from inside the Earth
This HEAT leaves the Earth as hot LAVA
So…if heat from inside the Earth is making it all the way to the surface…MAYBE this movement of heat can move continents too

27. What Makes the Plates Move
What Makes the Plates Move? A concept in Science that Wegener KNEW, but did not imagine it could move continents.
The plates move due to the transfer of HEAT energy from the Earth’s core
Heat leftover from Earth’s formation and produced by radioactive decay creates DENSITY differences in the mantle.
This causes the fluid mantle to flow.
The flow of mantle material pulls on the crust above it…like a leaf on a stream

28. Watch THIS!

29. Complete the Demo Analysis Sheet

30. The of Plate Tectonics Evidence:
THEORY
The of Plate Tectonics Evidence:
Convection currents in the mantle move the plates around…and have been doing so for more than 4 billion years (1:10)
Convection cell movement causes plates to collide, rip apart, and plunge back into the mantle

31. We’re not sure which model is correct.
This current model (A) predicts that convection cells are limited to the outermost plastic mantle.
This current model (B) predicts that convection cells extend through the mantle toward the Lehmann discontinuity.
We’re not sure which model is correct.
Don’t you just LOVE the
uncertainty of Science?

32. Which model has the New York State Ed Dept selected for you?

33. Current Scientific Theory “Plate Tectonics”
The Earth’s crust is composed of about 22 plates
The plates are rigid and may contain CONTINENTAL or OCEANIC crust, or BOTH
CONTINENTAL CRUST is mostly Granite
OCEANIC CRUST is mostly Basalt

34. The Plates…IN COLOR

35. Evidence cont’d 2. Age of seafloor
Oceanic igneous rock is much younger than continental igneous rocks
Oceanic rock gets younger as you approach the mid-ocean ridge (mountain range which runs through all world’s oceans)

36. Map showing
Ages of oceanic crust

37. Reading Passage
Please open your text book to page 337 and read the passage titled “Seafloor Spreading” to the end of 339

38. Magnetic pattern in rocks
Earth’s magnetic pole reverses
Magnetic crystals line up with earth’s poles when the magma hardens
Patterns in ocean rocks show parallel strips on either side of the ridge that match in width, age, distance from the ridge, and magnetic polarity

39. What pulls the lithosphere apart?

40. Types of Plate Boundaries
Divergent / Rift
Convergent/ Subduction
Transform

42. Divergent/ Rift
Plates move apart from one another
New basaltic crust is formed
Mid-ocean ridge: volcanic mountain range which circles the earth beneath the oceans

46. Mid-ocean ridge
Volcanic eruption in Iceland.
March 21, 2010

47. Rift valley

50. Black
Smoker,
East Pacific Rise

51. Marie Tharp & Bruce Heezen used echo soundings to build up a picture of the ocean floor
Continent
Continent
Mid-ocean ridge
Sea mount
Central rift zone

52. trench
Mid-ocean ridge
seamounts

53. Convergent Boundary Plates collide Continental/ oceanic crust
Oceanic/ oceanic crust
Continental/ continental crust
Mountains grow: Volcanoes, or continental ranges

54. Ocean- Continent collision with subduction

55. Ocean- Continent collision with subduction

56. Andes Mountains

58. Ocean-ocean collision with subduction

59. Ocean-ocean collision with subduction

62. Hugo Benioff suggested that this Earthquake pattern shows a plate subducting (sinking) into the mantle (1940s discovery)

68. Continent-continent collision (Subduction has ended)

69. Continent-continent collision (Subduction has ended)

75. 1963 Tuzo Wilson
Developed the hypothesis of hot spots to explain islands like Hawaii & a third kind of plate boundary called a transform plate boundary

76. Transform Boundary Plates slide past one another
Ex. San Andreas fault
Crust is neither created nor destroyed

78. Hot Spots Places where magma reaches earth’s surface
Typically not associated with plate boundary
As plate moves over hot spot, island chains form
Example: Hawaii

80. Theory of Plate tectonics
So by the mid-60’s all the evidence came together to form the
Theory of Plate tectonics
This theory states that the Earth crust is broken into a series of plates which are constantly on the move.

81. Convection computer model.
The most current understanding.