1. Plate Tectonics

2. Alfred Wegener German Scientist
Ph.D in astronomy, interested in meteorology and climatology
Served in German Army weather service
Proposed supercontinent Pangea separated 200 mya
Found paper in library that listed fossils of identical animals and plants across the Atlantic

4. Evidence for his theory
1) Similar coastlines (jigsaw puzzle)

5. Evidence for his theory
2) Identical fossils along joining coasts
Ex. South America and Africa

6. Evidence for his theory
3) Identical age and rock types along joining coasts
Ex. Brazil and West Africa
4) Similar mountain chains across joining coasts
Ex. Appalachians and mountains in Scotland and Northern Europe
5) Climactic changes in geologic record
Pangea over south pole = glaciers in South Africa and South America
Tropic or subtropic swamps in NA = coal deposits in WV and WY

7. Wegener’s Problem No mechanism to cause continental drift
Proposed continents were moving through the ocean’s crust by centrifugal and tidal forces
If so, continents would be deformed
There isn’t enough force from either to move continents
His theory was not accepted until after his death

8. Later Support 6) Sea floor spreading
Found young rocks along Mid-Atlantic ridge in 1947
Ridge is a break in Earth’s crust
Ocean floor is separating and new crust is forming
Ocean floor moving = continents moving
Animation:

11. Later Support 7) Paleomagnetism Earth as a giant magnet
Arrangement of minerals along mid-ocean ridges
Bands of rock oriented toward N or S pole
Dating rocks supports EM reversals in the past
His hypothesis was fully supported

12. Plate Tectonics Continental crusts and oceanic crust
Lithosphere – crust and upper mantle
-The lithospheric plates float on the asthenosphere, carrying the continents with them
There are 8 large plates and 9 small plates
Some are moving towards each other, some away and some are sliding past each other
This movement has made most major surface features on the earth
Ex. Mountains ranges, trenches

15. Plate Boundaries
3 Types
Divergent
Convergent
Transform

16. Divergent Where plates move in opposite directions
Sea floor spreading (ocean ridges)
Creates Rift Zones, on land they’re called rift valleys
Asthenosphere rises to take up the space
Ex. Mid-Atlantic ridge; Rift Valley, Africa

17. Divergent Boundary

18. Convergent Boundaries
Where two plates are colliding
Located on the opposite side of plates from divergent boundaries
3 Types
Oceanic – Continental
Continental – Continental
Oceanic – Oceanic

19. Oceanic - Continental Creates a Subduction Zone
Oceanic crust is denser and pushed beneath continental crust (subduction)
Forms a trench
Oceanic crust heats up, releases water, and causes the mantle to melt
Magma produced then rises and forms volcanic mountains
Ex. Andes Mountains, South America

20. Subduction Zone 

22. Continental - Continental
Plates have same density, so neither is subducted
Are crumpled and uplifted
Forms mountains
Ex. Himalayas

25. Oceanic - Oceanic One plate is subducted Forms a trench
Subducted oceanic crust melts, releases water and causes magma to rise and make a chain of volcanic islands
(Island Arc)

27. Transform Boundaries Where plates slide past one another
Grind as they pass each other in short quick movements, causing earth quakes
Ex. San Andreas Fault, CA

30. Carrizo Plain, CA (san Andrea Fault)

32. Causes for plate motion
Convection
Seen in boiling water
Movement of material due to temperature differences
Act like conveyor belts that the plates ride on

34. Microplate Terranes (Suspect Terranes)
Continents made of a variety of lithospheric chunks, each with a different geologic history

35. Theory of Continental Drift
Alfred Wegener (German Scientist)
Proposed hypothesis that all the continents were once part of one large land mass called Pangaea (all lands)
200 MYA they started to separate and have led to the world we see today

36. Evidence Coastlines fit together like a jigsaw
Identical fossils found along joining coasts
Ex. South American and Africa
Age and rock types along joining coasts
Ex. Brazil and West Africa
Similar mountain chains
Appalachians and mountains in Scotland and Northern Europe
Climactic changes seen in the geologic record
Thought that Pangaea was once positioned over the South Pole
Ex. Glaciers in southern Africa and South America,
Coal deposits in North America (land was once covered with tropical or subtropical swamps)

37. http://upload. wikimedia

38. Seafloor Spreading Areas along sea floor where plates are separating
Cause a underwater mountain range
Actually is a rift, or break in the crust
New magma rises to fill the gap
Mid-Atlantic Ridge

40. Paleomagnetism Earth is one giant magnet
As minerals rise and solidify in crust, they orient themselves toward the N pole
Found rock bands along these ridges that were oriented toward the S pole
Suggests that the Earth’s magnetic poles have switched throughout history

43. Sources http://www.platetectonics.com/book/images/Pangaea.gif