1. Bellringer: Looking at the world map, what do you notice about the shape of the continents? Write a 1 paragraph response about what you notice.

2. Plate Tectonics

3. Continental Drift and Plate Tectonics
From the time maps of the globe became available, people wondered about the arrangement of the continents and oceans. Hundreds of years later, valid explanations were constructed.

4. side-by-side. He called the supercontinent Pangaea.
In the early 20th century a meteorologist named Alfred Wegener created the theory of continental drift, the idea that all of the present-day continents were connected,
side-by-side. He called the supercontinent Pangaea.
Greek for ‘all lands’.

5. 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

6. Wegener’s summary was based on a number of careful observations:
Wegener’s Evidence
Wegener’s summary was based on a number of careful observations:
-- matching rock, fossil, glacier, and structural relations among different parts of different continents

7. Glacial Evidence
-Large ice masses carve grooves in the rocks over which flow.
-Such masses tend to flow outward (generally downhill) from a central location.
-Glaciation patterns indicate a common ice cap at the South Pole.

8. Continental Drift: Rock Ages
-Using geochronology, rock dating, rock ages showed strong correlation across the Atlantic.
-Mountain ranges of similar ages across the Atlantic also show a correlation that they used to be part of the same mountain ranges.

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

10. But how is this possible?!?!?
-Wegener never lived to see the general acceptance of continental drift, largely because of the lack of a mechanism.

11. So how do the continents move?

12. Plate Tectonics Theory
The lithosphere is divided into a number of large and small tectonic plates and the plates are floating on the mantle.
The plates move at a rate of cm’s per year.

14. Convection Currents
Hot magma in the Earth moves toward the surface, cools, then sinks again.
Creates convection currents beneath the plates that cause the plates to move.

15. Bellringer: Name and explain what process this diagram is depicting
Bellringer: Name and explain what process this diagram is depicting. Then, explain how this is connected to what we are studying.

16. What evidence do we have to support this idea of plate tectonics?
Sea-floor spreading
Magnetic reversal
Earthquakes
Mountains
Volcanoes
Subduction

17. Seafloor Spreading
As the seafloor spreads apart at a mid-ocean ridge, magma rises to the surface and solidifies and new crust forms.
Mid Ocean Ridges – underwater mountain chains that run through the ocean floor
The older seafloor moves away from the ridge in opposite directions.
This helped explain how the crust could move—something that the continental drift hypothesis could not do.

18. So is the Earth getting bigger?No
Plates are destroyed as fast as they are created (2 ways)
Plates may be subducted and melted or may be pushed upward to form mountains.

19. Polar Reversal Magnetism Polar reversal magnetism proves that the ocean floor is moving away from the ridges

20. Bellringer
The 3 types of plate boundaries are shown in the pictures below. Name each boundary and describe its motion.

21. Plate Boundaries

22. 1-Divergent Boundaries
Boundary between two plates that are moving apart or rifting
 
RIFTING causes SEAFLOOR SPREADING

23. Geographic Features of Divergent Boundaries
Mid-ocean ridges (sea-floor spreading)
rift valleys
volcanoes

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

25. Divergent Boundary – Arabian and African Plates
Arabian Plate
Red Sea
African Plate

26. 2- Convergent Boundary: plates are moving toward each other and are colliding (3 types)

27. Type 1 Oceanic-Continental
Subduction Zone: where the more dense plate slides under the less dense plate
VOLCANOES occur at subduction zones

28. Oceanic-Continental Collision

29. Type 2
Oceanic-oceanic
The more dense plate slides under the less dense plate creating a subduction zone called a TRENCH

30. Oceanic-Oceanic Collision
Island arcs are created
(a pattern of volcanic islands created from a subduction zone that is located off the coast)

32. The Mariana Trench is the deepest part of the world's oceans
The Mariana Trench is the deepest part of the world's oceans. (About 36,000 ft)

33. Type 3 A continental plate colliding with another continental plate
Have Collision Zones:
a place where folded and thrust faulted mountains form.

34. Continental-Continental Collision
Mountain ranges are created

35. Himalayan Mountains
Mountains 2:46

36. 3- Transform Boundary
Plates are neither moving toward nor away from each other, they are moving past one another.
The plates may move in opposite directions or in the same directions but at different rates and frequent earthquakes are created

37. San Andreas Fault, California