1. Plate Tectonics

2. Continental Drift Evidence for Continental Drift
A. Theory of continental drift is the idea that the continents have moved horizontally to their current locations.
1. This theory was developed by Alfred Wegener.
2. Wegener believed
that all of the continents
were connected as one
large land mass (he
called Pangaea) about
200 million years ago.
Alfred Wegener ( )

3. How Could the Continents Drift?
The continents fit together like a puzzle (in a super continent called Pangaea)
Wegener’s theory was often rejected because no one could explain how the continents moved.

4. EVIDENCE FOR PLATE TECTONINCS:
B. Fossils of Mesosaurs have been found in South America and Africa.
C. Glacial deposits and grooved bedrock were found in southern areas of South America, Africa, India, and Australia (Climate).
D. Appalachian mountains (Rocks) in the eastern US are similar to those found in Greenland and western Europe.

5. Theory of Plate Tectonics
A. Theory of Plate Tectonics is the idea that the Earth’s crust and upper mantle are broken into sections called plates that move around on the mantle.
B. Composition of the Earth’s plates:
1. Lithosphere – the crust and part of the upper mantle
2. Asthenosphere – the plastic-like layer below the lithosphere

6. Mantle Convection
Magma in the mantle is heated by the earth’s core, it rises and sinks create cycles (like a conveyer belt that moves the plates)

8. Plate Boundaries Convergent Boundaries Transform Boundaries
There are three different plate boundaries:
Divergent Boundaries
Convergent Boundaries
Transform Boundaries

9. Divergent Boundaries Divergent (Define below your foldable)
two plates that are moving away from each other.

10. Draw this in your notebook on the “Divergent: Continental-Continental” Flap
Continental Crust
Continental Crust
Magma

11. Divergent Boundaries (Continental-Continental)
Landforms: Rift Valley (Continental rift) Example: African Rift Valley forms as the Nubian plate and Sumali plate move away from eachother.

13. Erta’ale Volcano in the Danakil Depression (Rift Valley)-Ethiopia

14. Draw this in your notebook on the “Divergent: Oceanic-Oceanic” Flap
Oceanic Crust
Magma

15. Divergent Boundaries (Oceanic-Oceanic)
Sea floor spreading occurs at divergent boundaries:
Sea floor spreading-the process by which new oceanic crust is created at mid-ocean ridges as older crust moves away
Landforms: Mid-ocean ridges (mountain system under the ocean)
Example: Mid-Atlantic Ridge forms as the North American plate and the Eurasian plate move away from each other.

17. Convergent Boundaries
Convergent (Define this under your foldable)
two plates that are moving towards each other.

18. Draw this on your “Convergent: Continental-Continental” Flap

19. Convergent Boundary-(Continental-Continental)
Landforms: Mountains
Example: Himalayas were formed when the Indian plate collided into the Eurasian plate.

20. Draw this on your “Convergent Boundary: Oceanic-Oceanic” Flap
Oceanic Crust
Oceanic Crust

21. Convergent Boundary (Oceanic-Oceanic)
Landforms: Deep ocean trenches and volcanic island arcs
Example: The Mariana Trench and Mariana Island Arc is formed when the Pacific plate subducts under the Mariana plate.

23. Draw this on your “Convergent Boundary: Oceanic-Continental” Flap

24. Convergent Boundary: (Oceanic-Continental)
Landforms: Trench, continental volcanic arc, subduction zone
Subduction zone: as sea-floor spreading occurs, old oceanic plates sink (recycle) back into the mantle at the edges of oceanic plates
Example: Andean volcanic arc and Peru-Chile trench form as the Nazca plate subducts under the South American plate.

28.  Oceanic-Continental
Oceanic-Oceanic 
 Continental-Continental

29. Transform Fault Boundaries
Transform (Define this under your foldable)
Boundaries between two plates that are sliding horizontally past one another.

30. Draw this on the “Transform Boundary” Flap

31. Transform Boundaries
Landforms: Earthquakes and Faults; Tension builds up over and time and get released causing an Earthquake.
*Earthquakes can occur at any plate boundary*
Example: San Andreas Fault in California forms between the Pacific and North American Plates

33. Tsunamis Tsunamis are also a result of tectonic activity.
A tsunami is a series of great sea waves caused by an underwater earthquake, landslide, or volcanic eruption.

34. Causes of Plate Tectonics
Mantle Convection is the driving force of plate tectonics in which hot, plastic-like material from the mantle rises to the lithosphere, moves horizontally, cools, and sinks back to the mantle.
The convection currents provide enough energy to move the plates in the lithosphere.

35. Quick Review of Plate Boundaries

36. Check for Understanding
Summarize how rocks, fossils, and climate provided evidence of continental drift.
Why was Wegener’s idea of continental drift rejected at first?
Explain why oceanic crust is younger than continental crust.
Describe how plate tectonics results in the development of Earth’s major geologic features.
Explain how the Himalayan Mountains were formed.