1. Bellwork: 3/3
Which model of the layers of the earth is shown below Physical or Compositional?
What do they use to divide the layers the layers in this model
Complete 1-6 on review sheet

2. Bellwork 3/4 How does igneous rock form?
How does sedimentary rock form?
How does metamorphic rock form?
When the earth is divided into layers based on chemical composition, how many layers are there
How do Earth’s compositional layers correspond to the physical layers?
In what physical layer would you find the Rocky mountains? What plate movement formed them?

3. After the test; carefully read the article “The Restless Continents” and answer the following questions in complete sentences
Who came up with the theory of Continental Drift?
In the first sentence it says that the idea of continental drift was met with ridicule. What does this mean?
At first continental drift was not widely accepted. What were 2 reasons scientists did not accept the theory
What new evidence was helped support the theory of continental dirift
How did the mid atlantic ridge form?
What is sea-floor spreading?
What new theory based on the theory of continental drift was proposed in the 1960’s
What happens to the plates where magma rises to the surface?
What forms where 2 plates push directly against eachother. _____ draw and label a diagram
What is it called when one plate is driven under another plate? Draw and label a diagram
How do moving plates cause earthquakes?

4. (thin rocky outer layer) Dense layer made up of the
Layers of the Earth
Crust
(thin rocky outer layer)
Mantle
(molten rock)
Liquid
Iron
Outer
Core
Solid
Iron
Core
Lithosphere
Dense layer made up of the
Crust and upper mantle

5. Bellwork 3/5 Which layer of the Earth is made up of tectonic plates
What is a scientific Theory?
Why might a scientific theory change?
Which type of crust is more dense ocean or continental?
What causes movement in the mantle?
What does the movement in the mantle cause? (these are 2 different questions)

6. Bellwork answers: Lithosphere
An explanation of what happens based on evidence
Better technology, new evidence
Oceanic is thinner but less dense
Convection currents
Cause the tectonic plates to move.

7. Evidence for Plate Tectonics
Plate Tectonic Theory
Evidence for
Plate Tectonics

8. EQ: What are the theories of Continental Drift & Plate tectonics
Describe the theory of Continental Drift and the evidence to support it
Describe the theory of Seafloor Spreading
SC.7.E

9. What is the theory of CONTINENTAL DRIFT?
in the early 1900’s Alfred Wegener proposed the hypothesis that continents were once joined together in a single large land mass he called Pangea (meaning “all land” in Greek).

10. CONTINENTAL DRIFT
He proposed the theory of continental drift - which hypothesized that the continents have moved slowly to their current locations.

11. Pangaea about 200 million years ago, before it began breaking up.
Wegener named the southern portion of Pangaea Gondwana, and the northern portion Laurasia.

12. The continents about 70 million years ago
The continents about 70 million years ago. Notice that the breakup of Pangea formed the Atlantic Ocean. India’s eventual collision with Eurasia would form the Himalayan Mountains.

13. The position of the continents today
The position of the continents today. The continents are still slowly moving, at about the speed your fingernails grow. Satellite measurements have confirmed that every year the Atlantic Ocean gets a few inches wider!

14. Quick Check
Turn and tell your neighbor who came up with the continental drift theory.

15. What was Wegener’s Evidence for Continental Drift?
1. Continents fit together like a puzzle
the Atlantic coastlines of Africa and South America.
The Best fit includes the continental shelves (the continental edges under water.)
Picture from

16. What was Wegener’s Evidence for Continental Drift?
2. Fossil Evidence: fossils of plants and animals of the same species found on different continents.
Picture from

17. Fossils
Matched Up!

18. What is the Evidence for Continental Drift?
3. Mountains - he noticed that mountain chains matched up on the continents

19. Mountains and Rocks match up!

20. 4. Rock layers - Layers on different continents show similarities .
Wegener showed that the same three layers occur at each of these places.
Picture from

21. What was the problem the theory of continental drift?
One reason scientists had a problem with Wegener’s theory is that there was no mechanism for the continents motion.
Wegener could not explain how the continents moved so his theory was rejected

22. Other questions/problems scientists had with the theory of continental drift.
But wouldn’t we feel the movement?
Shouldn’t there be evidence to show that the continents were still moving today?
Wegener was a meteorologist (weather scientist – not a geologist)
So his theory was not well accepted.
(He died on an expedition in Greenland collecting ice samples)

23. What is the theory of Seafloor Spreading?
In the 1960’s, new technology was developed that helped support Wegner’s theory.
Using new radar, Henry Hess discovered that the seafloor has both trenches and mid-ocean ridges.
He proposed the sea-floor spreading theory.
Picture from USGS

24. What is the theory of Seafloor Spreading?
It was believed that the bottom of the ocean was flat and featureless
New technology after World War Two allowed us to map the bottom of the Ocean

25. Seafloor Spreading
As the seafloor spreads apart at a mid-ocean ridge, new seafloor is created.
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.
Old
Rock
New Rock
Forming

26. cools, and forms basalt, and New seafloor is created
When new seafloor
Is created, it spread
The ocean floor
In two directions
When molten rock
reaches the surface, it
cools, and forms basalt, and
New seafloor is created
Hot molten rock rises, and is
forced upward at the ridge

27. Plate Tectonic Theory
Both Hess’s theory of sea floor spreading and Wegner’s continental drift theory combined into what scientists now call the Plate Tectonic Theory.
Theory of plate tectonics:
The Earth’s crust and part of the upper mantle are broken into sections, called plates which move the soft mantle

28. Exit:
Finish the summary questions on the back of your notes sheet

29. Bellwork Where does sea floor spreading happen
Where is the older crust and newer crust in sea floor spreading
What is the difference between the theory of continental drift and plate tectonics?
What are tectonic plates?

30. Sea floor spreading is the Mechanism for Plate Tectonics
Seafloor Spreading provided insight to the mechanism for how the continents moved.
The magma which pushes up at the mid-ocean ridge provides the new land pushing the plates, and the subduction zones gobble up the land on the the other side of the plates.
Picture from
The mechanism was convection currents!

31. Plate Tectonic Theory Plate Tectonics explains Earthquakes Mountains
Volcanoes