1. Chapter 10: Plate Tectonics
Table of Contents
Chapter 10: Plate Tectonics
Section 10.1: Continental Drift

2. Continental Drift 1
Pangaea
(1) German meteorologist Alfred Wegener proposed the hypothesis of continental drift.
According to the hypothesis of continental drift, continents have moved slowly to their current locations.

3. Continental Drift 1
Pangaea

4. Continental Drift 1
A Controversial Idea
(2) He was unable to explain exactly how the continents drifted apart.
He proposed that the continents plowed through the ocean floor, driven by the spin of Earth.

5. Fossil Clues 1 (3a) Shape of continents.
Continental Drift 1
Fossil Clues
(3a) Shape of continents.
(3b) Fossils provided support for continental drift.

6. Continental Drift 1
Climate Clues
Fossils of (3c) warm-weather plants were found on islands in the Arctic Ocean.
To explain this, Wegener hypothesized that the islands drifted from tropical regions to the arctic.

7. Continental Drift 1
Climate Clues
(3d) Glacial deposits and rock surfaces scoured and polished by glaciers are found in South America, Africa, India, and Australia.
This shows that parts of these continents were covered with glaciers in the past.

8. Continental Drift 1
Rock Clues
(3e) Similar rock structures are found on different continents.
Parts of the Appalachian Mountains of the eastern United States are similar to those found in Greenland and western Europe.

9. Mapping the Ocean Floor
Seafloor Spreading 2
Mapping the Ocean Floor

10. Mapping the Ocean Floor
Seafloor Spreading 2
Mapping the Ocean Floor
In some of these underwater ridges are rather long (5) rift valleys where volcanic eruptions and earthquakes occur from time to time.
In the Atlantic, the Pacific, and in other oceans around the world, a system of ridges, called the mid-ocean ridges, is present.

11. Seafloor Spreading 2
The Seafloor Moves
In the early 1960s, Princeton University scientist (6) Harry Hess suggested an explanation.
His now-famous theory is known as seafloor spreading.

12. Seafloor Spreading 2
The Seafloor Moves

13. Evidence for Spreading
Seafloor Spreading 2
Evidence for Spreading
In 1968, scientists aboard the research ship Glomar Challenger began gathering information about the rocks on the seafloor.
(7) Scientists found that the youngest rocks are located at the mid-ocean ridges.

14. Composition of Earth’s Plates
Theory of Plate Tectonics 3
Composition of Earth’s Plates
The rigid plates of the (9) lithosphere float and move around on the asthenosphere.

15. Theory of Plate Tectonics3
Plate Boundaries
When plates move, they can interact in several ways.
They (10) can move toward each other and converge, pull apart or slide past each other.
(11) Where the plates meet and interact, the result of their movement is seen at the plate boundaries.

16. Theory of Plate Tectonics3
Plate Boundaries

17. Theory of Plate Tectonics3
Plates Moving Apart
The (12) boundary between two plates that are moving apart is called a divergent boundary.
In the Atlantic Ocean, the North American Plate is moving away from the Eurasian and the African Plates.

18. Theory of Plate Tectonics3
Plates Moving Apart
(12) Features: mid-ocean ridges and rift valleys.
Examples: Mid-Atlantic Ridge, Great Rift Valley

19. Plates Moving Together
Theory of Plate Tectonics 3
Plates Moving Together
(13) As new crust is added in one place, it disappears below the surface at another.
The disappearance of crust can occur when seafloor cools, becomes denser, and sinks.
This occurs where (14) two plates move together at a convergent boundary.

20. Plates Moving Together
Theory of Plate Tectonics 3
Plates Moving Together
When an oceanic plate converges with a less dense continental plate, the denser oceanic plate sinks under the continental plate.
The (15) area where an oceanic plate subducts, or goes down, into the mantle is called a subduction zone.

21. Continent/Ocean convergent
Theory of Plate Tectonics 3
Continent/Ocean convergent
(16) Ocean plate bends and subducts under the continent.
Features: volcanoes and trenches
Examples: Andes, Cascades (Mt. St. Helens)

22. Ocean /Ocean convergent
Theory of Plate Tectonics 3
Ocean /Ocean convergent
(17) One ocean plate bends and subducts under the other one.
Features: volcanic island arcs and trenches
Examples: Japan, Philippines.

23. Continent/Continent convergent
Theory of Plate Tectonics 3
Continent/Continent convergent
(18) Two landmasses collide and build up into mountains.
Features: folded mountains
Examples: Himalayas, Appalachians

24. Plates Slide Past Each Other
Theory of Plate Tectonics 3
Plates Slide Past Each Other
(19) Plates slide past each other
Features: large faults and earthquakes.
Example: San Andreas Fault

25. Causes of Plate Tectonics— Convection Inside Earth
Theory of Plate Tectonics 3
Causes of Plate Tectonics— Convection Inside Earth
The cycle of heating, rising, cooling, and sinking is called a convection current.
Scientists suggest that differences in (20) density cause hot, plastic like rock to be forced upward toward the surface.

26. Features Caused by Plate Tectonics
Theory of Plate Tectonics 3
Features Caused by Plate Tectonics
It is the transfer of (21) heat inside Earth that provides the energy to move plates and cause many of the Earths Surface Features

27. (22) 3 Divergent boundary Subduction Zone Continent
Theory of Plate Tectonics 3
(22)
Mid-Ocean Ridge
Volcanic Island
Continent
Trench
Divergent boundary
Subduction Zone

28. Where do volcanoes occur?
Volcanoes and Earth’s Moving Plates 1
Where do volcanoes occur? .

29. (24) A. Divergent boundaries where plates are moving apart. Iceland
B. Convergent boundaries where plates are moving together. Cascades, Andes, Japan
C. Hot Spots. Hawaii

30. What controls eruptions?
Types of Volcanoes 2
What controls eruptions?
(25) explosive eruptions throw out rock, dust and gas (tephra). Whereas quiet eruptions have lava quietly flowing from a vent

31. What controls eruptions?
Types of Volcanoes 2
What controls eruptions?
Two important factors control whether an eruption will be explosive or quiet.
One factor is the (26a) amount of water vapor and other gases that are trapped in the magma.
The second factor is the (26b) type of magma– granitic or basaltic.