Solved Part 5: Theory of Plate Tectonics Directions: Use the ... - Free Printable

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Part 5: Theory of Plate Tectonics

#### Directions: Use the following words to fill in the blanks below:
- asthenosphere
- lithosphere
- plate tectonics
- convection
- plates

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1. The theory of ________ states that Earth’s crust and upper mantle are broken into sections.
✔ Answer: *plate tectonics*
> Explanation: The theory of plate tectonics explains that Earth's outer shell is divided into several large and small pieces called tectonic plates.

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2. These sections, called ________, are composed of the crust and a part of the upper mantle.
✔ Answer: *plates*
> Explanation: The tectonic plates include both the crust and the uppermost part of the mantle.

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3. The crust and upper mantle together are called the ________.
✔ Answer: *lithosphere*
> Explanation: The lithosphere is the rigid outer layer of Earth, consisting of the crust and the top part of the mantle.

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4. Beneath this layer is the plasticlike ________.
✔ Answer: *asthenosphere*
> Explanation: The asthenosphere lies beneath the lithosphere and is a semi-fluid layer where rocks flow slowly due to heat and pressure.

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5. Scientists suggest that differences in density cause hot, plasticlike rock to be forced upward toward the surface, cool, and sink. This cycle is called a ________ current.
✔ Answer: *convection*
> Explanation: Convection currents in the asthenosphere are driven by heat from Earth's core, causing mantle material to rise, cool, and sink—driving plate movement.

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Directions: Four diagrams are shown in the table below. Label and describe each diagram in the space provided in order to complete the table.

We now analyze the four diagrams (6–9):

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#### Diagram 6:
- Visual Description: Two plates moving away from each other, with new crust forming in the middle.
- Type of boundary and motion: Divergent boundary – Plates move apart.
- ✔ Answer: Divergent boundary; plates are moving away from each other, creating new crust at the mid-ocean ridge.

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#### Diagram 7:
- Visual Description: Two plates moving toward each other, one overriding the other (subduction).
- Type of boundary and motion: Convergent boundary – Oceanic-continental or oceanic-oceanic convergence.
- ✔ Answer: Convergent boundary; plates collide, one subducts under the other, forming deep trenches and volcanoes.

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#### Diagram 8:
- Visual Description: Two plates moving toward each other, but both appear to be continental (no subduction), pushing up mountains.
- Type of boundary and motion: Convergent boundary – Continental-continental collision.
- ✔ Answer: Convergent boundary; two continental plates collide, forming mountain ranges (e.g., Himalayas).

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#### Diagram 9:
- Visual Description: Two plates sliding horizontally past each other.
- Type of boundary and motion: Transform boundary – Plates slide laterally.
- ✔ Answer: Transform boundary; plates move horizontally past each other, often causing earthquakes (e.g., San Andreas Fault).

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✔ Final Answers:

#### Fill-in-the-blanks:
1. plate tectonics
2. plates
3. lithosphere
4. asthenosphere
5. convection

#### Diagram Table:

| Diagram | Type of boundary and motion at boundary |
|--------|------------------------------------------|
| 6 | Divergent boundary – plates move apart, new crust forms |
| 7 | Convergent boundary – plates collide, one subducts beneath the other |
| 8 | Convergent boundary – continental plates collide, forming mountains |
| 9 | Transform boundary – plates slide past each other horizontally |

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This completes the solution based on the principles of plate tectonics and the visual representations in the diagrams.