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Plate Tectonic Theory

1. What are these things called plates?

2. What do plates do?

3. What is the evidence for the existence

of plates?

4. How do plates move?

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What is a Plate?

• A plate is a large section of crust that shifts position over time.

• There are typically 7 major plates and several other minor plates

• The major plates are the north American, South American, Eurasian, Arctic, African, Australian, and Pacific plates.

Plates

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What do colliding plates do?

• They form convergent boundaries and produce mountains, volcanoes, and earthquakes. They pile crust or get rid of it.

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What do separating plates do?

• They form divergent boundaries to produce earthquakes, rift valleys, and a few volcanoes. They form new crust.

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What do sliding plates do?

• They form transform boundaries that produce earthquakes, They generally do not form new crust or destroy it.

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Boundary Types• Boundaries are the joints between two or

more pieces of the crust• Divergent Boundaries: Crusts moving

away from one another• Convergent Boundaries: Crusts moving

toward one another• Transform Boundaries: Crusts sliding

alongside one another

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How do plates move?

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Theory of Plate Tectonics

• Like a broken eggshell

• States that Earth’s crust is moving around not just the continents

• Crust is the outermost layer of Earth’s body and is fragmented

• Crust floats on molten rock

• Molten rock below upper crust has heat currents that push crustal rock (convection currents)

• Slab pull and ridge push aid in movement of oceanic plates and some continental plates.

•Theory is generally accepted