4 2 the theory of plate tectonics
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4.2 The Theory of Plate Tectonics PowerPoint PPT Presentation


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4.2 The Theory of Plate Tectonics. Tectonics – ( G reek ) meaning “construction” Tectonics: The study of the formation of features in the earth’s crust. Open textbook to p . 72. Two types of crust: Oceanic crust Continental crust. Lithosphere & Asthenosphere.

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4.2 The Theory of Plate Tectonics

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4.2 The Theory of Plate Tectonics

Tectonics – (Greek) meaning “construction”

Tectonics:

The study of the formation of features in the earth’s crust

Open textbook to p. 72

  • Two types of crust:

  • Oceanic crust

  • Continental crust


Lithosphere & Asthenosphere

Lithosphere – made up of the crust and the rigid upper mantle

The lithosphere is broken into separate plates that ride on thedenser asthenosphere.

Asthenosphere – layer of plastic rock; a solid rock that slowly flows(like putty) when under pressure.


Plate Boundaries

Divergent boundaries– where plates move away from each other


Plate Boundaries

Convergent boundaries – where plates collide (3 types)

1. Ocean & Continent – forms a subduction zone;

usually forms an ocean trench and mountains on land


Plate Boundaries

Convergent boundaries – where plates collide

2. Two Continental plates –

neither plate is subducted, so both are crumpled and uplifted


Plate Boundaries

Convergent boundaries – where plates collide

3. Ocean & Ocean – forms deep ocean trench when one plate issubducted; subducted plate melts and forms volcanic chain(Island Arc)


Plate Boundaries

Transform fault boundaries – forms where two plates are grinding past each other.

Can you think of an example?


San Andreas Fault


Causes of Plate Motion

Convection Currents – cycle of warm water rising and cool water sinking


Suspect terranes

Theory of suspect terranes -

Continents are patchwork of terranes, each with its own distinct geologic history.

3 identifying characteristics:

Terrane contains rock and fossils that differ from the rocks and fossils of neighboring terranes.

There are major faults at the boundaries of a terrane.

The magnetic properties of a terrane do not match those of neighboring terranes

See Figure 4-9 on p. 77


Suspect terranes


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