4 2 the theory of plate tectonics
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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

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 & 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

Plate Boundaries

Divergent boundaries– where plates move away from each other


Plate boundaries1

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 boundaries2

Plate Boundaries

Convergent boundaries – where plates collide

2. Two Continental plates –

neither plate is subducted, so both are crumpled and uplifted


Plate boundaries3

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 boundaries4

Plate Boundaries

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

Can you think of an example?


San andreas fault

San Andreas Fault


Causes of plate motion

Causes of Plate Motion

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


Suspect terranes

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 terranes1

Suspect terranes


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