4.2 The Theory of Plate Tectonics

1. 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

2. Lithosphere & Asthenosphere Lithosphere – made up of the crust and the rigid upper mantle The lithosphere is broken into separate plates that ride on the denser asthenosphere. Asthenosphere – layer of plastic rock; a solid rock that slowly flows(like putty) when under pressure.

3. Plate Boundaries Divergent boundaries– where plates move away from each other

4. 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

5. Plate Boundaries Convergent boundaries – where plates collide 2. Two Continental plates – neither plate is subducted, so both are crumpled and uplifted

6. Plate Boundaries Convergent boundaries – where plates collide 3. Ocean & Ocean – forms deep ocean trench when one plate is subducted; subducted plate melts and forms volcanic chain (Island Arc)

7. Plate Boundaries Transform fault boundaries – forms where two plates are grinding past each other. Can you think of an example?

8. San Andreas Fault

9. Causes of Plate Motion Convection Currents – cycle of warm water rising and cool water sinking

10. 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

11. Suspect terranes