1. Structure of the Earth and Plate Tectonics
Know the structure of the earth
Evidence of plate tectonics
Driving force of plate tectonics
Know three types of plate boundaries and their features

3. Earth’s Layers
Core: composed of iron with some nickel, – 5000 degrees C
Inner core = solid
Outer core = liquid

4. Mantle: 1800 to 2800 degrees C
Upper layer of mantle = solid and together with the crust forms the lithosphere
Upper mantle below the lithosphere = fluid and is called the asthenosphere.

5. Earth Structure continued…
Crust:
Mostly igneous rock, with large proportions of metamorphic rock and a thin layer of sedimentary rock.
Two types of crust:
Continental – composed mostly of granite rock (light in color).
Oceanic crust – composed mostly of basalt (dark in color)
Note: Oceanic crust is denser than continental crust thus does not float as high on the mantle as the continental crust does.

6. Evidence of Plate Tectonics
Continents “fit” together like puzzle pieces.
Fossils and plant evidence

7. 4. Location of earthquakes and volcanoes
3. Location the Mid- ocean ridge: a continuous chain of submarine volcanic mountains that encircles the globe (like the seems on a baseball).
Sea floor near the ridge is very young, and older moving away from the ridge (due to sea floor spreading).
4. Location of earthquakes and volcanoes
Sea floor also consists of ridges and trenches
Earthquakes cluster around ridges and volcanoes are concentrated near trenches

8. 5. Magnetic bands (anomalies): Magnetism of rocks on the sea floor
About every 700,000 years the earth’s magnetic field reverses direction (polarity reversal)
Cause: movement of material in the earth’s molten core (mostly iron).
Geologists found patterns of magnetic bands in the sea floor running parallel to the mid ocean ridge.

9. Driving Force Behind Plate Tectonics is Heat!
Heat is produced by radioactive decay of unstable isotopes in the crust and mantle!

11. Plate Boundaries Convergent – plates move toward one another
Divergent – plates move away from each other
Transform – plate moves sideways from each other

12. Plate Boundaries

13. Plate Boundaries

14. Divergent Plates

15. Transform Plates
San Andreas
Fault