Plate Tectonics

1. History of the idea: Continental Drift
        a. Alfred Wegner (1880-1930)
                i. Supported the idea that all continents were once bound together
                ii. Supercontinent was called Pangaea
        b. Evidence of Continental Drift
                i. Continental Jigsaw
                ii. Fossils
                iii. Rock Types

2. Continental Jigsaw
        a. Wegner was criticized about the idea
                i. "Wegner is tied down by awkward, ugly facts."
                ii. Accusations were made, taking into account the shape of the continents

3. Fossils
        a. Wegner claimed there were fossils of the same species oceans apart
                i. Mesosaurus was one of the fossils found
                ii. Critics said that the animal could've swum but the body shape of the animal is not water suitable

4. Rock Types
        a. 2.2 billion year old igneous rock in Brazil matched a 2.2 billion year old igneous rock in Africa
        b. Supports that the continents were once joined for two continents to have the same type of rock

5. Mechanism
        a. Convection currents within the Earth's mantle move the plates and the lithosphere
        b. Movement of Convection Currents
                i. Heated mantle material closer to the core of the earth is less dense, causing it to rise and particle movement slows
                ii. Cool mantle material right underneath the crust becomes denser and sinks and particle movement quickens
                iii. This causes a circular cycle/motion in which the mantle of Earth is always moving, causing plates to move as well

6. Types of Boundaries
                i. Convergent
                ii. Convergent - continent to continent
                iii. Divergent
                iv. Transform

7. Convergent
        a. When an oceanic plate meets a continental plate, the less dense oceanic plate dives down underneath the continental plate
        b. The material of the continental plate is melted again into magma
        c. These boundaries can create earthquakes and volcanoes

8. Convergent - continent to continent
        a. When continental plates converge, the lithosphere is pushed upward to become mountain chains
        b. This is what is happening where India is running into Asia

9. Divergent
        a. When two plates move away from each other, new mantle material rises from the center of the Earth to fill space
        b. This is what is happening at the mid-ocean ridge

10. Transform
        a. Sometimes plates slide past each other horizontally
        b. Because this movement is not always smooth and even, these boundaries are often subject to an earthquake

11. Magnetism of Rocks on Ocean Floor
        a. Iron was originally in lava but as it cooled, it aligned with the Earth's magnetic field
        b. Provides a clear symmetric record of field reversals