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Plate Tectonics Continental Drift I Alfred Wegener 1915 A. Super continent =Pangaea, What he used to prove his theory 1. Puzzle fit of continents 2. Fossils A .mesosauras (animal) B. glossopteris (plant =fern) 3. Mountain Types/ Rock Record (same age and composition) 4. Evidence of similar climates and glaciers 5. Other evidence a. Coal deposits b. Coral reefs B. Idea was dismissed because- He didn’t have the mechanism to prove how it worked C. Renewed Interest in 1950 1. Sea Floor Spreading - Harry Hess a. Mid Atlantic ridge 2. Paleomagnetism E. Types of Plate Boundaries 1. Divergent= dividing plates a. Mid Atlantic Ridge b. Red Sea c. East African Rift Zone 2. Convergent= plates colliding a. Continent to continent – India / Eurasia b. Continent to ocean- N and S. America / Pacific Coast c. Ocean to ocean = Volcanic islands = Indonesia, Japan, Philippines 3. Transform = sliding side by side in opposite directions- Often associated with the Mid Atlantic Ridge Example: San Andreas Fault line in California F. 1968= Plate tectonics (Name change because the ocean crust moves as well as the continents)) G. Mechanism that moves the plates? Convection Currents occurring in the mantle- heat From the radioactive core rises II Seismic Waves A. Types 1. Primary or P Waves, Push and pull, fastest seismic wave, travels thru solid & liquids 2. Secondary waves or S Waves, side to side, destructive, passes only thru solids 3. Surface Waves, Long Waves or L waves slowest, roll along the surface B. Seismic waves change speed when they reach the crust/mantle boundary = Moho 1. S waves due not travel through the outer core, therefore it must be a liquid