1. Sea-Floor Spreading

2. Who developed the theory of continental drift? A)Wegener B)Einstein C)Beethoven D)Alexander Graham Bell

4. Tube Worms - live in the Pacific Ocean about one mile deep near the hydrothermal vents.

6. Who is this? A)Mr. Crabbs B)Spongebob C)Plankton

7. .

9. Worms & Crab

10. 1. Describe the mid-ocean ridge. It is the longest chain of mountains in the world (more than 50,000 km) on the ocean floor.

11. Mid-Ocean Ridge

12. 2. What device is used to map the ocean floor? SONAR (sound, navigation, & ranging) SONAR Simulation

13. Yes or No SONAR stands for Sound, Navigation, and Ranging

14. Harry Hess An American geologist who studied mid-ocean ridges. He suggested that the ocean floors move like conveyor belts, carrying the continents along with them.

15. Who’s theorized about seafloor spreading? A)Harry Hess B)Alfred Wegener

16. 3. Explain the process of Sea-Floor Spreading At the mid-ocean ridge, molten material rises from the mantle and erupts. It spreads out, pushing older rock to both sides of the ridge.

18. 4. What evidence supports Sea- Floor Spreading? A. Evidence # 1 Molten Material Explanation: Pillow lava has been found along the mid-ocean ridge.

19. Submersible Recovery The submersible, Alvin, found strange rocks shaped like pillows or like toothpaste squeezed from a tube. Such rocks can form only when molten material hardens quickly after erupting under water.

23. B. Evidence # 2 Magnetic Reversals Explanation: Iron-bearing minerals in the rock of the ocean floor hold a record of reversals in Earth’s magnetic field. The pattern of reversals is the same on both sides of the ridge. Seafloor Spreading Simulation

24. Magnetic Stripes

25. C. Evidence # 3 Drilling Samples. Explanation: Younger rocks were found in the center of the ridge, older rocks were found farther away from the ridge at the trenches. Glomar Challenger

27. 5. What are deep-ocean trenches? Trenches are deep under water canyons that form where the oceanic crust bends downwards.

29. 6. Explain the process of Subduction. A process where the old ocean floor sinks beneath a deep-ocean trench and back into the mantle. Subduction Simulation

30. Subduction

32. 7. Why is the Pacific Ocean shrinking? The trench swallows more oceanic crust than the mid-ocean ridge can produce.

33. 8. Why is the Atlantic Ocean expanding? There are only a few short trenches around the Atlantic Ocean so the spreading oceanic crust has nowhere to go. Wilson's Cycle Simulation

34. In conclusion, A)Hess’ theory supports Wegener’s theory B)Wegener’s theory supports Hess’ theory C)Each are independent theories that stand on their own