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Sea-Floor Spreading

Sea-Floor Spreading. Blue Ridge Middle School 8 th Earth Science. Tube Worms - live in the Pacific Ocean about one mile deep near the hydrothermal vents. Worms & Crab. 1. Describe the mid-ocean ridge.

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Sea-Floor Spreading

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  1. Sea-Floor Spreading Blue Ridge Middle School 8th Earth Science

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

  3. .

  4. Worms & Crab

  5. 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.

  6. Mid-Ocean Ridge

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

  8. 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.

  9. 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.

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

  11. 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.

  12. 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

  13. Magnetic Stripes

  14. 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

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

  16. 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

  17. Subduction

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

  19. 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

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