1. Sea-Floor CH 4 Prentice Hall p.123-129 CH 4 Prentice Hall p.123-129 Spreading

2. Harry Hess- American Geologist 1960- Proposed Sea-Floor Spreading – The process that continually adds new material to the ocean floor. – Occurs at the mid-ocean ridge, new material rises from the mantle and erupts. The molten material spreads out pushing older rock to the side. Sea-Floor Spreading CD Rift Evidence

3. Occurs at the mid-ocean ridge, new material rises from the mantle and erupts. The molten material spreads out pushing older rock to the side. Sea-Floor Spreading CD Rift Evidence

4. 1900’s Scientists Mapped the Ocean Floor Used Sonar- a device that bounces sound waves off of underwater objects and records echoes of the sound waves. Climate Mapping the Ocean Floor

5. Climate Mapping the Ocean Floor Mapped the Mid-Ocean Ridge – East Pacific Rise – Mid-Atlantic Ridge Rift Valley, a central valley twice as deep as Grand Canyon

7. The Ocean Floor

8. Alvin- a submersible unit traveled to the central valley of the mid-ocean ridge. – Found Pillow Lava Indicates that new molten material has formed. It cooled quickly underwater Molten Material

9. Magnetic Reversals Earth has a Magnetic North and a South Pole The poles have reversed in the past. The reversals are recorded in the igneous rock. – Serve as a record of the magnetic field. CD Rift Evidence

10. Magnetic Reversals Basalt contains iron The bits of iron line up in the direction of the poles. When the rock hardens completely, the direction of the poles is recorded in the rock. – Permanent “magnetic memory” CD Rift Evidence

11. Glomar Challenger- A drilling Ship – Drilled through 6km of water. – Determined that the age of the rock was younger at the ridge and older away from the ridge. – Shows that sea floor spreading is taking place. Drilling the Ocean Floor CD Rift Evidence

12. Parts of the Ocean Floor CD Rift Evidence

13. Convection and Sea