Sea-Floor CH 4 Prentice Hall p CH 4 Prentice Hall p Spreading

Harry Hess- American Geologist 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

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

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

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

The Ocean Floor

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

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

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

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

Parts of the Ocean Floor CD Rift Evidence

Convection and Sea