What’s the sea got to do with it?

I can understand what sea-floor spreading is by using evidence from the Continental Drift Theory. 3 IMPORTANT THINGS to LOOK for and KNOW 1. What is seafloor spreading? 2. Which scientist suggested that seafloor spreading supported the Continental Drift Theory? 3. How does Seafloor Spreading support the Continental Drift Theory? Mid-Ocean Ridges ● What are they? Mid-Ocean Ridges curve like the seam of a baseball along the Earth’s sea floor. They are very similar to mountains and valleys in the ocean.

Sonar Sonar - short for Sound Navigation and Ranging, helps to explore and map the ocean because sound waves travel farther in the water than do radar and light waves. Sonar A device that The time it takes bounces sound waves for the echo to off underwater arrive indicates objects and then the distance from records the echoes the object. of these sound waves.

Harry Hess ** ● The mapping of mid-ocean ridges made scientists curious to know more about them by trying to explain how they are formed. ● Harry Hess, an American geologist was curious about mid-ocean ridges. Harry Hess ● He began to think about the ocean floor in relation to the problem of continental drift. ● In the 1960’s Hess suggested that the continents do move in a process called sea-floor spreading. Sea-floor Spreading Sea-Floor Spreading The sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added.

As a result, the ocean floors move like conveyor belts, carrying the continents along with them. Sea-Floor Spreading ** Molten material erupts through the valley that runs along the center of some mid-ocean ridges. This material hardens to form rock on the ocean floor. Stop and Think? So, what happens to the rock along the ridge when new molten material erupts? Evidence of Seafloor Spreading**

Several types of evidence support Hess’s theory of seafloor spreading.

★ Eruptions of Molten Material ★ Magnetic Strips in rock of the ocean floor. ★ The ages of rocks themselves. Eruptions of Molten Material ● In the 1960’s, scientists found evidence that new material is indeed erupting along mid-ocean ridges. ● During their deep water dive in a specialized submarine (Alvin) they discovered strange rocks shaped like pillows and toothpaste that had been squeezed out of the tube. Eruptions of Molten Material ● Such rocks only form when molten material harden quickly after erupting underwater. ● These rocks showed that molten material has erupted again and again along the mid ocean ridge. Magnetic Strips in rocks of the ocean floor ● Scientists discovered the rocks that make up the ocean floor lies in a pattern of magnetized “stripes.” Magnetic Strips in rocks of the ocean floor ● The rock on the ocean floor contain bits of iron. When the new molten rock being to harden and take form the bits of iron line up in the direction of the Earth’s magnetic poles giving the rocks permanent “magnetic memory.” The Age of Rocks Themselves ● This proof came from rock samples obtained by drilling into the ocean floor. ● They found that the farther away from a ridge the samples were taken, the older the rocks were. ● The youngest rocks were always in the center of the ridges. In your notebook: Please answer the following question. You must use complete sentences and explain your understanding of the material presented. This will be graded for a 10 point homework grade.

How does seafloor spreading support the theory of continental drift?