Continental Drift Theory Flaws

2. Continental Drift Theory Flaws • 1st What force could push large mass over great distances • 2nd How the continents could move were through something solid like earth’s crust • They questions were the reasons why Wegener’s theory was rejected until the 1950s

3. Seafloor Spreading • Until 1900’s most people believed • that the oceans floors were flat • Ocean floor was not changing • Ocean floor was older than continental crust War and Technological advancement changed all misconceptions

4. WWII Sub Warfare • Sonar tech was improved in order to create detailed maps and way to navigate • Magnetometers: device that detect small changes in magnetic fields, towed behind boats to locate enemy subs • Data from these sources revealed vast underwater mountain chains called ocean ridges and deep sea trenches • Text p 474 figure 17.8

5. Ocean Rocks & Sediment Rock Analysis • The age of the rocks varies and the variations were predictable • Samples near the ocean ridges were younger than the samples taken near the trenches..

6. Ocean Rocks & Sediment Sediment Analysis • Thin layers of sediment compared to continents • Thickness of sediment increased with distance from an ocean ridge

7. Seafloor Spreading • Theory that explains how new ocean crust is formed at ocean ridges and destroyed at deep sea trenches • Vital key that supports Wegener’s continential drift theory

8. In Class Activity • Turn to p 477 figure 17.13 • P. 478 read Visualizing Seafloor Spreading

9. ANY QUESTIONS?