1. Topic 4 The Moving Crust

2. Layers of the Earth 6-50 km

3. Continental Drift Scientists used to wonder why it looked like the earth’s land masses (continents) appeared like a puzzle, and was it possible they would together? Look at the map of the world……what do you see?

4. Alfred Wegener He did more research on it…..what did he find out? Biological evidence – fossils of the same species were found in totally separate parts of the world. (see p. 383) Wegener’s theory – the continents had gradually moved to their present location. He called this theory…CONTINENTAL DRIFT

5. He found more “ROCK-solid” evidence Geologists had found similar rocks on both sides of the Atlantic Ocean Appalachian Range Britain

6. Trilobites – ancient sea creatures From bottom of the ocean to the top of the world, found in the Himalayas These ancient ocean dwellers are fossilized at the top of the mountain range.

8. What happened then? The Supercontinent PANGAEA

9. Advances in Technology These helped to prove Wegener’s theory SONAR – sound wave technology helped to map the ocean. It amazed everyone There were mountains just like on land. Mid-Atlantic Ridge – a mountain range from North to South along the middle of the Atlantic ocean. (see Google Earth)

10. Sea Floor Spreading Scientists could confirm that the sea floor was spreading when they gathered samples in submersibles. Older rock was further away from the ridge, newer rock was close to the ridge. New Igneous Rock

11. The Conclusion is??? Theory of Plate Tectonics Theory of Plate Tectonics -The earth’s crust is made up of plates, like rafts, and they are always moving on the liquid Mantle.

13. How do plates move? Converging Plates – plates pushing together, against each other. Causes mountain ranges, volcanoes Two continental plates = mountains Continental + oceanic plate = volcanoes Diverging Plates – plates moving/pulling away from each other Causes rift valleys on land, ocean ridges

16. What causes plate movement? Convection currents – Warmer magma rises in the mantle, cooler magma falls