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Earth’s Moving Continents

Earth’s Moving Continents. Ch. 5, Lesson 2 Part 1. Wegener’s Evidence. Land features- looked like pieces fit together, similar coal fields Fossils- fernlike plants and fresh water reptiles Climate- evidence that climate was colder in South Africa and had to be closer to South Pole .

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Earth’s Moving Continents

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  1. Earth’s Moving Continents Ch. 5, Lesson 2 Part 1

  2. Wegener’s Evidence • Land features- looked like pieces fit together, similar coal fields • Fossils- fernlike plants and fresh water reptiles • Climate- evidence that climate was colder in South Africa and had to be closer to South Pole

  3. Plate Movement Over Time • Pangaea- 260 million years ago • 225 million years ago, Pangaea began to split

  4. How Plates Move • Theory of Plate Tectonics- upper mantle is in slow, constant motion driven by convection currents in the mantle

  5. Mid-Ocean Ridges • An undersea mountain chain where new ocean floor is produced; a divergent plate boundary • Sonar- device that bounces sound waves off objects to determine their distance

  6. Sea-Floor Spreading • Harry Hess- studied mid-ocean ridges and proposed sea-floor spreading • Magma causes sea-floor to spread apart along a mid-ocean ridge. This molten material forms new ocean crust • Ocean floors move like conveyor belts taking the continents with them

  7. Evidence for Sea-Floor Spreading • 1. Molten Material- scientists found strange shaped rocks only formed when magma cools quickly after erupting under water

  8. Evidence for Sea-Floor Spreading • 2. Magnetic Stripes- molten rock cooled and the iron bits lined up in the direction of the magnetic poles

  9. Evidence for Sea-Floor Spreading • 3. Drilling Samples- samples of rock from the ocean floor showed rocks farthest away from the ridge were the oldest and the closest rocks were the newest

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