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Drifting Continents

Drifting Continents. Did Pangea Exist?. The Theory of Continental Drift. A German scientist named Alfred Wegener formed the hypothesis that the continents had moved! He proposed that all the continents had once been joined together in a single landmass and have since drifted apart.

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Drifting Continents

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  1. Drifting Continents Did Pangea Exist?

  2. The Theory of Continental Drift • A German scientist named Alfred Wegener formed the hypothesis that the continents had moved! • He proposed that all the continents had once been joined together in a single landmass and have since drifted apart. • Wegener named this supercontinent Pangea.

  3. The Theory of Continental Drift • Wegener’s idea that the continents slowly moved over the earth became known as continental drift. • Unfortunately Wegener could not provide a satisfactory explanation for the force that pushed or pull the continents. Therefore most geologists rejected his idea.

  4. Evidence of Continental Drift • Evidence from landforms: • Mountain ranges and other features on the continents provided evidence for continental drift. • Mountain ranges in South Africa line up with mountain ranges in Argentina.

  5. Evidence for Continental Drift • Evidence from fossils • A fossil is any trace of an ancient organism that has been preserved in rock. • Glossopteris fossils have been found in rocks in Africa, South America, Australia, India, and Antarctica.

  6. Evidence for Continental Drift • Evidence from climate • Fossils of tropical plants have been found too far south to have survived. • Glacier deposits are found too far north to have existed. • These clues provide evidence that continental drift really happened.

  7. Rejection!! Even with the evidence, most scientists rejected Alfred Wegener’s theory for about a half a century, from the 1920s to the 1960s.

  8. Convection Currents in the Mantle • https://www.youtube.com/watch?v=Kpoko_l34ZE WATCH VIDEO • Energy is constantly on the move! • The movement of energy from warmer object to a cooler object is called a heat transfer • There are three types of heat transfer: radiation, conduction, and convection.

  9. Radiation • Radiation is the transfer of energy through empty space. • Heat transfer by radiation takes place with no direct contact between a heat source and an object.

  10. Conduction • Heat transfer by direct contact of particles is called conduction. • When your hands touches a metal spoon sitting in a boiling pot of soup, the heat from the bottom of the pot is transferred to you hand by conduction.

  11. Conduction

  12. Convection • Convection is the transfer of heat by the movement of a heated fluid. • Convection deals with density. • Density is the measure of how much mass is there in a volume of a substance.

  13. Convection • When a liquid or gas is heated, the particles move faster and the density decreases. • As the fluid becomes cooler, its density increases. • As density increases, the fluid sinks. • Heat Rises!!

  14. Convection • The heating and cooling of the fluid, changes in the fluid’s density, and the force of gravity combine to set convection currents in motion. • Without heat, convection currents will eventually come to a stop.

  15. Convection in the Earth’s Mantle • The heat source for these convection currents in the mantle comes from the heat of the Earth’s core.

  16. Radiation, Conduction, and Convection

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