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The Theory of Plate Tectonics

The Theory of Plate Tectonics. What is the difference between a scientific theory and a scientific law?. Scientific laws are true, theories are false. Laws are supported with evidence and theories are not. Theories are supported, but not proven, laws are supported and proven.

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The Theory of Plate Tectonics

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  1. The Theory of Plate Tectonics

  2. What is the difference between a scientific theory and a scientific law? • Scientific laws are true, theories are false. • Laws are supported with evidence and theories are not. • Theories are supported, but not proven, laws are supported and proven.

  3. Scientific Theory • A scientific theory is: • Thought to be true, and supported by a lot of indirect evidence, • Not actually seen (too old, too dangerous, too far away, too slow, too expensive) but they are good clues. • but has not been proven with direct evidence. • Can be seen/touched/done first hand, and can be reproduced over and over, always giving the same result.

  4. What is one example of indirect evidence that scientists use to study the interior of the earth? • Rock samples • Crust • Fossils • Seismic waves

  5. Indirect Evidence Did you say seismic waves? Yes!

  6. Some Scientific Theories Theory of Plate Tectonics The Big Bang Theory The Theory of Evolution

  7. Scientific Law • A scientific law is: • Based on direct evidence, and can be reproduced many times with the same result. Gravity!

  8. Plate Tectonics • Plate tectonics is the study of the processes that have formed the features of the earth. Mountains Mid Ocean Ridges

  9. Plate Tectonics • In the 1800’s Alfred Wegener developed the Theory of Continental Drift. • His theory simply stated that the continents were moving. • But no one believed him. 

  10. Why didn’t anyone believe Wegener? • He didn’t have enough evidence. • People thought a weatherman should stick to forecasting the weather. • Because Wegener wasn’t looking at the fossil evidence. • Because Wegener couldn’t explain HOW the continents were moving.

  11. Plate Tectonics • Harry Hess began mapping the ocean floor during World War II. • He discovered a chain of mountains in the middle of the ocean!

  12. What are these mountain chains called? • Ocean ranges. • Volcanoes. • Mid-Ocean Ridges. • Subduction zones.

  13. Plate Tectonics • Hess’ future work in the 1950’s focused on the Mid-Atlantic Ridge. • By studying the age of the rocks at various places in the ocean, Hess discovered that the Atlantic Ocean was getting bigger. • True or False? He called this phenomenon “Sea Floor Spreading.” • This discovery changed the Theory of Continental Drift into the Theory of Plate Tectonics.

  14. What is the cause of sea floor spreading? • Convection currents in the outer core. • Convection currents in the lithosphere. • Convection currents in the asthenosphere. • Conduction from the core.

  15. Plate Tectonics • The following are lines of indirect evidence that support the Theory of Plate Tectonics • Shape of the continents • Same type and age fossils found separated by oceans. • Same type and age rock found separated by oceans. • Evidence of glacial activity in present-day tropics. • Current plate movement causing earthquakes, volcanoes, and deep sea trenches.

  16. Plate Tectonics • We learned that Earth’s crust was broken into 24 pieces that scientists named Tectonic Plates. • The edges of the tectonic plates are called “boundaries”. • We’ll go into detail about the different types of boundaries later.

  17. Plate Tectonics • The plates have been moving for hundreds of millions of years thanks to convection in the mantle and DENSITY ! • Let’s take a look at where the continents have been, and where they might be moving to!

  18. 255 Million Years Ago

  19. 152 Million Years Ago

  20. 66 Million Years Ago The Extinction of the Dinosaurs

  21. Present Day Position

  22. 50 Million Years From Now

  23. 150 Million Years From Now

  24. 250 Million Years From Now

  25. Let's Review!

  26. What is the difference between a scientific theory and a scientific law? • Scientific laws are true, theories are false. • Laws are supported with evidence and theories are not. • Theories are supported, but not proven, laws are supported and proven.

  27. What is one example of indirect evidence that scientists use to study the interior of the earth? • Rock samples • Crust • Fossils • Seismic waves

  28. Which is not an example of a scientific theory? • Big Bang • Evolution • Gravity • Plate Tectonics

  29. Why didn’t anyone believe Alfred Wegener? • He didn’t have enough evidence. • People thought a weatherman should stick to forecasting the weather. • Because Wegener wasn’t looking at the fossil evidence. • Because Wegener couldn’t explain HOW the continents were moving.

  30. What are the mountain chains found in the ocean called? • Ocean ranges. • Volcanoes. • Mid-Ocean Ridges. • Subduction zones.

  31. What is the cause of sea floor spreading? • Convection currents in the outer core. • Convection currents in the lithosphere. • Convection currents in the asthenosphere. • Conduction from the core.

  32. How many tectonic plates are there? • 12 • 24 • 36 • 365

  33. Earth’s plates have been moving for millions of years and are still moving. • A) True • B) False (I always knew that Wegener was crazy)

  34. THE END

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