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Learning Goals:. Describe the historical events that led to the Theory of Plate Tectonics. Explain the mechanism for the movement of the plates. Development of the Theory: Alfred Wegener (in 1924).
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Learning Goals: • Describe the historical events that led to the Theory of Plate Tectonics. • Explain the mechanism for the movement of the plates.
Development of the Theory:Alfred Wegener (in 1924) • He proposed the theory of continental drift, based on his observations of similar fossils found on different continents and of the shape of S. America and Africa. They appeared to fit like a puzzle. • He believed that a super continent existed, called Pangaea, before they broke up. • He lacked an explanation of a mechanism for that movement.
Harry Hess (in the 1960’s) • contributed the idea of Sea Floor Spreading • which explained how the plates could move • and provided the mechanism for movement which supported Wegener’s hypothesis.
The Theory of Plate Tectonics was born • Earth’s lithospheric plates rest and move on top of the asthenosphere. • It explains the occurrence of volcanoes, earthquakes and mountain building.
How do the Plates Move? • Convection cells • As hot molten material rises, it splits the crust. • As the material cools, it sinks, pulling the crust with it. This is called the slab pull.
Convection Cell Demo • Fill out the worksheet as you watch and discuss the demonstration on convection cells.
Proof in Science • Imagine you are a scientist trying to prove or disprove life on other planet. • Besides any actual sightings (people, cars, buildings, etc.), give 3 pieces of evidence that would PROOVE life exists on other planets. • Give 3 pieces of evidence that would DISPROVE this theory. • Do you believe there is life out there?