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This review explores the theory of plate tectonics and continental drift, including Alfred Wegener's proposed theory in 1912. It discusses evidence from rock formations, fossils, and paleoclimatology, as well as the rejection and subsequent acceptance of the theory. The advancements in technology and evidence supporting the theory of plate tectonics, such as magnetometry, sonar, and radiometric dating, are also discussed. The major plates of the world, mechanisms of plate movement, and different types of plate boundaries are explained, including divergent, convergent, and transform boundaries. The identification of specific boundaries, like the Iceland Rift, oceanic-continental, oceanic-oceanic, continental-continental, and transform boundaries, is highlighted.
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Alfred Wegener (1880-1930) - German astronomer/meteorologist - Proposed Continental Drift in 1912
Theory of Continental Drift - Continental Drift • Earth’s continents had once been joined as a single landmass called Pangaea “all lands” • Broke apart 220 million years ago.
Evidence from Rock Formations - Same rocks are found in the Appalachians, Greenland and Europe.
Evidence from Fossils - Wegener found similar fossils of different land animals and plants on separated continents.
Paleaoclimatology Evidence - Coal • Coal forms from dead swamp plants. • Coal was found in Antarctica, therefore Antarctica must have been closer to the equator at one time.
More Paleaoclimatology Evidence - Glacial Deposits • 290 mya glacial deposits found in Africa, India, Australia, and South America.
Continental Drift was rejected. - Scientists rejected the hypothesis because: • People believed continents and ocean basins were fixed features. • Wegener could not explain what forces could cause a continent to move.
Theory of Plate Tectonics (1960) - Sea-Floor Spreading
New Technology - 1960s Technology: • Magnetometer –map changes in magnetic fields. • Sonar – used to map out the seafloor (found mid-ocean ridge). • Radiometric Dating – ages the rocks.
Theory of Plate Tectonics Evidence • Rock Age • Young Rocks –near ocean ridges. • Older Rocks –near deep-sea trenches • Seafloor Age – oldest part = 180 million years old. Oldest Continental crust = 3.8 billion years old. 2. Paleomagnetism • Investigated in ocean crust. • Shows that iron alignment has switched many times in past due to Earth’s magnetic reversals, supporting movement of continents.
Plate Boundaries - places where tectonic plates interact with one another. Plate Boundaries Three Major Types • Convergent • plates come together. • Divergent • plates move away from one another. • Transform • plates move horizontally past one another
