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Theory of Continental Drift and Theory of Plate Tectonics * Essential Questions * What were points of contention with the Theory of Continental Drift? How did the Theory of Plate Tectonics affirm the Theory of Continental Drift? Warm Up: What information can you gather from the Mosquito Creek cartoon? Mosquito Creek Theory of Continental Drift • Proposed by Alfred Wegener • States that the continents were once joined to form a supercontinent • Named the continent Pangaeaall land Continental Drift • Supporting evidence – Continental Puzzle – Matching Fossils – Rock Types and Structures – Ancient Climates Continental Drift • Continental Puzzle – Similar coastlines on opposite sides of South Atlantic Ocean • Counter Argument – Similar coastlines due to erosion Continental Drift-Evidence • Matching fossils – Fossils of same species found on different continents – Exp. Mesosaurus found in South America & Southern Africa • Counter Argument – Land bridges which occurred during glacial period Continental Drift-Evidence • Rock Types & Structures – Mountain belts occur on multiple continents – Exp. Appalachian Mountains Continental Drift-Evidence • Ancient Climates – Glacial evidence in southern Africa and South America – Large tropical swamps in Northern Hemisphere • Coal fields in eastern US, Europe, and Siberia • Counter Argument – Earth was very cold Continental Drift • Major problem – No mechanism of continent movement – Hypothesis rejected Plate Tectonics • Mechanism of continent movement • Solution came from seafloor mapping data • States: Earth’s crust is divided into distinct plates that float on molten interior -> continents move as plates move Plate Tectonic Theory • 13 different plates • Supporting Evidence – Paleomagnetism – Earthquake Patterns – Ocean Drilling – Hot Spots Plate Tectonic Theory-Evidence • Paleomagnetism – Rocks containing ironrich minerals are magnetized – Point towards the magnetic pole of creation – Strips of alternating polarity occur at ocean floor -> seafloor spreading Plate Tectonic Theory-Evidence • Earthquake Patterns – Along ocean trenches 1. Shallow focused earthquakes occur within trench/where descending plate interacts with lithosphere 2. Deep focused earthquakes occur toward mainland/ when oceanic lithosphere plunges into mantle Plate Tectonic Theory-Evidence • Ocean Drilling – Sediment closer to ridges will be younger – Sediments farther away will be older 4 3 2 1 Sediment age increasing 1 2 3 4 Sediment age increasing Plate Tectonics-Evidence Plate Tectonic Theory-Evidence • Hot Spots – Rising plume of mantel material – Melting of rock at/near surface -> volcanics – Plate moves creating successive volcanic mountains/chains Recap 1. The Theory of Continental Drift explains movement of continents over time 2. Theory of Plate Tectonics provides mechanism for movement. 3. Supporting evidence: C-Drift P-Tectonics Continental Puzzle Paleomagnetism Matching Fossils Earthquake Pattern Rock Types and Structures Ancient Climates Ocean Drilling/Ages Hot Spots