Theory of Plate Tectonics Page 248

Wegener’s Continental Drift New evidence = new ideas Better maps = Continental Drift 1915 – Alfred Wegener Continental Drift hypothesis Continents had once been joined to form a single supercontinent Pangaea = “all land”

Wegener’s Evidence The Continental Puzzle Matching Fossils Shorelines of new maps suggest South America and Africa were once joined Matching Fossils Fossils found of organisms in S. America and Africa are identical P 249

Wegener's Evidence 3. Rock Types and Structure The Continents exhibit same Rock types across the Atlantic Ocean When joined back together Appalachian Mountains are continuous with Caledonian Mountains in Scandinavia

Wegener’s Evidence Ancient Climates Ancient glaciers leave gashes in rocks after they recede We see the common gashes exhibited in India S. America Africa Australia This suggests they were all a part of the same land mass at one point

Wegener Rejected Although the evidence was compelling Wegner had no mechanism to explain how the continents drifted apart Suggested the Moon was tearing the crust apart Physicists quickly attacked that idea and rejected the whole lot.

Theory of Plate Tectonics Theory = Constructed to Explain Predict Master Phenomena = give mechanisms to explain events = model of reality More evidence = better theories

Theory of Plate Tectonics New Data by 1968 Study the Ocean Floor Earth’s Magnetic Field Earthquake activity Volcano activity In light of new evidence of Earth’s makeup Wegener’s evidence Theory of Plate Tectonics is best natural explanation and model of how the Earth moves