Pangaea – the first super-continent

1. Continental Drift Hypothesis – Wegner believed continents had once been joined, and over time they drifted apart Pangaea – the first super-continent • Alfred Wegner 1912 • Presented early fossil evidence • No evidence to explain how or why continents moved • Continental Drift Theory later developed into the theory of Plate Tectonics

2. Evidence supporting Continental Drift • Continental Puzzle – continents fit together • Matching Fossils - matching fossils (Mesosaurus) on cross ocean landmasses • Mountain chains and rock type – (Appalachian) • Ancient climates – (ice core data, scratched bedrock)

3. Plate Tectonics TheoryEarth's outermost layer, the lithosphere, is broken into 7 large, rigid pieces called plates: the African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates. Several minor plates also exist, including the Arabian, Nazca, and Philippines plates. • plates are moving ~ 5 cm per year in different directions and speeds • The place where the two plates meet is called a plate boundary • Plates are crust and upper mantle

4. Plate Boundaries and Actions • Seafloor spreading produces new lithosphere • San Andreas Fault is an example of a Transform Fault • East African Rift Valley is an example of a divergent plate boundary • Himalayas are an example of convergent continental/continental plates

5. Evidence and Testing for Plate Tectonics • Paleomagnetism – changing patterns of magnetized rocks • Earthquake patterns – link between plate boundaries and earthquakes • Ocean Drilling - age of seafloor sediment • Newest (ridge crests) • Oldest (continental edges) • Hot Spots – show plates move over Earth’s surface (Hawaii)

6. Cause of Plate Motion (tectonics) • Heat convection in the mantle is the basic cause of plate movement • Slab Pull and Ridge Push – downward convective flow of lithosphere (plate boundaries) • Mantle Plumes – upward convective flow (volcanoes, hot-spots)