Transcript Chapter 7
Chapter 7 Section 1: Continental Drift Section 2 : Sea Floor Spreading Section 3: Plate Tectonics Section 1 Continental Drift • Alfred Wegener – (1880-1930) – Proposed hypothesis of continental drift – Pangaea Evidence to support C.D. • Continents appear to fit together like a puzzle • Similar fossils have been found on different continents • Remains of warm climate plants in arctic zones and Arctic clues in tropical zones • Similar rock structures found on different continents Section 2: Seafloor Spreading • Magma below Oceanic crust pushes upward and outward forcing the crust into large underwater mountain ranges. • Mid Ocean Ridges Evidence for S.F.S • A theory – Has been proven to occur • Rocks increase in age as one moves away from the midocean ridges. • Continents are measure farther apart by 1 or 2 inches per year old new Section 3: Theory of Plate Tectonics • Combines the hypothesis of continental drift with the theory of sea floor spreading. • Earth’s crust and upper mantle broken into plates. • Shift on layer of molten rock. Earth’s plates • Lithosphere – Earth’s crust and upper mantle – Layer that shifts • Asthenosphere – -like layer of mantle. Earth’s crust • Continental crust – – – – Thick Less dense Older Forms land • Oceanic crust – – – – Thin Dense Younger Forms ocean bottom Plate Boundaries • Divergent – Where 2 plates move apart – Sea floor spreading! – Mid-Atlantic ridge – Rift Valley Plate Boundaries contd. • Convergent Boundary – Where 2 plates move together. – Oceanic / Continental plate collision – Subduction zone. – Volcanic Mtns. – Trench Convergent Boundaries contd. • Continental / Continental crust collision – Forms mountains – India plate moving north / Eurasian plate moving south. • Himalayan Mountains Himalayan Mountains • Oceanic/Oceanic convergent collision. • Creates a trench • Both subducted, but one more than the other Transform Boundaries • 2 plates sliding past each other • Strike-slip faults • Can move in different directions or the same direction at different rates. • San Andreas Fault in California. – Earthquake zone Transform Boundary Causes of Plate movement. • Convection Currents – The heating, rising, cooling, and falling cycle of molten rock in the earth’s mantle. Earth’s Plates and movement. Tectonic Plates and Land Forms.