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 mid-ocean 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 Asthenosphere Earth’s crust and upper mantle Layer that shifts Asthenosphere -like layer of mantle.

Earth’s crust Continental crust Oceanic 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.