1/27/2011 C H A P T E R 4 P L A T E T E C T O N I C S. Plate Tectonics. Highest pt=mt Everest, ft, 8848 m. Lowest pt. Marianas trench, -11,000 m

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1 C H A P T E R 4 P L A T E T E C T O N I C S Highest pt=mt Everest, ft, 8848 m Lowest pt. Marianas trench, -11,000 m Plate Tectonics A Revolution in Geology The Plate Tectonic Model 1

2 A Revolution in Geology Continental drift Proposed by Alfred Wegener Slow, lateral movement of continents along Earth s surface The puzzle piece argument Pangaea Continental shelf Continental slope Wegener proposed a supercontinent named Pangaea that split apart with continents moving to current positions. Main evidence was the match of coastlines. Hypothesis was ridiculed by geologists of the day. Plate Tectonics A Revolution in Geology The Puzzle-Piece Argument Evidence of Continental Drift: What is the true edge of a continent? Continent match gets better if you use continental Figure 4.2 shelves instead of modern coasts. 2

3 Evidence of Continental Drift: How well do the continents fit? Figure 4.2 Plate Tectonics A Revolution in Geology Matching Geology and fossils Evidence of Continental Drift: How well do ages match? Figure 4.3 3

4 Evidence of Continental Drift: What evidence did glaciers leave? Figure 4.3 a Glossopteris a 4

5 How well do the fossil records match? Figure 4.4 Plate Tectonics A Revolution in Geology Apparent Polar Wandering Paths Wandering poles? Positions of N pole for N. America and Europe. Since the pole really doesn t move, it means the continents did. If you rotate NA and Europe back together, the paths overlap. Evidence for the movement of the continents. Figure 4.5 5

6 The color bands represent volcanic rocks of the same magnetic polarity and age. They are symmetrical on either side of the mid-atlantic ridge. This shows new crust is formed at the ridge and moves in opposite directions. Figure 4.6 Sea floor spreading Seafloor spreading Each side is a tectonic plate. Figure 4.7 The mid-ocean ridge is a line of volcanoes. This is a vent from one of them spewing gas into the ocean. a 6

7 Direction and velocity of plate movement by GPS measurements a The Plate Tectonic Model Plate tectonic The movement and interactions of large fragments of Earth s lithosphere (i.e. plates) Below lithosphere- asthenosphere Weak due to hot temperature (near melting point) Fault A fracture in Earth s crust along which movement has occurred The Plate Tectonic Model 7

8 Divergent margins A boundary along which two plates move apart from one another Types of plate margins Types of plate margins Convergent margin A boundary along which two plates come together 8

9 Types of plate margins Subduction zone A boundary along which one lithosphere plate plunges into the mantle beneath another plate Collision zone between continents Deep oceanic trenches Arcs of volcanoes Types of plate margins Transform vault A fracture in the lithosphere where two plates slide past each other Earthquakes and plate margins Earthquake Tectonic movement produce pressure and friction. Friction is overcome, the block slips and pent up energy releases with a huge snap Focus Where earthquake begins Epicenter Point on earth s center directly over the focus 9

10 The search for a mechanism Earth s internal heat Conduction Slow release of heat Convection A form of heat transfer in which hot material circulates from hotter to colder regions, looses its heat, and then repeats the cycle 10

11 Hawaiian Islands Amazing Places: The Hawaiian Islands 11