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Chapter 4 – PLATE TECTONICS

Chapter 4 – PLATE TECTONICS. A Revolution in Geology. Introduction Continental drift Proposed by Alfred Wegener Pangaea Puzzle piece argument S. America & Africa. Matching Geology. Matching rocks Rock ages Radiometric dating Rock sequence correlation Continuous mountain chains.

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Chapter 4 – PLATE TECTONICS

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  1. Chapter 4 – PLATE TECTONICS

  2. A Revolution in Geology Introduction Continental drift Proposed by Alfred Wegener Pangaea Puzzle piece argument S. America & Africa

  3. Matching Geology Matching rocks Rock ages Radiometric dating Rock sequence correlation Continuous mountain chains

  4. Matching Geology Glacial evidence Striations & direction of ice movement

  5. Matching Geology Matching fossils Fossil record matches Glossopteris: ancient tree with large seeds found on several continents Mesosaurus: small reptile found in Brazil & S. Africa

  6. Apparent Polar Wandering Paths Paleomagnetism Study of Earth’s past polarity Apparent polar wandering Magnetic poles moved

  7. Seafloor Spreading Missing clue: Seafloor spreading Seafloor splits & moves apart along mid-ocean ridge Forms new oceanic crust along ridge

  8. The Plate Tectonic Model Plate tectonics Movement & interactions of large fragments (i.e. plates) of Earth’s lithosphere (i.e. crust & upper mantle) Asthenosphere “Weak sphere” due to hot temperatures Isostasy Relationship between lithosphere & asthenosphere Balance of gravity & buoyancy

  9. Types of plate margins Divergent boundary Plates move away from each another Creates crust

  10. Types of plate margins Convergent boundary Plates come together (i.e. collide) Destroys crust

  11. Types of convergent plate margins “Subduction” zone 1 plate plunges into mantle beneath another plate 1 or 2 ocean plates involved Ocean plates = higher density (heavier) due to composition (basalt) Continents = granite (less dense) Ocean trenches & volcanic arcs “Collision” zone 2 continental plates collide Form mountains

  12. Types of plate margins Transform boundary 2 plates slide past each other No creation or destruction of crust

  13. Volcanoes, earthquakes& plate margins

  14. Search for a mechanism Earth’s internal heat Conduction Slow release of heat Convection Hot material moves from hotter to colder regions, looses its heat, & repeats cycle Convection cells

  15. The tectonic cycle Tectonic cycle Movements/ interactions where rocks are cycled from mantle to crust & back Includes earthquakes, volcanism, & plate motion; driven by mantle convection Seafloor recycles itself every 200 million years Plate tectonics affects everything

  16. Hawaiian Islands • Mantle plumes • Localized hot areas not along plate boundaries • Move with plate • Eventually become inactive • Hot spot trail • Hawaiian islands

  17. Determining Plate Velocity • Velocity = distance traveled / travel time • Usually expressed in cm / year OR km / million years • Calculating plate velocities • Measure distance (usually in km) • Convert distance to cm (x 100,000) • Divide by travel time (millions of years) • Hint: for travel times, be sure you divide by correct # • I.e. 2.1 million years = 2,100,000 years

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