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  1. 1. Chapter 13: Earth Structure, Earth Materials, and Plate Tectonics Physical Geography Ninth Edition Robert E. Gabler James. F. Petersen L. Michael Trapasso Dorothy Sack
  2. 2. Earth Structure, Earth Materials, and Plate Tectonics
  3. 3. 13.1 Earth’s Planetary Structure <ul><li>Earth’s radius is 6400 km (4000 miles) </li></ul><ul><li>Structure and composition deduced by remote sensing </li></ul><ul><ul><li>Seismic waves </li></ul></ul><ul><ul><li>Seismograph </li></ul></ul><ul><ul><li>P (primary) waves </li></ul></ul><ul><ul><li>S (secondary) waves </li></ul></ul>
  4. 4. 13.1 Earth’s Planetary Structure <ul><li>Seismic Waves </li></ul><ul><li>Earth’s Internal Structure (crust, mantle, outer core, inner core) </li></ul>
  5. 5. 13.1 Earth’s Planetary Structure <ul><li>Earth’s Core </li></ul><ul><ul><li>1/3 of Earth’s mass </li></ul></ul><ul><ul><li>Enormous pressure </li></ul></ul><ul><ul><li>Iron and nickel </li></ul></ul><ul><ul><li>Inner core: Solid </li></ul></ul><ul><ul><li>Outer core: molten lava </li></ul></ul>
  6. 6. 13.1 Earth’s Planetary Structure <ul><li>Earth’s Mantle </li></ul><ul><ul><li>Largest of interior zones </li></ul></ul><ul><ul><li>Solid rocky material </li></ul></ul><ul><ul><li>Less dense than core </li></ul></ul><ul><ul><li>Plastic solid </li></ul></ul><ul><ul><li>Outermost layer behaves like an elastic solid (rigid) </li></ul></ul><ul><ul><li>Lithosphere (upper most mantle and crust) </li></ul></ul>
  7. 7. 13.1 Earth’s Planetary Structure <ul><li>Earth’s Mantle </li></ul><ul><ul><li>Asthenosphere: upper mantle </li></ul></ul><ul><ul><li>Tectonic forces come from movement of Asthenosphere </li></ul></ul><ul><ul><li>Moho discontinuity </li></ul></ul>
  8. 8. 13.1 Earth’s Planetary Structure <ul><li>Earth’s Crust </li></ul><ul><ul><li>1% of Earth’s mass </li></ul></ul><ul><ul><li>Exterior of lithosphere </li></ul></ul><ul><ul><li>Density </li></ul></ul><ul><ul><ul><li>Oceanic crust (basaltic) </li></ul></ul></ul><ul><ul><ul><li>Continental crust (granitic) </li></ul></ul></ul>
  9. 9. 13.2 Minerals and Rocks <ul><li>Minerals </li></ul><ul><ul><li>Building blocks of rocks </li></ul></ul><ul><ul><li>Inorganic </li></ul></ul><ul><ul><li>Naturally occurring </li></ul></ul><ul><li>Rock </li></ul><ul><ul><li>Aggregate (collection) of minerals or an aggregate of the same mineral </li></ul></ul><ul><li>Most Common Elements </li></ul>
  10. 10. 13.2 Minerals and Rocks <ul><li>Minerals </li></ul><ul><ul><li>Distinct and recognizable characteristics </li></ul></ul><ul><ul><ul><li>Hardness </li></ul></ul></ul><ul><ul><ul><li>Luster </li></ul></ul></ul><ul><ul><ul><li>Cleavage </li></ul></ul></ul><ul><ul><ul><li>Tendency to fracture </li></ul></ul></ul><ul><ul><ul><li>Specific gravity </li></ul></ul></ul><ul><ul><ul><li>Geometric shapes </li></ul></ul></ul><ul><ul><li>Chemical Composition </li></ul></ul><ul><ul><ul><li>Silicon, oxygen, and carbon </li></ul></ul></ul><ul><ul><ul><li>Silicates </li></ul></ul></ul>
  11. 11. 13.2 Minerals and Rocks <ul><li>Rocks </li></ul><ul><ul><li>Building material </li></ul></ul><ul><ul><li>Weathered and eroded </li></ul></ul><ul><ul><li>Bedrock </li></ul></ul><ul><ul><li>Regolith </li></ul></ul><ul><ul><li>Outcrop </li></ul></ul><ul><ul><li>3 Major Categories of Rocks </li></ul></ul><ul><ul><ul><li>Igneous </li></ul></ul></ul><ul><ul><ul><li>Sedimentary </li></ul></ul></ul><ul><ul><ul><li>Metamorphic </li></ul></ul></ul>
  12. 12. 13.2 Minerals and Rocks <ul><li>Igneous Rocks </li></ul><ul><ul><li>Molten rock material cools and solidifies </li></ul></ul><ul><ul><li>Magma (below surface) </li></ul></ul><ul><ul><li>Lava (at surface) </li></ul></ul><ul><ul><li>2 Major categories of Igneous: </li></ul></ul><ul><ul><ul><li>Extrusive </li></ul></ul></ul><ul><ul><ul><li>Intrusive </li></ul></ul></ul>
  13. 13. 13.2 Minerals and Rocks <ul><li>Extrusive </li></ul><ul><ul><li>Extrusive igneous rock (volcanic rock): solidifies at surface </li></ul></ul><ul><ul><li>Pyroclastics (fine fragments) </li></ul></ul><ul><li>Intrusive </li></ul><ul><ul><li>Intrusive igneous rock: molten magma solidifies (freezes) </li></ul></ul><ul><ul><li>Also called plutonic rock </li></ul></ul>
  14. 14. 13.2 Minerals and Rocks <ul><li>Chemical Composition of Igneous </li></ul><ul><ul><li>Felsic, Mafic, Dionite, Andesite </li></ul></ul><ul><li>Extrusive: </li></ul><ul><ul><li>Basalt, Andesite, Rhyolite </li></ul></ul><ul><li>Intrusive: </li></ul><ul><ul><li>Gabbro, Diorite, Granite </li></ul></ul>
  15. 15. 13.2 Minerals and Rocks <ul><li>Geometric patterns </li></ul><ul><ul><li>Columnar joints </li></ul></ul><ul><ul><li>Devil’s Postpile, CA and Devil's Tower, WY </li></ul></ul>
  16. 16. 13.2 Minerals and Rocks <ul><li>Sedimentary Rocks </li></ul><ul><ul><li>Accumulated sediment </li></ul></ul><ul><ul><li>Unconsolidated, minerals that have been eroded, transported and deposited </li></ul></ul><ul><ul><li>Clasts </li></ul></ul><ul><ul><li>Clastic </li></ul></ul>
  17. 17. 13.2 Minerals and Rocks <ul><li>Sedimentary Rocks </li></ul><ul><ul><li>Organic sedimentary </li></ul></ul><ul><ul><ul><li>Coal </li></ul></ul></ul><ul><ul><ul><li>Limestone </li></ul></ul></ul><ul><ul><li>Chemical sedimentary rocks </li></ul></ul><ul><ul><ul><li>Dolomite </li></ul></ul></ul>
  18. 18. 13.2 Minerals and Rocks <ul><li>Sedimentary Rocks </li></ul><ul><ul><li>Stratification </li></ul></ul><ul><ul><li>Strata </li></ul></ul><ul><ul><li>Bedding planes </li></ul></ul><ul><ul><li>Unconformity </li></ul></ul><ul><ul><li>Cross bedding </li></ul></ul><ul><ul><li>Fins </li></ul></ul>
  19. 19. 13.2 Minerals and Rocks <ul><li>Metamorphic Rocks </li></ul><ul><ul><li>Changed form due to enormous heat and pressure </li></ul></ul><ul><ul><li>Harder </li></ul></ul><ul><ul><li>Foliation </li></ul></ul><ul><ul><li>Two major Types: </li></ul></ul><ul><ul><ul><li>Foliated (presence of platy or wavy surfaces) </li></ul></ul></ul><ul><ul><ul><li>Nonfoliated (absence of platy or wavy surfaces) </li></ul></ul></ul>
  20. 20. 13.2 Minerals and Rocks <ul><li>Metamorphic Rocks </li></ul><ul><ul><li>Schist </li></ul></ul><ul><ul><li>Gneiss </li></ul></ul><ul><ul><li>Marble </li></ul></ul>
  21. 21. 13.2 Minerals and Rocks <ul><li>Rock Cycle </li></ul><ul><li>Q: What conditions are necessary to change igneous to metamorphic? </li></ul>
  22. 22. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Continental Drift </li></ul><ul><li>Plate Tectonics </li></ul><ul><li>Catastrophism </li></ul><ul><li>Uniformitarian </li></ul>
  23. 23. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Continental Drift </li></ul><ul><ul><li>Idea that continents and other landmasses have shifted </li></ul></ul><ul><ul><li>Wegener </li></ul></ul><ul><ul><li>Pangaea </li></ul></ul><ul><ul><ul><li>Gondwana </li></ul></ul></ul><ul><ul><ul><li>Laurasia </li></ul></ul></ul><ul><li>Q: How has continental movement affected the climates of landmasses? </li></ul>
  24. 24. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Supporting Evidence for Continental Drift </li></ul><ul><ul><li>Radioactive dating </li></ul></ul><ul><ul><li>Paleomagnetism </li></ul></ul><ul><ul><ul><li>Reconstructed locations of continents </li></ul></ul></ul><ul><ul><ul><li>200 mya continents joined together </li></ul></ul></ul><ul><ul><li>Similar fossil reptiles and plants </li></ul></ul>
  25. 25. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Supporting Evidence for Continental Drift </li></ul><ul><ul><li>Glaciation </li></ul></ul><ul><ul><li>Rocks of ancient mountain ranges </li></ul></ul><ul><li>Paleogeographic reconstruction </li></ul>
  26. 26. 13.4 Plate Tectonics <ul><li>Plate Tectonics </li></ul><ul><ul><li>Modern theory to explain movement of continents </li></ul></ul><ul><ul><li>Lithosphere is broken </li></ul></ul><ul><ul><li>Plates move in distinct and discrete units </li></ul></ul><ul><ul><li>Plates Diverge, converge, or move laterally </li></ul></ul><ul><ul><li>7 major plates </li></ul></ul>
  27. 27. 13.4 Plate Tectonics <ul><li>Plate Tectonics </li></ul><ul><ul><li>Q: Does every lithospheric plate include a continent? </li></ul></ul>
  28. 28. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Seafloor Spreading and Convection Currents </li></ul><ul><ul><li>Undersea mapping </li></ul></ul><ul><ul><li>Mid-ocean ridges </li></ul></ul><ul><ul><li>Parallel bands of matching magnetic patterns </li></ul></ul><ul><ul><li>Rocks on ocean floor very young! </li></ul></ul><ul><ul><li>Oldest rocks lie next to continents </li></ul></ul>
  29. 29. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Seafloor Spreading and Convection Currents </li></ul>
  30. 30. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Seafloor Spreading </li></ul><ul><ul><li>Polarity reversals </li></ul></ul>
  31. 31. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Seafloor Spreading </li></ul><ul><ul><li>Convection </li></ul></ul><ul><ul><li>Q: Why is plate tectonics a better name than continental drift for the lateral movement of Earth’s solid outer shell? </li></ul></ul>
  32. 32. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Tectonic Plate Movement </li></ul><ul><ul><li>Pulling apart, pushing together, or sliding alongside </li></ul></ul>
  33. 33. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Plate Divergence (pulling apart) </li></ul><ul><ul><li>Seafloor spreading </li></ul></ul><ul><ul><li>Shallow earthquakes </li></ul></ul><ul><ul><li>Creates new ridges </li></ul></ul><ul><ul><li>Most occur near oceanic ridges (e.g. Iceland) </li></ul></ul>
  34. 34. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Plate Divergence (pulling apart) </li></ul><ul><ul><li>Rift Valley, Africa </li></ul></ul>
  35. 35. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Plate Convergence (pushing together) </li></ul><ul><ul><li>Denser plate forced under lighter plate </li></ul></ul><ul><ul><li>This is known as subduction </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Nazca Plate subducts beneath South America </li></ul></ul></ul><ul><ul><ul><li>Japan </li></ul></ul></ul>
  36. 36. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Plate Convergence </li></ul><ul><ul><li>Deep ocean trenches </li></ul></ul><ul><ul><li>Mountain ranges (ocean-continent) </li></ul></ul><ul><ul><ul><li>Cascades </li></ul></ul></ul><ul><ul><ul><li>Andes </li></ul></ul></ul><ul><ul><li>Islands (ocean-ocean) </li></ul></ul><ul><ul><ul><li>Aleutians </li></ul></ul></ul><ul><ul><ul><li>Kuriles </li></ul></ul></ul>
  37. 37. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Plate Convergence </li></ul><ul><ul><li>Larger Landmasses (continent-continent) </li></ul></ul><ul><ul><li>Continental Collision </li></ul></ul><ul><ul><ul><li>Himalayas </li></ul></ul></ul><ul><ul><ul><li>Tibetan Plateau </li></ul></ul></ul>
  38. 38. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Transform Movement </li></ul><ul><ul><li>Plates slide pass each other </li></ul></ul><ul><ul><li>Examples </li></ul></ul><ul><ul><ul><li>San Andreas Fault, CA </li></ul></ul></ul><ul><ul><ul><li>Ocean plates </li></ul></ul></ul>
  39. 39. 13.3 Continents in Motion: The Search for a Unifying Theory <ul><li>Hot Spots </li></ul><ul><ul><li>Almost stationary molten masses that rise to surface </li></ul></ul><ul><ul><li>Hawaiian Islands </li></ul></ul>
  40. 40. 13.4 Growth of Continents <ul><li>Origin of continents still debated </li></ul><ul><ul><li>Continental shields (ancient crystalline rock) </li></ul></ul><ul><ul><li>Example: Canadian Shield </li></ul></ul><ul><ul><li>Accretion </li></ul></ul><ul><ul><li>Microplate terranes </li></ul></ul>
  41. 41. 13.4 Growth of Continents
  42. 42. 13.5 Paleogeography <ul><li>Paleogeography </li></ul><ul><ul><li>Reconstruct the past environment of a geographical region based on geologic and climate evidence </li></ul></ul><ul><ul><li>Earth History </li></ul></ul><ul><ul><ul><li>Eras </li></ul></ul></ul><ul><ul><ul><li>Periods </li></ul></ul></ul><ul><ul><ul><li>Epochs </li></ul></ul></ul>
  43. 43. 13.5 Paleogeography <ul><li>Q: How has the environment at the location where you live changes through geologic time? </li></ul>
  44. 44. Physical Geography End of Chapter 13: Earth Structure, Earth Materials, and Plate Tectonics

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