Marine 11 4-11


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Marine 11 4-11

  1. 1. Under the Sea!! The creation and destruction of the sea floor
  2. 2. Constant state of change <ul><li>Constant creation and destruction through SEAFLOOR SPREADING </li></ul><ul><li>New crust emerges from rift valley in MID OCEAN RIDGE </li></ul><ul><li>Old floor sinks in the TRENCHES </li></ul><ul><li>Whole cycle takes 185 to 200 million years </li></ul><ul><ul><li>Same rate at which your fingernails grow! </li></ul></ul>
  3. 3. Seafloor spreading
  4. 4. Four types of evidence for sea floor spreading <ul><li>Radiometric dating </li></ul><ul><li>Sediment samples </li></ul><ul><li>Rheology </li></ul><ul><li>Magnetometer Data </li></ul>
  5. 5. Radiometric Dating <ul><li>Radiometric dating </li></ul><ul><ul><li>Determine age of rocks by looking at half life </li></ul></ul><ul><ul><ul><li>What is half life? </li></ul></ul></ul><ul><li>Found that seafloor rock is significantly younger than rock in the center of the continents </li></ul><ul><ul><li>Seafloor: 200 million years old </li></ul></ul><ul><ul><li>Continent: 3.9 billion years old </li></ul></ul><ul><li>Why is that? </li></ul><ul><li>Where would the oldest crust be located on the sea floor? </li></ul>
  6. 6. Sediment Samples <ul><li>Coring: drilling holes in the ocean floor for samples </li></ul><ul><ul><li>Level of sediment buildup on top of the hard ridge </li></ul></ul><ul><li>Question: If you know that the youngest ocean floor is near the mid ridge and older floor is near the trenches (continents) which section of the ocean would you expect to have the most sediment? </li></ul><ul><li>Alvin </li></ul>
  7. 7. Rheology <ul><li>Rheology: Study of how matter flows </li></ul><ul><ul><li>Measure the temperature of the ocean water </li></ul></ul><ul><li>Where do you expect the temperature to be higher? Near the trenches or ridge? </li></ul><ul><li>Temperature of water decreases as you move away from the ridge. </li></ul>
  8. 8. Magnetometer Data <ul><li>Magnetometer : measures the polar orientation and intensity of magnetism of minerals </li></ul><ul><ul><li>1961 studied the polar orientation magnetism of seafloor basalt </li></ul></ul><ul><ul><ul><li>Minerals are often magnetic and align themselves to the poles as they settle. </li></ul></ul></ul><ul><li>Found a pattern </li></ul><ul><ul><li>Earth reverses its magnetic poles and the minerals reflected the switch! </li></ul></ul><ul><ul><li>Switched about 10 times over 4 million years. </li></ul></ul>
  9. 9. Hydrothermal Vents <ul><li>Found on the ocean floor well below the photic zone </li></ul><ul><ul><li>No sunlight </li></ul></ul><ul><li>Many unique life forms: clams, giant tubeworms, crustaceans </li></ul><ul><li>How can life survive down there? </li></ul><ul><ul><li>Heated vent provides adequate temp for productive ecosystems </li></ul></ul><ul><ul><li>High levels of dissolved hydrogen sulfide </li></ul></ul><ul><ul><ul><li>Chemosynthesizers </li></ul></ul></ul>
  10. 11. Plate Tectonics <ul><li>Seafloor spreading : explanation of how continents spread </li></ul><ul><li>Explanation for Island formations away from plate boundaries! </li></ul>
  11. 12. Hot Spots = Island Chains <ul><li>Hot Spots: areas within mantle where thermal plumes cause magma columns to push up intensely, breaking through crust </li></ul><ul><ul><li>Hot spots do not move because they are located within mantle </li></ul></ul><ul><ul><li>The plate moves over the hot spot over millions of years forming islands in chains </li></ul></ul>
  12. 14. Types of Boundaries
  13. 15. Divergent Boundary <ul><li>Divergent Boundary: two plates are moving apart </li></ul><ul><ul><li>Creation of new sea floor </li></ul></ul>
  14. 16. Convergent Boundary <ul><li>Convergent Boundary: two plates are pushed together </li></ul><ul><ul><li>Oceanic - oceanic convergence </li></ul></ul><ul><ul><li>Continental-continental convergence </li></ul></ul><ul><ul><li>Oceanic - continental convergence </li></ul></ul>
  15. 17. Types of Boundaries Diagrams
  16. 19. Convection <ul><li>Convection in the mantel drives seafloor spreading and continental drift </li></ul><ul><ul><li>Vertical circulation pattern in a gas or liquid cause by hot material rising and cold material sinking </li></ul></ul>
  17. 20. Pangea <ul><li>Pangea In Action </li></ul>
  18. 21. Changes are still happening today! <ul><li>Florida and the Gulf of Mexico </li></ul><ul><ul><li>Changes in land mass due to </li></ul></ul><ul><ul><ul><li>Continental spreading </li></ul></ul></ul><ul><ul><ul><li>Rising ocean levels </li></ul></ul></ul><ul><ul><li>Formed about 300 million years ago and still forming! </li></ul></ul><ul><li>Andes are still forming </li></ul><ul><li>Pacific Ocean is getting smaller </li></ul>
  19. 22. Florida then and now