Part II The rest of the Story!

  About 20 years after Wegener’s death, the missing mechanism was discovered. Several scientist were mapping the middle of the Atlantic ocean and notice a ridge ( a steep mountain chain with a narrow valley in the center). The sediments near the ridge were thinner and younger than the sediments farther away form the ridge. Mid Ocean Ridges

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  In 1950’s, a geologist named Harry Hess suggested a new hypothesis. It was called SEA FLOOR SPREADING.  Hess suggested that the sea floor was moving, if this were true, then the continents would be moving also.  Evidence to support Hess’ idea was discovered in the 1060’s. Sea Floor Spreading

  The magnetism of the rocks told the story. As magna hardens, the iron rich minerals align with the earth’s magnetic field. Evidence: 1. Paleomagnetism

  Scientist have dated rocks with magnetic polarity and found that the Earth’s magnetic field has not always pointed North!! ( Who knew) A  All rock with magnetic fields pointing north are said to have normal polarity; rocks with magnetic fields that point south have reversed polarity.

  Scientist also noticed a striped magnetic pattern on one side of a mid-ocean ridge is mirror image of the striped pattern on the other side of the ridge

  The patterns indicate that new rock forms at the center of a ridge and then moves away from the center in opposite directions.  This supports sea floor spreading and Wegener’s idea that the continents are drifting. What does all of this mean??

  Check out the youtube video on sea floor spreading.  Complete the concept map for section 10.1