B2 Review Questions
  1. What two major geologic features about the oceans were discovered as a result of studies that commenced during WWII?
    2. These studies revealed the existence of an underwater ridge of mountains that completely circled the globe. They also revealed the presence of deep sea trenches, usually near the margins of continents or island chains around the Pacific, that had a depth of several kilometers (several miles).

    1. According to these studies, what was the maximum age of the seafloor?
      2. None of the sediment or rock samples taken were older than 180 million years.

    2. Why was this result so significant?
      3. This was significant because the age of the ocean floor was significantly less than the age of continental crust. Continental crust had ages measured in billions of years.

  3. Why is the Curie temperature such a significant property of magnetic materials?
    4. Magnetic materials lose all magnetic properties when the surrounding temperature is above the Curie temperature. As the material solidifies at temperatures below the Curie temperature, the orientation of the Earth’s magnetic poles becomes “frozen” in the material’s magnetic grains.

    1. How did Vine and Matthews explain the phenomenon of magnetic striping on the ocean floor?
      2. They stated that the magnetic striping was due to paleomagnetism. The striping revealed magnetic reversals in the Earth’s poles as oceanic crust moved away from the mid-oceanic ridges by seafloor spreading.

    2. Why was the Vine and Matthews explanation of magnetic striping considered to be so significant?
      3. It was the piece of evidence that finally convinced scientists that seafloor spreading was a reality since it clearly demonstrated that new oceanic crust was constantly being created at the mid-oceanic ridges.