E4 Review Questions
  1. Match each scientist from column A with the most appropriate item from column B:

      Column A Column B
    3 Beno Gutenberg 1. Density of Earth
    5 Gabriel Auguste Daubrée 2. Crust-Mantle Boundary
    4 Richard Dixon Oldham 3. Mantle-Core Boundary
    2 Andrija Mohorovičić 4. P Wave Shadow
    1 Henry Cavendish 5. Nickel-Iron Core

  2. Why did Cavendish's density calculation indicate that the composition of the Earth’s interior was different from the composition of the Earth’s surface?

    Cavendish’s published value of 5.48 g/cm3 for the average density of the Earth was quite different from the 2.8 g/cm3 value for the average density of rocks on the Earth’s surface. The conclusion was that the interior of the Earth was much denser than the Earth’s surface, and therefore, must have a different composition.
  3. What led Gabriel Auguste Daubrée to speculate that the Earth might have a nickel-iron core?

    Many meteorites were mainly up mainly of nickel-iron, and a similar composition for the Earth’s core would help account for Cavendish’s large value for the density of the Earth.
  4. What led Andrija Mohorovičić to conclude that there was a distinct boundary layer underneath the Earth's crust?

    He noticed that P waves from the same earthquake had different travel times. P waves that traveled deeper in the Earth actually arrived sooner than P waves that had traveled near the Earth’s surface. Mohorovičić concluded that the only way this could happen was if there was a rigid layer below the crust where seismic waves traveled faster because of the increased density of the rock.
  5. Why is the existence of a P wave shadow between 104 degrees to 140 degrees significant?

    It indicates that there was another major change in composition in the Earth’s interior (in this case, the core).
  6. Why does an S wave shadow provide evidence for a molten core?

    S waves cannot travel through liquids.