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Homework Help: Density displacement

  1. Jan 19, 2009 #1
    A block of lithospheric crust that is 10 cm (height) by 10cm (width) by 10cm (depth) is "floating" on the athenosphere. 4 cm of the block protrudes up above the interface with the athenosphere and 6 cm is submerged. a) if the density of the athenosphere is 4.5 g/cm^3, what is the mass of the block of crust? b) what is the density of the crust? c) Do you think that it is continental or oceanic crust? d) Would you get the same density if the block of crust was 100km by 100km by 100km and 40km was protruding above the interface?

    Remember an object will displace a volume equal to the weight of the object and that density=mass/volume.

    4 l l
    cml l
    6 l crust l
    c l l
    m l_________________l asthenosphere

    My thoughts are that the density of the block is 60% of the value of the asthenosphere. If that's true, then the density of the block of crust would be 2.7 g/cm^3 and with a volume of 10x10x10. then the mass would be 2700g. The density of continental crust is 2.7 g/cm^3 and oceanic crust is 2.9 g/cm^3, so if my calculation methods are correct that would make this continental crust. And then i'm guessing raising the values while keeping the same proportions wouldn't change the answer correct?
    What are yall's thoughts?
  2. jcsd
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