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Thread: What evidence do we have that the Earth's core is iron?

  1. #1
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    What evidence do we have that the Earth's core is iron?

    I know that seismic data is one source, but there must be many more lines of reasoning.
    What are some of the other sources of evidence? Thank you in advance.

  2. #2
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    It must be very dense. Not only is the earth as a whole very dense, but it's moment of inertia shows that that density is concentrated in the core.

  3. #3
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    We have some planetary scientists and geologists here who will give better answers, but just filling in for the short term, there is the magnetism, and density of the planet, which IIUC were the earliest indicators that made us think the core was Fe/Ni
    Forming opinions as we speak

  4. #4
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    Plus there's seismology. Knowing the speed at which earthquakes travel through the core gives even more info. This is, of course, very much simplified.

  5. #5
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    Here is the answer from the University of Hawaii's "Ask an Earth Scientist" page.

    - density and mass of Earth
    - measurement of seismic waves to get density and state (solid or liquid)
    - composition of solar system bodies, meteorites
    - direct measurements of composition of crust and mantle; experiment determination of how seismic waves travel through materials of such compositions as a function of pressure
    - Earth's magnetic field
    - "balance sheet" calculations of overall composition minus composition of crust and mantle
    At night the stars put on a show for free (Carole King)

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  6. #6
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    ^
    I was just going to mention meteorites, specifically, iron meteorites. They're the best window we have on planetary differentiation.

  7. #7
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    well starting before the earth

    there was star that went super nova

    how big was that star
    what % became iron
    why is that iron so concentrated in our core

    why do we find gold and other super heavy metals on or near the surface
    should there be a denser clump of gold ect at the very center of the core

  8. #8
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    Quote Originally Posted by nota View Post
    well starting before the earth

    there was star that went super nova

    how big was that star
    what % became iron
    why is that iron so concentrated in our core

    why do we find gold and other super heavy metals on or near the surface
    should there be a denser clump of gold ect at the very center of the core
    I've actually commented on this. It is a similar reason to why we don't find vanes of gold in meteorites.
    There is gold in the core but the amount of gold is to small to overcome the convection that will keep it mixed within the iron nickle medium it finds itself in.
    http://cosmoquest.org/forum/showthre...table-Elements

  9. #9
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    Quote Originally Posted by nota View Post
    why is that iron so concentrated in our core
    The core is mostly iron because iron is by far the most common heavy element in the universe. Other heavy elements are there, but they're overshaddowed by the iron.

    why do we find gold and other super heavy metals on or near the surface
    Because differentiation is not a perfect process. It takes time for heavier elements to settle out in a viscous medium such as molten rock. All of it will not settle out before the crust hardens. Some may be brought back to the surface by volcanism. Also, chemical processes may interfere with differentiation.

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