How do we know the structure of the Earth's core?

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Offline chrissylynn

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how do we really know that the Earth's core is molten? how do we know what we have "discovered" is the middle of the earth? how do we know if no one has ever seen it or dug that deep of a hole? all Ive heard about is people sending or receiving some sort of sound waves..how does that show us whats there?

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« Last Edit: 22/10/2008 08:53:00 by chris »

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Offline Bass

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Re: How do we know the structure of the Earth's core?
« Reply #1 on: 20/10/2008 06:41:11 »
Great question- and you're right, all of our evidence is indirect.

That evidence indicates that inner core (or true core of the earth) is solid nickel-iron alloy surrounded by a molten nickel-iron outer core.

What evidence? - the mass of the earth, it's heat, the magnetic field, the composition of meteorites, and especially seismic (not sound) waves.  Seismic waves speed up, slow down, are stopped or are deflected by the different layers inside the earth. 

Certain seismic waves are attenuated (stopped) when they encounter fluid (molten) layers.  Measuring the speed and deflection of other seismic waves suggest the core is composed of two layers, an outer molten layer surrounding an inner solid sphere. 

The magnetic field is difficult to generate without the dynamo created by the molten outer core. 



« Last Edit: 20/10/2008 06:42:45 by Bass »
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Offline JimBob

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Re: How do we know the structure of the Earth's core?
« Reply #2 on: 21/10/2008 03:15:53 »
Oh my gosh, geophysics - I should transfer this to the physics section but can't Justify it.
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline Evie

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Re: How do we know the structure of the Earth's core?
« Reply #3 on: 21/10/2008 15:50:52 »
JimBob, NOOOOOOOOOOOOOOOOOOOOOOO!!!!!

We get few enough threads in the geology section, and you would trade one off just because it has to do with a little geophysics?  [;)] [;)]
====================================================
"There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy."
Hamlet
Act I, scene 5

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Offline Bass

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Re: How do we know the structure of the Earth's core?
« Reply #4 on: 22/10/2008 01:35:41 »
Oh my gosh, geophysics - I should transfer this to the physics section but can't Justify it.

Actually, they do it with mirrors.  Maybe this thread should be moved to "That CAN'T Be True!"
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Offline chrissylynn

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Re: How do we know the structure of the Earth's core?
« Reply #5 on: 22/10/2008 02:27:52 »
thanks for the info

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Offline JimBob

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How do we know the structure of the Earth's core?
« Reply #6 on: 22/10/2008 19:39:34 »
JimBob, NOOOOOOOOOOOOOOOOOOOOOOO!!!!!

Dang! You would think that I had said the earth was flat (which it is, as we all know.)

The mind is like a parachute. It works best when open.  -- A. Einstein