why is the earth's core still molten?

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paul.fr

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why is the earth's core still molten?
« on: 09/09/2007 18:06:52 »
Why has it not cooled down to a solid? Is it actually cooling down at all?

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Offline Bored chemist

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why is the earth's core still molten?
« Reply #1 on: 09/09/2007 20:29:06 »
Among other things it is kept warm by the energy released from radioactive decay of things like uranium.
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Offline Jimbob12321

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why is the earth's core still molten?
« Reply #2 on: 09/09/2007 20:56:26 »
The earths core itself is not actually molten it is made of solid iron but the outer core is molten. There are two reasons that the earths outer core is molten and cooling down so slowly. One is the continual decay of radioactive elements and the other is the heat from when the planet was initially created. The reason it stays so hot and cools down so slowly is because of convection where the mantle keeps the heat from the core in.

Take mars for instance, the reason why it is such a hostile planet is because its core has cooled down so it is solid. 

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Offline Bass

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why is the earth's core still molten?
« Reply #3 on: 09/09/2007 21:02:55 »
Actually, the inner core is solid- only the outer core is molten.  
Potassium is far more plentiful than uranium, and is thought to contribute much more heat due to radioactive decay.  Also, intense pressure helps preserve the heat, but without radioactivity, the earth would have cooled eons ago.  
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another_someone

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why is the earth's core still molten?
« Reply #4 on: 09/09/2007 21:05:58 »
The reason it stays so hot and cools down so slowly is because of convection where the mantle keeps the heat from the core in.

I would have thought that convection would cool it down rather than protect it from cooling.  The problem being that the molten outer core, I would have thought is sufficiently viscous that convection is a very slow process.

The other factor you have not mentioned is the heat generated by compression under the force of gravity.

Take mars for instance, the reason why it is such a hostile planet is because its core has cooled down so it is solid. 

One question this leads to is whether there are signs on Mars that the planet has shrunk as it cooled, and so causing observable features in the crust?

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Offline Ophiolite

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why is the earth's core still molten?
« Reply #5 on: 12/09/2007 12:09:25 »
I'm with another someone on this point. The convection within the mantle does actively cool the planet, it just isn't very efficient. the mantle is solikd, so the movement is very slow. If I recall correctly the heat loss from the Earth over an entire year is only sufficient to melt a layer of ice less than 1cm thick.
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