GeologyRocksWhat Fuels The Inner Core?
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I was taught a variation on
Tue, 09/20/2011 - 14:18I was taught a variation on your option 1.
Radioactive elements are (generally) heavy therefore under gravity they tend to sink to the centre of the Earth. Add in majority of the heavy elements from the mars-sized impactor which generated the moon and you have a core which is oversized for it's planet. The compression of the radioactive elements creates natural nuclear fission reactors generating the heat which drives mantle convection causing plate tectonics and creating the wonderful science of geology.
I've not heard of your option 2.
Option 3 just seems a little silly. If it were true then the surface would be the hottest place on the planet because it receives the solar energy. The problem is that we know the Earth under our feet is hotter.
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HotCore
Tue, 09/20/2011 - 16:58The Earth is likely engaged in a differential rotation all the way to the core. This means that the surface is lagging behind the deeper parts. The reasons for this are the Moon's drag, the Moon's tidal forces. I saw this on this web site called HotCoreEarth.com He gives his own explanation. But it seems plausible.He says as the Moon kicks the Earth up to a higher orbit, it loses rotation, but it loses more rotation at the surface than at the depths.
In essencee he is saying that over billions of years the difference between core and surface rotation causes friction and this causes heating all the way to core.
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Except that that would cause
Mon, 09/26/2011 - 16:02Except that that would cause higher temperatures closer to the surface because there is a greater area over which the friction would act. It also doesn't explain density differences and solid and liquid layers which are known about through seismology. It would also struggle to explain the convection which is known to occur within the mantle, or account for the 'friction' that this convection should be generating.
Not buying this new theory yet without some more evidence.
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What Fuels The Inner Core?
Submitted by dmpase on Tue, 09/13/2011 - 15:51.What actually fuels the inner core? Can anyone comment here? I've heard several different arguments and I would like feedback on them.
The first line of reasoning goes: (a) If it were only gravitational compression the earth would be solidified by now (a la Mars), (b) the heavy, radioactive elements are more dense than iron, therefore (c) heavy metals sink near the center, form nuclear furnaces and a significant amount of heat comes from radioactive decay. Of course, if it gets too hot, convection can break up the pockets of nuclear material, too. I think this argument sounds the most plausible.
A second line of reasoning follows: (a) most uranium compounds (with the exception of uranium sulfide) are lighter than iron, (b) therefore they float around in the mantle and don't sink to the core, therefore (c) radioactive decay does not play a major role in keeping the core hot and it must be all gravitational contraction.
A third line of reasoning is: (a) solar input nearly matches earth thermal output, so (b) therefore it's all solar. (Gravitational contraction supplied most of the heat until the earth cooled to the point where it was balanced with solar input, and now it's in a state of equilibrium until solar output changes significantly.)
I don't have numbers on any of this so I can't really tell which is right, if any, and which are wrong. The second argument seems wrong to me, though it is also very popular. I imagine chemistry breaks down (e.g., all uranium would be elemental) at temperatures of 7,500 - 10,000 degrees (F) such as are found at the core. Is that not the case, or am I missing something (e.g., the effects of pressure)?