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)?
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What Fuels The Inner Core?
Submitted by dmpase on Mon, 08/29/2011 - 12:33.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)?