I am doing a school project and need to know...
Will the Earth's mantle or core ever cool? If so, how?
Thank you!
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6$\begingroup$ Does Could earth's core lose its heat? answer your question? Or do you need to also know about the mantle cooling too? (although that's likely a similar answer) $\endgroup$– hichris123 ♦Commented May 24, 2016 at 3:04
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$\begingroup$ It's absolutely answered in the question you've linked, but the question isn't exactly the same. Flagged anyway for review by mods. $\endgroup$– Ben MSCommented May 24, 2016 at 3:20
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$\begingroup$ The Earth's core is cooling, and has been cooling for a long, long time. Evidence: The Earth has a solid inner core (which couldn't exist if the core wasn't cooling), and it has a magnetic field (which couldn't exist without a high heat flux through the outer core). $\endgroup$– David HammenCommented May 25, 2016 at 15:23
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Yes. It's kept warm by slowly decaying primordial radioactive elements. They are: Uranium (238) and Thorium (232). The half life of the first is 4.4 billion years, the second around 14 billion years.
They heat the surface even to this date, and it's around 0.2K warmer than if they were absent.
Owing to their continued decay, this temperature differential will decrease .
Extension: On the most popular models (and David Hammen's comment :-) ), Uranium and Thorium are in the crust and mantle, and not in the core. Despite that, their radioactive decay heats the Earth.
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$\begingroup$ Most geophysicists think there is very little uranium and thorium in the Earth's core. Both are incompatible lithophile elements. $\endgroup$ Commented May 25, 2016 at 15:18
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$\begingroup$ @DavidHammen 1) Ok, but chemistry in 6000K and some 100000 bar isn't a little bit different? 2) Any idea, what heats the core then? 3) They are also the heaviest elements, any idea where could they are? 4) What is with their ores? They are mined in large quantities. They are not incompatible? $\endgroup$– peterhCommented May 25, 2016 at 21:55