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What is the total Earth's interior energy budget?

  • What is the heat flux per m2 that warms the Earth surface because of the Earthy's internal heat.
  • How much of that heat is replenished from the radioactive decay?
  • How much of that heat is replenished from Moon's tidal forces?
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  • $\begingroup$ Internal heat is per m^3, surely? $\endgroup$ – Semidiurnal Simon Oct 13 '14 at 10:38
  • $\begingroup$ I meant the heat flux out through the surface, not the total energy per volume. $\endgroup$ – Irigi Oct 13 '14 at 11:21
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If you see wikipedia here: en.wikipedia.org/wiki/Earth's_internal_heat_budget

They have a nice summary of the answer I think you are looking for:

The flow of heat from Earth's interior to the surface is estimated at 47 terawatts and comes from two main sources, the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust and the primordial heat left over from the formation of the Earth. Earth's internal heat powers most geological processes and drives plate tectonics. Despite its geological significance, this heat energy coming from Earth's interior is actually only 0.03% of Earth's total energy budget at the surface, which is dominated by 173,000 TW of incoming solar radiation.

You can divide by the surface area of the Earth to get your rate per square meter.

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  • $\begingroup$ Thank you for your answer! Is it also known how much of the internal heat flux comes from: Initial heat from planetary formation, tidal forces from the Moon, Radiactive decay? $\endgroup$ – Irigi Oct 20 '14 at 9:41
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    $\begingroup$ @Irigi The links says: "Chemical and physical models give estimated ranges of 15–41 TW and 12–30 TW for radiogenic heat and primordial heat, respectively, and recent results indicate their contributions may be roughly equal." I don't know how tidal forces would compare, but presumably are much smaller. $\endgroup$ – farrenthorpe Oct 20 '14 at 18:17
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According to Towards closing the window on strongly interacting dark matter: Far-reaching constraints from Earth’s heat flow PHYSICAL REVIEW D 76, 043523 (2007) and references cited therein, the heat flux from Earth's interior to the surface is $44.2 \pm 1$ terawatts, or $0.087 \pm 0.002 W/m^2$.

Of the 44.2 TW, 40% is attributable to radioactive decay of uranium and thorium.

The remainder is usually attributed an unknown amount from potassium decay and cooling from an initial high temperature; however, it cannot be ruled out that a significant fraction is from interaction of dark matter with Earth.

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I calculated the tidal heating of the Earth from the conservation of angular momentum (total angular momentum of Earth-Moon system remains constant) and the fact that the Moon drifts away with rate 3.8 cm / year. The resulting heating is approximately 3.2 TW, which finishes the list. Combining the answers from DavePhD and farrenthorpe and Wikipedia, the total budget seems to be:

  • Radioactive decay: 15-41 TW
  • Residual heat: 12-30 TW
  • Tidal heating: 3.2 TW
  • Total: 44.2 TW

I also found a nice overview here.

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    $\begingroup$ The 44.2 TW value is based upon temperature measurements in thousands of bore holes, so I think it excludes tidal heating of ocean and atmosphere as being above the solid surface. $\endgroup$ – DavePhD Oct 22 '14 at 11:10

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