Heat created by lunar bulge

Question

How much heat is created by the lunar bulge. Is heat transfer fast enough to prevent a constant build up of heat within the Earth?. Can't find references when searching why the earth is molten. REASONS GIVEN ARE 1. Left over heat from creation. 2 friction of heavier material sinking through magma. 3. Un proven theory of radioactivity as the main source of heat. The moons around Jupiter and others are probably active for the same reason.

Answer 1

Hi Craig K.,

You need to specify exactly what you mean by "the lunar bulge". Usually that refers to the tidal ocean level perturbation; because that is a gravitational drag (generates torque) on the Earth it doesn't dissipate heat, by friction for example. I would go with reason (3) for Earth; reason (1) was calculated a long time ago (though not as old as the Earth is!) to have cooled in a few million years, I think it is. And reason (2) has no particular reason to generate much heat -- denser elements may have segregated gravitationally, but remember, as some descend, others must rise! One reason you left out -- dissipation of magnetic field as the outer core magneto currents churn. I don't know how or if anyone tries to calculate that, it's dynamically complex to model.

The moons of Jupiter are generally thought to be heated by gravitational flexure generated by Jupiter's gravity. But recall that M(Jupiter) = 318 * M(Earth),*81 =~ 25758 M(Luna). That's quite a gravitational difference factor!

Now here's a puzzle for you. The tides of Earth slow down the rotation of Earth, and the Moon drifts further away (to preserve system angular rotation) as a result. But when Jupiter heats up Io, for example, by gravitational flexure, would you expect that moon to also drift further away (from Jupiter)?

--Cheers, --Mr. d.