What Would Happen if the Earth's Core Cooled Completely?

[FeynmanMH42]

If the Earth's core lost its heat, what would the temperature at the Earth's surface be?
In other words: how much of our heat comes from the Sun, and how much from below?
Assuming we had some other way to generate a magnetic field and the core burnt out, would we be able to survive?

 

[Bystander]

Crustal heat flow is measured in mW/m².

 

[Mk]

Doesn't the magnetic field spin the core, and not the other way around?

 

[daveb]

I can't really fathom how such a thing could happen in the first place since much of the interior heat comes from the decay of radioactive elements.http://www.physlink.com/News/121103PotassiumCore.cfm" shows that as much as 1/5 could come from radioactive potassium alone.

 

[LURCH]

If the core lost its heat, we'd have far more immediate problems to worry about than the chill. Without the extreme temperatures currently found there, the core would solidify. As it did so, it would contract. Those of us riding the techtonic plates would be quite crust-fallen!

 

[chroot]

Those of us riding the techtonic plates would be quite crust-fallen!

- Warren

 

[AO eye 5]

As a foggy anecdote (2+ years), I recall somewhat from intro Geology that Mantle heat flow is quite "slow," that is, mechanical motion of the Earth's interior exceeds it's own thermal conductivity in heat transfer. So, interior Earth heat is insulated for some time, and the amount (mass) of planet interior should relate to sustained radioactive heating.
If you want to examine this aspect of planets further look into some material on Mars for further information on core solidification and the halt of dynamo action in active planetary cores--but note that Mars has less mass than Earth.
Finally, PBS Nova ran something on Earth magnetic flux variation and pole-reversal which may address some of your wonderings on human habitability.

 

[Andre]

If the core lost its heat, we'd have far more immediate problems to worry about than the chill. Without the extreme temperatures currently found there, the core would solidify. As it did so, it would contract. Those of us riding the techtonic plates would be quite crust-fallen!

That would probably be one of the smaller problems. Although the complete core, including the fluid outer core would contract indeed, the cooling of the solid inner core would cause increased solidification and it would expand. And in doing so, it picks up orders of magnitudes more angular inertia and angular momentum from the fluid outer core, to the fifth power of it's radius.

Why is that important? James Vanyo explains:

http://www.me.ucsb.edu/dept_site/vanyo/core_mantle.pdf

As the many pertubations in the Earth's orbit and spinning act differently on the solid inner core and mantle and cause a precession tendency like the precession of the equinoxes, and the more angular momentum the inner core gains, the more stress on the dynamic mantle core coupling caused by the different precession logcs.

What would happen if eventually this the coupling was broken and the aligment of mantle spin axis precesses away from the solid inner core spin?

 

[ranroun]

well if the core lost its heat , we would all die in a fraction of a second due to the cosmic rays that constantly hit the Earth and that we are protected from only by the fact that the core of the Earth is liquid and generates movement and magnetic field.(and i don't think u could try to generate a magnetic field as strong as the one generated by the core -thats to remove the possibility of an alternative way of generating a magnetic shield
But anyways , it is logical that most of the temperature of the Earth would come from its core because the heat is generated by nuclear reactions of elements such as uranium and plomb and so on , and these reactions generate a lot of heat.
But if u want to know the part the Sun has , u can measure the heat difference of the Earth let's say between when we are the closest to the sun and when we are the furthest ,it would be helpful to know the variation.

 

[chroot]

ranroun,

Welcome to PF. Please note that we have a policy of not permitting posts which spread misinformation. Your previous post is such a post -- there is no evidence that we would all die "in a fraction of a second," nor is there any evidence that the heat liberated by nuclear reactions in the Earth's core is in any way significant when compared to the energy input from the Sun. In fact, both of these statements are false.

If you're going to make statements like these, you need to provide some kind of reputable evidence. If you do not truly know what you're talking about, please refrain from posting.

- Warren

 

[-Job-]

There go 50% of my posts.

 

[billiards]

At the Earth's surface the outgoing geothermal heat flux is spread evenly at 60 Wm^-2. The incoming solar radiation is 1368 Wm^-2, however, because the projection area is a quarter of the Earth's surface area, the average solar radiation is 342 Wm^-2. Also it is important to realize that the geothermal heat is outgoing, it is released at the surface of the Earth as long wave radiation.

From Stefan's Law we find that the surface of the Earth (mostly ocean) should have an average temperature of about 5 degrees centigrade. This is an underestimate due to the greenhouse effect.

 

[Andre]

No, it's about 254.6K or -18C, using 1367 w/m2 and an albedo of 30%.

 

[billiards]

You used different numbers, but the underlying point remains unchanged.

 

[Andrew Mason]

If the Earth's core lost its heat, what would the temperature at the Earth's surface be?
In other words: how much of our heat comes from the Sun, and how much from below?
Assuming we had some other way to generate a magnetic field and the core burnt out, would we be able to survive?

Since the Earth is in thermal equilibrium, and since the Earth can only lose energy by radiation (there being nothing to conduct or convect it away - save a miniscule amount of mass in the solar wind), the amount of radiation leaving the outer surface of the Earth must be equal to the amount of radiation coming from the sun (ignoring all other sources of radiation as they are many orders of magnitude smaller).

If you knew the Earth's emissivity (a number between 0 and 1, 1 for a perfect blackbody, 0 for a perfect reflector) you could calculate the temperature that the Earth's radiating surface must have in order in order to reach equilibrium.

I think if you did all the calculations, you would find that any geo-thermal radiation is a tiny fraction of the radiation from heating due to the sun. Or to put it another way: if you want the snow to melt, you have to wait until spring.

AM