Molten Centre

[magpie]

given that the earth is approx. 4.5 billion years old why is there still molten rock under the crust?
what keeps it liquid?
will the core ever cool down?
if it does what would be the consequences for the planet?
would it affect the orbit and the rotation of earth?
would it affect the eco-system, biosphere and climate?
i welcome any thoughts on the subject

[Old_Geezer]

It'll cool down eventually, give it time. Mars did.

You don't want it to do so too soon though or all the magnetic field will disappear and leave us at the mercy of the solar wind.

I don't think there will be much left here after that happens. We'll all be radiated to oblivion.

[Zacs-Master]

This might help:
http://phys.org/news62952904.html

[bhg481]

It's still molten because it has the crust around it which acts as an insulator.

It will cool down, just very slowly, so not in your lifetime.

I don't believe the orbit would be affected because there's no change in mass but the day-length would be - spin an egg and a hard-boiled egg and see the difference.

Eco system and climate would change significantly.

[Clanad]

I think, all things considered, the chances of the Earth's center cooling to the point our planet becoming cold and dead are pretty slim... We know stars (of which our sun is a fairly middle aged example) become much larger as they begin to die which would result in our planet (and nearly all of the solar system) becoming engulfed in the red ball giant expanding to turn us into a cinder.

Additionally, this from the "New Scientist" indicates Mars did and still does have a liquid, molten center:

"It has been known since 2003 that at least part of Mars' interior is molten, based on how easily the Sun's gravity distorts the planet's shape, but no one knew whether it is completely liquid, or whether there is a solid inner core like Earth's.

Now a team of scientists, led by Andrew Stewart of the Swiss Federal Institute of Technology in Zurich, Switzerland, has succeeded in creating in the lab the high pressure and temperature expected in Mars' core..."

[beso]

Much of the heat inside the planet is generated by nuclear fission of radioactive elements. If it was just a matter of insulation of the heat from the original melting due to kinetic energy of colliding bodies it would have been cold long ago.

William Thomson (Lord Kelvin) made an early calculation of the age of the Earth based just on cooling and came up with 20 million to 40 million years. Of course at the time it was widely dismissed as ridiculously long.

The long term impact of the core going cold would be enormous. The convection from this heat drives the tectonic plate movements that are responsible for the recycling of minerals from the bottom of the ocean back to the peaks where they can get involved with the ecosystem again.

It is interesting to note that a molten core alone does not cause tectonic plate movement. At some point the planet was hit by something that started the cycle by splitting crust catastrophically and starting the cycle without which life would have run out of resources long ago.