<p>For the same (an more prosaic) reason milk skin floats over boiling milk - because it is lighter than the layer below. During the formation of the planet it went through a process called <em><a href="http://en.wikipedia.org/wiki/Iron_catastrophe" rel="nofollow noreferrer">Iron Catastrophe</a></em>, were a large parcel of the denser materials like iron and nickel sunk to the core, leaving the lighter materials close to the surface.</p>

<p>Nice graph with relative densities follow:</p>

<p><img src="https://i.sstatic.net/vESUp.png" alt="enter image description here"></p>

<p>Fission contributes to keep our internal engine super-hot and well-oiled, allowing for our metallic core to spin and generate our magnetosphere. Eventually we'll run out of heat, the outer core will solidify and stop spinning.</p>

CC BY-SA 3.0
2014-02-19T15:03:20.170Z
2014-02-19T15:13:09.757Z
2014-02-19T15:13:09.757Z
OnoSendai
<p>From what I know the sun (or any other star) nuclear fission keeps it from collapsing under its own gravity until the fuel runs out, if that's so why doesn't the earth surface like the tectonic plates collapse to the earth's core? is it because of similar processes that happen in the earth's outer core (nuclear fission)? and if so what would happen if they would once stop?</p>

CC BY-SA 3.0
2014-02-19T15:11:30.717Z
A.K, I'm sorry but Earth science questions are off topic here. You could ask it on Physics.SE or wait for the Earth Science proposal to hit beta.
called2voyage
<earth><gravity>
Why doesn't the earth's surface collapse onto itself?
A.K
# Why doesn't the earth's surface collapse onto itself?

(Asked by: username_0 on 2014-02-19)

From what I know the sun (or any other star) nuclear fission keeps it from collapsing under its own gravity until the fuel runs out, if that's so why doesn't the earth surface like the tectonic plates collapse to the earth's core? is it because of similar processes that happen in the earth's outer core (nuclear fission)? and if so what would happen if they would once stop?

**Tags:** earth, gravity

> **Comments:**
> **username_1**: username_0, I'm sorry but Earth science questions are off topic here. You could ask it on Physics.SE or wait for the Earth Science proposal to hit beta.  

---

## 1 answers

### Answer by username_2 on 2014-02-19. Score: 2

For the same (an more prosaic) reason milk skin floats over boiling milk - because it is lighter than the layer below. During the formation of the planet it went through a process called *[Iron Catastrophe](http://en.wikipedia.org/wiki/Iron_catastrophe)*, were a large parcel of the denser materials like iron and nickel sunk to the core, leaving the lighter materials close to the surface.

Nice graph with relative densities follow:

![enter image description here](https://i.sstatic.net/vESUp.png)

Fission contributes to keep our internal engine super-hot and well-oiled, allowing for our metallic core to spin and generate our magnetosphere. Eventually we'll run out of heat, the outer core will solidify and stop spinning.


---

