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Asked by abbley to Adam, Catherine, Karen, Leila, Nazim on 15 Mar 2012.
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Adam Stevens answered on 14 Mar 2012:
So we think that the Earth’s interior looks like this:
At the very centre there’s a big ball solid iron, surrounded by more molten iron that spins around in a complex way, which is why the Earth has a magnetic field.
Around the core is a massive layer of molten rock called the mantle. This actually has a couple of different layers. Since the rock is molten it can move around, rising and falling and sometimes bursting through the crust to make volcanoes.
On top of the liquid mantle sits the solid crust, which is split up into plates. These plates float around on top of the mantle, which is why we have plate tectonics.
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Leila Battison answered on 15 Mar 2012:
The inside of the Earth is really hot because of the pressure of all of the rock above it, and because there are radioactive elements decaying and creating extra heat. This melts the iron in the outer core, but the iron right in the middle is even more crushed by pressure, so it stays as a solid, even though it is really hot.
Because iron is magnetic, and the earth is spinning, the liquid iron in the outer core also spins and creates out magnetic field, which is good for navigating with, but also stops the solar wind from stripping away our atmosphere.
The hot outer core heats up the rock of the mantle next to it, making it convect, just like water in a kettle convents, only much much slowly. The mantle isn’t actually molten, but is so warm and moves so slowly, just like plasticine.
The solid plates of rock on the surface are made up of sediments or volcanic rock, and these move around and crash into eachother as the convecting mantle pushes them around.
We know all of this because we can use earthquakes as a kind of X-ray for the earth, and they give a picture of how deep and how hot things are.
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Karen Masters answered on 17 Mar 2012:
I don’t really unerstand what you’re asking, but Adam and Leila seem to! It’s very hot down there.
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Nazim Bharmal answered on 21 Mar 2012:
As Adam said, except that there is a theory that what happens on the outside (the plates that float on the mantle) can affect the middle, the inner core, and that could be why the magnetic poles can flip around so that the North and South on a compass point in opposite directions.
So it is really complicated! The clever thing is that we know a lot just by studying earthquakes (because we can’t look into the centre) and measuring when they appear at different points on the surface of the Earth.
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