Question: How Does Earth's Interior Work?

Sam Geen answered on 28 Jun 2013:

It’s a shame you guys voted off the vulcanologist! 😛

So the Earth’s surface is made of solid rock, but as you go further down the rock on top presses down, causing a lot of pressure and hence heat. At the “Mohorovičić discontinuity” (Andrija Mohorovičić was Croatian, hence the accents!), the crust becomes the mantle, where the solid rock becomes a viscous fluid. The crust and part of the upper mantle are together the “lithosphere”, which mostly moves around elastically, making up the plates that move around and slide under and over each other (it’s the plates moving against each other that cause earthquakes). Below this is the asthenosphere, which is also part of the mantle is more fluid. Then, below this all is the core, divided between the inner and outer core, made of mostly iron and nickel. It’s this that creates the Earth’s magnetic field, which helps deflect a lot of dangerous particles coming from the Sun that might otherwise blast away the atmosphere. The centre of the Earth is nearly 6000 degrees, about the same temperature as the surface of the Sun!