Structure of the Earth’s Interior
We can use seismic waves generated by
earthquakes to “see” inside the Earth. We find that it has a “liquid”
iron/nickel core, surrounded by a “plastic” mantle. The crust of solid rock is thinner
than
an eggshell in relative terms. Thus, the Earth is still basically a molten ball.
The denser stuff is in the middle because it sunk there – “differentiation”.