Can someone explain this-the density of the earth as a whole is more than the average density of the crust?

Question

Can someone explain this-the density of the earth as a whole is more than the average density of the crust?

Answer 1

The crust has to float on top of the liquid mantle, so it's obviously less dense than the mantle. Being on top means the crust is the least dense out of everything that makes up the earth, so the average is obviously higher than the density of the crust.

Answer 2

Most of the Earth (Crust and Mantle) is Rock, but the core is Iron, which is much denser.  The Crust is least desnse as it effectively "floats" on top of the rest of it, hence plate tectonics.

Answer 3

And to add to the answers above, the earth's core is under extreme pressure from the surrounding mantle and crust, hence it's the most dense part of the planet.