A boiled egg can be used to represent the layers of the earth. Because eggshell is the outermost layer of the egg, it can be compared to the earth's crust. Following, we can consider that the egg white is the earthly mantle and the egg yolk is the nucleus.
The Earth's crust is the surface layer of the earth, the outer manifestation of rocks and minerals. Another possible definition also for the earth's crust is to consider it the solid layer of the planet, although many geologists believe that the inner core portion is also solidified.
The egg shell would be most representative of the Earth's Mantle or "Crust", the yolk and white would represent the molten metal inside the earths core I assume.
