The earth is composed of many different layers. A knowledge of earth's interior is essential for understanding plate tectonics. A good analogy for teaching about earth's interior is a piece of fruit with a large pit such as a peach or a plum. Most students are familiar with these fruits and have seen them cut in half. In addition the size of the features are very similar.
If we cut a piece of fruit in half we will see that it is composed of three parts: 1) a very thin skin, 2) a seed of significant size located in the center, and 3) most of the mass of the fruit being contained within the flesh. Cutting the earth we would see: 1) a very thin crust on the outside, 2) a core of significant size in the center, and 3) most of the mass of the Earth contained in the mantle.
Source: geology.com
Earth structure
