The earth is made up of four different layers. Geologists believe the earth wasn't always made up for four layers. Instead, they believe that as the earth cooled as rapidly as it did that the heavier materials sank into the inside of the earth and the lightest materials rose to the top. This explains why crystal rock, oceans, and atmosphere are on the surface of the earth and the much heavier things such as iron are located in the earth's core.
The Crust - the part of the earth that we live on
The Mantle - a hot area that has the ability to flow which includes:
the lithosphere or upper mantle, the solid rock plates resting on the lower mantle
the asthenosphere, the layer that flows very slowly to move the plates of the earth
The Outer Core - the heaviest parts of earth in a hot liquid state
The Inner Core - the heaviest parts of earth in a solid state
