Composition & Internal Structure of the Earth
Any group of diverse materials can be classified by chemistry or physical properties. Chemistry refers to different materials, and physical properties refers to such things as whether the materials are solids or liquids, etc. Some physical layers in the earth consist of 2 chemical layers and some chemical layers consist of 2 physical layers.
The chemical layering of the earth formed as part of the earth's differentiation-resulting from the heat generated during the process of planetary accretion. As a general rule, denser materials settled to the center of the earth, leaving lighter materials on top. Thus, the earth consists of successive layers of material getting less dense as you approach the surface. The major compositional layers are:
Core is made of iron with minor amounts of nickel, and
lies at the center of the earth
Because of variations in temperature and in pressure, the materials inside the earth vary in there physical properties with depth.
Inner Core is the central part of the iron-nickel core.
It is a solid iron sphere. The reason that the iron is solid is
that the pressure at the center of the earth is significantly higher than
the pressure above, while the temperature is only slightly higher.
While higher temperature would tend to melt materials, higher pressures
tend to create solids.
The lithosphere "floats" on the asthenosphere. The asthenosphere accommodates the floating lithosphere by flowing. If a load is placed on the surface of the earth (like the weight of water of a large lake) the surface of the earth will sink under the added weight. Mountains are like icebergs: the higher the mountain is, the thicker the crust is underneath it, and the more displaced is the asthenosphere. Thus mountains have "roots".