A fault is formed in the Earth's crust as a brittle response to stress. ... Generally, the movement of the tectonic plates provides the stress, and rocks at the surface break in response to this. Faults have no particular length scale.
As the earth's history was formed by a collision that led to the formation of the moon that took place about some 4 billion years ago and the earth was a then a blob of molten rock with just a thin solid film on its outer surface.
<u>What can be inferred about the different density of the earth is the earth atmospheric at that time was warm and solar radiation with a relative density and the oceanic crust has relatively more dense matter settled down and in the process known as the planetary differentiation.</u>
