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>
You could make like a building somewhere high so when everyone gets a warning that a flood is coming they can go and leave there let’s there or like a boat like Noah’s arc