Scientists now understand that the Earth consists of layers, with the densest materials in the core. What allowed the differentiation of the Earth's layers to happen?

the early Earth must have been so hot it was like a liquid and heavier things sank to the middle.

Explanation:

The scientist believed that the earth has been one time or another became a liquid which now gives other things to become embedded in it, before solidifying again.

The differentiation of the earth, as described or explained by the scientists include

* Crust ... which is regarded as the outermost layer of the planet, comprising of variety of rocks. This include the oceanic and continental crusts.

* Core ... is known to be central part and the most important part of the earth.

* Mantle ... is considered as the largest part of the earth with about 85% of earth total volume.