Final answer:
The large-scale melting of the Earth between about 4.5 and 4.0 billion years ago led to the differentiation of the Earth into its major compositional layers.
Step-by-step explanation:
The large-scale melting of the Earth between about 4.5 and 4.0 billion years ago led to the differentiation of the Earth into its major compositional layers. During this process, the molten Earth gradually separated into a dense metallic core, a semi-fluid mantle, and a solid crust. This differentiation was a result of the Earth's internal heat and pressure. As the Earth's surface cooled, igneous rocks formed, which are still present on Earth today.