The Earth Contents

1. Structure

The differences between the core, mantle and crust were initiated by melting

Melting allowed the material comprising the early Earth to segregate. The very dense liquid iron sank to the centre of the Earth and on top of this floated the residual relatively light scum of silicon and non-ferrous metals (calcium, magnesium, sodium, potassium and aluminium). This molten scum would initially have solidified to form igneous rocks. However, a comparison between the average composition of igneous rocks and the composition of the crust still reveals some differences particularly in oxygen and silicon content.

Granite Basalt Magma
Granite Basalt Magma

Describe how the differences between the core, mantle and crust arose.