A Molten Planet Figure 1. Structure of the Earth. Above the core lies the mantle , which is made up of dense silicates, and the crust , which is the outer layer of the solid Earth. The oceans and atmosphere are the outermost layers. As we have already mentioned, the Earth must have been largely molten at some early stage in order to have been differentiated into several zones or layers.
Differentiation is perhaps the most significant event in the history of the Earth.
It led to the formation of the core and the mantle and a crust with continents. Differentiation initiated the escape of gases from the moving interior, which eventually led to the formation of the atmosphere and oceans. It occurred over 100's of millions of years or it could have been a more catastrophic event. The earliest Earth was probably an unsorted conglomeration, mostly of silicon compounds, iron and magnesium oxides, and smaller amounts of all the natural elements. It became increasoingly hotter as the protoplanet grew.