According to scientists, what was the early earth composed of?

1 Answer
Oct 20, 2017

Hot rocks and metals. It is a long-ish story, best read from one of the references below.


A stable crust was apparently in place by 4400 Ma, since zircon crystals from Western Australia have been dated at 4404 Ma.

The Proto-Earth grew by accretion, until the inner part of the protoplanet was hot enough to melt the heavy, siderophile metals. Due to their larger densities such (now liquid) metals began to sink to the Earth's center of mass.

During the accretion of material to the protoplanet, a cloud of gaseous silica must have surrounded the Earth, to condense afterwards as solid rocks on the surface.

The compositions of the Earth and Moon have nearly identical abundances of oxygen isotopes. Most planetary scientists agree that the Moon formed as the result of a giant impact with the proto-Earth.

Cosmochemists do not agree about everything concerning the compositions of the Earth and Moon. Two particularly controversial issues are the abundances of refractory elements - elements that boil at high temperatures and hence condense first from a gas of solar composition, such as thorium, uranium, rare earth elements, and zirconium.