Because the Earth lacked an atmosphere immediately after the giant impact, cooling must have occurred quickly. Within 150 million years, a solid crust with a basaltic composition must have formed. The felsic continental crust of today did not yet exist. Within the Earth, further differentiation could only begin when the mantle had at least partly solidified again. Nevertheless, during the early Archaean (about 3.0 bya) the mantle was still much hotter than today, probably around 1600°C. This means the fraction of partially molten material was still much larger than today.
Fossil Scyphocrinites Crinoids, Sea Lilies, Morocco Upper Silurian (420 million years ago)
