An Fe-Si-Ni solidification model of the Earth's layering

The physical process creating layered structure in planetary rocky bodies is considered here to be multicomponent solidification. This is a unified alternative approach to the present interpretations where each layer is reasoned and matched individually. The Earth's solidification is modelled using the ternary phase diagram Fe-Si-Ni. The four cotectic concentrations and the four corresponding seismic discontinuity radii have been used to show that the silicon concentration as a function of the distance R from the centre of the Earth can be modelled by C(Si) = G(R/Re)(R/Re) where G = 0.583, Re is the Earth's radius and the Ni/Fe ratio is 0.072. Earth would have up to 13 chemically different layers. This model predicts that there are three to four chemically slightly different sublayers in the D" layer and two boundaries in the inner core at radii 870 km and 1050 km. The observed hemispheric asymmetry in the inner core could follow if the Ni-concentration slightly varies locally. Although this model can account for all the layers using only three elements it can not, of course, match the full chemistry of the real Earth.