PHYSICAL-PROPERTIES OF THE EARTHS CORE

The core plays a major part in the Earth's dynamics. It is essentially molten iron with about 10 to 15 wt% light elements in solution, proba bly mostly silicon and sulfur' with some oxygen that can be dissolved at high pressure from the mantle oxides. At the pressure of the inner core boundary, the outer core freezes to form the inner core. Experime ntal and theoretical determinations of the melting point of iron at th ese conditions are still scattered, but they lead as to believe that t he temperature at the inner core boundary is not far from 5,000 K. The inner core may be constituted by a new high-pressure phase of iron. T he transport properties of the core (electrical and thermal conductivi ty, viscosity, diffusivity) are close to those of iron al melting poin t under atmospheric pressure.