Chemical Differentiation
Note that although bulk materials differentiate outward or inward according to their density, the elements that are chemically bound in them fractionate according to their chemical affinities, "carried along" by more abundant materials that they're associated with. For instance, although the rare element uranium is very dense as a pure element, it is chemically more compatible as a trace element in the Earth's light, silicate-rich crust than in the dense metallic core.
Read more about this topic: Planetary Differentiation
Famous quotes containing the word chemical:
“We are close to dead. There are faces and bodies like gorged maggots on the dance floor, on the highway, in the city, in the stadium; they are a host of chemical machines who swallow the product of chemical factories, aspirin, preservatives, stimulant, relaxant, and breathe out their chemical wastes into a polluted air. The sense of a long last night over civilization is back again.”
—Norman Mailer (b. 1923)