Lead primitive mantle composition

The familiar continental crust of the Earth on which most of us live is of unique importance because it formed the platform above sea level on which the later stages of evolution occurred leading to the appearance of Homo sapiens. The conditions for the production of massive granitic cmsts are probably unique to the Earth and require three or more stages of derivation from a primitive mantle composition. The Earth has transformed less than 0.4% of its volume to continental cmst of intermediate composition and less than 0.2% of its volume into granitic continental crust (i.e., upper continental cmst) in over 4000 million years, so that the process is inefficient. The highland feldspathic crust of the Moon, about 12% of lunar volume, formed in contrast within a few million years. 

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