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Seismic reflection studies reveal lateral and vertical heterogeneity of the deep crust that is comparable to that indicated by geologic observations. In a crust this heterogeneous, the concept of a ''Conrad Discontinuity'' has little meaning. Near-horizontal reflectors in the deep crust are formed by horizontal movements in metamorphic rocks and magmatic crystallization within the earth's gravity field. Supracrustal rocks in the lower crust suggest that much of the crust was built up as a supracrustal pile. Mean crustal composition is approximately quartz dioritic to granodioritic. The composition cannot be achieved by simply adding material through accretion of andesitic island arcs but must account for more felsic material.