A quantitative model of gneiss dome formation must account for the spontaneous development of large structural relief, relative to surface relief, at the base of the brittle layer for appropriate physical parameterization of the crustal rheology and the modification of topography by erosion. An earlier model has been augmented to include (i) crustal necking, as well as contributions to dome initiation from (ii) density instability and from (iii) an erosional law in which sinusoidal components in surface topography are amplified at wavelengths L > L* and decay for L < L*. A further modification replaces a ductile halfspace...