Candidate models of the forces that oppose the sinking of slabs are still constrained to produce results consistent with the following observation: relative geoid highs, which one assumes are due to slabs, characteristically occur over subduction zones. However, certain models of subduction-induced flow, such as one based on a Newtonian half-space mantle, yield surface depressions and concomitant geoid lows that more than fully compensate the geoid highs due to the slab alone. This study has extended a published model of viscous corner flow in subduction zones in order to demonstrate that it can-in certain cases-produce that requisite net geoid highs. Specifically, the relative geoid highs are produced if mantle flow is distinctly non-Newtonian (stress exponent n>2). Results in the form of geoid slope or horizontal gravity profiles are computed for typical values of the slab parameters; they are compared with a representative profile of geoid slopes derived from SEASAT altimeter data in order to show qualitative similarities. It is concluded that the effect of non-Newtonian flow as opposed to Newtonian is to spread out the induced surface deformation, thereby stretching out the regional compensation to wavelengths (transverse to the trench) of many thousand kilometers.