f Variations in crustal and upper-mantle rigidity across South Africa

Most studies of the strength and isostatic behaviour of continental lithosphere have focused on its effective<br>elastic thickness (EET). This is because the EET can be relatively easily obtained from coherence or<br>admittance analyses between gravity and topography data (Forsyth, 1985). The EET has no specific<br>relation to a geologic or physical boundary but it can, however, be used to determine the thickness of the<br>competent lithosphere (CL) based on realistic continental rheology (Burov and Diament, 1996).