This doctoral dissertation examines the crustal and lithospheric structures of rift basins formed within the Turkana Depression (TD) in east Africa and the Trans-Southern African Orogen (TSAO) in southwest Africa. Both regions have undergone complex structural and petrological evolution since the Archean eon and exhibit belts of deformations that resulted from the assembly and fragmentation of both Rodina and Pangaea. Since the Cenozoic, the crust and the sub-continental lithospheric mantle beneath the TD and the TSAO have been significantly weakened and stretched by plume related dynamics triggering the southward and the southwestward propagation of the East African Rift System. The Precambrian suture zones and the Mesozoic rift basins have also influenced these zones of extensional deformations. This doctoral dissertation is designed to explore the spatial extent of these structurally complex tectonic entities and investigate the role of these structures in the nucleation and development of various zones of extensional deformations, particularly rift basins related to the East African Rift System. To this end, geophysical, remote sensing, and numerical methods have been implemented to model the upper crustal-, crustal-, and lithospheric-scale structures beneath the TD and TSAO. For the first time, this doctoral work also introduces improved methods to estimate depth to the Moho and the Precambrian crystalline basement using potential field data. The details are presented in the following chapters summarized as three independent projects.