The formation of Archean crust appears to involve processes unique to early earth history. Initial results from receiver function analysis of crustal structure beneath 81 broadband stations deployed across southern Africa re veal significant differences in the nature of the crust and the crust-mantle boundary between Archean and post-Archean geologic terranes. With the notable exception of the collisional Limpopo belt, where the crust is thick and the Moho complex, the crust beneath undisturbed Archean craton is typically thin (similar to 35-40 km), unlayered, and characterized by a strong velocity contrast across a relatively sharp. Moho. This crustal structure contrasts markedly with that beneath post-Archean terranes and beneath Archean regions affected by large-scale Proterozoic events (the Bushveld complex and the Okwa/Magondi belts), where the crust tends to be relatively thick (similar to 46-50 km) and the Moho is complex.