Age of volcanism and rifting in southwestern Ethiopia

It has been suggested that volcanism in the Ethiopian region of the Afro-Arabian Rift System has migrated with time, both laterally towards the present axial zone^1-3 and longitudinally southwards from the Red Sea^4,5. Field data and K-Ar isotopic ages from southwestern Ethiopia, summarised below, indicate that volcanism in this area began earlier than previously suspected, and that Quaternary volcanism was not restricted to the axial zone. That major rifting in this region did not happen until the late Miocene^6,7 is corroborated.