Pulsatory volcanism in the Main Ethiopian Rift and its environmental consequences

The East African Rift is one of Earth’s largest continental landforms. It is recognized as a critical region for understanding hominin evolution yet has also undergone important transformation through ongoing tectonic and volcanic activity. An understanding of the interplay of rift kinematics, magma genesis and geomorphic evolution requires firm geochronology but this has been lacking for much of the East African Rift. Here we present detailed stratigraphic observations and high-precision 40Ar/39Ar ages for major volcanic units in the Central Main Ethiopian Rift. Our new data identify a volumetrically major episode of explosive volcanism between circa 3.85–3.42 million years ago, after aproximately 5-million years-long quiescence. Four other pulses followed but with intensity and magnitude declining over time. We suggest that the observed temporal clustering and the pulsatory volcanic activity may have influenced environmental conditions in the area, with possible implications for hominin evolution. Five major explosive volcanic pulses in the Main Ethiopian Rift took place in the last four million years with intensity and magnitude declining over time, based on stratigraphic and geochronology data of volcanic units.