Investigating continental break up in the Afar Rift system

In collaboration with the Universities of Bristol (UK), Rochester (US), Imperial College London (UK) and Addis Ababa University (Africa), the Southampton team have been exploring the dynamic processes that occur during plate rifting in the Afar region of Africa. This is an ideal study area because continental breakup is transitioning to sea-floor spreading, and forming a new ocean basin.

Continental breakup is caused by some combination of heating and stretching. The Afar Rift system is an example of active continental rifting, where a mantle plume probably weakened the lithosphere through thermal erosion and magma infiltration. However, the location and degree of plume influence today are debated. During this recent research,  Southampton geophysicists Dr Catherine Rychert, Dr Nick Harmon and Dr Derek Keir used seismic S-to-P receiver functions to image the mantle structure beneath Afar. They identified the transition between the lithosphere and underlying asthenosphere at about 75 km depth beneath the flanks of the continental rift. They found this boundary was actually absent beneath the rift itself and they instead observed a strong increase in seismic velocities with depth, at about 75 km. Using geodynamic modelling, the team found that the velocity increase at this depth was explained by decompression melting of the mantle and the absence of a strong thermal plume. Their work concluded that, although the absence of mantle lithosphere beneath the rift implies a plume may have once been active, the influence of a thermal plume directly beneath Afar today is minimal.