Surface processes and rift evolution in the Ethiopian Rift, East Africa

The Main Ethiopian Rift (MER) is characterized by a significant along-strike variation in rift evolution and strain accommodation mechanisms. The northern MER is at a transitional stage, whereas the central MER is at an intermediate stage of rifting. Previous geophysical and geological observations suggest that rift obliquity, age of onset of rifting and/or presence/absence of magma could be responsible for the observed difference in deformation style. Here, we use the geodynamic modelling software ASPECT that has recently been coupled with the landscape evolution model FastScape to understand the role that surface processes (such as erosion and sedimentation) play in controlling the style of deformation at the central and northern sectors of the MER. Our results show that the deformation in the central MER can be well explained by efficient surface processes. However, our models fail to fully capture the deformation in the northern MER implying that magma plays a significant role in this sector of the rift. We show that the MER is a unique plate boundary where surface and magmatic processes control the style of deformation at different sectors within the same tectonic setting.