Fault Evolution in Magma-Rich Rifts using Quantitative Geomorphology: Insights from Central Afar, Ethiopia

A major challenge in magma-rich continental rifts, such as Afar, is to understand the evolution of fault networks in space and time. This is due to the lack of subsurface seismic reflection data and the presence of complex, variable-age lava flows at the surface. Most past studies have focussed on establishing tectonic history and fault evolution of onshore continental rift systems, with the help of geodynamic and analogue models. The dynamic response of fluvial landscapes to tectonic activity is an additional tool that can be used to better understand fault network evolution. However, little to no work has been done to date using quantitative geomorphology to understand the evolution of normal faults in magma-rich continental rift systems.

To deepen our understanding of fault evolution in these tectonic settings, this study focusses on the graben systems in the Central Afar region in Ethiopia, and small-scale streams that crosscut the graben fault systems. This study uses a combination of GIS DEM analysis, river long profiles, integrated with available ages of the lava deposits on the surface, to quantify landscape and geomorphic responses of river systems to extension in the Afar Region. The work done in this study provides new insights into the timing and magnitude of fault growth and interaction associated with normal faulting over timescales of 100,000 years.