Evolution of continental-scale drainage in response to mantle dynamics and surface processes: An example from the Ethiopian Highlands Andrea Sembroni a, ⁎, Paola Molin a , Frank J. Pazzaglia b , Claudio Faccenna a , Bekele Abebe c a Department of Science, Roma Tre University, 1 Largo San Leonardo Murialdo, Rome 00146, Italy b Department of Earth and Environmental Sciences, Lehigh University, 31 Williams, Bethlehem, PA 18015, USA c Department of Earth Sciences, School of Earth Sciences, Addis Ababa, Ethiopia abstract article info Article history: Received 9 September 2015 Received in revised form 7 January 2016 Accepted 20 February 2016 Available online 23 February 2016 Ethiopia offers an excellent opportunity to study the effects and linkage between mantle dynamics and surface processes on landscape evolution. The Ethiopian Highlands (NW Ethiopia), characterized by a huge basaltic pla- teau, is part of the African Superswell, a wide region of dynamically-supported anomalously high topography re- lated to the rising of the Afar plume. The initiation and steadiness of dynamic support beneath Ethiopia has been explored in several studies. However the presence, role, and timing of dynamic support beneath Ethiopia and its relationship with continental flood basalts volcanism and surface processes are poorly defined. Here, we present a geomorphological analysis of the Ethiopian Highlands supplying new constraints on the evolution of river net- work. We investigated the general topographic features (filtered topography, swath profiles, local relief) and the river network (river longitudinal profiles) of the study area. We also apply a knickpoint celerity model in order to provide a chronological framework to the evolution of the river network. The results trace the long-term progres- sive capture of the Ethiopian Highlands drainage system and confirm the long-term dynamic support of the area, documenting its impact on the contrasting development of the Blue Nile and Tekeze basins. © 2016 Elsevier B.V. All rights reserved. Keywords: Ethiopian Highlands topography River network Knickpoint celerity model Landscape evolution 1. Introduction Topography is the result of the complex interaction of deep Earth and surface processes. These leave a unique mark on the landscape quantifiable with topographic metrics including local relief, drainage pattern, hypsometry, river longitudinal profiles, channel concavity and steepness indices, and channel slope–basin area relationship (e.g., Wells et al., 1988; Pazzaglia et al., 1998; Wegmann and Pazzaglia, 2002; Tomkin et al., 2003; Molin et al., 2004, 2012; Lock et al., 2006; Wobus et al., 2006; Wegmann et al., 2007; Roy et al., 2009; Scotti et al., 2013). These parameters can be used to quantitatively characterize the feedback between crustal tectonics, mantle dynamics, and geomorphology (Molin et al., 2012). Ethiopia offers an excellent opportunity to study the effects and linkage between mantle dynamics and surface processes on land- scape evolution. Northwestern Ethiopia (Fig. 1) is characterized by a huge basaltic plateau (Ethiopian Highlands) which is part of the African Superswell, a wide region of dynamically-supported anoma- lously high topography related to the rising of the Afar plume (Davies, 1998; Ebinger and Sleep, 1998; George et al., 1998; Lithgow-Bertelloni and Silver, 1998; Ritsema et al., 1999; Gurnis et al., 2000; Şengör, 2001; Nyblade, 2011; Faccenna et al., 2013). The initiation and steadiness of dynamic support beneath Ethiopia have been explored in several studies. Early ones (Dainelli, 1943; Beydoun, 1960) proposed the impingement of a plume at the base of the lithosphere in the Upper Eocene preceding both the flood ba- salts event and the main rifting episodes. In contrast, later authors (Mohr, 1967; Baker et al., 1972; McDougall et al., 1975; Merla et al., 1979; Berhe et al., 1987) suggested a more complex Tertiary history of unsteady uplift and volcanism. Pik et al. (2003), based on thermo-chronological analysis on the Blue Nile drainage network, argued that erosion in the Blue Nile canyon ini- tiated as early as 25–29 Ma and that the elevated plateau physiography has been maintained since the Oligocene. A more recent study, focusing on the incision of the 1.6 km deep Gorge of the Blue Nile (Gani et al., 2007), suggests that an uplift of ~2 km occurred episodically in three different phases since 29 Ma: a slow and steady uplift between 29 and 10 Ma (phase I), an increased up- lift at 10 Ma (phase II) and a further dramatic uplift at 6 Ma (phase III). Similarly, Ismail and Abdelsalam (2012) carried out a quantitative anal- ysis on Ethiopian Highlands drainage system finding that its evolution was influenced by three tectonic and geological events: (1) the uplift of the plateau caused by the rising of the Afar plume at 30 Ma; (2) the shield volcanoes constructional event at 22 Ma; and (3) the rift-flank uplift on the western escarpments of the Afar Depression and the Main Ethiopian Rift (MER). Geomorphology 261 (2016) 12–29 ⁎ Corresponding author at: University of Roma Tre, 1 Largo San Leonardo Murialdo, 00146 Rome, Italy. E-mail address: andrea.sembroni@uniroma3.it (A. Sembroni). http://dx.doi.org/10.1016/j.geomorph.2016.02.022 0169-555X/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph