MORPHO-TECTONIC EVOLUTION OF THE LAKE PLATEAU REGION IN SUB-SAHARA AFRICA: A REMOTE SENSING APPROACH

The interplay between tectonic processes and geomorphology has been a topic of great interest to geoscientists. The Lake Plateau Region (Burundi, Congo, Kenya, Rwanda, Tanzania and Uganda) in sub-Sahara Africa is an ideal place for examining such interplay because the East African Rift System (represented by the Eastern and Western Branch surrounding the Tanzania craton) has shaped and continued shaping the Nile drainage system and its associated lakes. This work examines aspects of the morpho-tectonic evolution of the Nile drainage system in the Lake Plateau Region by focusing on possible development of different lake types. It implements remote sensing data including the Landsat Thematic Mapper (TM) spectral data and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) in connection with previously published geological and geomorphological information. The study shows that the lakes of the Lake Plateau Region can be divided into three types resulting from different morpho-tectonic processes. The first type of lakes is represented by the NE-elongated Lake Albert, Edward, and Kivu formed as rift lakes within the grabens of the Western Branch of the East African Rift System. Rift segmentation at ~2.5 Ma resulted in dividing a once continuous long lake (Paleo-lake Obweruku) into the three lakes of present day. The second type of lakes is represented by the dragon-shaped Lake Kyoga. This lake was formed as a result of natural damming of a once west flowing dendritic drainage system. Uplift associated with the onset of the Western Branch of the East African Rift System at 8-9 Ma resulted in drainage reversal (from west flowing to east flowing), damming of the dendritic drainage system and over-flooding to form Lake Kyoga. The third type of lakes is represented by the elliptical-shaped, ~250 km Lake Victoria. This lake is centered on the Tanzania craton between the East and West Branches of the East African Rift System. It started forming when uplift on the East and West Branches resulted in re-directing of the drainage to flow eastward and westward towards the negative topography region occupied by the present day Lake Victoria. It is not clear what the cause of this negative topography was. However, it is tempting to consider it as a negative dynamic topography associated with the thick root of the Tanzania craton.