Abstract
Lake Afdera is a hypersaline endorheic lake situated at 112 m below sea-level in the Danakil Depression. The Danakil Depression is located in the northern part of the Ethiopian Afar and features an advanced stage of continental rifting. The remoteness and inhospitable environment explain the limited scientific research and knowledge about this lake. Bathymetric data were acquired during 2 weeks expeditions in January/February 2016 and 2017 using an easily deployable echosounder system mounted on an inflatable motorized boat. This study presents the first complete bathymetric map of the lake Afdera. Bathymetric results show that the lake has an average depth of 20.9 m and a total volume of 2.4 km3. The maximum measured depth is 80 m, making Lake Afdera the deepest known lake in Afar and the lowest elevation of the Danakil Depression. Comparison with historical reports shows that the lake level did not fluctuate significantly during the last 50 years. Two distinct tectonic basins to the north and the south are recognized. Faults of different orientations control the morphology of the northern basin. In contrast, the southern basin is affected by volcano-tectonic processes, unveiling a large submerged caldera. Comparison between the orientation of faults throughout the lake with the regional fault pattern indicates that the lake is part of two transfer zones: the major Alayta–Afdera Transfer Zone and the smaller Erta Ale–Tat’Ali Transfer Zone. The interaction between these Transfer Zones and the rift axis forms the equivalent of a developing nodal basin which explains the lake’s position as the deepest point of the depression. This study provides evidence for the development of an incipient transform fault on the floor of the Afar depression.
Highlights
Lake Afdera is a hypersaline endorheic lake (Martini, 1969) located in the southern part of the Danakil Depression, in the Afar region, in northern Ethiopia (Figure 1)
This study provides a present state of knowledge of the lake Afdera from its discovery in 1920 to the different attempts to estimate its depth
The bathymetric data indicate that the morphology of the northern basin is controlled by tectonics with faults oriented in three different directions, forming a triangular graben structure
Summary
Lake Afdera is a hypersaline endorheic lake (Martini, 1969) located in the southern part of the Danakil Depression, in the Afar region, in northern Ethiopia (Figure 1). Vinassa De Regny in 1919, Nesbitt in 1928 and Franchetti in 1929 all managed to cross the Danakil desert and collect geographical and geological data (Lupi, 2009). Despite having visited the region a decade later, Nesbitt and Franchetti were the first to publish their results on the Danakil Depression in 1929 and 1930, respectively. Nesbitt called the lake “Egogi Bad,” a name given by his local guide. Franchetti named it lake Giulietti, as a tribute to Giuseppe-Maria Giulietti after discovering the remains of the explorer and his team near Beylul (Nesbitt, 1935; Taillibert, 1996). Franchetti extensively explored the lake, and his name was assigned to one of the two endemic fishes of the lake Afdera: Danakilia franchettii (Vinciguerra, 1931; Getahun, 2001)
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