Lake Yoa

Salt lake

The Lake Yoa (also Jua Lake) is the second largest of the lakes of Ounianga in the Ennedi region in the northeast basin of the Chad. These lakes stand out for their runs in the north-south direction headlands. They are remnants of a much larger lake, during the so- called green Sahara period, which lasted from around 10000-1500 BC, filled this basin. There are currently fifteen lakes in the basin with a total area of about 20 km ².

Hydrogeology

The Lake Yoa is characterized by a complex underground exchange process, which he has in common with all the lakes in Ounianga.

Climate change

The Lake Yoa is recently for studies of global climate change is of interest. A team from the University of Cologne Stefan Kropelin at the top took a core sample of sediment from the bottom of the lake. Since the Lake Yoa continuously existed since the wet period, the sediments at the bottom of the water were protected from erosion and dispersal. After analyzing the pollen in the core could determine Kropelin and his colleagues that the transition from forest to desert gradually in the vicinity of Lake Yoa took place. In between were periods with bush and grass land before the area was full for desert. This conclusion is in contrast to the work of Peter de Menocal and his colleagues at Columbia University, who took a core sample of the oceanic sediments off the west coast of Mauritania in 2000. Because of the dust in this core de Menocal and his co- authors came to the conclusion that the desertification took place quickly, over a period of only a few hundred years.

The difference between these two results is not surprising upon closer inspection. The ocean - core represents the response across the entire northern part of the African landmass, while the Lake Yoa data provide further details on the conditions in the areas south and west of it. These areas provided the material with which the prevailing trade winds in the Holocene covered the Lake Yoa. It is possible that both happened: North Africa was rapidly drier, and in certain areas, the process of desertification took place through a series of ecological transitions ( Ranson 2008).