Bodélé Depression (Nigeria, February 2004).
At the southern edge of the Sahara Desert, the Bodélé Depression used to be part of the floor of a much larger Lake Chad, but it is now slowly being transformed into a desert landscape. In the mid-1960s, Lake Chad was about the size of Lake Erie. Since then, persistent drought conditions, along with increased demand for freshwater for irrigation, have reduced the lake to about 5% of its former size.
As the waters receded, the silts and sediments on the lakebed were left to dry in the hot sun. The small grains of silty sand are easily swept up by strong gusts of wind that occasionally blow over the region. Once aloft, dust from the Bodélé Depression can be carried for hundreds, even thousands, of kilometres.
Lake Chad is the olive-green part surrounded by the tan and light brown colours of the surrounding landcape, where Chad, Niger, Nigeria and Cameroon share borders.