Lake Chad and a Bodele dust plume
This east-looking photograph, taken by astronauts from the International Space Station on 12 February 2015, shows the arid landscapes of the Sahara and the darker vegetation of the wetter, semi-arid woodland known as the Sahel.
The dark green marshes of Lake Chad stand out in the foreground. Even though it is more than 200 kilometres (120 miles) long, modern Lake Chad is just a small remnant of a vast lake that has repeatedly occupied the most of this landscape in the recent geological past. This lake basin stretches almost 1000 kilometres (600 miles) from the foreground of the image to the foot of the Tibesti Mountains. The lowest slopes of the Tibesti show the remnants of great deltas.
The image also captures an active dust plume, though it is partly obscured by the "Canada Arm" of the Space Station. The dust rises from the white mud flats of the ancient lake bed, likely from the Bodele Depression. Lofted into the atmosphere by northeasterly winds, dust from this basin often reaches the Atlantic Ocean, which is thousands of kilometres to the west. Occasionally this dust is even carried by weather systems as far as the Americas.
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Credit: NASA Earth Observatory