File:Dust Storm across North-central Africa (MODIS 2023-12-17).jpg

English: Pulses of light tan dust swept across north-central Africa in mid-December 2023. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a true-color image of the impressive dust storm on December 12.

The color and location of the dust marks it as originating from the Bodélé Depression, which is located in Chad. This low-lying, sand-rich depression was once the northernmost portion of Lake Megachad—an ancient lake that once spanned an area greater than all the Great Lakes combined. Over at least 7,000 years, Megachad evaporated, leaving behind only a small remnant (Lake Chad) and dry desert. Today, the Bodélé Depression and former lakebed are among the world’s most prolific sources of atmospheric dust. According to one estimate, it generates about half of the mineral dust that leaves the Sahara Desert.

Mountain ranges to the northeast of the depression create a natural wind tunnel that focuses and strengthens winds as they rake across fast-moving sand dunes. The dunes are comprised mainly of bits of diatomite, a light-colored sedimentary rock formed from the skeletal remains of diatoms. These common, single-celled algae live in water and are encased by distinctive silica-rich cell walls, which are light in color.