The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this natural-color image on Sept. 23, 2011.
The dust plumes sport a wave-like appearance”bands of thick dust alternating with bands of relatively clear air. Some waves extend westward while others curve toward the south in giant arcs. At the end of one curving wave of dust, a line of clouds extends southward over the sea. These ribbon-like patterns might result from atmospheric waves.
Sand seas sprawl over much of Mauritania, and the abundant sand provides plentiful material for dust storms. This dust storm hasn't yet reached Cape Verde, which lies to the southwest, but the dust appears headed in that general direction.
NASA image courtesy MODIS Rapid Response Team at NASA GSFC. Caption by Michon Scott.