File:Dust storm off West Africa (MODIS 2015-06-25).jpg

English: A massive river of dust poured off of the arid lands of western Africa in mid-June 2015. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA�s Terra satellite captured this true-color image on June 14.

The heaviest dust and sand blows from inland over the coast of Senegal. The dust is so thick and the colors of the dust and the land are so well-matched that it is impossible to discern the country�s coastline. A broader but thinner veil of dust blows from Western Sahara and Mauritania, both to the north of Senegal. This dust arcs to the southwest over the Atlantic Ocean, and covers the Cape Verde Islands.

Dust is abundant in this region, and winds are often strong enough to move great quantities of dust. A clue to the cause of this particular dust storm can be found in the southeast section of this image. A tight, circular cloud sits off shore of Guinea-Bissau. This appears to be a depression, a tropical system with relatively low surface wind speeds (38 mph/61.5 kph or less). Although such winds are not considered dangerous, they are more than strong enough to move huge quantities of sand and dust.