Sandstorms that occur in the deserts. As a thunderstorm is ending there is a decrease in water droplet fall. The desert's air is extremely dry and able to evaporate the water as winds rush towards the desert's surface. As winds continue to hit the surface they form a circular wind pattern containing sand which increases in force and speed to form the sandstorm. In the summer of 2011 a haboob hit Phoenix Arizona USA that was 100 miles wide and a mile high. Sandstorms blowing west off Africa take phosphate out towards the Atlantic Ocean and sometimes even as far as South America. This phosphate may be an important source of phosphorus in phosphorus-limited biomes.