Differences in temperatures create wind (in this case, with temperature differences from 130 F to 75F in the desert of Iraq, a big difference) winds that can push the storm across the desert at up to 65mph (110kmp). Because there is no moisture and no vegetation to hold down all the sand and dust, a huge cloud of dirt is created. Sometimes so much debris is flung into the air that it can block out the sun, as seen here. The sand particles aren't beach sand, but more along the lines of dust particles some of them microscopic that will get inside of EVERYTHING. This storm raised the air temperature almost 20 degrees F, reduced visibility to virtual zero, and you could taste the dust just like you were licking the dirt under your shoes.