A sandstorm is exactly what it sounds like; a very strong windstorm, especially in the desert, that carries clouds of sand or dust, and greatly reduces visibility. These are also known as dust storms. This wind is usually caused by convection currents (which are created by intense heating of the ground), and is usually strong enough to move entire sand dunes. Air is unstable when heated, and this instability in the air will cause the mixture of higher winds in the troposphere with winds in the lower atmosphere, producing strong surface winds. Sandstorms can interfere with travel, and sometimes obliterates entire roads, and dry, flat regions, such as parts of the western United Sates. They can be seen as solid walls of sand that are up to 5,000ft high. Similar dust storms from windborne particles can be found on the planet Mars, and are thought to be seasonal. In the United States of America, sandstorms are very rare due to the lack of large deserts, the development of proper agricultural techniques, and the common cloud cover, which will block out some of the sun's heat. The last recorded devastating sandstorm in American history was the Dust Bowl which caused the depression. One that occurred near Tucson, Arizona, on July 16, 1971, was extensively documented by meteorologists. Deforestation and excessive cultivation of farmland can cause a sandstorm problem. Over-grazing and excessive use of water resources can also cause sandstorms. In order to protect themselves from sandstorms, some people wear protective goggles and suits. Special air filters can be installed in some cars to prevent sand from getting into the engine. In Kuwait, the month of April is known as 'sandstorm month'. Sandstorms that come from Northern Africa and drift across Europe are called 'Sahara Sand Storms'. Sand storms can cause hacking coughs, and the sand and dust have also been known to be capable of carrying 'infectious diseases'. Sand particles, unlike dust ones, will clog air passages, and cause the person who breathes them in to choke. Dust particles may simply cause an allergic reaction

The first image is of a sandstormbeginging, courtesy of ttp://www.pcsympathy.com/modules/coppermine/albums/userpics/10002/normal_sandstorm.jpg The second picture is of the sand settling back down as a sandstorm ends, courtesy of http://members.shaw.ca/axeman/sandstorm.jpg