Dust Storm 2011, Phoenix, Arizona

Physical and environmental impacts
A sandstorm can move whole sand dunes. Dust storms can carry large amounts of dust, so much so that the leading edge of one can appear as a solid wall of dust as much as 1.6 km (1 mile) high. Dust and sand storms which come off the Sahara Desert are locally known as a simoom or simoon (sîmūm, sîmūn). The haboob (həbūb) is a sandstorm prevalent in the region of Sudan around Khartoum; storms are very common around Khartoum every summer. When it happens you can't see anything but a wall of sand covering your view.
The Sahara desert is a key source of dust storms, particularly the Bodélé Depression and an area covering the confluence of Mauritania, Mali, and Algeria.
Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s, causing topsoil loss in Niger, Chad, northern Nigeria, and Burkina Faso. In Mauritania there were just two dust storms a year in the early 1960s, but there are about 80 a year today, according to Andrew Goudie, a professor of geography at Oxford University. Levels of Saharan dust coming off the east coast of Africa in June (2007) were five times those observed in June 2006, and were the highest observed since at least 1999, which may cool Atlantic waters enough to slightly reduce hurricane activity in late 2007.