A massive, 50-mile wide dust storm overtook Phoenix, Arizona on Tuesday night, knocking down power lines, delaying flights and blanketing the air with a blinding layer of dust. While the magnitude of the storm was unusual -- a National Weather Service spokesperson told The Associated Press that many residents described the dust storm as the worst they'd seen -- dust storms are a frequent occurence across the world. Below are some amazing photos of what happens when powerful winds and dust combine.