A rare weather phenomenon that affects the area only about once a decade, filled the Grand Canyon in the U.S. with a dense, white fog at the end of November. The phenomenon, known as "temperature inversion," happens when the temperature profile of the atmosphere is inverted from its usual state, and cooler air is trapped at the earth's surface by warmer air above.

Typically, the temperature of air in the atmosphere falls the higher up in altitude you go. This is because most of the suns energy is converted into heat at the ground, which in turn warms the air at the surface. The warm air rises in the atmosphere, where it expands and cools. When temperature inversion occurs, the temperature of air actually increases with height. The warm air above cooler air acts like a lid, trapping the cooler air and fog at the surface and preventing it from rising.