August 02

a dust devil Photo Credit: thomasina (CC BY-NC-SA 2.0)

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Dust Devils

A dust devil (also known as a dirt devil, djin, dancing devil, Nevada tornado, sand pillar, and Chicago tornado) is a spiralling whirlwind of dirt or dust. Unlike tornados, which descend from a cloud, a dust devil originates at the ground and is not associated with thunderstorms. Formed in areas where the surface of the ground (such as a desert floor or tarmac) becomes hot through solar heating and where nearby vegetation cools the air, a dust devil is created by the convective interaction of the hot air rising and the cooler air falling. As the air spirals, it picks up dirt and dust from the ground -- up to 10 pounds of debris per acre it traverses. The mineral content of the debris helps to dictate the color of the column.

Dust devils don't tend to get too big, averaging out at three feet in diameter at their base and reaching only 100 feet in the air. Usually, they last less than a minute, with wind gusts averaging 45 miles per hour. However, they can grow to nearly 300 feet in diameter and 1,000 feet tall with sustained winds of 60 mph and can last up to 20 minutes. Most dust devils are relatively inocuous, but those larger, more severe ones can damage structures (which, in turn, could cause fatalities) and even smaller ones can cause injuries from being struck by flying debris.

Dust devils also occur on the surface of Mars, where they tend to grow much bigger and more destructive than those on earth.

Check out our Science of Weather collection to learn more about meteorology. These Science NetLinks resources deal particularly with wind:

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