Dust Whirl

Sand auger, sun devil, ghost wind, dust whirl, whirly-whirly, chindi and even djin are all names used to describe the weather phenomenon of a dust devil. Many myths tie dust devils to the realm of the supernatural, claiming that the phenom is actually a visiting spirit. The direction of its rotation determined whether the spirit was good or bad. How exactly does this friendlier kin of the tornado and waterspout form?

First off, certain conditions must be present for the dust devil to form. The land must be flat and ideally dessert, asphalt or bare land. Sand and dust are not required for a dust devil to form but they make seeing it easier. The skies will be clear or almost clear and only light wind and cool atmospheric temperatures will produce a dust devil. Another requirement for formation is heat; the ground must get very hot.

When the ground reaches sweltering temperatures over a large area it heats the air closest to the ground. This hot air rises swiftly because it is lighter than the cooler air farther from the ground, as the warm air rushes up the cool air speeds inward towards the base of the forming dust devil. The ascending pocket of air stretches vertically and will begin to rotate faster and faster, sucking in more hot air to replace the hot air that has risen. The dust devil will begin to travel across the ground as it absorbs more hot air. A perfect dust devil will have hot air swirling around and up, while cooler air rushes down the center.

The dust devil’s existence can consist of mere minutes to about an hour depending upon how vast the area of heated air extends. Once it runs out of hot air, the dust devil will disperse. Typically, the dust devil is short lived and causes little damage considering the average diameter is three feet wide and winds only reach about 45 miles per hour. Occasionally they will grow larger and have faster winds but it is rare because of the temperature the ground must reach and the amount of flat ground needed to sustain it.

Because of the extreme temperatures and vast barren lands located on Mars, dust devils are frequent and far more destructive than here on earth. Martian dust devils can reach fifty times wider and ten times as high as their earthly counterparts can, posing a risk to technology used to explore Mars’ terrain.

While science has proven their existence to be purely natural, dust devils remain a fascinating occurrence that is entertaining to behold.