Thursday, March 5, 2009

Dust Devils

A whooshing suck roared out of the earth as if some ginny had been released from the metallic fiber of the inner world. The spiral of dust and air danced across the field inhaling rocks, sticks, seeds and centipedes, a commotion unto itself on an otherwise hot and calm day.

Dust Devils, also known as Remolinos, in west Texas, are brief whirl winds that form when hot air from the earth’s surface rise unevenly, like bubbles in a Topo Chico. Cooler air rushes in to the column of hot air to fill the voids and the reciprocating air of unlike densities begins to spin. Slowly at first until, like the arms and legs of an ice skater tucked in tight for the encore, the atmospheric vortex of the dust devil becomes fully formed spinning at speeds of up to 70 mph and demonstrating the science principle of conservation of angular momentum.

As the vortex bops across the surface, more hot air is sucked in along with dust and debris, lowering the air pressure inside and causing the dust devil to rise. These augers of sand and dust can change colors depending on the landscape they run over and can even be transparent if formed over a clean grassy area.

Like tornados, they are weather phenomena, but most dust devils form under sunny conditions during fair weather and are seldom dangerous with few lasting longer than a minute. They generally form in arid and semi-arid regions and a flat barren terrain increases the likelihood of the hot air fuel. Diameters of three feet are common but some grow as large as 300 feet across the base, lasting thirty minutes and can lift more than 15 tons of dust and debris into the air. The whirling particles inside the vortex become electrically charged and create a magnetic field that helps lift more dust off the ground.

The Viking orbiters of the 1970’s, photographed Dust Devils on the planet Mars climbing out of craters, creating columns of Martian dust ten times higher than those found on earth.

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