Dust Devils

By Grant Alan Idso

Summer Saturdays are special times for my brothers and me. After eating an early lunch, we usually take a large jug of water and drive with our dad to the Gila Indian Reservation a few miles south of our home in Tempe, Arizona, to look for dust devils. There, on dry fields that don’t have any crops growing on them, giant swirling columns of dust regularly form and march across the landscape. We like to run into them and release colored balloons or smoke bombs, while our dad takes pictures of them. These pictures help him understand how whirlwinds are created and how they grow and finally disappear.

Usually when we search for dust devils we can see several at a time, but if a field has just been irrigated or if it has recently rained, there often won’t be any dust devils. They need a dry surface that becomes very hot when the sun warms it. Then the hot ground heats the air next to it. This air becomes lighter than the air just above, and it starts to rise like a bubble. As the wind wraps itself around the rising bubble of warm air, it starts to rotate. When this happens, a dust devil is born.

Dust devils come in many shapes and sizes. There are big ones that rotate and that can last for half an hour or more, and strong narrow ones that last for only a minute or two. Most people are surprised to learn that a strong dust devil can be more powerful than over half of all the tornadoes that occur in the world. They act like tornadoes in many other ways too.

My dad says scientists believe that the worst damage caused by tornadoes comes from strong “mini-funnels” located within the wall of the main funnel. Although these mini-funnels have only been seen once or twice in real tornadoes, we see them regularly in our dust devil chases. Usually there will be three or four of them at a time. Just recently, however, we observed a huge dust devil that had at least eleven within it. One of the larger ones even had its own smaller mini-funnels dancing inside.

Arizona does not have very many tornadoes, but my dad has pictures of some that look just like many of the dust devils we’ve seen. He thinks that although tornadoes and dust devils are usually formed in different ways, their winds may be practically identical.

As a result of Dad’s study, three different groups of scientists have visited us to study dust devils, hoping to learn more about tornadoes. One of the groups was trying to find special sounds coming from them that could be used to develop a warning system for tornadoes. The other two groups had a laser beam that could be pointed at a dust devil. The part of the beam that was reflected off the dust devil back to their equipment told them how fast the winds in the dust devil were moving.

One time I was just about to put my finger in the place where the invisible laser beam came out, and one of the scientists shouted and told me that it could burn right through my hand. To prove it, he came over and put a tablet of paper where I was going to put my finger; and all of a sudden there was a brown and smoky hole right through the tablet!

Studying about dust devils is really fun. When I get big I’m going to be a scientist just like my dad. Then I’ll be able to understand more about the world that Heavenly Father made for us to live in.

Photographs by Dr. Sherwood B. Idso