“…the observer never fails to be amazed at a simplicity of form, an exactitude of repetition and a geometric order unknown in nature on a scale larger than that of crystalline structure. In places vast accumulations of sand weighing millions of tons move inexorably in regular formation, over the surface of the country, growing, retaining their shape, even breeding, in a manner which, by its grotesque imitation of life, is vaguely disturbing to an imaginative mind” – Ralph Alger Bagnold , 1941 “The Physics of Blown Sand and Desert Dunes”
As many of you know, I love to meander alone in Nature while looking for blog ideas and doing my Nature photography. Twice now, I’ve visited the Mojave National Preserve (MNP) about 100 miles southwest of Las Vegas. If you are a Nature buff, this desert preserve is a potpourri of interesting places including some really neat sand dunes. I like sand dunes because I’m fascinated with their patterns and how they are formed,
But, first I must tell you that the National Park Service’s romantic description of the MNP Kelso Dunes is a bit deceptive. I was all excited about the idea of photographing dune ripples and critter tracks. The fact is that the place has been overrun with humanity. I tried to find a clear section of sand with virgin ripples and areas with clean runs of Kangaroo Rat tracks. Instead, the sand was inundated with human foot traffic, dog tracks, and doggie poop. So, I spent a good deal of time carefully framing my camera so as to cut out the human element.
OK, on to sand.
What I find really fascinating about sand ripples and dune structures is their beautiful self-similarity. Self-similarity means that an object’s shape (or form) looks the same no matter what level of magnification you choose to use. No matter whether you are looking at an entire dune system or at a small segment of the sand’s surface, the shapes look roughly the same. You might want to look at my post on the fractal forest to get a taste of the idea of self-similarity.
Dunes are a fascinating and complex subject. Their formation is well studied. Instead of giving you a treatise on their development, I strongly recommend the post at Sand Dunes: A Phenomenon Of Wind for a very good description of dune formation. Suffice it to say that three elements are necessary to create dunes. You need a supply of sand, a steady wind, and a terrain that creates interruptions in the surface wind currents that permit sand particles to settle down in certain locations.
If you are at all familiar with self-similarity, you can probably see that the dunes and the sand ripples look approximately the same. But, what I find interesting is that, while the physical shapes are self-similar, so is the process. The wind currents work the same no matter if the sand surface is a simple ripple or if it is a big dune. Wind drives the sand against the windward side of the slope. But on the leeward side of the dune or ripple, the sand particles lose their momentum and drop because the wind force and direction is drastically changed by the peak of the slope. This self-similar process is also responsible for the transport of entire dune systems where both ripples and dunes are gradually moved.
Self similarity is a phenomenon that is not only seen in sand dunes. It is is ubiquitous and critically important in much of Nature. For those of you who wish more detail, I strongly suggest the easily read article from Amherst College called “Nature Adores Self Similarity” . Without self similarity, our bodies would cease to function. The articles points out that:
“.. were it not for this elegant design strategy, we would be dire straits for at least five reasons. Our bodies would perform poorly and decay due to inadequate circulation if self-similarity did not exist. If our brains and nervous systems could not benefit from self-similar networking, our IQs would be roughly on a par with fence posts. Without the self-similar villi and microvilli in our intestines, our ability to digest food would be compromised. Moreover, there would be little food to eat in the first place because, in the absence of self-similarity, the Earth would be virtually devoid of vegetation, which directly or indirectly provides most of our food sources. Lastly, we would be unable to breathe without the critical self-similar architecture inside our lungs.“
I’ve emphasized the idea that everything in Nature is connected. Those connections are the essential conduits for energy flow in Nature. The actual energy connections are self similar fractal structures that I’ve previously described. As I stated in that post:
“The self-similar fractal structure is a manifestation of Nature’s interconnected being.“
So, you can now dazzle your friends by telling them that sand dunes, trees, our lungs, and a huge number of patterns in Nature have a common thread since they are all self similar.
Worth Your Extra Attention :
Three other places where you can see some great sand dunes are:
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My name is Bill Graham. As a Marine Biologist who has worked in the US and Mexico for 30 years, I am a student of Nature, a teacher, a researcher, and a nature photographer. Through my work, I have acquired an ever growing passion for how everything in Nature is connected. Today, I travel extensively contemplating about, writing about, and photographing Nature’s connections. I also work with conservation projects in the USA and Mexico and mentor talented youth.