Isn't nature fascinating when you get right down its structure of what seems like chaotic cause and effect, and then to discover that even a grain of sand has the ability to self-organize with those around it in response to the conditions it faces. One might think they are crafted by the winds of change in their life, having no say in the matter, and just blown around at the will of forces out of our control. Yet the subtle reality is that we have control in how we land and the future we shape for ourselves and our place in the community around us, despite that forces beyond our control happen to us. Here is a capture from Mesquite Sand Dunes, Death Valley National Park.

"Ripples in sand, found on both beaches and dunes, are one of nature's most ubiquitous and spectacular examples of self-organization. They do not result from some predetermined pattern in the wind that is somehow impressed on the surface, but rather from the dynamics of individual grains in motion across the surface. They arise whenever wind blows strongly enough over a sand surface to entrain grains into the wind. The subsequent hopping and leaping of these grains is called saltation. Saltating grains travel elongated, asymmetric trajectories: Rising relatively steeply off the bed, their path is then stretched downwind as they are accelerated by drag forces. They impact the sand surface centimeters to tens of centimeters downwind, typically at a low angle, around 10 degrees. It is this beam of wind-accelerated grains impacting the sand surface at a low angle that is responsible for ripples.

"An artificially flattened sand surface will not remain flat for long. (Try it on the beach or on the upwind side of a dune and see for yourself.) Small irregular mottles in the sand surface, perhaps a couple centimeters in wavelength, rapidly arise and grow once the wind starts to blow hard enough to initiate saltation. They then slowly organize themselves into more regular waves whose low crests are aligned perpendicular to the wind direction and begin to march slowly downwind. Typical ripple spacing is about 10 centimeters, whereas the typical height of the crests above the troughs is a few millimeters. The pattern is never perfect, but instead the ripple crests occasionally split or terminate, generating a pattern that looks remarkably like one's fingerprint. In cross section, the ripples are asymmetric, having low-angle upwind (stoss) faces and steeper downwind (lee) faces. Interestingly, the larger grains tend to accumulate on the crests of the ripples, leaving the troughs enriched in smaller grains." ~ Robert S. Anderson, associate professor of earth sciences at the University of California at Santa Cruz