Megaripples
Mar 06, 2009

A previous Picture of the Day article about the strange formations found in an area of Eastern Washington called the Channeled Scablands addressed the kilometers-long ripples that march through the landscape with hundreds of meters between their crests. Rather than being deposited by floods of water, it was suggested that they could have been formed by electric discharges.

Other examples of dune-like formations have been discussed, except they have been seen on other planets, such as Mars, as well as on Saturn's planet-sized moon, Titan. Along with the extraterrestrial examples, Australia's Simpson desert contains 1240 parallel, unmoving "string dunes" that run for over 300 kilometers.

They are not typical aeolian features, because they appear to be unaffected by the hot winds that frequently blow through the region—they do not travel. They are also associated with deep striations that are not easily explained through conventional geology, unless it is assumed that some processes occurred in the past that are no longer as active today.

It is possible that the dunes and the gullies are old enough that they correspond to the last interglacial periods when flowing water is supposed to have eroded Australia however, they do not have the appearance of great age. The dunes, especially, appear to be rather young. Appearances alone, are not sufficient evidence for any theory. However, one would think that exposure to the elements for tens of thousands of years would etch some sign into their faces, yet they look like they were recently created.

The Namib desert also reveals thousands of square kilometers that are covered by hardened ridges that are covered by a thin veneer of sand. Instead of being dunes, per se, they are actually solidified stone that look as if a violent wind blew across molten magma, setting the ripples in place.

One place where such hardened waves are found is Antarctica. Stone ripples are there, but even more anomalous snow dunes can also be seen. In 1997, the Canadian Radarsat satellite photographed gigantic megadunes 100 kilometers long, with separations of two kilometers between crests.

Ted Scambos of the National Snow and Ice Data Center and a glaciologist at the University of Colorado theorizes that it is the katabatic (or downhill) winds that shape the snow dunes. As air cools at the higher altitudes, it becomes denser and slides down the continental rise "...like maple syrup sloughing off a pancake.”

As the frigid air flows down over the ice sheet and hits the plateau, it begins to waver. The slight rippling of the air over centuries of time gradually assembles the dunes, according to Scambos and his colleagues.

Antarctica is the world's driest desert and the ice packs on at less than a half inch per year, so if wind and minute ice crystals are causing the snow dunes to form, no one can see it happening. Indeed, a comparison of images from the 1960s with more recent radar scans demonstrates that they have not changed shape or moved out of position for nearly 40 years.

As we have asked in several previous articles, what force can produce similar effects with disparate materials in such varied environments? Perhaps electricity flowing through conductive substances has a role to play.

The many faces of electricity have not yet been uncovered. There are aspects to its activity that are still poorly understood. It is not the intent of these papers to provide definitive answers to these questions, but to provide a possible alternative to the gradualism that underlies geological theories today.

Stephen Smith