Follow this link to skip to                                      the main content

Feature

Text Size

Space Chronicles on Ice #11
12.16.06
 
by Don Pettit

+ "Space Chronicles on Ice" index

Concentration by Wind
Dec 16, 2006:

Another proposed mechanism to concentrate meteorites is the wind. Planetary geologists have theorized that the wind can aid in meteorite concentration when they are blown about by wind. Before I arrived here and saw the wind effects first hand, I discounted this theory as nonsense.

The katabatic winds are second to none. We as humans living in our houses in cities have never seen the likes of wind like this. The winter time katabatics have hurricane force winds that last for weeks at a time. We occasionally see the effects of such winds when a hurricane blows through the Texas Gulf, turning everything upside down after only a few hours of such gales. It is beyond our normal human intuition for the effects these winds can have on the surroundings, especially when they persist for weeks to months on end. So, when Antarctic explorers propose wind blown rocks as a major mechanism for sculpting the countryside, those who have never been here tend to scoff and discount such theories as nonsense.

I scoffed at such ideas of flying rocks but now I am a true believer. On glacier ice, these winds move rocks, not just inches but kilometers. For multi-kilometers on the down-wind side of a nanatak, there are rocks scattered all over the blue ice surface. Not just little tiny pebbles, but fist-sized to basketball-size parcels, and occasionally even larger, all neatly sorted by size as a function of distance from the source as if they were books on a shelf and a planetary librarian was in charge of putting them in order.

The larger rocks will have a sizable pocket carved out around the up-wind side, probably the result of both wind (the stagnation point) and solar heating. Like a mother rock tending to its brood, this pocket is filled with a collection of neatly sorted baby rocks. Looking in this rock nest is a good place to find meteorites.

The wind is a major source of upheaval on the blue ice. The obvious signs are observed with terrestrial rock on the lee-side of nanataks. When meteorites are present, they will likewise be moved around, perhaps being concentrated in neat, little piles next to some mother rock.

The most complete theory then, for the concentration of meteorites in the blue ice regions of the Antarctic interior, contains elements of the "conveyor belt model," the "stranded ice model," and the "wind blown model." For the current state of knowledge, this seems to be the best we can do for arriving at a plausible explanation. We welcome anyone to add to or subtract from these ideas en route to a better theory.