Saturday, June 27, 2009

Guess What

I thought it was time for another mystery photo. Have a guess what this is an image of and post your guess as a comment. The answer will be revealed soon...
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3 comments:

Jethro Loader said...

Patterened ground in a permafrost region?

Photomacro said...

Walrus hide?

Tom said...

Well Jethro was right, Patterned ground. The result of cryoturbation, or frost heaving. The repeated anual freezing and thawing of the surface here causes a kind of convection, this convection occurs in cells. At the surface the cell has a core of fine grained material, usually clay or sand, with larger rocks around the perimeter. Because the subsurface is still frozen water cant escape into the ground so these features are often quite wet and have a thycksotrpoic (?) nature. if you stand on them and slowly move your feet you start to sink.
In this picture you see the gray areas of sandy clay surrounded by the coarser material that supports moss and occasionally a small salix (willow)
The shape of these features changes depending on the slope. on a flat surface they are circular or hexagoonal, as the slope increases they become elongated until they form ridges that run up and down the slope.