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A Tundra Phenomenon

They look like coral outcrops, or sand dollars scattered around the landscape, more like living things than dead, inorganic, random events.

Also known as patterned ground, this unusual and sometimes beautiful soil formation is often seen in the tundra areas of the world. During the bitterly cold winters, the soil contracts, and the resulting cracks may then fill with water during the following summer. As this water freezes again the following winter, the ice (being less dense than water) expands, forcing the cracks to widen. This ongoing cycle eventually forces the soil up and out, away from the original cracks, leaving a distinctive pattern of ridges on the surface.

The polygons vary in size from 2 - 30 metres, being smaller in areas of vegetation (typically grasses and sedges). The cracks themselves form a microclimate which encourages the formation of separate communities of life, further differentiating the polygons from the surrounding area.

Other formations associated with soil polygons include pingos and stone polygons (created through the process of particle sorting), where stones are pressed out around the periphery of the cracks.


Update: When the Phoenix Mars lander sent back pictures of the Martian polar landscape, toward the end of May 2008, I was delighted to see that the same features were present there. Soil polygons on Mars!

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