The elongated depressions on the tundra hide cold secrets. They are covered ice wedges, forming a peculiar polygonal pattern on the ground. Ice wedges are found mainly on even surfaces. The visible part consists usually of more or less inconspicuous, elongated depressions which are only a few centimetres deep and some decimetres wide, running many metres through the tundra and forming a network of polygons, mostly pentagons and hexagons measuring 10-25 metres in diameter. Occasionally, the shallow depressions become enlarged by small rivers and thus develope into trenches that can
Ice wedges
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