Polygons - Such structures are typical for tundra landscapes in the permafrost areas. When the ground freezes, it fractures. In summer water trickles into the cracks, freezes again in sub-zero temperatures and expands at the same time. In this way, a grid of cracks filled with water is formed, which dissects the tundra into polygons. These polygons measure up to 15 m in diameter. (aerial view)