low-centre polygon

Low-centre polygons are a type of polygonal ground found in permafrost regions, characterized by a network of shallow troughs that form polygons, typically 3 to 30 meters in diameter. These troughs are underlain by vertical ice wedges, which are large, wedge-shaped masses of ice that can be 0.6 to 3 meters wide at the top.12

The formation of ice wedges is explained by the thermal contraction theory. During cold winters, the frozen ground cracks. In spring, meltwater seeps into these cracks and freezes, forming an ice vein. As the ground expands and contracts with temperature changes, these ice veins grow into wedge shapes over time. Low-centre polygons can form when the ground adjacent to the ice wedge is upturned, creating ridges on either side and a lower area in the center, which may hold a pond. These features are indicators of active ice wedge growth and the presence of permafrost.312