Pingos

Pingos are ice-cored hills that form on permafrost landscapes in Arctic and subarctic regions. They are non-glacial features created by freezing processes of groundwater beneath thawing permafrost, rather than by ice flow from glaciers.

There are two main types: open-system pingos and closed-system pingos. Open-system pingos form where an unfrozen layer of ground, known as a talik, exists beneath the permafrost; groundwater rises, freezes at the top, and builds an ice core that lifts the surface. Closed-system pingos form entirely within frozen ground when a lens of water freezes in place, expanding and pushing up the overlying soil.

Pingos are usually circular or oval with steep sides, and they vary in height from a few meters up to about 70 meters, with diameters ranging from tens to hundreds of meters. They occur most commonly on continuous permafrost in Siberia, Alaska, northern Canada, and Greenland.

They develop slowly, often over thousands of years, and can persist for long periods. If the ice core melts due to warming, a pingo can collapse to form a depression or a shallow lake. Pingos are indicators of permafrost presence and dynamics and are of interest in studies of landscape evolution and paleoclimatology.