Pingos usually grow a few centimeters per year, and the largest take decades or even centuries to form.
Pingos eventually break down and collapse.
Evidence of collapsed pingos in an area suggests that there was once permafrost.
Pingo National Landmark protects eight of these features.
Two of the most famous pingos are Ibyuk and Split.
Ibyuk is estimated to be more than 1,000 years old.
In this area, lakes over two meters deep do not normally freeze solid in winter.
The year-round presence of water at the lake bottom protects the sandy lakebed from frigid winter temperatures.
Exposed to frigid winter temperatures, the waterlogged sand of the former lakebed freezes and its water expands.
The increased pressure pushes the surface upwards, supported on a lens of water.
A small, cone-shaped hill grows, and after a few years may be recognized as a pingo.
The pingo continues to grow while there is still unfrozen ground in the lakebed.
Throughout its growth, the pingo is supported by the pressure in the water lens.
A pingo will collapse if the ice core melts.
Aside from Canada, pingos occur in Greenland, Siberia, and the Norwegian island of Spitsbergen.
Sources:Parks Canada,Wikipedia
