Pingo

For the animated penguin, see Pingu.

A pingo is a mound of earth-covered ice found in the Arctic, subarctic, and Antarctica that can reach up to 70 metres in height and up to 600 hundred metres in diameter.

The name comes from the Inuit word for a small hill. The plural is 'pingos'.

Locations

Tuktoyaktuk in the Mackenzie Delta has one of the highest concentrations of pingos. Other places with pingos include Alaska, Greenland, and the Norwegian island of Spitsbergen.

In Siberia, pingos are known as bulganniakh, from the Yakut language.

Types

Pingos are generally classified as hydrostatic (closed-system) or hydraulic (open-system). Hydrostatic-system pingos result from hydrostatic pressure on water from permafrost, and commonly form in drained lakes or river channels. Hydraulic-system pingos result from water flowing from an outside source, and are less well understood.

Relict hydrostatic (closed-system) and hydraulic (open-system) pingos may be distinguished from each other by determining if lacustrine (lake) deposits are associated with the formation.

Formation

Pingos can only form in a permafrost environment. Evidence of collapsed pingos (ognip) in an area suggests that there was once permafrost.

Pingos usually grow only a few centimetres per year, and the largest take decades or even centuries to form. The process that creates pingos is believed to be closely related to frost heaving.

A large depression in a field left by a collapsed pingo that would have formed during the last ice age. One of many similar hollows and pingo lakes in the area of the Great Eastern Pingo Trail in Norfolk, England.

Pingos are generally classified as hydrostatic (closed-system) or hydraulic (open-system). Hydrostatic-system pingos form as a result of hydrostatic pressure on water from permafrost, and commonly form in drained lakes or river channels. Hydraulic-system pingos result from water flowing from an outside source, subpermafrost or intrapermafrost aquifers. Hydrostatic pressure initializes the formation of the ice core as water is pushed up and subsequently freezes. Open-system pingos have no limitations to the amount of water available unless the aquifers freeze. They often occur at the base of slopes and are commonly known as Greenland type.

Pingos eventually break down and collapse. The current estimate is that pingos can last about 1000 years.

History

The term pingo was first borrowed from the Inuit by the arctic botanist AE Porsild in 1938. Porsild Pingo in Tuktoyaktuk is named in his honor.

External links

• Pingos - article from the Open University Geological Society
• Pingo - entry in The Canadian Encyclopedia
• Ice Wedges, Polygons, and Pingos - diagrams of pingo formation