Cryospheric systems - Fundamentals of the Physical Environment - page 380

Plate 15.22 Unnamed closed-system pingo along the Arctic ocean coast of Canada.
Photo: Ken Atkinson

(a) Pressure (indicated by arrows) caused by an advancing freezing plane initiates ice lensing at the freezing plane
where the permafrost is the thinnest.
(b) As the permafrost thickens, the excess pore water continues to segregate into the ice lens at the freezing plane,
forcing the surface upward.
(c) The ice lens ceases to grow as the freezing plane penetrates deeply into the soil. Ice segregation in sediments
at depth results in slow pingo growth.

(a) (b) (c)

Ice Ice

Drained pond

Permafrost

Unfrozen Unfrozen Unfrozen

Figure 15.21 Stages of pingo development.
Source: After Mackay (1973)