Massive ground ice consisting of tabular bodies of almost pure ice is widespread in many permafrost regions of the world. It is common in the Beaufort Coastlands where it may be found under flat-topped hills along the western Arctic coast.

Massive ice along Tuktoyaktuk Coast.

A typical exposure of massive ice is found at Peninsula Point, 6 km southwest of Tuktoyaktuk. Here the massive ice has formed in response to permafrost aggradation at the contact between overlying fine-grained sediments and underlying coarse-grained sediments. When exposed to ablation, massive ice exposures generally initiate slump failures referred to as retrogressive flow slides. Massive ice often shows evidence of creep deformation with diapirs forming where differential loading occurs. Diapirs typically occur beneath ice wedges that, in some cases, may be penetrated by the wedge itself.

Other features associated with massive ice include the phenomena of reticulate ice and ice dikes, both of which occur in the sediments above the main body of the ice. Reticulate ice comprises a network of horizontal and vertical ice veins, usually forming a rectangular three-dimensional lattice within the sediment. Ice dikes originate at the top of massive ice, and may extend upward a distance of 8-10 m into the overlying sediment.

Ice wedge polygons.

Ice wedge.

Ice wedges are another form of massive ice that is widespread in regions of continuous permafrost. These wedge-shaped bodies contain vertical, to sub-vertical bands of ice that may be discoloured due to the presence of sediments, and whitish due to the occurrence of bubbles.

Cross-section of pingo showing ice.

Another example of segregated massive ice is the pingo. Pingos are conical to sub-conical hills ranging in height from a few metres to 50 m. These are intrapermafrost features that are common along coastal and inland regions of the Beaufort Coastlands, and are characteristically cored by massive ice. Typically they are formed in association with permafrost aggradation into drained lake basins.

Author: S.R. Dallimore
Geological Survey of Canada