Living with frozen ground: a field guide to permafrost in Yellowknife, Northwest Territories

In the District of Keewatin, west of Hudson Bay, numerous shallow lakes occupy depressions on the perennially frozen, glaciated terrain north of the treeline. Many lakes in the vicinity of Kaminak Lake have extensive shallow areas that are characterized by features of probable periglacial origin. Some features, such as polygonal patterns, frost-heaved boulders, and mudboils, are similar to those of the subaerial landscape.Digitate, cobble-covered ribs and boulder-filled troughs that commonly form a crenulate pattern on the shallow shelves adjacent to till-covered shores are thought to be the subaqueous equivalents of mudboils that are common on the adjacent till plains. They are composed of till and are underlain by an undulating frost surface that is raised beneath troughs and depressed under ribs.Holes with or without raised rims often occur singly or in clusters on loose, sandy silt bottoms in water depths less than 2.5 m. A frost table underlies the bottoms of these holes at depths of 30 to 50 cm in early August. Holes may be either sites of strudel scour or sites of final points of attachment of winter ice to the frost table, just before the buoyancy of the ice caused it to break free from the bottom in the spring, extracting frozen sediment from the surrounding unfrozen sediment, leaving a hole.The features described are restricted to water depths that are probably equivalent to the average maximum thickness of winter ice. Thus, they represent areas where the lake is seasonally frozen to the bottom, and may be restricted to portions of lake basins underlain by perennially frozen ground.

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Frost mounds at Bear Rock, near Fort Norman, Northwest Territories, 1975–1976

Canadian Journal of Earth Sciences ◽

10.1139/e78-027 ◽

1978 ◽

Vol 15 (2) ◽

pp. 263-276 ◽

Cited By ~ 31

Author(s):

Robert O. van Everdingen

Keyword(s):

Northwest Territories ◽

Soil Cover ◽

Yukon Territory ◽

East Side ◽

Frozen Ground ◽

North Fork ◽

Spring Area ◽

Empty Cavity ◽

Blackstone River ◽

Large Flow

A number of frost mounds of the frost blister type were observed at the site of a group of cold springs on the east side of Bear Rock, about 4 km west-northwest of Fort Norman, Northwest Territories, Canada. The mounds ranged in height from 2.0 to 3.0 m, with horizontal dimensions between 26 and 48 m. They contained a domed layer of ice, up to 85 cm thick, over an empty cavity up to 70 cm high, which was in turn underlain by frozen ground. Soil cover over the ice layer was 30–65 cm thick. The ice presumably formed from springwater injected under considerable hydraulic potential. New frost blisters are formed annually. Three recent frost blisters observed in June 1975 were partially destroyed by melting, slumping of the soil cover, and collapse of the ice dome by mid-September 1975. A portion of the ice lasted into summer 1976. Three new frost blisters, formed during the 1975–1976 winter, were observed in March 1976; two of these had completely collapsed by mid-June. An icing blister associated with one of them ruptured on March 21, 1976, producing a large flow of water, which lasted for several hours. A section of the icing blister subsequently subsided. Remnants of frost blisters have been observed in a spring area northeast of Turton Lake, Northwest Territories, and along the Dempster Highway in North Fork Pass and near the crossing of Blackstone River, Yukon Territory.

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