CGRG Bibliography of Canadian Geomorphology
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Author : Harris, S.A.
Date : 1998.
Title : A genetic classification of the palsa-like mounds in Western Canada.
Publication : Biuletyn Peryglacjalny
Issue : 37:
Page(s) : 115-130.
Abstract
In Western Canada, there appear to be five main groups of true palsa-like landforms. Floating palsas are developed entirely in peat and float like an iceberg. They exhibit increased ice content due to addition of meteoric water, but are under 60 cm high. Minerogenic palsas are developed in a thin peat cover, with the permafrost extending down into the mineral substrate. They represent the bulk of the palsas and their height is dependent on the expansion due to water changing to ice in their core. 2-4 m is typical, with ice contents up to 90% by volume in some layers. Lithalsas are developed entirely in a mineral substrate at sites where fen peat cannot develop. They go through a different sequence of stages and can develop a cover of ericaceous peat. A typical mature lithalsa has an average ice content of over 60% in its core, and its height and shape are similar to those of a minerogenic palsa. Floating peat plateaus differ from palsas by having a flat top rising only 1-2 m above the fen. The icy core is limited to the peat and contains less H (sub 2) O than the surrounding unfrozen peat. Air has replaced some of the water so that it floats considerably higher than the floating palsas. Where the icy core of a peat plateau extends down into a mineral substrate, an anchored peat plateau is produced. Since the rate of peat formation on the mound is half that in the fen, the anchored peat plateaus slowly drown and are eventually destroyed without the intervention of a climatic change. These true palsa-like landforms can be mimicked by other processes, e.g. intrusion of water producing pingos or seasonal frost mounds. Other examples described include permafrost that has subsequently developed in a blanket bog on a slope, and thermokarst caused by melting snow at the foot of slopes in areas of continuous permafrost. These are not considered to be palsa mounds, since palsas are regarded as distinct from other types of permafrost.
Bibliography of Canadian Geomorphology