Relict late Quaternary permafrost on a former nunatak at Plateau Mountain, S. W. Alberta, Canada
DOI:
https://doi.org/10.26485/BP/1997/36/4Keywords:
mountain glacier, ice Wedge, thermokarst, alpine vegetationAbstract
On Plateau Mountain in southwest Alberta is an example of relict alpine permafrost left from the Late Wisconsin glaciation. The flat mountain top was not glaciated during the Pleistocene and the relict permafrost on its summit is not yet in equilibrium with the present-day climate. The near-surface ground temperature becomes colder with depth and heat is moving slowly into the ground. This heat flow is accomplished by heat conduction and groundwater movement, but this is partly counteracted by air moving through block fields or cracks in the bedrock. Ground water and air movement produce large but localized ground temperature effects which may change location over time.
The surface shows inactive sorted patterned ground and thermokarst resulting from melting of ice wedges formed beneath the stony borders during a colder climate. At the north end of the mountain, an ice cave occurs in the surface of the relict permafrost. The alpine vegetation includes disjunct species from the floras of the Arctic from around the Atlantic Ocean, from eastern Siberia, and also from the west coast of the contiguous United States south to California. These distributions imply a migration of alpine floras during past cold events. Some local speciation has also occurred.
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