Altiplanation terraces and slope development in Vest-Spitsbergen and south-west England
DOI:
https://doi.org/10.26485/BP/1962/11/11Keywords:
frost shattering, periglacial features, krioplanacjaAbstract
Conspicuous among periglacial modifications of recently deglacierized dolerite terrain in Ekmanfjord, Vest-Spitsbergen, are rock benches and terraces on moderately inclined slopes (7-25°) lying between 50 and 100 metres above sea-level. Field observations suggest that the benches are fashioned primarily by frost heaving, frost shattering and the gravitative transfer of debris. Their continuing development is converting formerly ice-smoothed, convex-upward slopes into stepped, but overall rectilinear, slopes which retain their steepness as they retreat.
A similar origin is suggested for terraces hillslopes displaying features akin to altiplanation terraces which are very characteristic of the higher parts of south-west England. The demonstration that these landforms are periglacial features not only supports the conclusion that many parts of Southern England exhibit relict periglacial landscapes. It also suggests that in some cases cryergic processes have created rather than smoothed out irregularities of slope. The mature or equilibrium slope of cryoplanation is indeed smooth and compounded of accordant elements the inclination of each of which represertts the slope limit appropriate to the calibre of the debris that is moved across it. But the achievement of cryoplanation on certain moderately inclined initial slopes is effected via the production and development of altiplanation terraces or congelifraction benches. These are characteristic of those parts of Southern England of which for one reason or another the complete periglacial metamorphosis was never realized.
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