Geoscience Reference
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Fig. 5.6 Platy ( top ) and
blocky ( bottom ) structures
resulting from
cryodesiccation
(Fig. 5.6 ). In ultraxerous cryosols (Anhyorthels and Anhyturbels) of Antarctica,
cryodesiccation is responsible for cracks that develop following melting of snow as
well as thermal contraction of soils with sand-wedge polygons (Fig. 5.7 ).
5.2.6
Ice Segregation
Ice segregation occurs when liquid moisture is transferred to other regions in the
soil during freezing. When ice forms in sandy soils, practically no migration of
moisture occurs, and interstitial ice generally develops during freezing. In contrast,
the freezing of fi ner textured soils induces the formation of inclusions of pure seg-
regation ice as lenses, layers, reticulations, etc. (see Figs. 2.8 and 3.2 ) .
5.2.7
Gelifl uction
Gelifl uction refers to the slow downslope fl ow of unfrozen earth materials on a fro-
zen substrate. Therefore, it is a mass-wasting process and not a cryopedogenic pro-
cess, but it is strongly infl uenced by frost. The term “solifl uction” normally is
restricted to downslope fl ow of unfrozen earth materials due to seasonal frost rather
than to permafrost. Gelifl uction is strongly infl uenced by the amount and distribu-
tion of segregation ice (Matusoka, 2001 ). Rapid movement is often restricted to a
superfi cial layer upper 5-10 cm thick, especially in fi ne-textured soils. Gelifl uction
can occur on slopes of less than 10°, and common surface velocities range from 1 to
3 cm/year.
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