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On frozen ground, sand movement begins when strong winds put loose
sand grains into motion (see pore-ice sublimation).
Other grains are put into motion by the impacts of sand grains saltating
over the cemented ground.
Saltating grains keep
more of their kinetic energy when they travel over hard surfaces
like frozen sand. (On loose sand, some of the energy is dispersed
in the many small movements of grains during collisions with the
surface.) Therefore, saltating grains can bounce higher and travel
further on frozen ground than they can on loose sand.
Winter processes can
transport sand further inland or over dune systems than sand movement
during other seasons. One reason for this is that the saltating
grains are travelling over frozen surfaces. Very strong winds, less
resistance from vegetation, and snow/sand deposits smoothing out
the topography are other reasons for longer transport distances.
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Photo of loose sand deposits on frozen surface. (Hoffmaster State
Park in December 2001.)
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