1 Stones smaller in size than the spacing between the ice lenses in a frost susceptible matrix are pushed up by basal ice segregation. This nucleation takes place in a dessiccation crack open at the base of the stone (shrinking). 2 Stones bigger
in size that the spacing between the ice lenses use to be pulled up by frost heaving. Nevertheless, in very humid conditions, the frost pull effect can be enhanced by a frost push effect resulting of a basal segregation occurring in a drawing crack