freeze-thaw

The weathering of rock which occurs when the water, which has penetrated the joints and cracks, freezes. This process is, therefore, probably effective only in well-jointed rocks. Water expands by 9% when it freezes, and it has been suggested that this expansion causes the rock to shatter. Freeze-thaw is most active where there is a maximum number of temperature oscillations around 0 °C; it is therefore more frequent in periglacial, rather than polar environments.

In glacial geomorphology, some writers distinguish between the freeze-thaw active within a glacier (See bergschrund), and a similar process acting above the glacier, which may be termed frost shattering. This effect has shaped the Cuillin Hills of Skye, for example, above the snowline. Some geomorphologists believe that this force is insufficient to break up any but the softest rocks, and that what has been called frost-shattering is really hydro-fracturing. Alternative terms are: congelifraction, frost-shattering, gelifraction, and gelivation.