Weathering

In many locations, changes in temperature and moisture content of the environment cause significant physical weathering. When rock is warmed, it expands; when it cools, it contracts. In some regions, rocks are heated to relatively high temperatures during the day and then cooled to much lower temperatures during the night. The constant expansion and contraction of the rocks may result in pieces being broken off.

This effect is likely to be more pronounced if water is present. Suppose that water fills the cracks in a rock during the day. At night, if the temperature drops far enough, that water will freeze and form veins of ice in the rock. But water expands as it freezes. Therefore, the veins of ice are likely to break apart pieces of the rock, a process that is repeated day after day and night after night when temperatures follow the pattern described above.