Freeze-thaw weathering is a process of erosion that happens in cold areas where ice forms. A crack in a rock can fill with water which then freezes as the temperature drops. As the ice expands, it pushes the crack apart, making it larger. When the temperature rises again, the ice melts, and the water fills the newer parts of the crack. The water freezes again as the temperature falls, and the expansion of the ice causes further expansion to the crack. This process continues until the rock breaks.