Frost weathering is when the water in rocks and soil freezes and then thaws repeatedly. When it freezes, it expands and makes the rock or soil crack. This happens because water takes up more space when it freezes than when it is just liquid. Think about how a balloon gets bigger when you blow it up. When the water thaws, it contracts and the cracks become bigger. This can happen over and over again, and eventually, pieces of the rock or soil break off. It's kind of like when you build sandcastles at the beach and water freezes in the sand overnight, making it hard and easy to break apart the next day. Frost weathering is important because it can shape mountains and create natural rock formations like arches and pillars.