The other major process that shapes the surface of planets is erosion. The sediment is usually removed from its source rock and transported somewhere else by the process of erosion. Streams can carry silt, rivers can carry sand as well as silt and floods can move sometimes the largest boulders. When liquid water freezes, it expands. This expansion can crack rocks if there is no place else for the water to go.
Ice also forms large masses called glaciers.
Sand dunes are formed by wind and are moved by the wind. The sediment carried by the wind can impact other rocks and weather them as well. The last agent of erosion is impact cratering . Impacts break up rock and throw it out of the crater. On planets without atmospheres, there is no air to slow down and break up incoming meteors.