Agents of Weathering
Plants and Animals
Plants can break rocks. As trees or shrubs grow, their roots may enter through small cracks in rocks. As the roots grow bigger, they eventually wedge the rocks apart. This action of plant is called root wedging. Root wedging shows how trees in concrete plant boxes and pavements break cement.
Animals are also a factor in weathering. Heavy animals with big hooves or feet, such as elephants and hippopotamuses, may step on big rocks, causing them to crumble into bits. The digging and burrowing of animals like rabbits and moles move deeply buried rocks to the surface, exposing them to different conditions in the environment. Animals such as earthworms also make burrows, which allow air and water to penetrate the soil more easily.
