Weathering of rock Weathering is the process by which all rocks at the earth's surface gets broken down. Physical weathering - Rock gets broken into pieces but its chemical composition remains unchanged.
Water expands when frozen which forces rocks open.
Biological weathering - Roots of plants grow into cracks and force cracks open. A mass of igneous rock may be exposed which expands upwards forming a dome. As it expands it breaks into sheets parallel to the surface. Chemical weathering is faster for limestone than sandstone and is speeded up by heat. Chemical weathering occurs fastest at the sharp edges of rocks as they have a large surface and less volume so they can be eroded quicker.