Physical weathering, also called mechanical weathering, refers to the process of breaking rocks apart while retaining their chemical composition, according to the American Geosciences Institute. It means that rocks slowly wear away due to physical changes, such as temperature changes, freezing and thawing, wind, rain and waves, explains the BBC.
Physical weathering caused by temperature changes often occurs in deserts, as it is extremely hot during the day but very cold at night, states the BBC. When rocks are heated and cooled repeatedly, cracks form and the rocks gradually break off in small pieces. The wind causes weathering by blowing small grains of sand that wear away rocks over long periods of time. Water is also an agent of physical weathering, as it is capable of breaking rocks when it expands and freezes into ice. Water seeps into cracks and expands the cracks as it freezes. This process of freezing and thawing continues until the cracks grow very big and cause pieces of rocks to fall.
The AGI says that swiftly moving water is capable of lifting rocks from the stream bottom for short periods of time. Rocks collide with other rocks when they drop, breaking off small pieces of rocks. Plant roots can also grow in cracks and cause rocks to fall apart.