Weathering refers to the physical, chemical, and biological processes that break down rocks and minerals on the Earth's surface. Ice wedging is a type of weathering caused by the expansion of water as it freezes, which can crack rocks. Oxidation is a chemical weathering process that occurs when oxygen reacts with minerals in rocks, causing them to break down. Tree roots breaking rocks is an example of biological weathering, as the roots exert pressure and force, causing the rocks to break apart. However, a car crash is not an example of weathering as it is a sudden and violent event caused by human activity, rather than a natural process of rock breakdown.