Weathering is the breaking down of rocks by elements and effects of the weather.
For these purposes, the term weathering is divided into mechanical and chemical weathering. When rain falls, the water hits on the surfaces of rocks and erodes small particles. This is an example of mechanical weathering. On the other hand, the oxygen and rainwater may combine with iron particles in rocks to form a new substance, thereby breaking down the rocks also. This is an example of chemical weathering.
The root of a tree near to a concrete sidewalk may grow under the sidewalk and cause it to crack. This is an example of mechanical weathering. In mountainous regions, water may collect in cracks and crevices. This water freezes during winter and melts in summer. The repeated freezing and unfreezing of water in the cracks and crevices of rocks tends to push it further apart. This is another example of mechanical weathering.
Eventually, weathering breaks down rocks into soil. Weathered rocks become soil only when they are able to support plant or vegetation life.