These can be seen in the local mountains, in Yosemite, in areas where once deep-seated rocks are now exposed at and near the Earth's surface. Frost wedging is another type of physifcal weathering. This type results from the ability of water turning into ice exerting pressure as the change of state increases the volume. Ice can exert a pressure of 30,000 pounds per square inch when it is confined in a crack in rock, as in water trickling into a crack in the rock and freezing. This can wedge out angular block of rock that have been exfoliated.
Gravity takes over once a rock is free to move.
The movement downslope of rock blocks reduces the size and rounds the material. Chemical weathering not only breaks down the original rock, it also breaks apart the bonds that form the minerals, allowing them to reconfigure into new minerals. The process may be inorganic or organic. Oxidation is the chemical reaction with oxygen that breaks down minerals containing iron. For instance biotite contains SiOAlFeMg.