The major factors that determine the rate of weathering are properties of the parent rock and the climate. Other factors include soil conditions and length of exposure. The amount of surface area exposed also affects the rate of weathering.
Weathering refers to the chemical or mechanical process by which rocks are broken into smaller particles. In chemical weathering, rocks may be converted into clay or dissolved. Examples include dissolving minerals, silicates changing into clays and oxidation. Mechanical weathering is the physical breakdown of rocks.
Different types of rock, in terms of mineralogy and structure, have different susceptibilities to weathering. For instance mafic silicates, which include olivine and pyroxene, weather much faster than felsic minerals such as quartz and feldspar. The composition of rock also affects its solubility in water, which greatly influences weathering rates. For instance calcite dissolves more readily in water than feldspar.
The structure of a rock also influences its rate of weathering. For example, rocks such as granite do not have planes of weaknesses, so they are more resistant to weathering. On the other hand, layered sedimentary rocks that consist of bedding planes are easy for water to infiltrate and this often tears them apart.
Rainfall and temperature in the vicinity of the rock also determine the rate at which it weathers. Greater rainfall and high temperatures increase the rate of weathering. Tropical regions that receive adequate rainfall therefore often contain rocks that weather more quickly.