Factors affecting rate of Weathering :
Some minerals are more susceptible to weathering. The dark minerals are also more affected by thermal weathering than light coloured ones. A rock that is polymineralic is more subject to destruction than one that is monomineralic. This is because coefficients of linear expansion and therefore undergo different deformations with variations in temperature with protracted temperature variations, mutual cohesion between individual grains is disrupted and the rock disintegrated.
In principle, the finer grained rock is the greater the surface area exposed and hence the greater the surface area are exposed and hence the greater intensity of weathering.
However, if a rock has coarse grains that are easily weathered, the great holes left may weaken the rock rapidly and therefore enhance the rate of weathering.
These provide surfaces along which weathering can take place easily (i.e. where agents of chemical weathering can penetrate and act). They include joints, faults, bedding planes and cleavage. The fractures are gradually widened by weathering until the rock is completely split into parts.
Regions with large diurnal range (daily temperatures variations) undergo the most intensive thermal weathering.
This is most pronounced in deserts.
Importance of weathering:
1. Leads to the breakdown of rocks into smaller particles until soil is formed which is valuable agricultural uses
2. Weathered land forms are tourist attractions.
3. Weathered land forms are used for research purposes.
4. Weathering products transported to the sea by rivers as dissolved solids make sea water salty and serve as nutrients for many marine organisms.
5. Some metallic ores, such as those of copper and aluminum, are concentrated into economic deposits by chemical weathering.