Weathering is a process of breaking up rock materials under the influence of air and water. It designs the Earth’s surface by shaping it through different physical and chemical processes. Each of these processes has a different effect on rocks and their minerals, and different rocks react differently to weathering, depending on their structure. The three types of weathering processes are mechanical (or physical), chemical and biological weathering.
Effects of Mechanical Weathering
Mechanical or physical weathering includes two main processes: fracturing and abrasion, which may be intense in wet and dry regions. Wind, rain, snow, ice and other geological events cause mechanical weathering. This type of weathering leads to splitting of rocks and minerals into fragments. Big and sudden changes in air temperature, which are very common in deserts, or water temperature changes always cause expansion or contraction of minerals. For example, when water enters a crack and freezes, it widens the crack and eventually leads to breaking of the surface. Plant roots have a similar effect when they grow so big that they reach the crack in the rock. At some point, the rock will fall apart.
Effects of Chemical Weathering
This type of weathering changes the mineral composition of rocks by chemical processes and it can sometimes lead to dangerous conditions. Water is the basic agent in chemical weathering because it initiates the whole process. Some of its effects are oxidation (rusting), hydration and carbonization. Chemical weathering also causes loss of chemical elements by solution in water. Caves, stalactites and stalagmites are created by different chemical processes of weathering.
Effects of Biological Weathering
Biological weathering is a process of rock and mineral disintegration caused by physical and chemical agents of living organisms. Whether weathering is caused by bacteria or a plant or an animal, it may have both physical and chemical effects on the surface. These effects include breaking of particles, movement and mixing of materials, production of carbon dioxide by breathing and a biological process of chelation (production of organic substances). Organisms also have an effect on the pH of the soil.
Resistance to Weathering
Rock resistance to weathering depends on its mineral composition and porosity. Physically soft minerals may be easily crushed and broken apart, while it is not so simple to do with harder minerals. The arrangement of a rock’s mineral grains and their size is what controls the process of weathering.