Weathering is an important natural process where rocks, soils, and minerals are broken down by the various forces such as contact with waters, biological organisms, and the earth's atmosphere. Weathering takes place without involving movement, and therefore it is on site, and there is little to no movement, unlike erosion.
The Different Processes Of Weathering
There exist two important classifications of weathering processes namely; chemical and physical weathering which might involve a biological component.
Physical weathering also known as mechanical weathering involves the disintegration of soils and rocks as a result of direct contact with atmospheric conditions such as water, pressure, ice, and heat.
Chemical weathering is also known as biological weathering is the disintegration of soils, minerals, and rocks as a result of direct exposure to atmospheric chemicals or biologically formed chemicals. Chemical weathering is hastened in hot and wet climates whereas physical weathering is most intense in extremely dry or cold environments. However, the two types of weathering take place at the same time with one accelerating the other.
The materials that remain after the rock has been disintegrated are mixed with the organic material to create soil. The mineral content of the soil is dependent on the parent material hence soil derived from a solitary rock can lack in one or more minerals essential in good fertility whereas weathered soil from different types of rocks usually make up a more fertile soil
Types of Physical Weathering
The primary process involved in mechanical weathering is known as abrasion which is the process by which particles are disintegrated. Abrasion through wind, ice or water processes that are rich in sediment can have an outstanding cutting power.
Thermal stress weathering sometimes known as isolation weathering occurs due to expansion and contraction of rocks as a result of changes in temperature. A good example is when rocks heat up because of sunlight or fire causing their constituent minerals to expand as well. Different minerals expand to varying degrees, therefore, creating different stress levels that cause the rock to disintegrate. Since some rocks are either colder or warmer on the outer surface, they tend to weather through exfoliation which is the peeling of the outer layer.
Thermal stress weathering consists of two main types which are thermal fatigue and thermal shock. Thermal weathering takes place in the desert like regions where temperatures vary considerably from scorching hot during the day to chilling cold at night time. Thermal heat such wildfires can create significant weathering of boulders and roc where the heat expands the boulders, and thermal shock transpires.
Frost weathering is also known as cryofracture, frost wedging or ice wedging is the common name used for the various processes of frost weathering involving ice. These different stages include freeze-thaw weathering, frost wedging, and frost shattering. Extreme frost shattering propagates enormous chunks of rock particles known as scree which is usually located on mountain slopes. Frost weathering is a conventional process in mountain regions where temperatures are at the same level of water’s freezing point. Weathering action caused by freezing occurs in places where the environment has adequate moisture, and the temperatures fluctuate between high and low freezing points. Chalk is an example of rock that is most prone to weathering due to frost.
Rocks specifically found around the coastal region experience weathering caused by ocean waves. Weathering in the coastal geography can either be gradual due to wave action or abrupt due to salt weathering.
Pressure release which is also known as unloading is a weathering process caused by the expansion and fracturing of underlying rocks through the removal of overlying substances mostly through erosion. Igneous rocks such as granite are found deep below the earth’s surface are usually under immense pressure due to the overlying materials. When the overlying materials are moved due to erosion the intrusive rock in this case granite is exposed, and the pressure is released. Due to the exposure, the rocks’ outer layer will start to expand causing fractures and the gradual breaking away of sheets of rocks through exfoliation or sheeting.
Weathering through salt crystallization is also known as haloclasty which causes rocks to disintegrate when saline solutions permeate into rock cracks and joints and dehumidify leaving behind the salt crystal. Weathering through salt crystallization is common in arid climates or coastal regions where intense evaporation caused by strong heating causes the crystallization of salt.
Types Of Chemical Weathering
Chemical weathering alters the composition of rocks, therefore, influencing them to create a variety of chemical reactions when water interacts with the minerals. Chemical weathering is a gradual process since it involves the adjustment of rock mineralogy.
Dissolution And Carbonation
Weathering through carbonation is a process where carbon dioxide in the atmosphere causes disintegration of rocks through solution weathering. Carbonation typically takes place on rocks such as chalk and limestone that comprise of calcium carbonate. Carbonation weathering takes place when rainwater mixes with an organic acid or carbon dioxide to form a carbonic acid solution which reacts with limestone to form calcium bicarbonate. Weathering occurs faster during cold temperatures since cold water can contain significant amounts of dissolved carbon dioxide. Glacial weathering is mainly caused by carbonation.
Weathering through hydration takes place when rock minerals absorb water, and the increased volume causes stresses on the inner layer of the rock. A good example of hydration is iron oxides which are converted to iron hydroxides causing weathering.
Hydrolysis is a type of chemical weathering that affects carbonate and silicate rock minerals. In hydrolysis pure water slightly ionizes reacting with minerals and silicates thus causing weathering.
Oxidation is a type of chemical weathering that occurs in a variety of metals. The most common weathering through oxidation is the combination of oxygen, iron, and water. Rocks that have been affected by oxidation retain a reddish-brown color on the outer layer which easily disintegrates thus making the rock weak. The process that occurs as a result of oxidation is commonly known as rusting even though this process is different from the metallic rusting.
Living organism plays a huge role in both mechanical and biological weathering through various processes. The attachment of some living organisms to rock surfaces help in the disintegration of rock surfaces
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