What is weathering
Weathering is the wearing away or breaking down of rocks, soils and minerals as well as wood and artificial materials by agents present in the atmosphere like temperature, moisture, frost and biological organism. Two important classification of weathering processes exist physical and chemical weathering each sometimes involves a biological component.
Physical weathering involves the breakdown of rocks and soil through direct contact with atmospheric conditions. Such as heat, water, ice and pressure. Second classification chemical weathering involves a direct effect of atmospheric chemical or biological produced chemicals also known as biological weathering in the breakdown of rocks, soils and minerals. while physical weathering is point up in very cold or very dry environment, chemical reactions are most intense where the climate is wet and hot.
- What is weathering
- Types of weathering :-
- Significance of weathering
- Weathering and People
The materials left over after the rocks break down combined with organic material creates soil. The earth’s surface is subject to constant changes. Both nature and humans are responsible for such changes.The extent to which a landscape is modified depends on many factors such as internal process , external forces, nature of rocks and the length of time these processes that have been acting upon.
Internal processes are the processes which take place beneath the earth’s surface and modify the earth’s shape These include movement of tectonic plates, volcanic eruptions, and earthquakes. internal processes may produce lava plains, plateaus, rift valleys, geysers, mud pools, etc.
The external processes take place on the surface of the earth. These processes work slowly. Weather, rivers, glaciers, wind, waves etc. are some of the major agents responsible for external processes.
Types of weathering :-
The wearing away or breaking down of rocks by agents present in the atmosphere like temperature, moisture and frost is known as weathering. weathering is considered as the phase in the gradation of landscape, because it prepares rock materials which are transported by other agents of erosion . there are mainly three types of weathering.
- Physical weathering
- Chemical weathering
- Biological weathering
a) Physical weathering:
It refers to mechanical disintegration of rocks without any changes in their chemical composition. Temperature, Ocean waves, pressure release and frost are the some main factors which are responsible for physical weathering. For example cracks exploited by physical weathering will increase the surface area exposed to chemical action.
1)Temperature or thermal stress :
There are extreme temperature difference, the rocks break down and converted into pieces. In area of extreme range of temperature, rock surface is exposed daily to intense heating during the day and intense cooling during the night. The intensive heating expand the rocks and intense cooling contract them. As a result of the daily cycles of expansion and contraction, rocks are weakened and they break apart. It is called isolation weathering result from the expansion and contraction of Rock caused by temperature changes. for example heating of rocks by sunlight or fires can cause expansion of their constituent minerals. As some minerals expand more than others temperature changes setup differential stresses that eventually cause the rock to crack apart because the outer surface of rock is often warmer or colder than the more protected inner portion.
In cooler regions, water that fills up the cracks in rocks, freezes and turn into ice which expands at night. During the day ice melts and the water seeps further into the cracks. At night the water again freezes, widening the cracks. This continuous widening of the cracks leads to disintegration of rocks. This is called as frost action, ice wedging is the collective name for several processes include Frost shattering, Frost wedging and freeze liquate weathering. Several frost shattering produces huge piles of Rock segments called scree which may be located at the foot of mountain areas or along slopes. Frost weathering is common in mountain areas where the temperature is around the freezing point of water.
3) Ocean waves
It is formed by the the weathering of wave actions over geological time or can happen more casually through the process of salt weathering.
4) Pressure release
It is also known as an loading overlying materials are removed by erosion or another processes which caused underlying rocks to expand and fracture parallel to the surface intrusive igneous rock are formed deep below the Earth’s surface. They are under tremendous pressure because of the overlying Rock materials. These intrusive rocks are exposed and the pressure on them is released.
Chemical weathering changes the minerals composition of the rocks. Air and water are the main agents of chemical weathering. water is the main agent of the chemical weathering. For example, when carbon dioxide from the atmosphere or decaying matter combines with water, a weak acidic solution is produced that can dissolve calcium carbonate in the rocks and create cracks .
Chemical weathering changes the composition of rocks often transforming them when water interacts with minerals to create various chemical reactions. Chemical weathering is a gradual and ongoing process as the mineralogy of the rock adjusts to the near surface environment. New minerals develops from the original minerals of the rock. Chemical weathering is enhanced by such geological agents as a pressure of water and oxygen.
A number of plants and animals may create chemical weathering through release of acidic compounds the effect of moss growing on roof is classed as weathering. Mineral weathering can also be initiated or celebrated by soil microorganism.
plants, trees, and animals also contribute to the weathering. Roots of the trees may grow into the cracks in the rocks in search of nourishment or the seeds of a tree may sprout in the soil that has collected in a cracked rocks. Burrowing animals and human beings also contribute to this process.
The gravity of earth pulls all materials downwards. This downhill movement occurring under the pull of gravity is collectively known as mass wasting or mass movement. mass movements like landslide, mud flow ,etc. bring changes in the earth’s surface.
Factors that affect weathering:
The following factors that affect weathering are:
(1) Rock structure:-
All physical and chemical characteristics of rocks are included in the structure such as hardness and mineral composition of rocks. The physical properties and mineral composition of rocks determine how they will be affected by weathering. For example, the process of chemical weathering in rocks with porous and soluble minerals is rapid. The position of the rock layer also affects the activation of weathering. The rocks in which the layers are in a vertical position have disintegration and dissociation action quickly, whereas in horizontal layers rocks the weathering is not very quick.
2) Climate: –
Due to difference in climate, there is a considerable difference in weathering. In other words, the rate and type of weathering are controlled by temperature and humidity. Mechanical weathering is more prevalent in cold climate and desert regions while chemical weathering is more effective in hot and humid climate.
The process of weathering is also influenced by the structure of the topography. The thick covering of soil reduces mechanical weathering in areas with less relief. The flow of water in an area intensifies chemical weathering. The rapid gradient of the topography also affects the weathering.
(4) Natural vegetation:-
Weathering is limited in areas covered by vegetation. Desertification is directly affected by weathering in the absence of vegetation. The roots of the vegetation keep the rocks organized, which reduces the effect of weathering, but these roots disintegrate the rocks and also cause cracks in them, causing fragmentation in the rocks.
Significance of weathering
- The process of weathering is responsible for erosion. If there is no weathering of rocks, erosion will not have any meaning that weathering helps in erosion and shortening of relief.
- The process of weathering divides the rocks into small pieces and provides a route for soil formation. Hence weathering is an important process of soil formation.
- The weathering and deposition of rocks is very important for the national economy as it aids in the enrichment and concentration of valuable minerals such as iron, manganese, aluminum and other ores.
Weathering and People
Weathering is a natural process, but human activities can speed it up.For example, certain kinds of air pollution increase the rate of weathering. Burning coal, natural gas, and petroleum releases chemicals such as nitrogen oxide and sulfur dioxide into the atmosphere. When these chemicals combine with sunlight and moisture, they change into acids. Then it fall back to earth as acid rain. Acid rain rapidly weathers limestone, marble, and other kinds of stone. The effects of acid rain can often be seen on gravestones, making names and other inscriptions impossible to read.
At last we can say that the changes on the earth’s surface is continuous process.Both nature and humans are responsible for such changes.