Soil forms through the mechanical and chemical weathering of rocks and sediments, and the

accumulation and decay of organic matter. It is for this reason why this piece of academic
writing aspires to explain how soil is formed by the three types of weathering and describe four
characteristics of each soil type. Thereafter it will also discuss how the three types of rocks are
formed and lastly describe the types of soil erosion, explain the causes of soil erosion and
methods of reducing soil erosion.

Parent Material, the mineral from which the soil is formed is termed the parent material. Rocks
are the source of all soil minerals. The parent material is chemically or physically weathered and
transported which then deposits to form layers of soil. Usually, the bedrock is the parent material
but there have been cases wherein soil gets transported due to factors like the wind and water.
Now the actual process of formation of soil is a cumulative combination of a number of
processes. Soil formation also known as Pedogenesis is first kicked off by weathering and
variations come according to the weather conditions.

Glacier: as glaciers move from one part to another, they push the soil further with them. The
drifted material gets deposited miles away from the place of its formation. When the glaciers
melt, huge mounds of soil are left behind, a part of which is carried by the stream.

Water: as rivers flow, the soil particles are transported along with the water. The smallest
particles travel the farthest. Heavier particles, such as sand and rock get settled earlier. Soils
deposited along the river banks are termed alluvial soil, which is very rich in mineral content.
Rainfall also plays an important role. Rainfall washes off the soils in exposed lands.

Wind: air plays the most important role as it transports a huge amount of soil from one place to
another. Loose soils are carried away by the wind from one place to another.

Chemical weathering, decomposition of rocks and minerals by various chemical processes is

called chemical weathering. It is the most important process for soil formation. Chemical
weathering takes place mainly at the surface of rocks and minerals with disappearance of certain
minerals and the formation of secondary products (new materials). This is called chemical
transformation. Chemical weathering becomes more effective as the surface area of the rock
increases. Since the chemical reactions occur largely on the surface of the rocks, therefore the
smaller the fragments, the greater the surface area per unit volume available for reaction. The
effectiveness of chemical weathering is closely related to the mineral composition of rocks.

Mechanical Weathering is the most commonly seen near the earth’s surface. Physical weathering
is named for the fact that it is impacted by physical factors such as water, wind, and temperature.
Physical weathering and dispersion are other terms for mechanical weathering. Moisture,
whether solid or liquid, is the primary agent for mechanical weathering. Thermal stress is caused
by temperature changes and contributes to mechanical weathering. Whenever the temperature
fluctuates from cold and hot, the composition of the rock deteriorates. The stone compresses
whenever the weather is cold and expands whenever the temperature is hot. This rock structure is
weakened as a consequence of all this.

Formation of Igneous Rocks: Igneous rocks (from the Latin word for fire) form when hot, molten
rock crystallizes and solidifies. The melt originates deep within the Earth near active plate
boundaries or hot spots, then rises toward the surface.

Formation of Sedimentary Rocks: Sedimentary rocks are formed from deposits of pre-existing
rocks or pieces of once-living organism that accumulate on the Earth's surface. If sediment is
buried deeply, it becomes compacted and cemented, forming sedimentary rock.

Formation of Metamorphic Rocks: Metamorphic rocks started out as some other type of rock,
but have been substantially changed from their original igneous, sedimentary, or earlier
metamorphic form. Metamorphic rocks form when rocks are subjected to high heat, high
pressure, hot mineral-rich fluids or, more commonly, some combination of these factors.

Good, fertile soil and clean, healthy water are invaluable resources for agricultural producers.
Soil erosion is a serious threat to both. Splash Erosion, splash erosion starts with a fall of rain,
which might be why it’s sometimes called raindrop erosion.

Sheet Erosion, if rainwater begins to move the soil that’s been loosened by splash erosion, the
erosion of the soil progresses to a new stage. It’s now called sheet erosion. A heavy rain or
runoff that crosses a shallow surface can allow enough water to gather to pull the loosened soil
particles from surfaces and sweep them away.
Rill Erosion, picture a sandbox after a child has trailed their fingertips through it. While the scale
tends to be a bit bigger than that, and it only expands with more time and water, that’s the basic
effect that rill erosion has on the land. As water continues to move through these lines, it begins
to erode the surrounding soil. Shallow rills can generally be removed by tilling, but if they’re
allowed to progress, they can form gullies.

Gully Erosion, if rills aren’t tended to, the erosion will continue. Eventually, the narrow strips of
land separating the multitude of rills will be swept away, leaving one larger scar behind. Once
again, the erosion has evolved to a new stage. A gully is a channel that is too deep to be
eradicated with normal tillage methods.

Gully erosion can carve fierce scars across fields. These features can create real hazards for
livestock and farmers. If awkwardly located, they may make sections of fields inefficient to farm
or outright unusable.

Wind Erosion, while pictures of tumbleweeds and windstorms are often associated with the
American West, the reality is that wind erosion can steal valuable topsoil from any location
where the soil is dry, bare, and unprotected by vegetation.

Floodplain Erosion, the areas along waterways are often incredibly fertile. They also offer easy
access to water for irrigation and may even provide a way to transport goods to market. With the
benefits they offer, it’s no wonder that agricultural operations have often settled alongside
waterways whenever possible. However, there is a danger lurking: floodplain erosion.
Flooding can do a lot of damage. Floodplain erosion may not be the kind that makes headlines,
but it is a very real concern for those who count on quality soil for their livelihoods.

In addition, Soil erosion is an ongoing battle between various forces. On one side, you have the
wind and water that would steal the soil particles away. On the other, you have gravity and the
proactive efforts of people who want to protect a valuable natural resource. While it may take a
little thought and energy, those efforts can make a real difference.

In sheet and raindrop erosion, water causes the removal of soil cover and in gully erosion, water
and wind both cause the removal of soil erosion. There are some preventive measures for
reducing soil erosion including mulching, terrace farming, intercropping, contour ploughing,
shelterbelts, contour barriers etc.
There are several causes of soil erosion and some of them are given below: Loss of Vegetation –
The roots of plants are firmly bound to the soil. But due to the absence of vegetation on the soil,
it can be moved by wind and flowing water. Thus, soil erosion is more severe in areas with little
or no surface vegetation, such as deserts or bare lands.

Defective Methods of Farming, improper methods of farming such as ploughing in the wrong
way i.e. up and down the slope form channels for the quick flow of water leading to soil erosion.
Wind, wind is a powerful natural process which causes soil erosion because of its ability to
remove soil and transport it. Erosion due to the wind is significant in arid and semi-arid regions.
Water, erosion due to running water is significant in regions with heavy rainfall and steep slopes.
Water erosion is more serious and occurs extensively in different parts of India, taking place
mainly in the form of sheet and gully erosion. Increasing population, due to the increasing
human population the demand for land also increases. Forest and other natural vegetation are
removed for human settlement, cultivation, grazing animals and for various other needs. Thus,
this is also a significant cause of soil erosion.

In order to prevent soil erosion, there are some methods that can be used are explained below:
Mulching, in the mulching method, bare ground between plants is covered with a layer of
organic matter like straw which helps to retain soil moisture. Contour Barriers, a contour barrier
means building a barrier with stones, grass, and soil along contours. Trenches are made in front
of the barriers to collect water. Rock Dam, in the rock dam method, rocks are piled up to slow

down the flow of water which prevents gullies and further soil loss. Terrace Farming, terrace
farming is a farming method in which steep slopes are made so that flat surfaces are available to
grow crops. This reduces surface run-off and soil erosion. Intercropping, in intercropping,
different crops are grown in alternate rows and are sown at different times to protect the soil
from rain wash.

In conclusion, this essay has explained how soil is formed by the three types of weathering and
described the characteristics of each soil type. And also it has discussed how the three types of
rocks are formed and lastly describes the types of soil erosion, explained the causes of soil
erosion and methods of reducing soil erosion.
 REFERENCES

Birkeland, Peter W. (1999). Soils and geomorphology (3rd ed.). New York: Oxford University
Press.

Careers in Soil Science. National Resources Conservation Service / United States Department of
Agriculture. Accessed 2020-08-05.

Robert J. (1996). Petrology: igneous, sedimentary, and metamorphic (2nd ed.). New York

Scholten, Thomas. (2020). Controlling Soil Erosion Using No-Till Farming Systems.

Scott Elliott. (2016), Weathering and Modeling. U.S. Department of Agriculture Agricultural
Research Service

Smith, C.A.; Darr, C.A. (1999). "The effects of weathering on the mechanical performance of
automotive paint systems". Progress in Organic Coatings.

Thornbury, William D. (1969). Principles of geomorphology (2d ed.). New York: Wiley.