Soil and Soil Pollution: Definition of Soil, Constituents of Soil, Factors Affecting Soil Formation (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction to Soil

  • The fine particles covering the outer layer of the earth are called soil.
  • It is also an abiotic component.
  • It is a mixture of organic matter, minerals, gases, liquids along with other organisms supporting life.


  • It is the outermost layer of the Earth composed of soil.
  • It exists at the interface of the lithosphere, atmosphere, hydrosphere, and biosphere.
  • Four major functions:
    • It works as a medium for plant growth.
    • It works as a habitat for organisms.
    • As a modifier of Earth՚s atmosphere.
    • Also, as a means of water storage, supply, and purification.

Constituents of Soil

  • Rocks
  • Minerals
  • Water
  • Air
  • Humas (remains of dead plants and animals)
  • Some of the common minerals found in soil are:
    • Iron
    • Potassium
    • Calcium
    • Sulphur

Formation of Soils

  • It is formed from huge rocks and minerals.
  • The breaking down of rocks and minerals over thousands of years resulted in the formation of the fine particles of soil.
  • These rocks are known as the parent rocks and the process is known as weathering i.e.. the breaking down or dissolving of rocks and minerals on Earth՚s surface.
  • Weathering of rocks includes processes
    • Physical
    • Chemical
    • Biological
Various Layers

Factors Affecting the Formation of Soil


  • Weathering starts due to the uneven expansion and contraction, which eventually cracks the rocks.
  • It is due to the hot and cool temperatures during the day and night that causes contraction and expansion.


  • It helps in transfer of soil from one place to another.
  • Wind causes one rock to strike against the other.
  • The rock gets weared down into small pieces due to continuous collisions.


  • This widens the cracks and breaks them further.
  • Erosion occurs due to the heavy water flowing carries smaller rocks colliding with the other rocks.

Soil Pollution

  • The fertility of the soil has been spoiled or degraded due to the use of fertilizers and other chemicals.
  • The contamination of soil with anomalous concentrations of toxic substances is called soil pollution.
  • Soil pollution causes infertility by killing micro- and micro-organisms in the soil.
  • The nutrient level has also decreased.
  • The number of barren lands was also raised.

Causes of Soil Pollution

  • Excessive use of pesticides
  • Excessive industrial activity
  • Poor disposal of waste
  • Road debris
  • Intensive farming
  • Mining activities
  • Ammunitions, chemical agents, other agents of war.
  • Electronic waste

Preventive Measures for Soil Pollution

  • Excavating soil and taking it to a disposal site away from ready pathways for human or sensitive ecosystem contact.
  • Containment of the soil contaminants such as by capping or paving over in place.
  • Using fungus to metabolize contaminants and accumulate heavy metals.
  • Aeration of soils at the contaminated site.


Q 1. What are the common minerals found in soil?

Answer: Some of the common minerals found in the soil are Iron. Potassium, Calcium, Sulphur.

Q 2. What are the causes of Soil Pollution?

Answer: There are many causes of Soil Pollution namely Excessive use of pesticides, Poor disposal of waste, Intensive farming, Electronic waste, Ammunitions, chemical agents, other agents of war, etc.

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