Grade 2, Science Olympiad (CBSE) - Soil and Rocks 

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Grade 2  |   Science  |   Soil and Rocks, Air, Water and Rocks, Olympiad, CBSE, ICSE, SOF, ITO

Soil

Topmost layer of soil in which plants grow is called soil. It is generally black or brown in color. It consists of organic matter, clay, sand, silt and rock particles. It also contains water and air. The soil is very important as it supports plants and other life forms. 

Soil takes several years to form. The soil is formed by weathering of rocks.
Big rocks are broken into small pieces over time with the effect of wind, sun and water. This process is called weathering.


Gradual wearing away or washing away of top layer of soil is called soil erosion. Physical forces of wind and water are primary causes of soil erosion. Trees help in avoiding soil erosion as their roots firmly hold the soil. Deforestation is largely responsible for soil erosion.
 

 

Layers of soil

Following are the 5 layers of soil:

The topmost layer of soil is called humus. Humus is the organic matter which is made up of dead plants and animals. Humus is very fertile and helps plants to grow. Humus is dark brown or black in color.


Topsoil is below humus. It is very fertile and contains microorganism. It is rich in minerals.


The subsoil is below the topsoil. It is the home of earthworms.


Small rocks are weathered rocks below subsoil. Roots of very few trees reach up to this layer.


Bedrock is the bed of newly formed rocks. These rocks are big.

 

Actual layers of soil

 

Soil types

Major soil types are:

Clay
Clay has the smallest particle. It can retain water and water cannot easily flow through it.
Clay is not suitable for plants growth as it has small particles and there is almost no air between its particles and plants roots can't breathe.

Silt
Silt has slightly bigger particles than clay. It has less water retaining capacity then clay.

Sand
Sand has biggest particles. It cannot retain much water and water easily flow through it. Sand is usually found in coastal areas.


Loamy soil
Best soil for plants growth is loamy soil. Loamy soil is a mixture of sand, silt, clay and humus. It is the most fertile soil.

 

Rocks

3 types of rocks :

  • Igneous rocks are formed by cooling of molten rocks or magma. Granite and basalt are igneous rock.
  • Sedimentary rocks are formed by deposition and accumulation of sediments of small rocks, dust, soil and organic matter over time.
    Sandstone, chalk and limestone are sedimentary rocks.
  • Metamorphic rocks are formed when existing rocks like igneous rocks or sedimentary rocks are subjected to extreme heat and pressure over a long period of time.
    Marble, quartzite and slate are metamorphic rocks.
    Marble is formed by metamorphosis of limestone.

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Soil
Note : This video is the property of MakeMeGenius. We really appreaciate the hard work and brain put in by the team of MakeMeGenius to bring out this video. We suggest you to visit their channel on youtube for more science videos. They have a huge collection of informative science videos.


Soil Formation
Note : This video is the property of Smart Learning For All. We really appreaciate the hard work and brain put in by the team of 'Smart Learning For All' to bring out this video. We suggest you to visit their channel on youtube for more science videos. They have a huge collection of informative science and maths videos.


Soil Types
Note : This video is the property of MakeMeGenius. We really appreaciate the hard work and brain put in by the team of MakeMeGenius to bring out this video. We suggest you to visit their channel on youtube for more science videos. They have a huge collection of informative science videos.


Layers of soil
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3 types of rocks
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Weathering and soil erosion
Note : This video is the property of MakeMeGenius. We really appreaciate the hard work and brain put in by the team of MakeMeGenius to bring out this video. We suggest you to visit their channel on youtube for more science videos. They have a huge collection of informative science videos.



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