4th Class Science Rocks and Soil / चट्टानें और मिट्टी Layers of Soil

     Layers of Soil

Soil is defined as the upper layer of the earth's surface, which contains sand, organic matter (dead animals or plants), minerals with little amount of water and air. It is the one of the most important natural resources, which is capable of supporting life on earth. Soil support and nourish plant life. It is also home to many small animals and microorganism.

Soil profile is the vertical section of the soil, from the surface to the bedrock below. Each layer of the soil has different colour and texture. These layers are called horizons. A typical soil profile has four different layers.

       Different Layers of Soil  

             A Horizon or Topsoil

This is the dark coloured uppermost layer rich in humus.

           Horizon or Subsoil

This is middle layer generally coarse and rich in minerals. It is light in colour due to very less amount of humus

           Horizon or Weathered Rocks

This is the third layer which is made up of small lumps of rocks crevices cracks. It is the zone of infertility.

           Horizon or Bedrocks

The fourth layer is made up of unweathered, non-porous and impervious parent rocks. This is the bedrock. This layer is hard and very difficult to dig. This layer provides the base for the upper three layers

      Which one of the following is the uppermost layer of the soil?

(a) A-horizon

(b) B-horizon

(c) C-horizon

(d) D-horizon                                    

(e) All of these

Answer: (a)

       Julia took some soil in a covered container. She heated it slowly, after some time she observed some droplets of water under the cover of the container. What does this show?

(a) Soil has humus

(b) Soil has sand

(c) Soil has gravel  

(d) Soil has moisture                      

(e) Soil has air

Answer: (d)