Class 8 Geography
Land, Soil, Water
- Land covers about 30% of the total area of the earth’s surface.
- Due to variations in topography, all parts of the land may not be habitable.
- 90% of the world population lives only on 30% of the land area.
- The remaining 70% of the land is either sparsely populated or uninhabited.
- Plains and river valleys are densely populated because they are suitable for agriculture.
- On the other hand, steep slopes and water logged areas are sparsely populated.
Land is used for various purposes; like agriculture, forestry, mining, building houses, roads, industries, etc. Factors which affect the use of land are topography, soil, climate, minerals and availability of water. Human factors also determine the land use pattern. Ownership of land also determines the land use pattern.
Increasing population means there is an ever growing demand for land. But the availability of land is limited. Land degradation, landslides, soil erosion, desertification are the major threats to the environment.
Human encroachment has led to large scale destruction of forest cover and arable land. This is creating a danger for quality of land. Land degradation can be prevented by afforestation, land reclamation, regulated use of chemical pesticide and fertilizers, and by checking overgrazing.
The topmost layer of land which is composed of grainy substance is called soil. Soil is made up of organic matter, minerals and weathered rocks. Soil formation takes place because of weathering of rocks. The soil becomes fertile because of the right combination of minerals and organic matter.
The arrangement of different layers of soil at a place is called soil profile. The typical soil profile is composed of following layers:
- Topsoil: Topsoil is composed of humus and fine particles of clay and sand.
- Subsoil: This is the second layer of soil. It is composed of sand, silt and clay.
- Weathered Rock Material: The third layer is composed of large pieces of rocks.
- Bedrock: The last layer of soil profile is composed of huge rocks.
Factors of Soil Formation:
Following are the factors of soil formation:
- Parent Rock: The parent rock determines the colour, texture, permeability, chemical property and mineral content of the soil.
- Climate: Temperature and rainfall influence the rate of weathering.
- Relief: Altitude and slope determine the accumulation of soil at a place.
- Flora, fauna and microorganism: These are the biotic factors which affect the rate of humus formation.
- Time: Time determines the thickness of soil profile.
Removal of topsoil is called soil erosion. Deforestation, overgrazing, overuse of chemical fertilisers or pesticides, rain-wash, landslides and floods are the factors which lead to soil erosion.
Methods of Soil Conservation:
- Mulching: In this method, the bare ground is covered with organic matter like straw. Covering the soil helps in retaining the moisture in soil.
- Contour Barriers: Contour barriers are made by placing stone, grass or soil along the contour. Trenches are made in front of the barriers to collect water. Contour barriers help in preventing soil degradation which may happen due to rainwash.
- Rock Dam: Rocks are piled up to make a dam. Such dams slow down the flow of water. Thus, it prevents gullies and soil loss.
- Terrace Farming: Terrace farming is done in hilly areas. Plots are made in the shape of terraces to ensure flat surface for growing the crops. It helps in reducing soil erosion which may happen because of run-off.
- Intercropping: In this method, different crops are grown in alternate rows. Crops are grown at different times. It helps in preventing soil erosion from rain wash.
- Contour Ploughing: In this method, ploughing is done parallel to the contours of the hill slope. This helps in forming a natural barrier and prevents water from flowing down the slope.
- Shelter Belt: This method is used in coastal areas and in dry regions. Rows of trees are planted along the boundary of the farmland. This helps in preventing soil erosion from wind.