Class 8 Social Science Natural Resources Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.
Covers the following topics:
- Introduction
- Land Resources
- Soil Resources
- Water resources
Introduction
Earth is the only known heavenly body in the universe which has suitable environmental conditions for the survival of human beings, animals and plants. The surface of the earth is made up of land (about 29 percent) and water (about 71 percent). We satisfy most of our needs from our immediate natural environment. The different elements of the environment, such as land, water, soil, plants, animals etc. acquire meaning and value with reference to the needs of people living in the region.
The needs of the people are not the same everywhere and depend mostly on the level of cultural and technological development of the people. The natural resources of the earth acquired value as a result of technological development. The gifts of nature become resources only when human beings locate them or find a use for them or propose to use them. For example, river is a gift of nature and it becomes a resources when we utilise the water in the river for irrigation, power generation, navigation etc. The distribution and possible uses of the various types of natural resources, especially land, water and soil are examined in this chapter. These natural resources are greatly influenced by the natural environmental conditions, such as different elements of weather and climate, hydrogical cycle, weathering of rocks etc.
Land Resource
Land is actually solid portion of the surface of the earth. It is a product of nature. It is that part of the earth which supports life and has usefulness in various ways. Land is a very important resource needed by human beings, it is ubiquitous and inexhaustible in nature. It is one of the most important gifts of nature for the growth of life and development of human civilisation. In fact, it is both a renewable and non-renewable resource.
The concept of land resource was first defined and developed by a geographer named Barloe in 1950 A.D. He defined land resource as: "There is no difference between land and nature; it is basically identified with natural environment including man, water, soil and variety of other things."
Land includes all the earth's surface in addition to building sites, farms, soil, growing forests, mineral deposits and water resources. It takes many physical forms, climatic characteristics, possesses many vegetation belts and soil patterns, etc. It provides a base for production and also a field where every human activity can take place.
Land is:
♦ Ubiquitous (found everywhere)
♦ Provides base for all natural and manmade phenomena
♦ Fixed in nature and is immobile
♦ Never ending and renewable
♦ A property and capital
The land surface has a variety of landforms, such as mountains, hills, plateaus, plains, river valleys , deserts, marshlands etc. Thus all parts of the land surface are not equally habitable. The uneven distribution of population on the surface of the earth is mainly due to the varied relief features and highly variable climatic conditions.
About 90 percent of the total population of the world occupies about 30 percent of the total land area. Rest of the land area does not have suitable conditions for the survival of human beings. The thickly populated areas in the world are the river valleys, coastal plains, plateaus which are rich in mineral resources and industrial centres. The sparsely populated areas are hot and cold deserts, grasslands, rainforests and the mountainous regions.
The land is put to different uses and it varies from one region to another and also from time to time in the same region. Recently in many parts of the world. forests have been cleared to provide land for cultivation, mining or other uses resulting in the reduction of total land under the forests.
→LAND USE
Land use is characterised by the arrangements, activities and inputs by people to produce, change or maintain a certain land cover type. This land use is determined by various environmental factors such as soil, climate, topography and vegetation. Land use is governed mainly by two sets of factors which are as following:
1. Physical Factors: It includes temperature, moisture, soil and terrain. These influence the capability and use of land.
2. Non-physical Factors: This includes physical conditions and technoeconomic status, demands, etc.
Factors Affecting Land Use
1. Physical Features: Various physical features like mountains, plateaus, plains, rivers, hills, slope of land, etc. influence land use pattern in numerous ways which indirectly have a great bearing upon the human beings.
2 Geology : Rocks like igneous, sedimentary and metamorphic help in the soil formation. These rocks disintegrate by various agents of gradation and form the soil of a particular region. So the geology or the rocks also determine the land use.
3. Climate : Climate includes rainfall, temperature, pressure and humidity conditions. Climate also influences the land-use pattern of a particular place Extreme climatic conditions do not support human habitation.
4. Population Characteristics: Population of an area also has a great impact upon the land use pattern.
Densely-populated areas of the world experience intensive land use pattern as compared to the thinly or sparsely populated areas.
5. Slope: As it is evident that steeper the slope, difficult will be the life and gentler the slope, more degree of freedom will be there for movement and simpler life conditions. People prefer to settle on gentler slopes rather than steeper slopes.
6. Human Wants and Needs: At different places, man's wants and needs are different. Hence people living in urban areas require land for construction of buildings, stadiums, hotels, restaurants, roads and railways, etc. and people living in rural areas require land mainly for agricultural purpose. Hence land use pattern is affected according to the human wants and needs .
7. Other factors :
(a) Presence or absence of soil cover.
(b) Availability of surface or underground water.
(c) Level of technology available.
(d) The improvement value of the available land.
→ DISTRIBUTION OF LAND
(i) Land covers only about 30 % of the total area of the earth's surface.
(ii) About 90% of the world's population occupies roughly 30% of its land area.
(iii) Remaining 70% is either sparsely inhabited by 10% of population or is uninhabited.
(iv) Sparsely populated areas mostly include the deserts and grasslands of Asia and Africa, tropical forests of South America, Africa and Southeast Asia and polar areas.
(v) Antarctica is uninhabited except for temporary occupation by few scientists conducting research
(vi) The subtropical and mid latitude zones are occupied by approximately 66% of world population because of availability of arable land.
→ LAND USE PATTERN
Physical factors such as topography, soil and climate availability of water and mineral resources determine the probable use of land, for example fertile plains are used as croplands, occurrence of mineral deposits favours mining, in densely populated areas land is used for other human requirement like buildings houses, roads, rails etc Land use pattern of few countries of the world.
The above table shows :
(i) India has a very high percentage of arable land, but the forest cover is quite low 57% of the total land falls under croplands and 22% under forest
Land use pattern in India
Croplands - 57%
Pasture - 41 %
Forest - 22 %
Other uses - 17 %
(ii) Some countries like Australia and U.K have high percentage of pasture lands
(iii) Japan has 67% of land under forests
Land use can also be divided on the basis of private land and community land. Private land is owned by individuals whereas community land is owned by the community for common uses like collection of fodder fruits, nuts or medicinal herbs. These community lands are also called common property resources.
People and their demands are ever growing but the availability of land is limited. The quality of land also differs from place to place. People started encroaching the common lands to build up commercial areas, housing complexes in the urban areas and to expand the agricultural land in the rural areas. Today the vast changes in the land use pattern also reflect the cultural changes in our society. Land degradation, landslides, soil erosion, desertification are the major threats to the environment because of the expansion of agriculture and constructional activities.
LAND DEGRADATION
Degradation is a Latin word which 'reduction' in the quality or quantity. Land degradation is any change in the land that reduces its condition or quality and hence its productivity or productive potential. It has become a universal problem. In the developing countries, it is a symptom of underdevelopment. Followingare the factors responsible for land degradation:
1. Soil Erosion: It is one of the serious factors for land degradation. It removes huge amount of nutrients in suspension or in solution from place to place causing depletion of nutrients. Various agents of gradation like wind, water, ice (glaciers) and ocean, etc. transport soil from one place to another. Besides these, there are several other factors which are responsible for soil erosion. Some of them are tremendous population pressure on land, deforestation, faulty agricultural practices, etc.
2. Desertification: Land degradation also takes place due to the expansion of deserts. This process is mainly related to the arid and semi-arid areas. Land becomes degraded mainly when the pressure of population is high on land. Fringe areas are very sensitive and any disturbance leads to the desertification or expansion of deserts. These deserts advance during the drought time and retreat during the wet seasons.
3. Encroachment on Agricultural Land : As we know, most of the population in the world is concentrated in and around the fertile agricultural land (including river valleys and plains). Urban areas are continuously expanding with the time. The outward expansion is leading to the accumulation of fertile agricultural land at the outskirts of the cities. Urban areas promote the land degradation in various ways, some of them are as follows:
(i) Alteration in climate, vegetation and overall encroachment
(ii) Pollution and garbage dumps
(iii) Alteration in hydrology of those specific areas
4. Degradation due to Mining Activities : Earth surface is a storehouse of metals and non metals and precious elements. These metals and non metals are extracted from the earth by mining activities. There are numerous places all around the world which were sites of mining operations but now have become degraded and derelict (abandoned sites). For example:
(i) Appalachian Mountains of USA
(ii) Chotanagpur plateau in India
(iii) Ruhr basin in Europe
5. Degraded Forest Lands : Forest soils contain most of the organic matter. These soils become degraded when the forests are cleared and the trees are burnt due to which the organic matter is depleted.
Conservation of Degraded Land
1. Controlling salinisation and alkalinisation
2. Clearing the waterlogged lands
3. By practising crop rotation
4. Terrace farming can be practised
5. Afforestation
6. Check upon overgrazing
7. Planned use of land
8. Control of land pollution
9. Checking urban expansion on good quality agricultural land
B. SOIL RESOURCES
Introduction
The word 'Soil' is derived from the Latin word 'solum' which means floor or ground. The term 'pedology' is the study of soil and the term "pedogenesis" refers to the process involved in the formation of soils. "Soil is the loose and unconsolidated material derived through the wearing down or disintegration of rocks." Soil may contain minerals along with the organic and inorganic matter which is helpful for the growth and development of the plants and animal life.
Soil : It is the upper most layer of the earth's crust consisting of the loose I products obtained by the disintegration of the rocks mixed with organic matter. Generally, soil includes four types of materials weathered rocks, organic materials, water and air. The mineral matter is sand and clay, while the organic materials include decayed leaves dead tissues of organisms, minute bacteria and earthworms. The rocks on the surface of the earth are broken into smaller pieces by the various agents of weathering.
Eventually, a thin layer of broken rock fragments may cover the underlying rocks. The upper layer may remain undisturbed over a long period of time. Over a period of time, chemical and organic changes lead to the formation of soil. The underlying rock is called bedrock and the rocks from which soil is formed are called the parent rocks.
→ FORMATION OF SOIL
Soil formation is an extremely slow process. It takes hundreds of years to form one centimeter of soil layer soil formation is controlled by five factors.
(i) Nature of parent rock : Original rock from which the soil is formed determines its basic characteristics, such as colour texture chemical properties, mineral content and permeability for example, shale contributes clay, while sandstones contribute sand grains.
(ii) The relief and topography - Altitude and slope determine the accumulation of soil. On a steep slope there is no accumulation of weathered rocks while In plains and areas with gentle slope soil are accumulated without any hindrance.
(iii) Climate : Temperature and rainfall influence, rate of weathering and formation of humus etc. for example frequent temperature changes and presence of water quicken the soil formation through increased weathering.
(iv) Flora, Fauna and micro organism in the soil : It affects the rate of humus formation. Dead plants and animals provide humus to the soil. Organisms like earthworm and ants through their movements create space for air and water in the soil.
(v) Time : It determines thickness of soil profile . Longer the time for soil formation. deeper is the soil layer.
→SOIL PROFILE
Soil formation is a slow process and it may take thousands of years to form even a thin layer of soil. As soil develops, it forms layers, which are called horizons. These horizons make up the soil profile. In a mature soil, four distinct horizons can be seen. These are called the horizon A, B, C and D from the top layer downwards.
The top layer is horizon A, which is also called topsoil. It has most of the minerals and organic materials needed for the growth of plants.
Below the topsoil is horizon B, which is also called subsoil. This layer has enough minerals, but less organic materials. The subsoil may have some living organisms. Horizons. A and B form the true soil. Below the subsoil is horizon C, Which has partly weathered rocks. These rocks are actually producing new soil, but this layer is not affected by biological process
At the base of the soil profile is the unbroken solid rocks, This is below horizon C and is called the horizon D.
→SOIL EROSION
Soil is a very important natural resource not only for man but for the whole of the biotic world. Soil erosion is the process of detachment and transportation of soil particles.
Soil Erosion : The accelerated process of soil removal brought about by the human interference with the normal disequilibrium between soil building and soil removal is designated as soil erosion.
→ TYPES OF SOIL EROSION
1 Sheet Erosion: Gradual and fair removal of the surface soil. It may occur so slowly that one is not aware that it is taking place.
2 Rill Erosion: It is more rapid and visible type of erosion. Rills are simply small streamlets cut into the soil's surface by the running water.
3. Gully Erosion: When the rills become too large, they become a gully or we can say; gully erosion is an advanced state of rill erosion in which water accumulates in channels and washes away soil to depth ranging from two feet to as much as seventy five or hundred feet. For example, Yamuna and the Chambal area.
→CAUSES OF SOIL EROSION
1 Deforestation: Tress and forests hold the soil firmly but when they are cut down, the soil is easily carried away by the wind or water.
2 Faulty Agricultural Practices: Ploughing the land along the slope leads to the easy removal of soil particles by the wind or water. Ploughing land against slope reduces the soil erosion.
3 Faulty Cropping Pattern: Growing a single crop in a field over the years leads to the depletion of the nutrients and essential nitrogenous components from the soil. The time for regeneration of these essential components is so short that the soil becomes devoid of nutrients within few years.
4. Shifting Cultivation : Under this type of cultivation, forests are in order to make land available for
cultivation. It is practised in many parts of the world by many tribal groups. In India it is practised in
Northeast region popularly known as Jhumming cultivation.
→ CONSERVATION OF SOIL
1. Afforestation : The roots of trees and plants hold the soil very tightly and do not let it loose. So the problem of soil erosion can be better dealt with planting more and more trees.
2. Strip Cropping : On slopy regions, crops can be planted on contour strips which prove effective in checking soil erosion.
3. Crop Rotation: It means growing of crop one after another every year alternately. It helps in reducing erosion and also increases the fertility of soils.
4. Terracing : Terracing fields do prevent erosion and conserve moisture. It has been practised in many parts of the world. Terraces control the water runoff because they are spaced in a series like steps down the slopes. Terrace acts like an embankment which is constructed across a slope in such a way that it tends to control water runoff and minimises erosion.
5. Bunding : Bunding refers to the construction of small bunds across the steps of the land as a contour. These bunds act as a barrier to check water runoff.
6. Shelter Belts : These are actually the green belts of trees which help in checking the strong winds from picking up the loose soil from ground.
7. Gully Reclamation : Due to carelessness at times small gullies are formed. These gullies prove dangerous and aggravate the soil erosion. The best method of controlling them is to grow some vegetation.
8. Check upon Overgrazing : The plants once eaten away by the animals do not grow again. It mostly happens in hilly regions. It is essential to put a check upon overgrazing.
9. Mulching : The part of the field, which is bare, is covered with layer of straw . It does not allow quick evaporation and the wind is also not able to blow away the soil.
10. Contour barriers : Some barriers are developed with the help of stones or grass along the contour lines in the field. Trenches are also dug in front of the barriers to collect water.
11. Rock dams : These involve the building of dams with stones across the gullies to check the flow of water. These can check the flow of flood water and help in filling the gullies with slit
12. Inter-cropping : In this method, different crops are grown in the alternate rows, and also sown at different times. The soil can possibly be protected from rain-wash as the field remains under some crop throughout the year.
13. Contour ploughing : In this method, the fields are ploughed and sown along the natural contours of the hills, in place of up and down the slop. they form a natural barrier for water to flow down the slope.
C. WATER RESOURCES
→ INTRODUCTION
Water is an essential resource for life on earth. We use it for drinking, bathing, relaxing, fishing, keeping cool, cooking food and irrigating the field. Most of the ancient civilisations flourished and developed along the river valleys. For example, Nile, Indus, Tigris and Euphrates, etc. It tends to provide a base for the life to sustain.
→ CHARACTERISTICS
1. It is the most widely distributed substance on earth.
2. Seventy-one per cent of the earth's surface is covered with it.
3. It is present in all the three states, i.e. solid, liquid and gas.
4. It's a renewable resource.
5. It is abundantly found on earth.
6. It is home to the marine life .
→ UTILIZATION OFWATER
(i) Water is essential for all forms of life. Water is a major body constituent of several plant and animal species. 70% of the human body consists of water. Human uses water for domestic purposes, agriculture, industries and generation of electricity.
(ii) Increasing population, rising demands for food and cash crops, increasing urbanisation and rising standards of living are the major factors leading to shortages in supply of fresh water either due to drying up of water sources or water pollution.
In 1975, the consumption of water for human use was 3850cu km/year. It soared to more than 6000 cu km/year in the year 2000.
→ DISTRIBUTION OFWATER
(i) Water is a vital renewable natural resource.
(ii) Three-fourth's of the earth's surface is covered with water. It is therefore appropriately called the 'water planet'.
(iii) The oceans cover two-thirds of the earth's surface and support a rich variety of plant and animal life. The ocean water is however saline and not fit for human consumption.
(iv) Fresh water accounts for only about 2.7 per cent. Nearly 70 per cent of this occurs as ice sheets and glaciers in Antarctica, Greenland and mountain regions. Due to their location they are inaccessible.
(v) Only 1 percent of freshwater is available and fit for human use. It is found as ground water, as surface water in rivers and lakes and as water vapour in the atmosphere. Fresh water is therefore, the most precious substance on earth.
(vi) Total volume of water remains constant. Its abundance only seems to vary because It is in constant motion, cycling through the oceans, the air, the land and back again, through the processes of evaporation, precipitation and run-off. This is known as 'water cycle'.
→ PROBLEMOF FRESHWATER
(i) There is scarcity of water in many regions of the world. Most of Africa, West Asia, South Asia, parts of western USA, north-west Mexico, parts of South America and entire Australia are facing shortages in fresh water supply.
(ii) The region between equator and 20º north and south, and north and south of 40º latitude are the areas of surplus precipitation.
(iii) In both hemispheres between 20º and 40º latitudes evaporation exceeds precipitation. Hence this has created deserts e.g. the Sahara, the Arabian, and the Gobi desert in Northern Hemisphere and the Atacama the Namibia Kalahari and the Western Australian desert in southern Hemisphere,
(iv) The surface water run off from a large area gets collected in the form of small streams, which unite together to make big rivers.
(v) In 1999, 26 countries were experiencing. water scarcity; by 2025, it is likely that 65 countries including India, Korea, Nigeria, Peru and Poland will face acute water scarcity.
(vi) Poor countries are located in the climatic zones most prone to drought and they cannot afford to import water.
(vii) The drier areas are the Australia, Africa, parts of South America, West and South Asia, Western U.S. and North-West Mexico.
(viii)More than 3 billion people are affected by water shortages.
→ PROBLEM OF WATER QUALITY
(i) Untreated or partially treated sewage, agricultural, chemicals and industrial effluents contaminate water with nitrates, metals and pesticides.
(ii) Human and animal wastes introduce pathogens that cause serious diseases.
(iii)The diseases spread by contaminated water are typhoid, cholera, amoebic infections, dysentery and diarrhea.
(iv) Child mortality rate has also increased due to water pollution .
→ WATER POLLUTION
Water pollution means contamination of water due to any external material which makes it unsuitable for human consumption.
Sources of water pollution
1. Industrial Wastes : Industrial generate wastes in variaous ways and in variety of forms (solid, liquid and gas). This waste is discharged into the river and streams without treatment.
2. Radioactive Wastes : Various elements like radium, uranium and thorium are very harmful. These can cause various ailments if exposed to humans. They also cause water pollution.
3. Organic Wastes : Organic wastes are discharged by both agricultural and industrial sectors. Presence of organic wastes increases the growth of bacteria and more oxygen is consumed by them leading to the death of fish
4. Inorganic Wastes : Inorganic wastes are very harmful and very common in manufacturing soaps, detergents, drugs, paints and fertilisers etc.
5. Domestic Effluents and Sewage : In our daily life we use water for so many things such a bathing cooking and washing etc. This waste water is discharged in to the rivers and streams which causes pollution.
→ CONSERVATION OFWATER
The important methods of conserving water are -
(i) Surface run off can be slowed down by forest and other vegetation cover to improve underground storage.
(ii) Rain water harvesting - It is another method of conserving water. Rain water can be collected in storage tanks. Rain water harvesting is the process of collecting rain water from roof tops and directing it to an appropriate location and storing if for future use. On an average, one spell of rain for two hours is enough to save 8,000 liters of water.
(iii) Efficient Irrigation - Over irrigation should be avoided. Seepage losses from canals can be minimized by lining them.
(iv) Use of Sprinklers - They are very effective and efficient tools of irrigation. In dry regions drip or trickle irrigation is very useful
(v) Use of recycled water - Industrial water and domestic water can be recycled and used again. Waste water of kitchen may be used for gardens.
(vi) Using water economically and preventing wastage
(vii) Rational use of underground water
(viii) Purification or treatment of waste water
(ix) Treatment of waste before discharging with river and streams
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