The Earth—Its Motions and their Effects
The earth has two motions, viz., (1) Rotation around its axis or the daily motion. The axis of the earth is an imaginary line inclined at 66.5° to the plane of the orbit of the earth. The earth rotates round its axis from west to east once in 24 hours. Effects: Days and nights are caused. The sun, moon and other heavenly bodies appear to revolve round the earth from east to west. Direction of winds and currents is changed.
(2) Revolution round the sun on its orbit, or the annual motion: The earth revolves round the sun once in about 365.25 days. Effects: It causes seasons; days and nights are of unequal length at the same place.
Important elements in the earth’s crust
The five most abundant elements in the earth’s crust are: Oxygen, Silicon, Aluminium, Iron and Calcium. (The other three are Sodium, Potassium and Magnesium.)
Oceans—Their Importance
Oceans are the source of all water on earth as the evaporated water from over their surface is brought to earth by the winds passing over them. They are the highways of the world and most of the world trade is carried through the sea. Innumerable fish and other animals living in the oceans are a great source of food to mankind. Minerals like salt, iodine etc. are derived from the ocean waters and sea-weeds.
Ocean Currents: are rivers of warm or cold water flowing in an ocean. Their banks and beds also consist of water.
Natural Regions
A natural region is a large area in which the topography, climate and vegetation are largely similar, and therefore there is a certain uniformity in human activities.
Natural Regions of the World
(1) Equatorial Region (2) Hot-Grassland Region (3) Monsoon Region (4) Hot Deserts Region (5) Mediterranean Region (6) Steppe Region (7) Tundra Region (8) Warm Temperate Region (9) Cool Temperate Region.
Natural Regions of India
(1) The Himalayas and the adjacent mountains; (2) The Sutlej-Ganga plains; (3) The coastal plains of Western and Eastern ghats; (4) The Deccan plateau.
Factors Determining Climate of a Place
(1) Distance from the Equator (2) Height above sea-level (3) Distance from the sea (4) Winds (5) Direction of Mountains (6) Ocean currents (7) Slope of land (8) Nature of the soil (9) Forests.
Factors Determining Temperature
(i) sun rays, (ii) height above sea-level (iii) movements of atmospheric winds, (iv) ocean currents.
Rainfall
Two important conditions must be satisfied in order to have rain: (1) There should be moisture-laden air, (2) There should be some means whereby air is cooled and condensation takes place. The air obtains water vapours by evaporation from the surface of large bodies of water, usually from the sea.
Monsoons in India
Monsoons are periodic winds which blow from sea to land for six months in summer and from land to sea for six months in winter. Monsoon winds prevail over India at different seasons.
South-West Monsoons: These are rain-bearing winds which prevail from about the end of May to the end of September. During summer, the sun’s rays fall vertically on the Tropic of Cancer making the Indian plains intensely hot. But the rays of the sun fall obliquely over the Indian Ocean during this period. The land is hotter than the sea, there is, therefore, low pressure over the land and high pressure over the sea. The winds blow from high to low pressure i.e., from the sea to the land, and are therefore wet winds. Because of the rotation of the earth, the monsoon winds blowing over India deflect to the right after crossing the Equator and become south-west winds. These are, therefore, called south-west monsoons.
India depends largely on these rain-bearing south-west winds. These winds give to India about 90% of the total rainfall. During their prevalence, the chief crops cultivated are rice, cotton, tobacco, tea, jawar and bajra.
North-East Monsoons (or Winter Monsoons): During the months of November to January i.e., in winter, the sun’s rays fall vertically on the Tropic of Capricorn. The air over the Indian Ocean during this period thus becomes hot and light and there is low pressure. The sun’s rays fall obliquely on the plains of India during these months with the result that the air over these plains is cold and heavy and there is high pressure. The winds, therefore, blow from plains to the Indian Ocean. While crossing the Equator, they deflect to the left and are known as north-east monsoons.
The North-East Monsoons bring only about 10% of the total rain to India as they are chilly and dry land winds. But the moisture that they pick from the Bay of Bengal, little as it is, is very useful. Wheat, barley, oats, oilseeds and sugarcane are cultivated during this season.
Thus these monsoon winds have much importance for India.
Weather and Climate
Weather means the atmospheric conditions e.g., temperature, rainfall, humidity, winds, sunshine and cloudiness of a particular place on a particular day. Climate, on the other hand, is the average condition of weather obtaining in a country or a place for a considerable period.
India has a great diversity of climatic conditions. Lying largely within the tropics and in the great Asiatic Continent and the vast expanse of the Indian Ocean to the South, the climate of India is essentially the tropical monsoon type. The average annual rainfall in India is 42 inches.
Types of Soil in India
The main categories of soils in India are: (i) Alluvial soils (ii) Black soils (iii) Red soils (iv) Laterite soils (v) Mountain and hill soils (vi) Terai soils (vii) Desert (or Arid) soil and (viii) Peat soils.
Alluvial soil and Black soil
Alluvial soil is that soil which is formed by deposition of silts brought down by the rivers. It is rich in hydrated oxides of iron and is very fertile. Black soil or the black cotton soil has a good water-holding capacity and is best suited for deep-rooted crops like cotton. The black soil in wet condition is compact and sticky.
The most extensive soil cover of India comprises alluvial soils.
Soil Erosion: The soils are usually six to twelve inches in depth. In course of time, the fertility level of the soil is depleted with the result that the soil no longer remains suitable for agriculture. Soil conservation is, therefore, necessary for continued agricultural prosperity.
The agencies of erosion are winds, water and waves of which the water erosion is most common. Rain water removes soil from the surface of sloping lands. Winds remove top soil of lands.
Laterite soils are formed by the weathering of laterite rocks. These can be distinguished from other soils by their acidity. Laterite soils are generally poor on the higher levels and cannot retain moisture. In the plains, however, they consist of heavy loams and clay and can retain moisture.
Laterite soils occur in Madhya Pradesh, Assam and along the Eastern and Western Ghats. Tea plantation requires acidity which is there in the laterite soil. It is, therefore, common in these areas.
The earth has two motions, viz., (1) Rotation around its axis or the daily motion. The axis of the earth is an imaginary line inclined at 66.5° to the plane of the orbit of the earth. The earth rotates round its axis from west to east once in 24 hours. Effects: Days and nights are caused. The sun, moon and other heavenly bodies appear to revolve round the earth from east to west. Direction of winds and currents is changed.
(2) Revolution round the sun on its orbit, or the annual motion: The earth revolves round the sun once in about 365.25 days. Effects: It causes seasons; days and nights are of unequal length at the same place.
Important elements in the earth’s crust
The five most abundant elements in the earth’s crust are: Oxygen, Silicon, Aluminium, Iron and Calcium. (The other three are Sodium, Potassium and Magnesium.)
Oceans—Their Importance
Oceans are the source of all water on earth as the evaporated water from over their surface is brought to earth by the winds passing over them. They are the highways of the world and most of the world trade is carried through the sea. Innumerable fish and other animals living in the oceans are a great source of food to mankind. Minerals like salt, iodine etc. are derived from the ocean waters and sea-weeds.
Ocean Currents: are rivers of warm or cold water flowing in an ocean. Their banks and beds also consist of water.
Natural Regions
A natural region is a large area in which the topography, climate and vegetation are largely similar, and therefore there is a certain uniformity in human activities.
Natural Regions of the World
(1) Equatorial Region (2) Hot-Grassland Region (3) Monsoon Region (4) Hot Deserts Region (5) Mediterranean Region (6) Steppe Region (7) Tundra Region (8) Warm Temperate Region (9) Cool Temperate Region.
Natural Regions of India
(1) The Himalayas and the adjacent mountains; (2) The Sutlej-Ganga plains; (3) The coastal plains of Western and Eastern ghats; (4) The Deccan plateau.
Factors Determining Climate of a Place
(1) Distance from the Equator (2) Height above sea-level (3) Distance from the sea (4) Winds (5) Direction of Mountains (6) Ocean currents (7) Slope of land (8) Nature of the soil (9) Forests.
Factors Determining Temperature
(i) sun rays, (ii) height above sea-level (iii) movements of atmospheric winds, (iv) ocean currents.
Rainfall
Two important conditions must be satisfied in order to have rain: (1) There should be moisture-laden air, (2) There should be some means whereby air is cooled and condensation takes place. The air obtains water vapours by evaporation from the surface of large bodies of water, usually from the sea.
Monsoons in India
Monsoons are periodic winds which blow from sea to land for six months in summer and from land to sea for six months in winter. Monsoon winds prevail over India at different seasons.
South-West Monsoons: These are rain-bearing winds which prevail from about the end of May to the end of September. During summer, the sun’s rays fall vertically on the Tropic of Cancer making the Indian plains intensely hot. But the rays of the sun fall obliquely over the Indian Ocean during this period. The land is hotter than the sea, there is, therefore, low pressure over the land and high pressure over the sea. The winds blow from high to low pressure i.e., from the sea to the land, and are therefore wet winds. Because of the rotation of the earth, the monsoon winds blowing over India deflect to the right after crossing the Equator and become south-west winds. These are, therefore, called south-west monsoons.
India depends largely on these rain-bearing south-west winds. These winds give to India about 90% of the total rainfall. During their prevalence, the chief crops cultivated are rice, cotton, tobacco, tea, jawar and bajra.
North-East Monsoons (or Winter Monsoons): During the months of November to January i.e., in winter, the sun’s rays fall vertically on the Tropic of Capricorn. The air over the Indian Ocean during this period thus becomes hot and light and there is low pressure. The sun’s rays fall obliquely on the plains of India during these months with the result that the air over these plains is cold and heavy and there is high pressure. The winds, therefore, blow from plains to the Indian Ocean. While crossing the Equator, they deflect to the left and are known as north-east monsoons.
The North-East Monsoons bring only about 10% of the total rain to India as they are chilly and dry land winds. But the moisture that they pick from the Bay of Bengal, little as it is, is very useful. Wheat, barley, oats, oilseeds and sugarcane are cultivated during this season.
Thus these monsoon winds have much importance for India.
Weather and Climate
Weather means the atmospheric conditions e.g., temperature, rainfall, humidity, winds, sunshine and cloudiness of a particular place on a particular day. Climate, on the other hand, is the average condition of weather obtaining in a country or a place for a considerable period.
India has a great diversity of climatic conditions. Lying largely within the tropics and in the great Asiatic Continent and the vast expanse of the Indian Ocean to the South, the climate of India is essentially the tropical monsoon type. The average annual rainfall in India is 42 inches.
Types of Soil in India
The main categories of soils in India are: (i) Alluvial soils (ii) Black soils (iii) Red soils (iv) Laterite soils (v) Mountain and hill soils (vi) Terai soils (vii) Desert (or Arid) soil and (viii) Peat soils.
Alluvial soil and Black soil
Alluvial soil is that soil which is formed by deposition of silts brought down by the rivers. It is rich in hydrated oxides of iron and is very fertile. Black soil or the black cotton soil has a good water-holding capacity and is best suited for deep-rooted crops like cotton. The black soil in wet condition is compact and sticky.
The most extensive soil cover of India comprises alluvial soils.
Soil Erosion: The soils are usually six to twelve inches in depth. In course of time, the fertility level of the soil is depleted with the result that the soil no longer remains suitable for agriculture. Soil conservation is, therefore, necessary for continued agricultural prosperity.
The agencies of erosion are winds, water and waves of which the water erosion is most common. Rain water removes soil from the surface of sloping lands. Winds remove top soil of lands.
Laterite soils are formed by the weathering of laterite rocks. These can be distinguished from other soils by their acidity. Laterite soils are generally poor on the higher levels and cannot retain moisture. In the plains, however, they consist of heavy loams and clay and can retain moisture.
Laterite soils occur in Madhya Pradesh, Assam and along the Eastern and Western Ghats. Tea plantation requires acidity which is there in the laterite soil. It is, therefore, common in these areas.
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