Notes of Class 7, Social Science Class 7 (Hydrosphere).pdf - Study Material
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Hydrosphere, (Water), indispensable natural resource on earth. Water is found in all its forms, i.e., solid (ice),, Water is an, iauid (water) and gas (water vapour). Earth is also called the Blue planet as 71% of its surface is, avered by water and only 29% is land. All the water on the earth is found mainly in the rivers,, lakes, glaciers, seas, oceans and below the surface of the earth. These water bodies together form, the hydrosphere., Distribution of Water, The earth appears blue from the outer space, i.e. solid (ice), liquid (water), and water, vapours (steam). These three forms are called, the three states of water. These states are, because of its immense water bodies. Water, covers about 71% of the earth's surface., The following table shows the distribution of form a complete hydrological cycle., inter convertible. The changing state of water, water on the earth surface., Waterbodies, Discover more..., Volume, of Water, (in %), S. No., Nature of, Water, The maximum amount of water is found in the vast, oceans. There are four oceans on the earth. These are, connected with each other. Therefore, the level of water, in all oceans and seas is same everywhere. This uniform, level is called the Mean Sea Level., 1., Oceans, 97.3, Saline water, 2., Ice caps, 02.0, Fresh water, 3., Ground water, 0.68, Fresh water, The height of land and the depth, 4. Fresh water lakes, and inland seas, of water is measured from the, mean sea level. For example,, mount Everest is 8,848 m above, 0.009, Fresh water, 5., Salt lakes, 0.009, Saline water, from the sea level and Mariana, 6. Atmosphere, 7. Rivers, 0.0019, Fresh water, Trench is about 11,022 m deep, 0.0001, Fresh water, from mean sea level., 100.00, Hydrological (WVater) Cycle, Have you ever thought, what would happen if, water never changes its states? In that case, ocean water would always remains stable and, there would be no water circulation. And, we, would never experience rainfall. But, the, nature provides us a great gift in the form of, hydrological cycle., The hydrological cycle refers to the, circulation of water within the earth's, Different Forms of Water, As you see in the above given table that the, water is not only found in the rivers or oceans, but it is also present, in the polar ice caps, and atmosphere. In, the oceans, it is found, In its liquid form., Thus, we can say, hat water exists, n three different, hydrosphere in different forms i.e. the, liquid, solid and the gaseous forms. It is, the process by which water continually, Gao, orms or states, fchd, States of water, 27, 1
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It ensures the distribution of water to, areas of the earth's surface., It recharges the underground water., The hydrological cycle maintains continuon, supply of fresh water to the rivers., The Hydrologic Cycie (Water Cycle), Th, ndanast, Precipitation, Treuplration, The Distribution of Water, Th water available on the Earth's surface is d, Eveperation, two types- Fresh water and salt water : 970, of the earth's water is found in oceans, and, Lake, Oces, Pencelation, salty only 3% of the water on earth in fres, Groundwater, flow, water., Fresh Water, Water Cycle, Fresh Water is water that has very little sa, dissolved in it, unlike the water found in the, changes its form and circulates between, oceans, atmosphere and land., Water changes its states all the time due, to the processes of evaporation and, condensation., oceans and seas 69% of the fresh water, frozen in the form of glaciers and ice sheets 2., 30% is in the form of underground water. Onh, 1% of the fresh water is found in liquid form a, the earth surface as streams and lakes. The, converts into water vapours due to the biggest source of fresh water is precpitation of, Evaporation is the process in which water, heat of the sun., 3., rainfall., The sun's energy regulates the whole, process of water cycle., Through the process of evaporation, much, of water from the oceans and land enters, Surface Water, The water which is found in ponds, lakes,, rivers and streams is called surface water., into the atmosphere in the form of water Underground Water, Some water gets collected beneath the earth's, surface through seepage. This is called, vapours., On cooling, the water vapours change into, tiny water droplets and form clouds underground water., through the process of condensation., Condensation is the process in which, Ocean Water, Oceans forms the major part of the, water hydrosphere. The oceans are huge water, bodies that support marine life. While fresh, water contain very little dissolved salts, ocean, water, vapours, convert, into, droplets., The rain water runs into the sea from, where it gets evaporated, thus complete water contain a large amount of it. Salt makes, the hydrological cycle., The hydrological cycle is an endless, process. It has no beginning and no end., Importance of the Hydrological Cycle, It regains the water lost from the water, bodies., up 3.5% of the ocean., Major Oceans and their Water, Circulations, As earlier said that the oceans are the huge, reservoirs of the earth's water. There are five, oceans on the earth., 28, 2
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These are :, 1. Раcific осean, 2. Atlantic ocean, 3. Indian осean, Ch, L We, LAn, V D, upe, Spterence, R Dee, Bak, Enle, 4. Arctic ocean, RMav, LMchgar, NORTH, ATLANTIC, OCEAN, 5. Southern ocean, NORTH, PACIFIC L N, OCEAN, 1. Pacific Ocean, The deepest point,, called the Mariana, NORTH, PACIFIC, OCEAN, Mrancece, S Taea, TRiceca, INDIAN OCEAN, trench, is situated in, this ocean., SONTH, PACIFIC, OCEAN, SOUTH, ATLANTIC, OCEAN, SOUTH, PACF, OCEAM, eOrange, This ocean is roughly, triangular in shape., It is the largest ocean on the earth and, covers about 1/3 of the earth's surface., NOT TO SCALE, World-Major Lakes, Rivers and Oceans, It remains frozen for most part of the year., It is not a vast body of water but a vast, ice-sheet., 2. Atlantic Ocean, | Discover more..., It is an U-shaped oceans and provides the, busiest, осean, route, for, trade and, Salinity found in different seas of the world., Lakes, Location, transport., It is the second largest ocean in the world., Amount of, salinity, 330, per thousand grams, 250, per thousand grams, 1. Van lake, Turkey, 3. Indian Ocean, 2. Dead sea, Israel, It facilitates trade and travel between the, 3. Caspian sea, 180, per thousand grams, Eurasia, 4. Baltic sea, 4, per thousand grams, eastern and western hemisphere., It is named after the country, India., Eurasia, Movements of Ocean Water, 4. Arctic Ocean, The average salinity of the ocean water is, 1000, The ocean water move constantly. Both the, temperature and salinity are responsible for, its constant motion. Waves, tides and ocean, 35, grams, of salt, per, grams, of water., It surrounds the North pole. The ocean, water is not static, while it keeps moving of ocean water., currents are the different kinds of movements, from place to place. The ocean water is, saline in nature as it contains a large When water on the surface of the ocean rises, Waves, and falls alternately, they are called the, waves. These are caused by the winds, blowing over the seas. These are an important, agent of erosion and deposition in the coastal, amount of dissolved minerals like sodium, chloride, potassium, magnesium, etc., The salinity of water is high in the areas, of high evaporation., In the landlocked seas like dead sea, the, salinity is high., The amount of salinity in the oceans is, highly variable., 5. Southern Ocean, areas., Size of a wave is determined by how far,, how fast and how long the wind blows., Strong winds over long distances generate, long waves. This wave has many ripples., The highest point a ripple in water, This ocean joins the Pacific, Atlantic and, Indian oceans., 29, 3
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the stormy winds creates huge and destructiv, Waves can be seen near the sea coast. Slow, reaches is called the crest of a wave. The, wave's frequency., lowest point is called the trough. The, distance between the crest and trough is moving winds create medium sized waves a, called the wave height., The number of ripples in water that a waves, that cause a huge loss of life, wave passes in one second is called the property. Such waves are also called the tsuna, Tsunami, Tsunamis are commonly known as the tidal waves. Tsunami is a japanese word, eaning harbour wave. They have, however nothing to do with tides or waves. A, tsunami does travel like a wave. Tsunami is however, caused by an earthquake on the, ocean floor. The wave length, speed and height of these waves are very high. They ar, often very destructive in shallow ocean water, when they strike the coasts. In the, sea the tsunami waves are, however, lost in the vast expanse of ocean water., Devastating Tsunami : The earthquake on ocean floor of the west of Sumatra ir, Indonesia triggered a series of devastating tsunamis on December 26, 2004. The, magnitude of the earthquake was 9.0 on the Richter scale. These waves had not a, single source. They had risen from the sea bed displacing huge quantity of water. The, Tsunami travelled at a speed of about 800 km per hour and radiated outward covering., a distance of about 1,200 km radius. You can imagine the geographic area covered by, these waves. They rose to several metre high near the coasts. The waves touched raised, the level of sea bed and consequently mean sea level by about 0.01 cm. It was on this, account that Indira Point, the southernmost point of India was submerged under sea •, water. The destruction caused by these waves was enormous. Over three lakh people, were killed (2,75,000 in Indonesia, 10,000 in India and rest in nine other countries),, property worth billions of rupees was destroyed and great harm was caused to the, physical environment of many islands and sea coasts including the Andaman and, Nicobar islands., oper, Tides, The rise of sea water is called high tide (als, called spring tide) and falling of water, The sea water rises and falls twice daily at an, almost regular interval in response to the called low tides. Spring tides occur twice a, gravitational pull of the moon and the sun. month when sun, moon and earth are in &, This periodical rise and fall of seas water is straight line relative to each other. Thi, termed as the tides., happens during full moon and new moon., The rise and fall of the ocean is also the sun and moon are at the right angles to, termed as the high tide and low tide each other, low tides are caused. These are, respectively., The tides occur due to the gravitational occur twice a month at the first, pull of the sun and moon., also called neap or low tides. These tides also, quarters, and, the last quarter., 30, 4
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The warm current originates from the, areas lying near the poles and flow, towards the equatorial regions., High tide, (Spring tide), Low tide, (Neap tide), SUN, SUN, Kigh tde (Sprtng tide, The areas where the warm and cold, Low tide (Neap tide), currents meet, provide the best finishing, grounds of the world., Significance, 1., of, Oceans, and, Their, Movements, Discover more..., Oceans provide us a huge variety of, Importance of Tides, Tides are used to generate electricity. In France,, Russia and China there are big power stations which, minerals., They provide home for many mammals,, reptiles and marine plants., They provide transportation facilities., generate electricity from tides. India has also made, some significant progress in this direction., Tides are important for navigation. They enable big, ships to enter or sail out of the harbour. Hugli port in, Kolkata is a good example of the utilisation of tidal, water for flushing the part as facilitating entry and, departure of ships., Осean, used to generate, waves, are, electricity., Oceans provide natural link between the, Le, continents., Ocean Currents, ie, Ocean current also help in maritime, The ocean currents can be cold or warm., trade., Warm, currents, bring about, warm, Oceans are the main source of water, by, ed, temperature over land surfaces., The, vapours., ocean, current, influences, the, The meeting of warm and cold currents, result in the development of plankton., Plankton is the tiny form of plant and, is, temperature conditions of the area., ea, The movement of ocean water in constant, direction is termed as the ocean current., le, ),, he, nd, animal life that serve as food for fish., ARCTIC, O CEAN, ARCT IC, OCEA N, Se, Narwegian, Seb, North Atantic Dri, EURORES, NORTH, Iso, AMERICAT, Pacc Caent, is, Calfor, NORTH, PACIRIC, OCEAN, ARRICA, So Equalorial Cue, Noth Egoal Omt, Enutoral utaL Cunt, INEMAN OCEAN, his, If, Counter C, Equelrial Cuer, SOUTH, AMARIC A, SOUTH, ATLANTIC, OCEAN, REFERENCESs, to, DSTRALIA, Cold Currents, Warm Currents OUTH, El Nino, ire, AdiFIC, CEAN, Aga, Iso, FISHING, nd, High and Medium, Catch, Low Catch, Weet Wind Din, Wet Wind Di, NOT TO SCALE, Major Ocean Currents, 31, Pa