MAJOR LANDFORM FEATURES Major landforms are the major relief features of the earth‟s surface. They include mountains, plateaus and plains etc. Formation of Landforms Formation of landform is brought about by two main forces namely, Internal forces (tectonic forces) and external forces. Internal Forces: Internal forces are forces that lead to the movement of the tectonic plates either laterally or vertically. These movements generate stress in the form of compression (contracting of land surface) and tension (expansion of land surfaces), which lead to different landforms. EXTERNAL FORCES: Internal forces are also known as forces of denudation. They are the forces, which operate on the earth‟s surface to modify the relief features produced initially by the internal forces. They include weathering, erosion, transportation and deposition. A. MOUNTAINS:

These are greatly elevated land surfaces resulting from the intense action of internal forces. Steep slopes and prominent peaks or ridges characterize them. Based on their mode of formation, there are four types of mountains. They include: Fold Mountain; Block Mountain; Volcanic Mountain; Residual Mountain. FOLD MOUNTAINS: Fold Mountains are formed as a result of stresses caused by large- scale horizontal earth movement. Such stress subjects the rocks to compression. These compressional forces pushing horizontally from opposite ends cause sedimentary rock layers within the earth crust to wrinkle or fold. The wrinkles form upward folds called anticlines and downward folds called synclines. In simple folding, the upward folds form mountains known as Anticline Mountains while the downward folds in form valleys known as synclinal valleys. Jura Mountain in Europe is an example of young simple Fold Mountain while Udi Hills in Nigeria is an example of unfolds. When folding continues, simple up and down folds become pronounced to form asymmetrical fold. As the forces of compression continue to act on the folding area, some folds begin to lean over to one side to form over fold. Further folding of the over fold forms the recumbent fold. This complicated fold breaks off at base and slides over the adjacent

land. The sliding surface is known as the thrust plane while the sliding fold is known as the nappe Examples are

Rockies in USA and the Atlas Mountain etc. CHARACTERISTICS i. They consist of ridges with intervening narrow depression ii. They usually have a steep sides iii. They consist of different types of folds. iv. Examples of fold mountains are rock mountain USA, Andes (South America) and Atlas (North Africa)

BLOCK MOUNTAINS: FORMATION These are generally flat-topped and steep-sided when newly formed but their slope may be lost after long erosion when rivers may have dissected them. Faulting accompanied by tension and compressional forces causes Block Mountains. Faults refer to fractures along a line of weakness in rocks. There are two types of block Mountain; block Mountain and rift valley or Graben. When there is tension in an area of the earth‟s crust with two parallel normal faults, the land enclosed by the two parallel faults remain as it is. The land on either side of the parallel faults subsides. Then the enclosed central block now standing becomes the horst or block mountain e.g. Block forest of Europe. In the formation of Graben or Rift valley, there could be an area of the earth‟s crust with two parallel reverse faults, compression could force the area of land outside the area enclosed between the faults to slide upward thus rising above the land enclosed by the two parallel faults. The enclosed area forms a rift valley or graben. e.g. Central valley of Scotland. Other e.g. of block Mountains are the Fouta Djallon Mountain in Guinea, Tarkwa hill region between Konongo and Tarkwa (Ghana), the east Africa Rift Valley etc. CHARATERISTICS i. They consist of old hard rocks ii. They are usually associated with Rift valley iii. They have flat or slightly sloping surface iv. Examples are Hum struck of Germany, Vosges and Black forest of Europe

VOLCANIC MOUNTAINS: FORMATION Volcanic Mountains are formed when materials from the earth‟s crust are ejected through the cracks to the earth‟s surface. The materials include molten lava, volcanic bombs, caders, ashes, pyroclasts, dust and liquid mud. The materials fall around the vent in successive layers building up a characteristic volcanic cone. Volcanic Mountains are also called Mountains of accumulation because the materials that form them accumulate gradually to attain their heights. E.g. Mountain Fuji (Japan), Mountain Mayon (Philippines), Mountain Kilimanjaro (Kenya), Mountain Cameroon, Elgon Mountain, Ruwenzori, Mountain Merapi (Sumatra) etc.

CHARACTERISTICS i. They consist of hot rocks, lava, ashes, dust and liquid mud ii. Material are ejected through hole called vent or pipes iii. Material are built up to form mountain which may be conical or dome in shape iv. Examples are Kenya, Elgon and Cameroon in Africa

Original mountain surface Downward cutting by rivers RESIDUAL MOUNTAINS: FORMATION These are formed as a result of external forces of denudation acting on the landform after tectonic forces have structurally formed them. They are also referred to as Mountain of denudation. Residual Mountains are generally steep sided and rugged in shape. When forces of denudation act on fold Mountain, they attack the anticlines more easily; wear them down into valleys leaving the synclines to stand up as rugged Mountains. The eroded anticlines now become the valley called anticlinal valleys while the synclines form Residual Mountain called synclinal Mountain e.g. Matter horn in Switzerland. Residual Mountains may also evolve from plateaux, which have been dissected by rivers into hills and valleys. A volcano may be eroded leaving behind the hard solidified volcanic lava (duridust) to stand out as Residual Mountain known as volcanic plug. E.g. Wase rock behind Wase village in Benue valley, Tangase rock and Okene Plug in Nigeria. CHARATERISTICS i. They are hard and resistant rocks that are left standing after the surrounding areas have been reduced by agents of denudation ii. They are remains of old mountains that have been reduced by agents of denudation iii. They are called dissected mountain iv. Examples of residual mountains are Monadnock in USA

IMPORTANCE OF MOUNTAIN: 1. They are sources of rich mineral e.g. coal from Appalachian mountain, gold from cordillera in USA, tin and copper from the Andes and Bolivia. 2. They are sources of rivers e.g. Fouta Djallon highland and Cameroon mountain 3. They serve as recreational or tourism centers. 4. They modify the climatic condition of a place by lowering the temperature and produce an orographic rainfall. 5. They provide constructional materials for road and building 6. In the past, they serve as defensive barriers during inter tribal war.

B. PLATEAUX: These are elevated uplands with extensive level surface and usually descend steeply to the surrounding lowland. They are also referred to as tablelands. They have narrow valleys and sometimes form hydrological centers. Just like other highlands, they are subjected to erosional processes. As a result their original characteristics may be greatly altered. Plateaux may be divided into three groups according to their mode of formation and Physical appearance.

TECTONIC PLATEAUX:

FORMATION This is formed by internal forces (earth movement). These forces (tensional or compressional) cause uplift and fairly uniform altitude. The uplifted areas of level landform tectonic plateaux and the depressed areas form basins. E.g. the continental blocks such as Deccan plateau in India. Some of the plateau may also be lifted like the Mistral of Central Iberia or faulted like the Harz of Germany. VOLCANIC PLATEAUX: They are also called lava plateaux. They are formed when basic lava are ejected or erupts from the earth‟s crust and spread over the earth‟s surface to from successive sheets of basaltic lava. They spread out over a great distance thereby forming a highland with almost leveled tops known as volcanic plateau. The best Nigeria example is the Biu plateau. Other examples include Antrim plateau of Northern Ireland. The most remarkable plateau built by lava is the Columbia snake plateau, which covers an area almost twice as big as Malaysia. DISSECTED PLATEAUX: These are sometimes referred to as residual plateaux. They are formed when high and extensive plateaux are gradually attacked or worn down by weathering and erosion processes. This gives the plateaux an irregular surface. They can be cut by deep river valleys which break them up into smaller units, such plateaux are called dissected plateau e.g. the Scottish highlands, the edges of the Jos plateau and Fouta Djallon. Highlands of Guinea have been subjected to downward cutting by the various streams originating from them. Flat-topped remnants of such hills often capped by resistant rocks and are called Mesas. Smaller remnants of mesas are known as Buttes. The resistant rock is often duricrust (laterite) INTERMONTANE PLATEAUX: These are plateaux enclosed by Fold Mountains e.g. Tibetan plateau between the Himalayas and the Kunlun. Intermontane plateau are some of the highest and most extensive plateau in the world. Bolivian plateau and the Andes is another good example. USES OF PLATEAU 1. They form climatic barriers and thus shelter settlement on the leeward side from the harsh climatic conditions on the windward side. 2. Plateaux are rich in minerals e.g. Jos Plateau has tin and columbite. 3. In tropical lands cool plateau tops are conducive to human settlement e.g. Jos. 4. Some plateaux are centre of tourist attraction like Obudu and Jos plateau. 5. Some plateaux are sources of many rivers. 6. Plateaux also support the growth of pasture and grasses and legumes, which support the rearing of animals. 7. They form fertile soil for agricultural cultivation of specialized crops e.g. apples, tea, coffee C. PLAINS

A plain is an extensive or expanse of lowland area, which is either level or undulating and are usually few hundred metres above the sea level. They are areas of lowland and are gently undulating. They have low elevation and hardly rise above a few hundred meters above sea level. Plains can be low hills with rolling topography. TYPES OF PLAIN: Based on their mode of formation, there are three major types of plains; structural plains, depositional plain and erosional plains. 1. STRUCTURAL PLAINS: These are plains that have not been disturbed by earth movement (internal forces). They are formed by horizontally bedded rocks and are structurally depressed areas of the world. They make up the most extensive natural lowlands on the earth‟s surface e.g. Russian platform, the great plains of USA, the central lowlands of Australia. 2. DEPOSITIONAL PLAINS: These are plains formed by the deposition of materials that have been carried over a long distance by various agents of transportation such as wind, water (river), waves and glaciers. Depositional plains include; 1. Alluvial Plains, flood plains and deltaic plains that are formed by running water. 2. Outwash plain and till plain or drift plain formed by ice-sheets or glaciers. 3. Coastal plains formed by waves. 4. Loess plains formed by wind.

Alluvial Plains: This is common in areas where slopes decrease gently downstream. As a result of decrease in slope, the velocity of the flowing water reduces; this makes the water to deposit its eroded materials. The deposited materials

form the alluvial plains. Alluvial plains are associated with the old stage of a river e.g. fertile alluvial plain of Hwang Ho in North China. Flood plains: These are vast quantities of sediment deposited by a river at its lower course. The deposited materials gradually build up gently sloping surface called flood plain. Flood plains stretch widely on both sides of the river e.g. lowers Niger where it overflows its bank, the vast flood plains of the Ganges River in India and the Yang-Tze River in China. Deltaic Plains: These are formed when eroded materials are deposited at the mouth of a river. The deposited materials build up to form deltaic plains. Examples of such plains include the Niger Delta in Nigeria, the Nile delta in Egypt as well as the Mississippi and Ganges deltas in USA and India respectively. Outwash Plains: These are plains formed by wide spread deposits of unsorted sand and gravels by gradual melting of ice. They are usually infertile. Till or Drift Plains: Melting of ice also forms this but the materials deposited are made up of boulder clay a mixture of various sizes of boulders and clay. Examples are found in Northern Germany, Netherlands, mid-west of USA and East Anglia in England. Coastal Plains: They are formed when sediments or eroded materials are deposited by waves on some parts of the continental shelf or coast. The land is uplifted to form a gently sloping coastal plain. E.g. includes coastal lowlands of Belgium, the Netherlands and the gulf coast of USA.

When coastal lowland is raised slightly by uplift it is called Emergent coastal plain e.g. the coastal margins from Florida to Texas. Loess Plain: These are made up of very fine particles deposited by winds. The deposits are eroded materials from the desert loess help to level an undulating plain by filling up grooves and depressions e.g. pampas of Argentina. EROSIONAL PLAINS: Peneplains formed as erosion of uniform layers by running water progresses These are plains formed as a result of erosion or wearing down of the land to a level by agents of erosion (wind, rain, rivers and ice). These agents help to smooth out the earth‟s surface and even high mountains can be reduced to low undulating plains. Erosional plains include; pene plains, ice-scoured plains and pedi plains. Peneplains: These are formed when highlands are reduced by erosion to form gentle undulating lowlands. Peneplains are usually very large e.g. the great lake plain of the Hudson Bay area in North America. Rivers can deepen and widen their valleys to form river plains e.g. the Amazon basin is a river eroded plain. Inselbergs Pediplains formed as weaker rocks are eroded by wind Ice-scoured plains: These are the lowered land where continuous glaciations reduces the highlands to a very low level e.g. the plains of Finland Pediplains: These are plains formed as a result of winds erosion. They are common in semi-arid and arid regions where wind deflation sweeps away much of the eroded desert materials lowering the level of the land and forming extrusive plains. Weathering also wears back mountain slopes to leave gently sloping pediments or Pedi plains and some steep hills (inselbergs) remain. IMPORTANCE OF PLAINS 1. Plains provide good communication route ways such as roads, railways, airports etc. 2. They provide good pastures for roaming animals. 3. They provide good settlement and population concentration. 4. Plains provide rich fertile soils which favour intensive cultivation of crops e.g. flood plains. 5. They provide mineral resources such as coal, petroleum etc.

DEPRESSIONS OR BASINS: These are depressions in the earth‟s crust. They may be formed by erosion when the removal of soil by running water results in the formation of gullies or by tectonic activities such as convergence of plates. Where Tectonic Plates converge, the earth crust is often folded downwards as a result of subduction and this forms depressions on the earth crust E.g. Deep-sea trenches. Some depressions or basins may be filled with sediments deposited by wind or running water and such depressions often develop an external drainage system like the Congo Basin. Other depressions or basins have inland drainage e.g. the Chad Basin, El Djouf and Sudan Basins.

IMPORTANCE OF BASINS 1. Some of them serve as in-land drainages. 2. They can be very fertile and they are very valuable for agriculture e.g. Qattara depression in Egypt. 3. They are homes for submarine features e.g. Mariana trench etc. 4. Some of them serve as in-land drainages. 5. They can be very fertile and they are very valuable for agriculture e.g. Qattara depression in Egypt. 6. They are homes for submarine features e.g. Mariana trench etc. 7. Some of them serve as in-land drainages. 8. They can be very fertile and they are very valuable for agriculture e.g. Qattara depression in Egypt. 9. They are homes for submarine features e.g. Mariana trench etc

OCEANS Ocean is the large masses of salt ware that occupies a considerable portion of the earth surface. The ocean of the world occupies more than 71% of the earth total area of 510 million square kilometers. The ocean basins are the large depression on the earth surface, which are filled with a great mass of salt water.

There are four major oceans in the world. They include the Pacific Ocean which is the largest ocean, the Atlantic Ocean the second largest ocean, the Indian Ocean which is the third largest ocean, the Southern or Antarctic Ocean which is the fourth largest ocean and the Arctic Ocean which is the smallest ocean. Besides oceans, there are the seas of the world which are considerably large bodies of water. They include the Caspian Sea, Mediterranean Sea, Caribbean Sea, etc. The seas of the world are said to cover a total of about 25 million Km2 of the earth surface. S/NO OCEANS OF THE WORLD

AREA IN MILLION KM2

1. Pacific 155.557 2. Atlantic 76.762 3. Indian 68.556 4. Arctic 14.056 5. Southern (Antarctic) 20.327

Oceans are studied by oceanographers who find out the chemical composition of oceans water, its movement, its marine life, landforms, the influence of oceans on the continents and the importance of oceans to man. In their studies, they make use of various techniques such as echo sounding, satellite images, marine life observation and chemical analysis. THE OCEAN BASINS AND SEAS OF THE WORLD There are four main types of ocean in the world: Pacific, Atlantic, Indian and Arctic Ocean PACIFIC OCEAN: This is by far the largest ocean in the world occupying one third of earth surface and is made up of some of the greatest trenches, some of the trenches extend 5,000fathoms (900metres) deep. Pacific Ocean extends from the western coast of the Americas to eastern Asia and Australia ATLANTIC OCEAN: This is by far the most important ocean of the world. It is located between the eastern shore of the Americas to the western coast of Europe and Africa. It is the most important ocean of the world because most of the part which serves some of the most heavily industrialized nation of the world are along it ridges. It contains trenches but not as notable as that of the Pacific Ocean. Some of the trenches are Puerto Rico deep, the south sandwich trench, and the romanche deep. It also has an elongated ridge called the mid Atlantic ridgeINDIAN OCEAN: This is the third largest ocean in the world. It stretches more to the southern hemisphere than to the northern hemisphere. This ocean stretches from the coast of Africa, India and Indo – China and the coast of Australia, about 60% of its floor form the deep sea plain with a depth ranging from 2000 – 3000fathoms. ARCTIC OCEAN It is the smallest ocean in the world and surrounds the whole of the Arctic region. The Northern fringes of North America and Europe bind it. The Arctic Ocean occupies the sea around the North of North America and Eurasia. It is a shallow basin with a mean depth of 5,449metres and a total area of 14millin Sq km. The largest landmass in the Arctic Ocean is the Greenland. THE SEA The seas of the world cover an area of 25million Sq km and they include the Mediterranean, the Black, the Dead the Caribbean Sea etc THE NATURE OF THE OCEAN FLOOR (OCEAN PROFILE) The ocean floor is covered with several features that appear similar to those on ground. They include the continental shelf, continental slope, deep-sea plains, marine ridges and plateau, ocean deeps, trenches and ocean islands.

Relief profile of an ocean floor

THE CONTINENTAL SHELF: This is considered to be a continuation of the landmass into the ocean .It is the shallowest part of the ocean. It forms a gentle sloping edge extending under the sea to an average depth of about 180m. The continental shelf varies from one shelf to another. Some shelves stretch for a few meters while others stretch for up to 1200km. GEOGRAPHICAL SIGNIFICANCE/IMPORTANCE OF CONTINENTAL SHELF 1. One of the major importance of continental shelves to man is that they provide good fishing ground. The shallow nature of the water allows sunlight to penetrate through it and aid the development of plankton an essential fish food. Some of the fishing grounds include Grand Banks off Newfound land (USA), the shelf North Sea and the continental shelf extending from Mauritania to Senegal in Africa. 2. The shallowness of the continental shelf makes easy exploration of crude oil in the area. 3. The continental shelf brings about development of natural harbour as this has been reflected in the seaport of Southampton, London, Hamburg, Singapore, and Hong Kong etc. 4. They also bring about development of tourist centers. A common feature of a continental shelf is sand which sometime drifts out to from beaches. THE CONTINENTAL SLOPE: This marks the end of continental shelf. It links the continental shelf with the deep-sea plains or ocean floor. It extends to a depth of about 3000m where the deep sea plain begins. Along the continental slope, mud and red clay can be found. THE DEEP SEA PLAIN: This is made up of fairly undulating or level floor of about 2-3km below sea level and covering 2\3 of the ocean floor. It is also called abyssal plain. OCEAN RIDGE: This takes the form of either a ridge or a plateau, which rises from the deep sea plain. Examples include Mid-Atlantic ridge, South Pacific plateau etc. Some of the ridges and the plateaux rise above the ocean surface to form oceanic islands example the Falkland and Canary Islands, etc. Others are the peaks of ocean floor volcanoes example Hawaiian and Fiji.OCEAN DEEPS OR TRENCHES: These are long, narrow and steep-sided depressions that occur at the deep-sea plain and they could have a depth of about 10,000m or more. An example of ocean deeps is the Marianas Trench off the island of Guam in the Pacific Ocean with a depth of about 11,035. They occur mostly at the edge of the continents boarded by fold mountains example Atacama trench off the coast of Chile and Peru. SEA MOUNT: These are under water mounts that rise from the ocean floor. They could be about 3000m below the ocean surface. MARINE DEPOSITS The materials eroded from the earth, which has not been deposited by rivers, are eventually brought into the ocean bed; these materials are termed marine deposit. This deposition can be classify as follows 1. Muds: These are ferruginous deposit derived from land and are usually deposited on the continental shelves. 2. Oozes: These are pelagic deposit derived from the ocean; they consist of the remains of shelly, skeletal marine micro organism 3. Clay: These occur mainly as red clays on the deepest parts of the ocean basins and are mostly abundant in the pacific. OCEAN ISLANDS These are mountains that are deep seated in the ocean with their peaks extending above the sea level. They may be formed by folding or volcanic activity. Some ocean islands are detached from the continental landmasses but others are considered to be part of the continents where the coastlands have been partially submerged e.g. Madagascar is part of the African continental landmass but Hawaii is not attached to any continental land mass. Marine organisms whose shells are made of calcium, sometimes stick together to form solid land-like masses which are seen above the ocean surface. These features are known as Coral Reefs. SALINITY OF THE OCEAN Salinity of the ocean can be defined as the degree of saltiness or concentration of salt solution in oceans. Seawater contains dissolved mineral matter of which sodium chloride is common. They provide marine organisms with calcium carbonate needed for the formation of shells and bones. Magnesium chloride and magnesium sulphate are also found. The degree of saltiness varies from ocean to ocean and is often measured in parts per thousand grams. The average salinity of the ocean is about 35grams for every 1000 grams of water. In maps, a line called isohaline often joins all oceans having the same degree of salinity. In General, the salinity in semi-closed seas in the tropical areas is relatively high because of high evaporation. Salinity is also high in sub-tropical areas where there is a relatively small amount of water discharged into the sea. Examples include the Mediterranean Sea, the Great lakes of North America, the Red sea, and the Dead Sea of Jordan. The highest salinity is that of Lake Van in Asia Minor about 330 per 1000grams. FACTORS INFLUENCING OCEAN SALINITY The variation of salinity in the various seas and oceans is affected by the following factors:

1. RATE OF EVAPORATION: In high temperature areas, there is a consequent high rate of evaporation and as salt does not rise with evaporation water, it concentration increases, thus places with low rates of evaporation tends to have lower level of salinity. The high rate of evaporation in the Middle East accounts for the high level of salinity in seas within the area. The Dead Sea for instance, has the highest salinity in the world of about 250 parts of salt per 1000 parts of water. The water body with the highest salinity is Lake Van, which has about 330 parts of salt per 1000 parts of water. 2. AMOUNT OF FRESH WATER ADDED BY PRECIPITATION, STREAMS AND ICE BERGS: Salinity is lower than average of 35 per thousand in equatorial waters because of the heavy daily rainfall and high relative humidity, when these oceans becomes diluted with fresh water, their salinity decreases. 3. THE DEGREE OF WATER MIXING BY CURRENTS: In wholly, or partially enclosed seas such as the Caspian sea, the water does not mix freely with water from other oceans, thus the change in salinity is negligible. Where there is free mixing of high salinity ocean water with low salinity ocean water, the waters are diluted to bring about variation in their various levels of salinity. Salinity increases in the ocean with lower salinity and on the other hand, salinity becomes lower in the ocean with a higher salt contentOCEAN DEEPS OR TRENCHES: These are long, narrow and steep-sided depressions that occur at the deep-sea plain and they could have a depth of about 10,000m or more. An example of ocean deeps is the Marianas Trench off the island of Guam in the Pacific Ocean with a depth of about 11,035. They occur mostly at the edge of the continents boarded by fold mountains example Atacama trench off the coast of Chile and Peru. SEA MOUNT: These are under water mounts that rise from the ocean floor. They could be about 3000m below the ocean surface. MARINE DEPOSITS The materials eroded from the earth, which has not been deposited by rivers, are eventually brought into the ocean bed; these materials are termed marine deposit. This deposition can be classify as follows 1. Muds: These are ferruginous deposit derived from land and are usually deposited on the continental shelves. 2. Oozes: These are pelagic deposit derived from the ocean; they consist of the remains of shelly, skeletal marine micro organism 3. Clay: These occur mainly as red clays on the deepest parts of the ocean basins and are mostly abundant in the pacific. OCEAN ISLANDS These are mountains that are deep seated in the ocean with their peaks extending above the sea level. They may be formed by folding or volcanic activity. Some ocean islands are detached from the continental landmasses but others are considered to be part of the continents where the coastlands have been partially submerged e.g. Madagascar is part of the African continental landmass but Hawaii is not attached to any continental land mass. Marine organisms whose shells are made of calcium, sometimes stick together to form solid land-like masses which are seen above the ocean surface. These features are known as Coral Reefs. SALINITY OF THE OCEAN Salinity of the ocean can be defined as the degree of saltiness or concentration of salt solution in oceans. Seawater contains dissolved mineral matter of which sodium chloride is common. They provide marine organisms with calcium carbonate needed for the formation of shells and bones. Magnesium chloride and magnesium sulphate are also found. The degree of saltiness varies from ocean to ocean and is often measured in parts per thousand grams. The average salinity of the ocean is about 35grams for every 1000 grams of water. In maps, a line called isohaline often joins all oceans having the same degree of salinity. In General, the salinity in semi-closed seas in the tropical areas is relatively high because of high evaporation. Salinity is also high in sub-tropical areas where there is a relatively small amount of water discharged into the sea. Examples include the Mediterranean Sea, the Great lakes of North America, the Red sea, and the Dead Sea of Jordan. The highest salinity is that of Lake Van in Asia Minor about 330 per 1000grams. FACTORS INFLUENCING OCEAN SALINITY The variation of salinity in the various seas and oceans is affected by the following factors: 1. RATE OF EVAPORATION: In high temperature areas, there is a consequent high rate of evaporation and as salt does not rise with evaporation water, it concentration increases, thus places with low rates of evaporation tends to have lower level of salinity. The high rate of evaporation in the Middle East accounts for the high level of salinity in seas within the area. The Dead Sea for instance, has the highest salinity in the world of about 250 parts of salt per 1000 parts of water. The water body with the highest salinity is Lake Van, which has about 330 parts of salt per 1000 parts of water. 2. AMOUNT OF FRESH WATER ADDED BY PRECIPITATION, STREAMS AND ICE BERGS: Salinity is lower than average of 35 per thousand in equatorial waters because of the heavy daily rainfall and high relative humidity, when these oceans becomes diluted with fresh water, their salinity decreases. 3. THE DEGREE OF WATER MIXING BY CURRENTS: In wholly, or partially enclosed seas such as the Caspian sea, the water does not mix freely with water from other oceans, thus the change in salinity is negligible. Where there is free mixing of high salinity ocean water with low salinity ocean water, the waters are diluted to bring about variation in their

various levels of salinity. Salinity increases in the ocean with lower salinity and on the other hand, salinity becomes lower in the ocean with a higher salt content

OCEAN WARM CURRENT COLD CURRENT Atlantic Ocean North Atlantic Drift current, Florida

current, Gulf Stream current, cayenne current, Guinea current.

Labrador current, canaries current, Irminger current

Pacific Ocean Kuroshio current, North Pacific Drift current, Oyashio current.

California current, Okhotsk current.

OCEANS OF THE WORLD