Geh Chang Leong1) All stars revolve around earth in elliptical orbit. All planets revolve anti-clockwise from west to east except Uranus.

Q Give the examples that shows earth is sphere and not flat ?A Equatorial diameter is more than the poles. This shows that earth is not a perfect sphere. 1) The round the earth voyage of magellan led to the return at the same point pointing it as not flat. 2) The distant horizon appears as circular and it increases with increasing altitude. 3) The mast of a ship appears first rather than the mast, if earth were to be flat then whole ship would have been appeared together. 4) Sun rises and set differently in different part of the world. This shows earth is not flat. 5) Shadow cast by earth on moon is circular. 6) With technology such as satellites, we can see that earth is sphere. 2) Rotation of earth causes day and night while revolution causes seasons and year. When sun is exactly over equator two times in a year. That is called as equinox as all parts of the world have equal days and nights. 21 June, sun is over tropic of cancer called as summer solstice. 22 december, sun is over tropic of Capricorn called as winter solstice. Beyond these lines sun is never overhead on any day. Q Why summers are warm and bright while winters are dark and cold ?

A During summer the suns rays are direct of less inclined to earth causing greater energy concentration on the surface. This leads to more heat while in winter the rays are oblique and scatter in longer area and hence per unit area heat capture is less. This leads to accumulation of less heat in atmosphere and hence cold climate. Days are longer than night during summer and have more heat while opposite is true for winter. 3) During the dawn and twilight, earth receives refracted or diffused light. Sun rises vertically at equator hence these periods are short while it increases towards poles due to obliqueness. 4) Latitudes are measured angular angles from equator. These are parallel to equator and hence called as parallels of latitude. The earth is flattened at the poles and hence linear distance between latitudes is greater. Longitude is the angular distance from prime meridian. These are called as meridians. 5) Earth rotates 1* in 4 minutes. Earth rotates from west to east and hence if we move east time is advanced and reduced on the other side. Q why the concept of local time arised ?

A If all towns keep time as per their longitude then time changes while moving from one longitude to another. Travellers have to change their watch frequently which is impractical. This reasoned for local time. 6) Perihelion is the nearest point to sun in the orbit of planet, asteroid and comet while aphelion is farthest. Q Why polar air routes follow great circles ?

A Great circle is any circle on a sphere which includes the centre. This circle provides the shortest route between two points and hence minimum navigation time.

Q Effect of latitude on temperature and day and night?

A With increasing latitude the sun rays become slant falling on larger surface with less energy received per unit area. This leads to less absorption and low temperature. During summer, higher latitudes have longer days and shorter night while opposite is true in winters. This is because earth is tilted at 22 * to is axis from vertical. The conditions are opposite in other hemisphere. Q Effect of longitude on time?

A One degree movement in east or west forward and retard time by 4 minutes.

Q Effect of altitude on temperature?

A Earth surface reflects the short wavelength sun rays with longer wavelength terrestrial waves. These are absorbed by gases such as water vapour, carbon dioxide keeping the atmosphere warm. These gases are mainly present in troposphere and hence temperature decreases with height as the waves are captured more near the surface than in the upper atmosphere.7) The earth crust is made up of: upper part forming continent is of granitic rocks or SiAl. The lower part is of basaltic rocks or SiMa which forms the ocean floor.

8) Types of rocks: 1) igneous rocks 2) metamorphic rocks 3) sedimentary rocks. 1) These are formed by cooling of molten magma. These are crystalline and do not occur in layers with no fossil fuels. When these contain high silica is acidic such as granite which are less dense and of light colour than basic rocks. Basic rocks contain more basic oxide such as magnesium, iron and aluminium and hence are dense and dark in colour. a) Plutonic igneous rocks: These are formed under the surface due to slow cooling of magma and hence are coarse grained. These are intrusive rocks. b) Volcanic igneous rocks: These are formed on the surface due to fast cooling and hence are fine grained. These are extrusive rocks and basalt is a good example. The molten lava may force its way through vertical and horizontal gaps forming dykes and sills respectively. Most igneous rocks are very hard and hence used in road making and monuments. 2) These are formed due to accumulation of sediments over long period of time usually under water. These are called as stratified rocks due to formation of layers. These rocks can be soft or hard or fine or coarse grained. These are non-crystalline and contain fossils. a) mechanically formed: These are formed due to accumulation and cemented. Sandstone is an example. b) organically formed: These are formed when hard shells of organisms after decomposition of organic part is accumulated under pressure. Calcareous is an example containing chalk and limestone. Carbonaceous rock is formed from vegetative remains of forests and swamps later becoming peat, lignite or coal. c) chemically formed: These are precipitated chemically from solutions of one kind or the another. Gypsum or calcium sulphate is formed after evaporation of salt lakes. 3) metamorphic rocks: All igneous and sedimentary rocks can become metamorphic rocks under heat and pressure. The character of rocks may change significantly. 9) Types of mountains: 1) Fold: These are widespread and most prominent. These are formed due to stress generation of the underlying rocks due to various reasons. These stresses cause wrinkling and folding along the weak lines. These shorten the earth crust and create syncline (up fold) and anticlines (down fold). Himalayas, rocky and alps are the examples. When stress is very high, fracture takes place and one part slides over the other part forming mountains of elevation. These contain rich mineral resources and volcanic activities. 2) Block mountains: When crust cracks faulting occurs. It may be caused by tension or compression causing a section to subside and another to rise. Subsided part is rift valley or graben and elevated part is horst or block mountain. In general these are more due to tension rather than compression. 3) Volcanic mountains: These are formed out of lava. These are called as mountain of accumulation. 4) Residual mountains: These evolve by denudation. Some resistant are may remain after denudation forming these mountains. 10) Plateaus: 1) Tectonic plateau: These are formed due to earth movement and are generally of large size and uniform altitude. When these are enclosed by folded mountains are called as intermont plateau such as Tibet and bolivian. 2) Volcanic plateau: Due to spread of successive layer of basaltic lava such as Deccan plateau. 3) Dissected plateau: Due to continuous erosion and weathering led to wearing down of surface, turning it into irregular relief feature. 11) Plains: 1) Structural plains: These are structurally depressed areas. 2) Depositional plains: These are formed due to deposition. 3) Erosional plains.12) Igneous landforms: because of narrowness, dykes seldom form dominating landforms. Due to denudation they may form the high standing walls or trenches depending upon the adjacent rocks. Laccolith is dome shaped with flat base formed inside crust due to pipe like feeding. Phacolith are formed when lava fills an anticline forming a lens like structure. 13) Volcanoes: 1) Basic lava: These are hottest lava and highly fluidic. These are rich in magnesium and iron but lack in silica. These are dark coloured like basalt. These flow quietly without much explosion. They spread over greater areas. They form flattened shield or dome of volcano. 2) Acid lava: These are highly viscous with high melting point. High silica, low density and light coloured. This flow slowly and covers smaller area. These congest the vent of volcano leading to explosions. Basic lava forms vast basic or basaltic plateaus. High fluidic lava forms shield volcanoes or lava domes such as volcanoes of Hawaii. These have gentle slope and broad flattened top. Less fluidic lava volcanoes are explosive forming ash and cinder cones with steep slopes and large crater. These are small volcanoes. Highest and most common volcanoes are composite cones or strato-volcanoes. These are built up after several layers of lava. Lava reaches to the surface through dykes or pipes and feed to parasitic cones. 14) Geysers and hot springs: Geysers are fountains of hot water and superheated steam associated with volcanic regions. Hot springs are more common where water seeps deep enough to get heated by interior forces. 15) Earthquakes are associated with volcanic regions.

Q Difference between cinder cones and lava domes ?

A Lava domes are formed due to high fluidic magma flow. Magma after eruption flows to longer distances. These have gentle slopes but cover a large area. Cinder cones are formed due to low fluidic lava. They do not travel longer distances and have steep slopes. They are explosive in nature. Most of the time crater subdues inside the opening forming large crater. Q Crater and caldera, difference?

A Both of these are depressions made at the top of the volcano. Craters are formed when magma erupts making an opening at the top causing the surrounding rocks to fall down into it. Caldera: It is formed when due to creation of cavity beneath the ground due to emptying of lava causes the overlaying rocks to collapse creating bigger depression then crater. It is a circular crater with vertical sides. Later lava fills the floor of the caldera and hence it is a feature as well as a process. 16) Denudation: It consists of four processes: 1) Weathering 2) Erosion 3) Transportation 4) Deposition. 1) Chemical weathering: It is a slow process that occurs due to exposure to air and water. These agents contain chemical elements sufficient to start chemical reaction with the rocks. These may dissolve the whole rock, a part thereof causing loosening of it leading to weakening of whole surface. Some parts of weathered material are carried away by water and air causing erosion but most part is responsible for soil formation by staying at the point of origin. When soil exists the chemical weathering intensifies as it captures moisture and keeps the reaction going. Rain water takes organic acid from the soil and makes the process stronger. Three major process of it are: 1) Solution: Rain water dissolves many minerals especially when it is rain water as presence of carbon dioxide makes it a weak acid. It severely erodes limestone rocks. The rate of solution is affected by mineral present and also its structure. Sedimentary rocks have pores between grains which are captured by air and water. More the number of cracks, stronger will be the process. The warm climate with heavy rainfall increases the intensity of chemical reactions. Dry climate hinder this process. 2) Oxidation: This involves the oxygen in air or water with minerals in the rock. Iron converts to iron oxide and falls down causing weathering of rocks containing iron. 3) Decomposition by organic acids: The bacteria present in the soil thrives on plant and animal remains. They produce acids which on mixing with the water causes weathering. Sometimes micro-organisms and lichens live on bare rock taking minerals from it and produce acids causing both mechanical and chemical weathering. 17) Mechanical Weathering: These can start on fresh rock but generally work well on weakened rocks, due to chemical weathering. 1) repeated temperature change: in deserts rock are exposed to high change in temperature leading to expansion and contraction of outer surface but the effect on inner surface is not sever. This leads to breaking up of the outer surface. In crystalline rocks, different crystals expand and contract at different rates enhancing the process. Stresses are greater near the surface and place with sharp angles and hence rectangular blocks are rounded in the process. When outer layer of rounded blocks split up, process is called as onion peeling or exfoliation. 2) repeated wetting and drying: In tropical region, where rain wet the rocks and sun shine quickly dries them up. This also occurs in the coastal region where tides wet the rocks and sun dries them up. When rocks are wetted, outer layer absorbs moisture and expands and when dries this moisture evaporates and rocks shrinks. This is also important in desert due to semi-arid rain storms apart from temperature change. 3) Frost action: In temperate latitude, their effect is significant. Rock contains cracks and breaks. During rain water gets into these areas and during night when temperature falls, they freeze and expands. This expansion and later contraction breaks up the rock. 4) Biotic factor: In cracks, plants take roots. When these roots expand they break up the rock. 18) Mass Movements: It is the movement of weathered material down the slope under gravity. 1) Soil Creep: This is a slow but continuous movement down the hill slope. This movement is not visible when slope is gentle and covered with vegetation. These are common in damp region where water act as lubrication agent and soil particles move over one another and over rock. When animals move over the soil, due to vibration and slope soil starts to move. This causes tilting of trees, posts etc. 2) Soil flow of solifluction: When soil is completely saturated with water, soil particles easily move over each other. Soil acts like a liquid and a mud flow occurs. In temperate and tundra regions, frost melts on warming up causing soil flow. Peat soil absorbs moisture but if more moisture than saturation point, soil flow occurs and called as bog-bursts in Ireland. 3) Landslides or slumping or sliding: These involve rapid movement of material down the slope. These occur on steep slopes. Earthquake or volcanic activity or cloud burst can cause such actions. Slumping occurs where permeable debris overlies impermeable rock. The water sinks down and gives slippery surface to move over it. 19) Groundwater plays important role in weathering and mass movement. Porous rocks are those which have pores between grains. Water is easily absorbed in these pores and stored. Permeable or pervious rocks are those which allow water to pass through them. Clay is porous but not permeable due to small pores which clog on entering water. Granite is non-porous but permeable as crystals dont absorb water but cracks and joints let water to pass through. The permeable rock overlying impermeable rock storing water and getting saturated is called as aquifers. The upper surface of water is water table. Springs: When water level in a rock reaches a surface water comes out of it normally or as a fountain. In karst topography, water sinks down and by process of solution flows through the rock till it hits a impermeable rock. At this point it comes to surface as spring called as resurgence or vauclusian spring. Wells: Bores are dug until water table is reached. Artisan well: When rocks are down-folded in shape of a basin. When permeable rocks such as limestone or chalk are sandwiched between impermeable rocks, these permeable rocks come to surface only at the edge of basin. Water percolated down to the lower part of the basin. The lower and upper impermeable rocks saturate the basin and stop any movement above and below. The water is trapped under great pressure and when well is dug it comes out as fountain. Water may sometime be no appropriate for agriculture etc. because it may be hot and can contain minerals. Q Name the natural forces that cause weathering?

A The major natural forces are: Temperature, gravity, waves, snow, rain water. Q While internal forces are working to create the landforms and external forces are working to level it down. Discuss?

A Internal forces includes earthquake, volcano which occur due to internal energy due to radioactive decay and heat inside the earth crust. These forces change the face of earth by creating land forms such as hills, plateaus, faults and fissures. The external forces level them down by the process of weathering, erosion, transportation and deposition forming plains, levelling highlands etc. Q Screes accumulate at the foot of the mountains in temperate areas?

A Broken rock fragments due to weathering, due to gravity accumulate at the foot of the hills. These are called as screes. These are generally formed due to ice. In temperate areas, during rainfall water gets into cracks and joints. This due to drop in temperature freezes and causes mechanical weathering. Chemical and other type of weathering also plays their part. Q There are many forms in which spring can form?

A When water percolates down the permeable rocks and settles down at impermeable rocks. There are different ways for it to come out. It may come out when upper water level reaches the surface; in this process the outcome may be is in the form of fountain or normal flow tilted strata. It may come out where dykes or sills of impermeable rocks are penetrated into permeable rock and through them water comes to the surface. Jointed-rocks: water flows through joints till the time it comes to surface. Q Difference between chemical and mechanical weathering?A In chemical weathering no stresses are developed while mechanical weathering takes place due to formation of stresses. Mechanical weathering is the physical breaking up of the rock while chemical involves change in nature of mineral and agent chemically. Chemical weathering is prominent in warm and humid climate like equatorial region while physical weathering occurs well in temperate and arid regions. Physical weathering works with mechanical forces, such as friction and impact, while chemical weathering takes place at the molecular level with the exchange of ions and cations. Q What type of landforms chemical weathering by solution is most prominent?

A It is prominent in limestone structure as limestone dissolves easily in water. Sedimentary rocks have pores in which water and air can enter and increase chemical reactions. This is seen in granite rocks in Malaysia. 20) Initial stream from watershed is called as consequent stream. When underlying rock has equal resistance power to denudation by water tributaries join the consequent stream obliquely as insequent stream. But when underlying rocks are hard and soft, stream tends to follow the nature of rock system and if it allows, tributaries join at right angles as subsequent streams. The first pattern is tree like and hence called as dendric pattern. The second pattern will be rectangular in shape and called as trellised drainage. River Load: Material in suspension sand, silt and mud, material in solution and traction load such as pebbles, stones and rocks. Ability of river to carry load depends upon velocity, volume and load type. Corrasion and abrasion: This involves mechanical grinding of traction for with bed and bank. Lateral abrasion widens the V-shaped valley while vertical abrasion deepens the river channel. Corrosion or solution: chemical action of water on soluble or partly soluble rocks. Hydraulic action: mechanical loosening and sweeping away of material by river water itself. Water splashed along the bank and surges into the cracks. Attrition: wear and tear of transported material themselves when they roll and collide with themselves. 21) Courses of the river: 1) Upper stage: River flow speed is high due to steep slopes and vertical abrasion is significant leading to V-Shaped valleys. Lateral abrasion is not able to cope with the vertical in the upper stage. Places where rocks are very resistant, narrow steep sided gorges are formed. In arid, areas where little rainfall gives less incentive for side cutting, deep canyons are formed. Features: a) river capture: This is also called as river piracy or river beheading. It depends on head ward development or changes in source area. When one stream at source receives more rainfall than the other stream. It moves its head towards source capturing the catchment area of the other stream. The point at which this capture occurs is called as elbow of capture. The beheaded stream is called misfit. The valley below the elbow is wind gap and good for road and rail routes. b) rapids, cataract and waterfalls: These may occur in any part of the river but are most seen in the upper course due to abrupt and frequent change in slope. Hard rocks are eroded slower than soft rocks. The water sees small jumps during its course called as rapids. These jumps of bigger dimension are called as cataracts. When river plunges down a sudden height, it is called as waterfall. Waterfalls may form due to faults and plateau edge. Hanging or U-Valleys due to glaciations tributaries reaches to river with waterfall. Middle course: lateral erosion overtakes vertical. Banks widens leading to widening of V-valleys. Volume of water and load increases due to meeting of several tributaries. Some deposition but mainly transportation takes place in this course. Velocity does not decrease much but the erosion work is done in more subtle way opposed to upper course. Features: a) Meanders: Due to relief and flow of work under gravity, river does not flow straight. b) river cliff and slip-off slopes: When river flows in loops, it hits the outer side of the course eroding and creating steep features there and water piles up in this area due to centrifugal force, the lower end of the loop has gentle slope and hence deposition of sediments takes place here. The outer feature is river cliff and lower is slip-off slope. c) Interlocking spurs: when river progress with formation of menders, the bends area controlled due to interlocking spurs dictated by the topography. In lower course, meanders are fully developed in plains due to plain features. 22) Lower or Plain Course: Lateral cutting still goes on with vertical cutting almost stops. The river mainly does the depositional work developing bed and forming floodplains. Coarser materials are dropped and finer are carried to the mouth. Due to deposition of sediments on the bed, braided channels are formed. a) Floodplains: large sediments are deposited over the low-lying adjacent areas. These are called as fertile plains. When river flows with large sediments, they are deposited on the bed raising it and also along the banks forming levees. Water flows with the top of levees and in order to minimise the risk of floods, embankments are created on natural levees but this allows the river level to rise further. b) Ox-Bow Lakes: When meander becomes much pronounced. Outside bank is so much eroded that it becomes a complete circle. This later cut-off from the main river. The river then flow straight. c) Delta: Fine material is deposited at the mouth forming alluvial area. This is seaward extension of flood plains. Due to obstacles created by deposited sediments on the bed, river divides into several channels called as distributaries. Factors such as rate of sedimentation, depth of the river and sea-bed, tides, currents and waves influence their formation. Conditions favourable for delta formations: Extensive vertical and lateral cutting to provide adequate sediments, sheltered coast with minimum or no tides, sea adjoining the mouth should be shallow otherwise load will sink into the depth, no large lakes during the river course otherwise sediments will be diverted and no strong current running at right angle to river mouth washing away the sediments. 23) River Rejuvenation: Due to the shift in earth crust, river bed me be uplifted or depressed. Uplift of the river bed or fall in sea level will steepen the slope leading to sharpening of down-cutting. This cutting of flood plains leaves terrace formation on either side. The meeting point of old and rejuvenated profile involves some rapids. This point is called as knick point. If it occurs in upper course then river valleys are deepened and gorges are formed. In middle and lower course, vertical abrasion replaces lateral and meanders are also deepened. When movement of the earth crust is downward then it is called as positive movement raising sea level. This submerges the coast and valleys leading to weak erosive power of river. Large quantities of sediments are dropped. Lower course may be submerged and deposition takes place in middle course. Upper course is affected very little in this case. Advantages and disadvantages of features in three courses: rapids and waterfalls restrict navigation. Large deposition in lower course will silt up ports, dams etc. though dredging can be done but it is expensive, excessive floods will make floodplains not useful, gorges and valleys provides sites for hydro-electricity generation, this also leads to establishment of cement and other metallurgical industries due to cheap power, multipurpose projects help control floods, in regions of insufficient rainfall these are useful, the stream capture at the head of source help highways and rail route construction, fishing and tourism. Q- Describe features at the upper, middle and lower course of river.A Upper course: In the upper course, river flows with very high velocity and vertical cutting is prominent as compared to lateral cutting. This gives rise to V-Shaped valleys. Where rocks are more resistant gorges are formed. The places of low rainfall in upper course, not enough water leads to narrow but deep cutting of rocks called as canyons. Rapids are formed when alternative hard and soft rocks occur during the river course. The rapids on larger scale are called as cataract. When river flows down off fault, side of a plateau waterfalls are formed. Glaciers deposit the debris at the base of the valleys, forming U-valleys. Water flows down into these forming waterfalls. In this phase, erosion is the most important activity. Middle course: In this course, velocity of the river decreases but is still significant due to absence of very steep slopes. Sediment carrying capacity of the river depends on volume of water and it velocity. Q Describe constructive and destructive processes at work during the course of river.

Q Esturies and Delta.

A Delta: 1. The triangular deposits made by the rivers at their mouth form Delta. 2. Deltas are formed in the regions of low tides and coastal plains. 3. Deltas are fertile lands. 4. Ganga and Brahmaputra, Krishna, Kaveri and Mahanadi form delta. Estuary: 1. The sharp edged mouth of rivers, devoid of any deposits is known as Estuary. 2. Regions of high tides and rift valleys witness Estuaries. 3. Estuary does not have fertile lands. 4. Narmada and Tapi rivers form Estuaries.An estuary is an area where streams and rivers converge into the seawater from oceans. Bays, lagoons, harbours, inlets can be types of estuaries. Estuaries contains the mixture of salt and fresh water and results in brackish water.An estuary is all about meeting of a river with an ocean or a sea typically in a single line. It has no concerned with the distributaries of a river. On the other hand, delta usually gets developed when a river meets the still water body with many distributaries. A delta is formed in coastal areas which have plains and marked by low tides. On the other hand, an estuary gets formed in a coastal area marked by high tides. Deltas are rich in sediments, and therefore they are beneficial for agriculture, whereas the coastal areas near estuaries tend to be suitable natural harbours.Q Incised meanders are features of river rejuvenation.24) Glacier moves faster in the middle than the sides due to friction. Glaciation gives rise to Erosional features in the highlands and depositional features in the lowlands. Glacier erodes its valley by two processes 1) plucking 2) abrasion. By plucking, glacier freezes the joints and beds of rocks and tears them away with itself. By abrasion, glacier scratches, scrapes and polishes the valley floor with debris frozen in it. Rate of abrasion is determined by velocity of the flow, gradient of the slope, weight of the glacier, temperature of ice and geological structure of the valley. Features: 1) Corrie, cirque or cwm: When glacier moves downwards it leaves a depression. Plucking operates on back-wall, steepening it and movement of the ice abrades the floor, deepening it into a horse-shoe shaped basin called as cirque. It is also called as corrie in Scotland and cwm in wales. There is a ridge at the exit of corrie, when ice melts corrie lake or tarn is formed. 2) Aretes and pyramidal peaks: when two corries are cut on opposite side of mountain knife-edge ridges are formed called as artes. Their recession will form an angular horn or pyramidal peak. 3) U-shaped glacial trough: glacier while moving downwards, take ice from other corries like tributaries and wear away sides and floor. Interlocking spurs become truncated spurs and floor of the valley is deepened. This give rise to a valley with U-shape. After melting of ice, ribbon lakes are formed. 4) hanging valley: Main valley is eroded much faster than tributary valley as former contain more snow. When snow melts, tributary valley hangs over main valley, producing waterfalls. These are hanging valleys and may form natural head for hydro-electricity. 5) Moraines: Moraines are made up of pieces that are shattered by frost action, brought down with glacier. Those falls on side of glacier forms lateral moraines. When two glacier converges, their inside lateral moraines unite to form a medial moraine. Those which dragged along till glacier ice melts and spreads across the floor called as grounds moraine. The glacier eventually melts on reaching the foot of the valley, and pile of material left behind is called as terminal moraine.25) All deserts are confined to 15 30 N and S of equator. They lie in trade wind belt on the western side of continents where these winds are off-shore. They are bathed by cold current leading to less moisture in the atmosphere and less rain. In the interior of the continents such as gobi and Turkestan are characterised by extreme weather. Types: 1) Rocky desert: Bare rocks swept clear of sand and dust by the wind. Exposed rock is polished. 2) Stony desert: These are composed on pebbles and gravels which wind is not able to transport. These are accessible than sand desert, hence, large herds of camels are kept there. 3) Sandy desert 4) Badlands: Erosion due to water form gullies and revines. 5) Mountain desert: These are found on highlands such as plateau and mountain ranges.

26) Low precipitation, rapid evaporation, weathering, erosion together leads to formation of deserts. Due to little vegetation and moisture to bind the sand particles together wind erosion is enormous. Wind Erosion: 1) Deflation: It involves lifting and blowing away of loose material from the ground. It forms deflation hollows by lowering the land. 2) Abrasion: Sand blasting of rock surface is called as abrasion. It is most effective at the lower surface where wind carry large number of material. This is why telegraph posts are protected from the bottom by metal sheets. 3) Attrition: The particles flowing with the wind rolls against each other wearing each other. This forms fine grains. 27) Mushroom rocks: Due to abrasion, irregular edges are formed on rocks due to alternating soft and hard layers. Such structures are further eroded at their base where abrasion is greatest. Zeugen: These are tabular land; soft layer is lying under the hard layer at the surface. Mechanical weathering initiates their weathering. Wind then eats up the soft layer to create furrows, hard rock then stands on top of the furrow as a ridge. Yardangs: Similar to zeugen, but these are steep sided. Instead of horizontal layer of soft and hard rock, here these layers are arranged vertically and in the direction of the wind. Soft rock is eroded to form long vertical corridors. Mesas and buttes: It is a flat, table-like landmass with very resistant horizontal layer and very steep sides. Outside layer protests from wind and water erosion. It may form in canyon region. Continuous erosion for centuries may turn them in isolated table flatlands called as Buttes. Inselberg: These are isolated abruptly rising hills from ground. They have steep slopes and rounded tops. Deflation Hollows: Winds wear away lowlands. If there is some faulting, it can also initiate depressions and winds will erode rocks until water table is reached. Water the forms swamps. Large areas in western USA stripped off their natural vegetation for farming; these are then deflated by winds creating dust storms. This area is called as the great dust bowl. 28) Wind-borne material are shifted according to their coarseness, it can be expected that the coarser sands will be too heavy to be blown out of the desert limits. They remain as dunes or other depositional landforms within the desert themselves. These are not static and their migration depends upon size of particles, direction and velocity of wind, location and nature of surfaces over which these are transported and presence or absence of water and vegetation. Depositional landforms: 1) Dunes: These may be live or inactive, those with vegetation. These are most visible in sand deserts. a) Barchans: These are moon-shaped dunes occurring individually or in groups. These are live dunes. Most prevalent in sahara and Turkestan. These are initiated by chance, due to accumulation on obstacles. These occur transversely to the wind so that their horns thin out and become lower in the direction of the wind due to the reduced frictional retardation of the wind around the edges. The windward side is gently sloping and is convex, whereas leeward side is concave and steep. Crest of the dune moves forward as more and more sand is accumulated over it. Sand on reaching the crest slips downward making the dune to move. This invokes the threat that they may encroach upon the oasis. Long rooted trees and grass are planted to halt their advance. Seifs or longitudinal dunes: These are long and narrow ridges of sand lying parallel to the direction of wind. The crestline falls and rises with peak and saddles in regular successions. The gap between the dunes is kept clear by strong winds. The eddies that are set up in between the corridors have less power drop the sand to form the dunes. This leads to increase in length of dunes into tapering linear ridges while the occasional cross winds tend to increase the height and width of dunes. Loess: The fine dust blown outside the desert limit is deposited as loess. This material is yellow and fertile. This is extremely porous and rich in lime. Water sinks readily leaving the surface always dry. Streams cut deep valley out of these loess forming badland topography. These are so soft that road constructed soon sinks. 29) In deserts though rainfall is very less, but thunderstorms may drop large quantity of water in short interval. Due to little vegetation large material is washed in flash-floods. These form badland topography. 30) Limestone and chalk: These are sedimentary rocks or organic origin due to corals and shells. In pure form it is of calcium carbonate and when occurs with magnesium called as dolomite. Chalk is pure and soft form of limestone. Limestone dissolves in water and with carbon dioxide form weak acid. A region with limestone forms karst topography such as Yugoslavia. Karst Region: It has bleak topography, absence of surface drainage as most of the water flows underground, the water cuts through joints and fissures wearing them out and forming underground channel. When water reaches to non-porous rock, it emerges out in the form of spring called as resurgence. Limestone rocks are well jointed which helps in there chemical weathering. Water wears away these joints, forming trenches called as limestone pavements. On the surface there are shallow holes which are small depressions carved out by solution where rain water sinks into limestone at points of weaknesses. These are called as sinkholes. When water forms passages through limestone while passing, when roof of these passages collapses, gorges are formed called as limestone gorges. When a number of sinkholes join, doline is formed. Due to subsidence many doline joins to form uvala. During rainy season, areas which are near to water table become lakes while drier parts support villages. When subterranean stream descends from sinkholes to underground passages, a region where a number of cavities are linked just like a honeycomb is formed with caves. These may contain ponds and lakes. Some of them may contain lakes and ponds. Stalactites: These are sharp, slender, downward-growing pinnacles hanging from the roof. Water carries calcium with it, when water evaporates calcium form these structures. When moisture drops from the roof tickling down from stalactites, falls onto the floor to form stalagmites. These are shorter, fatter and more rounded. Ovetime, stalactites and stalagmites join each other forming pillars. 31) Most important area is N-W Yugoslavia, causses district of southern france, pennies of Britain etc. Karst region are mostly barren and atmost contain minimum soil. Porous rocks and absence of surface drainage make vegetation difficult. These areas support short grass and short turf. Some sheep grazing is possible. Limestone vegetation in tropical areas is rich due to rains throughout the year. The important mineral is lead which occurs in association with limestone. Good quality limestone is used in buildings and cement industry. 32) Chalk: these have different topography than limestone. There is little or no surface drainage and valleys which once supported rivers run dry. These are called coombes. Because of easy to crumble nature of rock, caves, sinkholes do not develop. Q Give outstanding features of krast topography?

A 1) No surface drainage. 2) Underground caves, passages and pillars. 3) Springs when water reaches non-porous rocks. 4) sinkholes, dolines and uvalas. Q Explain why krast topography has little surface drainage?

Q Why subterranean stream forms magnificent scenery?

Q Limestone areas have little agriculture and sparsely populated?

33) Caspian Sea is a lake, but due to its vastness is called as sea. Most of the lakes in the world are freshwater lakes fed by rivers and out-flowing streams. In areas of low precipitation and strong evaporation, rivers are not strong enough to go to sea and form inland drainage. Because of intense evaporation these lakes are saline. This is why; salt lakes are common features of water. Black sea is different as it has less salinity due to large river drainage. Lakes are temporary features which will be eliminated by draining and silting. In unreliable rainfall areas, lakes dry up during dry season. In hot deserts, lake dries up due to, evaporation, outflow and percolation. Formed by earth movement: 1) Tectonic lakes: Tectonic depression occurs, due to warping, bending and fracturing. Lake Titicaca is an example in intermontane plateau of Andes and is the highest lake in the world. Caspian Sea is largest followed by Lake Superior. 2) Rift Valley lake: Due to faulting, a rift valley is formed by the sinking of land between two parallel faults, deep and narrow and elongated in character. An example is east African rift valley. It includes Lake Tanganyika, worlds deepest lake. Dead Sea is worlds lowest lake. Lakes formed by glaciations: 1) Cirque lakes of tarns: Glacier while moving down the valley leaves circular hollows in the heads of the valleys up in the mountain. These are called as cirques and when filled with water is called as cirque lakes. Red Tarn in the English Lake District is an example. Those occupy glacial troughs are long and deep and are termed as ribbon lakes. Example: Lake Ullswater. 2) Kettle Lakes: These are outwash plains left by melting of ice of stagnant water. These are irregular because of uneven morainic surface and are never of any great size or depth. Keetle lake in Scotland and meres in England. 3) Rock hollow lakes: These are formed by ice-scouring when valley glaciers or ice sheets scoop out hollow on the surface. These are abundant in finland called as land of lakes. 4) Lakes due to morainic damming of valleys: Valley glaciers often deposit morainic debris across a valley so that lakes are formed when water accumulates behind the barrier. Both lateral and terminal moraines are capable of damming valleys. Lake windermere in England. 5) Lakes due to deposition of glacial drifts: in glaciated lowlands with a predominant drumlin landscape, where drainage is poor, there are intervening depressions. These get waterlogged forming small lakes such as county down in Ireland. 34) Lakes formed by volcanic activity: 1) Crater and caldera lakes: During eruption top is blown off leaving behind a central depression called crater. This may be enlarged by subsidence called as caldera. There are roughly circular in shape, bound by high cliffs and are normally dry. In dormant and extinct volcanoes these are filled with water forming the lakes. Crater lake in USA occupies a caldera, lake toba in Sumatra and lake avernus in naples. 2) Lava blocked lakes: Lava may flows across the valley damming it forming lava lakes. Galilee Sea in Jordan is an example. 3) Lake due to subsidence of volcanic land surface: The crust of hollow lava may collapse forming hollows, which when filled with water form lakes. Myvatn of Iceland is an example. 4) Lakes formed by erosion: 1) Karst lakes: Limestone forms sinkholes due to chemical weathering, these when filled with debris forms lakes. Collapse of walls of underground caverns exposes the underground lakes such as Lac de Chaillexon in Jura Mountains. 2) Wind deflated rocks: Deflation action of wind forms hollow. These may reach groundwater, where water seeps in forming lakes. Excessive evaporation leads them into salt lakes or playas. Great basin of Utah in USA. Lakes formed by deposition: 1) Lakes formed due to river deposits: Ox-bow lakes. 2) Lakes formed due to marine deposits: Action of waves and wind may isolate lagoons along coasts by building spits or bars. These lagoons are shallow and circled by narrow spit of land. In low tides, these get drained. These are found off the ganga and nile delta. Strong on-shore winds pushed coastal sand dunes landwards and these may enclose marshy lagoons such as in france in landes. 3) Lakes due to landslide, scree and avalanche: These are also called as barrier lakes. Landslides and scree may dam the river, these are short lived lakes. Sudden release of water due to opening of dam due to water force causes floods. 35) Man-made lakes: due to construction of dam for multipurpose and hydroelectric projects. Lake mead above hoover dam in USA over Colorado river is an example. Lakes made by animals: Animals such as beavers live in communities and construct dams of timber across the river, such dams are quite permanent and found in north America such as beaver lake in Yellowstone national park in USA. Other types: These includes ornamental lakes especially made to attract tourist. Fishing culture promotes inland fishing lakes, mining fill up forms lakes. 36) Lakes have played important role in human life. 1) Means of communication: Large lakes such as great lakes of north America provide cheap transport mode. 2) Economic development: early settlement and towns came up near lakes. Agriculture, fishing and industries development near lakes. 3) Water storage: For domestic and industrial use waste can be obtained. 4) Hydro-electricity generation: These furnish a good head of water in hilly areas. Natural lakes are preferred to artificial reservoirs because the volume of water in them varies little throughout the year. 5) Agriculture: When lakes dry up their bed provide fertile alluvial ground for agriculture. 6) Regulating river flows: A river with large number of lakes seldom experience flood or lack of flow. By absorbing excess water during rainy season, it helps in controlling floods and in fry season they provide steady flow of water. Climate moderation effect due to presence of lakes. They provide minerals: Salt lakes provides common salt, borax is mined in salt lakes of Mojave Desert. They attract tourists and create economic opportunities. 37) Coastal landforms: on calm days waves do little damage and also assist in beach formation. In storms, these damage coastal landforms. Tides and currents, on contact with the shores, make very little direct attack on the coastlines. Tides affect marine erosion mainly by extending a line of erosion into a zone of erosion. This zone corresponds to the area between the low water level and high water level. Current help to move eroded debris and deposit it as silt, sand and gravel along the coast. 38) Mechanism of marine erosion: Most powerful agent is wave. 1) Corrasion: Waves armed with debris charge against the cliff and wear them back by Corrasion. Oncoming currents and tides sweep away the eroded material. 2) Attrition: The material carried by waves, hurl towards each other and broken down by this process. This is responsible for fine sand deposited on the beach. 3) Hydraulic action: Waves splash against the coast may enter joints and crevices in the rocks. The air inside is compressed immediately. When wave retracts, the air expands explosively. This enlarges the cracks and leads to rock fragments. 4) Solvent action: on limestone coast, solvent action of sea water starts chemical changes in the rocks and disintegration takes place. This process is limited to limestone coasts. 39) Coastal features of marine erosion: 1) Capes and Bays: Due to hard and soft rocks on the coasts, erosion takes place irregularly. This is particularly pronounced when granite and limestone, hard rocks, and, soft rock, sand and clay, are found in alternate bands. Softer rocks are worn back into bays and hard rock persist forming capes. Even where same rock is found, irregularity may come due to changes in same rock. 2) Cliff and wave-cut platform: Any steep rock facing coast, forms a cliff. Best known cliffs are chalk cliffs of English Channel. At the base of cliff, a notch can be seen which collapses the cliff. 3) Cave, arch, stack and stump: At the base of cliff, waves forms caves in weak regions, when to caves approach and unites, they are called as arch. Further, erosion will collapse the arch. The seaward portion of the headland will remain as a pillar of rock known as stack. 4) Goes and gloups: The splashing of wave against the roof of a cave may enlarge the joints due to air compression and expansion. Natural shaft is formed which enlarge and pierce through the surface. This shaft is called as gloup or blow-hole. When due to prolonged action, roof collapses and called as goes. 40) Features of marine deposition: 1) Beaches: Sand and gravel loosened from the land and deposited along the shore are beaches. The longshore drift deposit material with moving windward direction. Backwash removes some of the material and deposits them on the off-shore terraces. The coarser material is deposited at the beach, finer are deposited closer to the sea. 2) Spits and bars: The longshore drift deposit material where there is a bay or cape at their inlet. On continuous deposition, embankments called as spit are formed, with one end attached to the land and other looking over the sea. 3) Marine dunes and dune belt: with the force of on-shore winds, a large amount of coastal sand is driven landward forming extensive marine dunes that stretch into dune belts. To stop there advance, marram grass and pines are planted. 41) Type of coasts: 1) Coastlines of submergence: These are formed due to sinking of land or rise in sea level. 2) Coastlines of emergence: These are due to uplift of land or fall in sea level. These are less common.

42) Coast of submergence:1) Ria Coast: During ice age, most water is frozen. With melting, the mountains which are perpendicular to the sea, valleys were filled by water with highlands separating them. They are not glaciated and their depth increases seawards. Rias are generally backed by highlands, they support few large ports though they have deep water and offer sheltered anchorage. They have been used for siting fishing ports and naval bases. 2) Fiord Coasts: These are submerged U-shaped glacial troughs. They mark the paths of glaciers that plunged down from the highlands. These have steep walls, with tributaries branches joining the inlet at right angle. Due to greater erosion, these are deep even in inland but shallow at the sea side. These are confined to high latitude of temperate regions which were once glaciated. Their mountainous background attract few settlements. Agriculture is confined to deltaic fans built up where stream flow down to fiords. 3) Dalmatian Coasts: These are longitudinal coasts running parallel to the coast. The submergence of coastlines produces long, narrow inlets with a chain of islands parallel to the coasts. Mountainous nature hinders communication inland. It has deep sheltered harbours but no distinguished ports. 4) Esturies coasts: In submerged lowlands, the mouth of the rivers are drowned so that funnel-shaped estuaries are formed. if these are not silted, they form good site for ports.

43) Coastlines of emergence: 1) Uplifted lowland coast: These produces smooth, gently sloping lowland. The off-shore water is shallow with lagoons, salt-marshes and mud-flats, where a deposit from continental shelves is deposited. 2) Emerged upland coasts: Faulting and earth movements may thrust up coastal plateaux so that the whole region is raised, with consequent emergent features. The raised beach is beyond the reach of waves. It has little potential for port sites. 44) Continental Islands: These are formerly part of the continent but not are detached. They are separated by shallow lagoon or deep channel. This may be due to subsidence of a part of land or rise in sea level, so that lowlands are filled with water. These may appear as: 1) Individual island: These lie outside the continent, very much associated with the characteristic features of mainland of which they were once part. 2) Archipelago or group of island 3) Fastoons or island arcs: These are the group of island in a loop at the edge of the continent showing the continuation of mountain range. 45) Oceanic Islands: These are generally small. The flora and fauna is unrelated to mainland unlike continental islands. There are sparsely populated. 1) Volcanic island: These are generally topmost part of the volcano. 2) Coral island: These are lower as compared to volcanic island and just emerge over the sea level. These are build up by coral animas found near the mainland and also in middle of the ocean. 46) Coral Reefs: In tropical seas, large colonies of coral animals such as coral polyps, calcareous algae and lime-secreting plants. Though they are small but with high capacity to secrete calcium carbonate. Polyps are most abundant and most important. Each polyp resides inside coral to form coral reefs. When they die their structure gets cemented to form the coral islands. There are also non-reef building species such as precious corals of the Pacific Ocean and red coral of the Mediterranean which can survive in cold and deep water. As a rule, they thrive only in warm and tropical areas. 47) Conditions for coral survival: 1) Water temperature must not fall below 20*C. This limits their distribution to tropical and sub-tropical areas. They dont flourish where cold currents because cold water upwelling lowers the temperature. This is the reason that coral reefs are absent on western margins of continents. Warming effect of warm currents such as Gulf Stream means that corals are found far to the north of the West Indies in Atlantic Ocean. Pacific and Indian Ocean have most numerous coral reefs. 2) The depth of water should not exceed 180 feet because sunlight cannot penetrate beyond this depth which is needed for photosynthesis. These are essential for microscopic algae on which corals thrive. There should be plenty of water as corals cannot survive for too long outside the water. 3) The water should be saltish and free from sediments. These survive in moving water away from silt coasts and muddy mouths of streams. Corals are best developed on seaward side of the reef, where moving water maintains an abundant supply of clean and oxygenated water. They also bring adequate supply of microscopic organism as food. 48) Types of reefs: 1) Fringing reefs: It is a corralling platform lying close to the shore extending outwards from the mainland. It is sometime separated from the shore by a shallow lagoon. These are widest when fringing a protruding headland but absent at the mouth of stream. Outer edge grows faster due to supply of fresh water and food. Slope is steeply seaward side. 2) Barrier reef: The reef is separated from land by deeper channel or lagoon. The reef is partially submerged. Where it lies above the water level and sand accumulates over it, little vegetation is possible. These reefs have narrow gaps at several places to allow water from lagoon to open sea. Such gaps are important as they are the only channel that provides access to ships. Great barrier reef, Australia. 3) Atolls: These are similar to barrier reef except these are circular in shape. Enclosing a shallow lagoon without any land in the centre. The encircling ring is broken at few places to allow free water to flow. On inside, limestone debris and sand collects and palm trees like coconut may grow. Such palm trees thrive well in brackish water of lagoon. 49) Relief of the ocean: 1) Continental Shelf: It is a shallow extension of continent of sea side. There shallowness enables sunlight to penetrate through the water, which encourages the growth of minute plants and other microscopic organisms. These are rich in planktons and hence these are richest fishing grounds. The low depth keeps out cold under currents and increases the height of tides. This hinders docking as ship can only enter and come out during tides. 2) Continental shelf 3) Deep sea plain: It covers 2/3 of ocean bottom and called as abyssal plain. 4) Ocean deeps: These are long narrow trenches. These trenches are mostly found near continents and not in midst of the ocean particularly in pacific. Oceanic deposits: The material derived from by the river when not deposited at the mouth drops into the sea. These sediments filters and deposits on the ocean floor layer by layer. 1) Muds: These are derived from the land and deposited on the continental shelves. The mud may be red, green or blue depending upon the chemical content. 2) oozes: These are derived from the ocean. These are made up of skeletons of marine organisms. These have fine; flour like texture and either occur as accumulated deposits or float about in suspension. 3) Clay: These are red clays which occur deepest parts of the ocean basin and are particularly absent in Pacific Ocean. The red clay is due to accumulation of volcanic dust. 50) Salinity: Baltic Sea where dilution is high, salinity is low. In red sea due to high evaporation and low fresh water addition, salinity is higher. In inland sea, salinity is very high, such as Caspian and Dead Sea. Lake Van is Asia Minor has highest salinity. This salt lake collects its salt from shore. The density of water is so high in Dead Sea and Lake Van that it is impossible to sink. Factors affecting salinity: 1) Rate of evaporation: Between 20* to 30* N and S, due to high temperature and humidity. Temperate oceans have lower salinity due to low temperature and humidity. 2) Amount of fresh water added by precipitation etc.: Salinity is lower in equatorial water because of high rainfall. Oceans where huge rivers such as amazon, ganga etc. drains have low salinity. Baltic, arctic and Antarctic have low salinity due to fresh water added by ice caps, low temperature etc. 3)Degree of water mixing by currents: In inland seas such as Caspian, Mediterranean sea , red sea and Persian gulf due to no contact ocean, salinity is higher. 51) The annual range of water temperature in oceans is lower as water heat up and cools slower than land. Reduction of temperature with latitude is not uniform due to cold and warm currents, air masses and winds. The highest water temperature is in inland seas of tropics like red sea. The water temperature decreases with depth first quickly and then slowly. 52) Ocean Currents: Current flowing from equator towards the poles are warm currents and those from poles towards equator are cold currents. Why currents follow pattern: 1) Planetary winds: between equator and tropics blow, the trade winds, move equatorial water pole wards and westwards and warm the eastern coasts of continents. N-E trade winds move Northern equatorial current such as Florida current and gulf stream westward to warm the eastern and southern coast of America. Similarly, South equatorial current warms the eastern coast of Brazil by warm Brazilian current. In the temperate latitude blow the westerlies, they are less reliable than trade winds, they result in N-E flow in northern hemisphere. Warm Gulf Stream is blown to western margins as cold north Atlantic drift. Similarly, westerlies in southern hemisphere drive the west wind drift equator wards as Peruvian current off south America and benguela current off south Africa. 2) Temperature: The temperature difference between equator and pole is high. The warm water move pole wards on surface and cold water move towards equator near the ocean floor. 3) Salinity: Water of high salinity region is denser than others. High salinity water move along the bottom while those of low salinity move on the surface towards each other. The water of Atlantic has low salinity and that of closed Mediterranean Sea has higher salinity, water from Atlantic move into the sea and from the sea move into ocean. 4) Earth Rotation: Earth rotation deflects towards right, in NH it is clockwise and in SH this is counter clockwise. 5) Land: Landmass obstructs and directs the current. The southern tip of Chile diverts part of west wind drift as Peruvian current. Similarly, Brazilian shoulder divides west flowing equatorial current. 53) Circulation of Atlantic Ocean: Trade winds move north and south equatorial current westward. The shoulder of N-E Brazil split the SEC into two streams, cayenne current which flows along the Guiana coast and another southward known as Brazilian current along the east coast of Brazil. In north Atlantic ocean, cayenne current is joined and reinforced by the north equatorial current heads north-westwards into Caribbean sea. Part of the current enters Gulf of Mexico and emerges as Florida current. The rest of the current move northwards east of Antilles to join the Gulf Stream off south-eastern USA. Gulf Stream is one of the strongest oceans current. It touches Cape hatteras of USA and deflects eastwards due to earth rotation and westerlies. It reaches Europe as north Atlantic Drift. This carries warm water to Europe. It divides itself into 3 branches, one eastward towards Britain, one northward towards Arctic and one southward towards Iberian coast, as cool Canaries Current. This southward current merges with north equatorial current completing the cycle. Within this ring, there is an area in the middle has no perceptible zone. Large amount of floating sea-weed gathers and the area is called as Sargasso Sea. Current from Arctic also enters North Atlantic. These cold currents move southwards due to prevailing winds. East Greenland current flows between Iceland and Greenland, cools the north Atlantic drift. The cold Labrador current drifts south-eastwards between west Greenland and Baffin island to meet the warm gulf stream off Newfoundland where iceberg carried southward by cold current melts. The collection of sea-weeds is not that distinctive in southern hemisphere. The current that moves south along the Brazilian coast has deep blue waters distinguishable with yellow, muddy water carried by the Amazon further north. On reaching much south, due to earth rotation and westerlies, it joins south Atlantic current. On reaching the west coast of Africa, is gets diverted northward as Benguela Current. It brings the Antarctic cold current into tropical region. Circulation of Pacific Ocean: North equatorial current flows westward with counter current in opposite direction. Due to less obstruction of land mass and much greater expanse of pacific, water volume is very high here. Trade winds blow this current to northward from Philippines coast into east china sea as Kuroshio or Japan current. This warm current is carried pole ward through north Pacific drift, keeping Alaskan coast ice free during the winter. Cold Bering current move southward from narrow baring strait and joined by Okhotsk current to meet the warm Japan current as oyashio. Cold water sinks beneath warm north Pacific drift, part of this move eastward as California current. South equatorial current moves southwest along the eastern Australian coast. Bringing warm water into temperate areas. It moves towards New Zealand in the east due to westerlies in the Tasman Sea and merges with cold west wind drift as the south pacific current. Obstructed by the southern tip of Chile, it moves northward as Peruvian current. This chills the air, leaving Chile and Peru rainless. The region is rich in microscopic plants and animals attracting a lot of fishes and birds. The beats of birds completely whiten the coastal cliffs, a valuable source of fertilizer. Q Explain with examples the effects of ocean currents on climate, navigation and economic activities.

Q In what ways, relief of ocean are different from that of the land.

Q The richest fishing ground are located on ocean shelf, Why?

Q The salinity of Baltic sea is less than dead sea, Why?

Q Temperature of ocean varies both horizontally and vertically, Why?

Q Dominant influence on ocean current is of wind?

54) Climate refers to the average atmospheric condition of an area over long duration of time. Climate of temperate areas is more variable than that of tropics. Climate of British Isles is changes so frequently that people say it has only weather and no climate and Egypts climate is so static that it has only climate and no weather. Death rates are high in tropics than in deserts as high temperature discourages germs from being transmitted in areas with high climate and low humidity. Elements of weather: 1) Rainfall: It is measured by rain gauge. Places with same annual rainfall fall on the line isohyets. 2) Pressure: Air pressure varies from place to place. The pressure is exerted due to the weight of gases present in atmosphere. Liquid is used in mercury as it is the heaviest liquid known, this helps in controlling the height generated in the barometer. Places with equal pressure fall on isobars. In temperate areas, pressure changes vary rapidly resulting in formation of cyclones and anti-cyclones. Pressure decreases with height because amount of air column above decreases. Barometer is also sensitive to gravitational forces and temperature. Mercury expands with temperature, hence corrective methods needs to be adopted with barometer. Barogram is used for continuous pressure monitoring, altimeter is used in aeroplanes to measure height where drop in the height of mercury is related to the height from surface in feet, mercury barometer which dips in mercury are not portable and hence aneroid barometer which is less accurate is used. 3) Temperature: Thermometer works on the principle that mercury expands and contracts with change in temperature. F = (1.8 x *C) + 32 F. To access the possible damages due to frost to agriculture in temperate latitudes grass temperature is used. Temperature that we know are of shades, i.e., of air and not that of direct sunlight. Large self-recording instruments are thermogram or hygrogram. The difference between maximum and minimum temperature of a day gives diurnal range of temperature. Isotherms shows the temperature lines, these lines are shows temperature reduced to sea level. 4) Humidity: It is a measure of dampness of the atmosphere. Absolute number of water vapour in air, gram/cubic meter, is absolute humidity. Relative humidity is the ratio of actual amount of water vapour to maximum amount air can absorb at a given temperature. Equatorial areas generally have high humidity due to high temperatures or warm air. The temperature at which air gets saturated is called as dew point. Hygrometer is used to measure humidity. 5) Winds: Wind wane or weather cock is used to measure wind direction. These needs to put in open areas to avoid any obstacle of buildings and trees. Winds are always named after from the direction they blow. The speed of wind is measured by anemometer. 6) Sunshine: It depends on latitude, clear and cloudy climate, revolution of earth. Tourist places in the temperate are concentrated based on hours they get sunshine; this is not a criterion as tropics get ample sunshine. Sunshine duration is measured by sun-dial. Places of equal sunshine lie on isohels. 7) Clouds: When air rises, it cools due to expansion. After dew point, condensation starts. Places with equal cloud conditions are joined by isonephs, as cloud very quickly, this line has little significance. Classification of clouds: 1) High Clouds: a) Cirrus of feathery: These are fibrous and small in blue sky. They represent clean weather and produces good sunset. b) Cirrocumulus: White globular mass forming ripples in the sky. c) Cirrostratus: This resembles thin white sheet, sky looks milky and sun and moon shines through it with halo. 2) Medium Clouds: a) Altocumulus: These are woolly, bumpy clouds arranged in layer and appearing like waves in the blue sky. They indicate fine weather. b) Altostratus: These are denser, greyish clouds with a watery look. These have fibrous structure and sun shines faintly through it. 3) Low Clouds: a) Stratocumulus: There is great contrast between bright and shaded part. Almost similar but more pronounced structure than altocumulus. b) Stratus: This is very low cloud, uniformly grey and thick, which appears like a low ceiling or highland fog. It brings dull weather with little drizzle. It reduces the visibility of aircrafts and thus dangerous. c) Nimbostratus: This is dark and dull cloud, clearly layered, and is also called as rain cloud. 4) Clouds with vertical extent: a) Cumulus: This has rounded top and horizontal base. Typical of humid tropical region, associated with uprising conventional currents. Its great white globular masses may look grey against the sun but it is a fair weather cloud. b) Cumulonimbus: It is an overgrown cumulus cloud. It has cauliflower top. These are seen in tropical afternoons. This are called as thunder clouds and are accompanied by lightening, rain and thunder. 55) Haze: This is caused by smoke and dust in industrial areas or may be due to unequal refraction of light in air of different densities in the lower atmosphere. This is referred in areas with low humidity and in relation to visibility. Mist: The condensation of water vapour in the air causes small droplets of water to float about forming clouds at ground level. Unlike haze, mist occurs in wet air, when relative humidity is above 75%. Fog: When water condenses on particles like smoke from houses and industries. It only occurs in lower strata of atmosphere. Thick smoky fog is called as smog, in industrial areas. A Hill fog occurs in mountains during morning and disperses as soon as sun shines. In temperate areas, during calm and clear nights after a hot day, fogs forms due to cooling of land due to radiation called as radiation fog. When damp stream is brought over cold ocean surface, sea fog develops. Fogs are more common over sea than land and are more prevalent over coastal areas. Dense fogs occur in high and middle latitudes rather than tropics. Dry interior experiences haze and mist. 56) Troposphere: Weather is confined to the lower layer called as troposphere. In this layer temperature falls with increasing height. The water content varies from place to place and this is the reason that there is great contrast in weather and climate over different part of the world. Stratosphere: This layer is very cold, no cloud, thin air without dust, smoke or water vapour but with remarkable seasonal change. Ionosphere: It has electrically conducting layer which reflects short-radio waves making their communication possible.

57) Insolation: Only source of energy on earth is sun. This energy reaches earth through radiation and called as insolation. This consist of visible light, infra-red and UV. UV causes sun-burn when exposed for too long. Infra-red rays can penetrate dust and fog and are used in photography. Only that part of suns radiation which reaches earth is called as insolation. On its entry, most part is reflected by cloud, dust and air molecules. Significant part is absorbed by carbon dioxide, water vapour and other gases. Its interception by air causes diffusion and scattering of visible light between infra-red and UV, this causes blueness in the sky. Earth surface gets heated, in turn heating the air near surface by conduction and then upper atmosphere by convection due to upward movement of the air. Land gets heated more quickly than water. Water is transparent and hence it is heated more slowly and it is always moving, hence absorbed heat is distributed over a greater depth and area. Opaque nature of land allows greater absorption and concentration of radiation raises the temperature rapidly. Land also cools rapidly than water. 58) Temperature: It influences the amount of water vapour in the air and hence controls the moisture carrying capacity of air. It decides the rate of evaporation and condensation and hence influences the stability of atmosphere. Relative humidity controls the type of cloud formation and precipitation; it is directly related to the temperature. Factors affecting temperature: 1) Latitude: Due to inclination of the earth, sun shine overhead between the tropics and its rays reaches beyond tropics in an oblique manner. This is why, temperature decreases as we move from equator to poles. The oblique rays travels through longer distance through which greater absorption takes place, also rays are concentrated on larger area, both these factor reduces the energy exchanges and hence lower temperature. In tropics, rays travel shorter distance leading to less absorption and also fall on smaller area, more absorption and hence high temperature. 59) Altitude: Atmosphere is mainly heated through conduction; hence places near the surface are warmer than those at a height. The rate of decrease is called as lapse rate and is never constant. It is usually more in summer than winter. It is greater during day than at night, also it is greater on elevated lands than on plains.

60) Continentality: Land is heated more quickly than water due to higher specific heat of water. This leads to warmer summer, colder winter and greater range of temperature of continental interiors as compared to maritime districts. 61) Ocean currents and winds: Both ocean currents and winds affects temperature by transporting their heat or coldness into adjacent regions. Cold currents lower the summer temperature especially when they are carried towards land by on-shore winds. On shore westerlies, draw warm currents with it to the shore in the winter. These westerlies bring cold current in summer and warm in winter towards the British and Norway coasts, and produce most significant moderation effect.

62) Slope, shelter and aspect: Steep slope expect more rapid change in temperature than gentle slope. Mountain range aligning east-west experience more temperature on southern slope which is sunny than northern which is sheltered side. Southern slope is best suited for vine cultivation and has a more flourishing vegetative cover. There are more settlement on southern side and is better utilised. In hilly areas, land gets heated during the day, if nights are calm and cloudless, air cools more rapidly at greater height causing it to move downward, this pushes warm air at the bottom to move up. This causes lower temperature at lower heights than at elevation, called as inversion of temperature. 63) Natural vegetation and soil: In forested region, such as Amazon, light never reaches the ground due to dense tree canopy, this sustains lower temperature in forest than open areas. Trees lose water by evapo-transpiration during the day; this cools the air above the forests. Relative humidity increases and mist and fog may form. Light soil reflects more rays than dark soil, this induces variation in temperature. Dry soil are more sensitive to temperature than wet soil such as clay, they retain more moisture and warm or cool more slowly.

64) Precipitation: When air is at its dew point, water vapour starts to condense around dust particles. When these float as water particles or as ice high above surface, they are called as clouds. When condensation occurs near earth surface, it takes the form of haze, mist or fog. In higher latitudes, where condensation takes place below freezing points, snowfall takes place. When moist air ascends rapidly to cold air, water particles freeze to form hails, which falls onto the surface in the form of hailstorms. Very these hails freezes and melts alternately while coming down, this forms sleet. 65) Rainfall: 1) Conventional Rainfall: This type of rainfall is common in regions which were intensely heated, such as tropics during the day and continental interiors in the summer. Air takes hear from surface and as it temperature increases, it expands and becomes lighter. The air rises due to convection, on rising it becomes cool due to expansion and lower temperature at altitudes. This causes condensation of water vapours forming cumulonimbus clouds with greater vertical extent. This reaches its maximum in afternoon when convectional system is well developed. Hot rising air has good moisture absorbing capacity, which is abundant in regions of high relative humidity. As air rises, it cools and on reaching saturation point rain occurs accompanied by thunder and lightning. Summer shower in temperate regions are equally heavy with occasional thunderstorms. 2) Orographic or relief rain: This occurs when moist air is force to ascend a mountain barrier. As the rain ascends, it cools due to expansion and subsequent decrease in atmospheric pressure and temperature at higher altitude. Most rain falls on windward side of mountain. On leeward side, decrease in altitude leads to increase in pressure and temperature, the air is compressed as warmed. This results in drop in relative humidity. 3) Cyclonic or frontal rainfall: This is associated with cyclonic activity whether in the temperate regions (depressions) or tropical regions (cyclones). This occurs basically due to the convergence of two different airmass. The cold landmass tries to remain near ground while warm tries to move upwards, at this front, rising air cools down causing rainfall. The colder airmass pushes up the warmer airmass up, clearing the sky again. 66) Pressure and planetary winds: 5* N and S of equator exists, equatorial low pressure belt. Due to intense heating, the air rises up. This belt is called as doldrums. It is the zone of wind convergence or ascending winds. At 30* N and S, occurs sub-tropical high pressure belt called as horse latitude. Winds here are dry, calm and light. This is a zone of wind divergence or descending winds. Anticyclonic activities are prevalent here. At 60* N and S, temperate low pressure belt occurs. This is a zone of convergence with cyclonic activity. These are best developed near oceans where temperature difference between summer and winter are negligible. At 90* N and S, temperatures are permanently low and are called as polar highs. Unlike watermass in south pole, north pole is dominated by landmass, this creates some pressure difference between summer and winter. Planetary winds: Winds tend to blow from high pressure to low pressure; these winds dont blow straight because of deflection given by Coriolis force. In southern hemisphere these are deflected towards right while in south the deflection is towards left. This is called as Ferrells law of deflection. Coriolis force is absent at equator and increases as one move towards poles. Due to this effect, winds blowing from sub-tropical high pressure belt when move towards equatorial low pressure belt deflects rightward and becomes N-E trade winds. While in southern hemisphere, winds become S-E trade winds. These winds are more regular of all planetary winds. These blow with great force and are constant in direction. These are helpful to traders while sailing and hence are called as trade winds. Since, trade winds are cold and dry; these have high capacity to hold moisture and bring heavy rainfall on eastern coast of the continents within the tropics. On the west coast, the loose most of the moisture, and hence deserts such as Sahara, Kalahari are formed on the western margins of the continents in tropics. From sub-tropical high pressure belts winds blow towards temperate low pressure belts, these are variable and called as westerlies. These blow from S-W in northern hemisphere to N-W in southern hemisphere due to Coriolis force. These are more variable in northern hemisphere, but bring warm ocean currents to western borders of temperate regions. These winds with local pressure difference generates variable climate in temperate lands dominated by cyclones and anti-cyclones. In southern hemisphere, due to vast ocean span, westerlies blow more constantly and power. They bring much precipitation to western coasts of the continents. The weather is damp and cloudy and seas are violent and stormy. Not all coasts receives westerlies throughout the year, this is because the belts shift with the position of the sun that depends on earths revolution. The Mediterranean part of southern hemisphere comes under the influence of westerlies and receives rain in June during summer solstice. While during winter solstice, Europe and California comes under the influence of westerlies and receives rain in December. Polar easterlies blow from poles towards temperate low pressure belt, these are less regular in SH than in NH. 67) Land and Sea breeze and Monsoon: Land and sea breeze are monsoon winds on a smaller scale. Both these blow due to temperature difference between land and sea. Former is diurnal in natural while later is seasonal. Land heats up faster than sea; this causes warm air to rise up forming a low pressure area. Sea remains cooler in comparison with high pressure area, this sets wind motion from sea to land called as sea breeze. These are stronger in tropics than in temperate region. At night, reversal takes place. In tropics fisherman takes advantage of land breeze and sails out in night and returns with sea breeze during the day. Monsoon is of similar nature, intense heating of continental inlands forms low pressure region, this creates an S-W wind system to fill up this low pressure area. Similarly, during winter, high pressure area is created over inlands and air moves out in the form of N-E monsoon. 68) Fohn and Chinook Winds: These are dry winds experienced on leeward side of the mountains. They get compressed due to increase in pressure while descending. Fohn winds are experienced in Alps mainly in Switzerland during spring. Fohn winds may rise temperature suddenly, causing melting of snow and avalanche. Chinook winds are experienced on eastern slope of rockeys in USA and Canada during winter. These winds are good too, because it melts the ice and helps in growth of crops and fruits and also frees snow covered pasture lands. 69) Cyclonic Activity: Typhoons, hurricanes and tornadoes are different types of tropical cyclones. These are well developed low pressure systems into which violent winds blow. Typhoons occur in China Sea, tropical cyclones in Indian Ocean, hurricanes in West Indies in Caribbean, tornadoes in West Africa and whirl-wind in southern USA and willy-willies in N-W Australia. Typhoons occur between 6* to 20* N and S, during July and October. These are smaller than temperate cyclones but with much steeper pressure gradient. Torrential rainfall is accompanied by thunder and lightning. Hurricanes have calm, rainless centres where pressure is lowest but wind strength around this eye. Tornadoes are small but very violent tropical and sub-tropical cyclones. It appears as dark funnel cloud. These are most frequent in spring but can occur at any time. These are common to USA and occur in Mississippi region. 70) Cyclones: These are called as depressions and are confined to temperate latitudes. Lowest pressure occurs in the centre. They remain quite stationary or move slowly. Wind blow inward into the low pressure region at the eye circulating in anticlockwise direction in NH and clockwise in SH. Rainfall occurs due to convergence of warm tropical air and cold polar air. Isobars are closer to each other in these. Cyclones are also characterized by low-level convergence and ascending air within the system.71) Anticyclones: These have high pressure region at the centre with isobars are far apart from each other. Pressure gradient is gentle and winds are light. These are accompanied by calm winds, fine weather and clear sky. In winter, intense cooling of lower atmosphere may cause fog formation. Winds blow outward and get deflected. These blows clockwise in NH and anticlockwise in SH. Anticyclones are usually characterized by low-level divergence and subsiding air. Anticyclones form from air masses cooling more than their surroundings, which causes the air to contract slightly making the air denser. Since dense air weighs more, the weight of the atmosphere overlying a location increases, causing increased surface air pressure.Q Why anticyclones are more frequent in summer?Q Without water vapour and dust there would be no weather. Explain?

Hot and wet equatorial climate: This is found between 5* to 10* N and S of equator. Its greatest extent is in lowland of Amazon. Away from equator due to trade winds, modified kind of climate with monsoonal effect occurs. Within tropics, at higher altitudes, we have cooler climates. Climate: Most outstanding feature of the equatorial climate is its great uniformity of temperature throughout the year. There is no winter, cloudiness and heavy precipitation causes moderation of daily temperature so that even at equator itself, climate is unbearable. Also, regular land and sea breeze assist in maintaining an equitable climate. Precipitation: There is no dry season and it experiences heavy rains throughout the year. There are two heavy rainfall season coinciding with equinoxes. This feature is not found in any other climate. But this pattern is upset by local conditions, coastal areas experiences monsoon climates. Due to great heat, mornings are sunny and bright. Both relief and conventional rainfall occurs here. There are some cyclonic rainfalls due to convergence in doldrums. Relative humidity is constantly high. Vegetation: High temperature and rainfall give rise to tropical rainforests. In Amazon lowlands, forests are so dense that they are called as Salvas. Growing seasons are not confined to particular part of the year. There are neither draught nor cold to check the vegetation. Great variety of vegetation: Evergreen forest provides hardwood trees such as mahogany and ebony. There are smaller tress like palm trees, climbers, parasitic plants and epiphytes. Distinct layer arrangement: Thick canopy of trees is only broken when there is a passing river. Struggle for sunlight gives unique character to vegetation. Ground tress can tolerate shade. Because trees cut out most of the sunlight, undergrowth is not dense. Multiple species: Unlike temperate areas, where few species are grown in particular areas, here no species are found in single stands. This makes commercial exploitation a difficult task. Hardwood does not float on water making their transport costly. This is why tropical countries are timber importers. Forest clearing: forests are cleared for shifting agriculture or lumbering. When these cleared regions are re-vegetated secondary forests called as Belukar in Malaysia springs up. These are characterised by short trees and dense undergrowth. In coastal areas, brackish water, mangrove forests are found. These areas are sparsely populated, primitive people practice hunting and gathering, while advanced ones practice shifting agriculture. Food is abundant in these regions. The most cultivated cash crop is natural rubber. Rubber trees are first found in Amazon, these were transported to Malaysia and Indonesia which are now leading producers. The home country Brazil now exports no rubber; this is because of tree disease and lack of commercial organisation of Indians in Amazon lowlands. Another tropical crop which is highly successful is cocoa. It is extensively cultivated in west Africa near gulf of guinea. Ghana and Nigeria are major producers. Most of the crop leaves for Europe and North America for cocoa and chocolate industry. Factors affecting development of equatorial region: Equatorial climate and health: More prone to diseases and low productivity due to high humidity, heat and rainfall. Prevalence of bacteria and pests: The climate promotes rapid plant growth, also encourages spread of insects and pests. As germs and bacteria are easily transmitted through moist air, equatorial conditions are ideal for the survival of such organisms. Rapid deterioration of tropical soil: tropical crops are fertile only in start, due to accumulation of heavy leaf-fall and their decomposition by bacteria; a heavy layer of humus is formed. But once it is cleared for shifting cultivation, heavy rainfall soon washes out most of the soil nutrients. Indonesian island of java is an exception due to its volcanic ashes and energetic local people. Livestock farming: It is handicapped by absence of meadow grass even on highlands. The grass is so tall and coarse that it is not nutritious. The animals in Africa are also attacked by tsetse flies causing deadly diseases. Q Plantation agriculture is best suited in equatorial regions, why?A This region has two rainy seasons starting with equinox. This provides for two growing seasons opposed to one per year in general.

Tropical monsoon and tropical maritime climate: Tropical monsoon lands are those which experience monsoon winds in form of S-W in summer and N-E in winter. This kind of climate is experienced in few geographical locations such as Indian sub-continent, Indonesia, Vietnam etc. Outside this range, its influence is moderated by trade winds leading to tropical maritime climate. Tropical monsoon lands: In summer, sun is overhead cancer, this creates low pressure area in central Asia, this draws SH trade winds and also from interior of Australia to come into NH in form of S-W monsoon. In winter, high pressure area over central Asia, forces wind to move out up to northern Australia in the form of N-E monsoon. Seasons: 1) Cool and dry season: October to February: temperature are low with heavy sinking air. Frost may occur in colder north. Centre of high pressure is over Punjab, Outblowing dry winds of N-E monsoon brings little rainfall. Punjab receives little rainfall from cyclonic sources which is essential for winter cereals. When N-E monsoon blows over BOB, it acquires moisture and brings rain over southern tip of India. Hot and dry season: March to mid-June: Temperature rises with sun being overhead cancer. Rainy season: heavy rainfall in summer is a characteristic of this climate. Retreating monsoon.

Tropical maritime climate: This is experienced along the eastern coast of tropical lands, receiving steady rainfall from trade winds all the time. The rainfall is both relief and conventional due to heating during the day and cooling at night. In summer, it is maximum but there is no distinct dry season. This climate is more suited for habitations but it is prone to cyclones.

Tropical monsoon forests: It depends upon amount of summer rainfall. Trees are deciduous due to dry spell in which they shed their leaves to withstand draught. In regions of heavy rainfall, dense forests are found. These forests have less species than equatorial forests. Most forests provide timber and known for their durable hardwoods. Teak is best known such tree. It is known for its great durability, immunity to shrinkage, fungus attack and insects. In northern Burma, teak plantation is widespread, teak takes more than 100 years to yield mature timber. It is heavy and hence difficult to float, for this re