geography gs must read

8/10/2019 Geography GS Must Read

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What are the Consequences of Population Migration?

1. The consequences of migration are complex, affecting the economic and social systems of both areas of origin anddestination.

2. The economic consequences on the area of origin (involving the sending of remittances), are usually regarded as positive,although they can produce negative features such as inflated land prices and increased consumer spending on imported

items.

3. Depopulation can be a serious consequence of migration in areas of origin, with young innovators often being the first toleave.

4. The economic impact on areas of destination is seen on the whole to be positive, although there are costs involved, such asthe provision of housing and other services to migrants and their families.

5. The social consequences of migration on destination areas are debatable. The establishing of new cultural groups canproduce cultural tensions but can also enhance the host community.

6. The impact of movement on the migrant often depends on the existence of a supportive receiving population and theability of the migrant to adapt to the host community. Very often, however, migrants face prejudice and even violence.

Migration can have significant effects on population distribution, composition and growth. Areas of net emigration becomedepleted of young adults whereas regions of net immigration show an increase in the proportion in that age group.

In the former, reduced growth generally results, owing to reduced birth rates; in the latter, growth is encouraged, owing toan increase in birth rates.

Yet the consequences of migration are far wider ranging and more complex than just these population changes, for itinvolves, in addition, the movement of culture, technology and way of life.

The movement of people undoubtedly leads to a flow of capital, which may give rise to economic expansion in areas of netimmigration and economic contraction in areas of net emigration.

The social problems that may be created by migration are not new. Wars in Canada during the 18th century and in SouthAfrica at the end of the 19th century resulted from the intermingling of diverse migrants.

Sometimes it can engender greater understanding between people and so help preserve peace. Certainly it could be arguedthat the universality of the English tongue, English standards and English institutions has done much to provide a bond offriendship between nations all over the globe.

Brief notes on the chief characteristics of Tropical Storms

The chief characteristics of these violent tropical storms are low central pressures and high wind velocities. A tropicalhurricane is a nearly circular vortex averating 500 to 600 km in diameter. It extends about 12,000 meters above the oceansurface.

The hurricane lasts for many days and, in certain cases, for more than a week. The central pressure in a well- developedhurricane may be 50 to 60 millibars lower than the pressure at its outer edge.

The lowest pressure ever recorded in the United States was 892.31 millibars, which was measured during a hurricane inSeptember, 1935.

According to Trewartha, there is a spiraling inflow of air at lower levels, a rapid upward movement at intermediate levels,and a spiraling outward flow aloft. It is the steep pressure gradient which causes the rapid, spiraling winds of a tropical

storm.

From the central low pressure core of the cyclone, winds converging from all directions are of whirled upward. As a result ofthe lifting of air, condensation starts producing cumulonimbus or clouds which give the inner structure of the storm apeculiar shape. Spiraling bands of cumulonimbus clouds surround the core of the hurricane.

The top of the hurricane is marked by divergent air flow which carries the ascending air away from the storm centre. Thisphenomenon is essential to maintain the inward flow at the surface.

What are the different types of tropical disturbances?
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Tropical disturbances are classified into four categories: (1) easterly waves, (2) tropical depressions, (3) tropical storms, and(4) hurricanes or typhoons.

(1) Easterly waves:

These are the migratory wavelike disturbances of the tropical easterlies. The easterly waves represent a pattern of waveperturbations which move from east to west with the current, but with a slower speed.

The source of their occurrence lies between 5 to 30 latitudes in both the hemispheres. These waves form in the easterlycurrent particularly over the tropical oceans. They never form exactly over the equator.

They originate at a certain height from the earth's surface. Because of these waves, isobars on the weather charts developindentations. These atmospheric disturbances are quite unlike the depressions of the middle latitudes.

These are mild pressure troughs which generally slope eastward with height. These waves travel in a east- to-west directionat the rate of 320-480 km per day. Ahead of the trough line there is divergence of air currents.

Since in this part of the disturbance there is subsidence, the weather tends to be dry and clear. On the contrary, behind thewaves, warm and moist air currents tend to ascend which leads to the development of cumulonimbus clouds andthundershowers.

When such a type of transverse wave passes an observer, the following weather sequence is generally produced: There is aridge of high pressure ahead of the trough. This is invariably associated with fine weather.

There are scattered fine-weather cumulus clouds floating in the sky. The lower air may have some haze, but close to thetrough line there are well-developed cumulus clouds with occasional showers.

The visibility near the ground gradually improves. Behind the trough, veering of the wind is observed. Because ofconvergence the heavy cumulus or cumulonimbus clouds develop yielding moderate to heavy precipitation.

This part of the wave is I also associated with thunderstorms. There is a slight decrease in temperature.

Most of the easterly waves formed over the Atlantic Ocean make an inverted-V wave-form in the low-level wind field. Thesedisturbances in the easterlies have a cyclonic circulation at about 600 mb level.

In view of the paucity of observational data, it is rather difficult to throw much light on the origin and development of wavedisturbances over the tropical oceans and in continental areas.

But, broadly speaking, about 80 percent easterly waves develop between 5 and 20 north latitudes, poleward of theequatorial trough, towards the western part of the oceans.

First of all, the easterly waves of the Caribbean Sea were studied and described. Since then investigations have been madeinto the origin and growth of similar waves in the easterlies in other tropical regions.

It was found that these wave disturbances occur near the boundary of the trade winds and the doldrum belt. They travelwestward rather sluggishly and are always associated with extensive cloud areas and rain areas.

It is a common characteristic of all such wave perturbations that bad weather follows the waves, whereas good weatherprecedes them. Sometimes acute instability develops in these waves and they intensify into hurricanes.

It may be pointed out that when easterly waves pass over the land areas the associated weather may largely be affected by theconfiguration of landforms.

As regards the regional distribution of easterly waves, they tend to develop in the Caribbean, when during summer andautumn the trade wind inversion happens to be weak or absent.

The winter and spring seasons do not favour the formation of easterly waves. Sometimes easterly waves originate in the

North Pacific as well. During summer, in the Caribbean and the Pacific easterly waves originate after every three and twodays respectively.

The easterly waves form in the equatorial troughs which are elongated in shape and extend up to hundreds of kilometers.

They extend in the north-south direction lying across the trade wind circulation. They travel long distances as distinctentities. Near the surface of the earth these waves appear to be feeble, but they are fully developed at a height of, say, 4000meters.

Their climatologically significance lies in the fact that such areas receive heavy rainfall by them as would have remained dryin their absence.


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(2) Tropical depressions:

Petterssen defines the tropical depressions as the centers of low pressure around which the wind velocity hardly exceeds 40km per hour. These depressions are liable to occur anywhere in the warm humid air of the tropics, but they are quitefrequent in the vicinity of inter-tropical convergence zone.

However, they are very rare in the trade wind belt. Many of these weak depressions never grow into storms of hurricaneintensity; rather they die out as weak disturbances.

(3) Tropical storms:

These low pressures centers are surrounded by winds having their velocities in the range of 40 to 120 km per hour. Mostfavourable atmospheric conditions for their occurrence exist during the summer season.

The Bay of Bengal and the Arabian Sea offer ideal conditions for the origin and growth of these storms. They are also presentin the West Indies and in the vicinity of the Philippines.

These storms produce heavy precipitation and bring about a change in the existing weather. Many storms of this typedevelop into more violent and destructive type of tropical storms.

(4) Tropical-Cyclones (Hurricanes or Typhoons):

Hurricane is a severe tropical cyclone having a maximum wind speed in excess of 119 km per hour. The name 'hurricane' isgiven to the tropical cyclones in the North Atlantic and the eastern North Pacific oceans.

The tropical cyclones of hurricane force in the western North Pacific are known as typhoons. In Australia this type of storm isgiven the name willy-willy, whereas in the Indian Ocean they are called cyclones.

These storms are known as baguio in the Philippine Islands. In olden days the Japanese called these severe storms asnowaki, but now they are called taifu. Elsewhere they are just called tropical cyclones.

Hurricanes represent the most violent, most awesome, and most feared of all the atmospheric disturbances.

Since these storms cause widespread damage over land areas, and are dangerous to shipping, the weather scientists havegiven considerable attention to them.

Aircraft reconnaissance flights during the periods of maximum hurricanes, radar observations of cloud and precipitation,and satellite photography have all been helpful in the investigation of such a very complicated and difficult weatherphenomenon.

According to Byers, the following are some of the most prominent distinguishing features which make the tropical cyclones

different from the middle latitude cyclones:

(1) Tropical cyclones are found at certain seasons in well-defined areas of the tropics.

(2) They form only over oceans having a high surface temperature (27C).

(3) They do not have fronts, nor are they associated with moving anticyclones.

(4) They are many times more intense than the extratropical cyclones.

(5) They do not form with any regularity, and they can exist only on oceans.

(6) They have a central core of calm or light winds. This is called the 'eye'.

(7) They derive their energy from the latent heat of condensation.

What are the differnt Types of Anticyclones?

On the basis of structure, storm tracks, and general characteristics, anticyclones are divided into the following four distincttypes:

(1) Subtropical highs:

These anticyclones develop in the subtropical regions. They are large in area, elongated in shape and very deep in verticalextent. They are almost permanent high- pressure systems positioned in the subtropical high-pressure belts.

They are most often stagnant. Whenever they move, they move very sluggishly. These anticyclones are well developed overthe oceans, while there is low pressure over the continents.
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(2) Polar Continental highs:

These cold anticyclones form over continental surfaces in winter. They are produced by radiational cooling of the earth'ssurface. At about 2500 meters above sea- level they lose their identity. They are made up of a very shallow layer of cold air.

(3) Highs embedded between cyclones:

These anticyclones are merely the sluggish systems which are found between the more vigorous individual cyclones. These

wedges of high pressure are Inert, and produce clear and fine weather after the more turbulent cyclonic weather.

(4) Polar-outbreak highs:

Generally the last member of a cyclone family is followed by a great outbreak of cold and dense polar air, which may moveeven into the tropical regions. Sometimes a well-developed depression in the middle latitudes draws on its rear rapidlymoving masses of cold polar air.

These anticyclones while moving equator-ward slow down. These cold and dry polar air masses pick up moisture from thewarm subtropical oceans and are transformed within a period of two or three days into subtropical warm anticyclones.

Brief notes on Travelling Anticyclones of Middle LatitudesOrigin and structure:

Anticyclones are high pressure systems around which the wind blows clockwise in the northern hemisphere, andcounterclockwise in the southern hemisphere. There are various types of anticyclones such as the cold-core anticyclones of

the high latitudes and the warm-core anticyclones of lower latitudes.

According to some other meteorologists there is a third category of anticyclones which are described as the sluggish systemsfilling the spaces between moving temperate cyclones.

Cold anticyclones of the middle latitudes are also called 'polar outbreak highs'. Sometimes the last member of a cyclonefamily draws cold air masses from the sub-polar regions in its rear part. These rapidly moving anticyclones move southwardtowards the lower latitudes.

This produces the cold waves so often experienced in the southern parts of the temperate regions. When they enter into thesubtropical regions, they undergo a gradual transformation and ultimately become warm anticyclones.

In North America they originate in northern Canada and, move southward and southeastward across the central easternUnited States. In Asia they originate in the eastern part of Siberia and move towards China and Japan.

The exact mechanism of the formation of anticyclones is still not clear. But the most probable cause of their formation seems

to be the radiational cooling of the layers of atmosphere lying close to the snow-covered surface.

According to Trewartha, the southward surge of extremely cold and dense polar air is caused by the combined effect of anupper-air long wave and an expulsion of cold Arctic Basin air aloft.

Since there is subsidence within these anticyclones, there is subsidence inversion produced in the atmosphere which resultsin atmospheric stability. Under certain conditions, an anticyclone may undergo distinct development and may becomeintense.

These developments are invariably associated with intense cyclonic activity in the neighbouring areas. Even then theanticyclones never develop such intensities as are acquired by well-developed cyclones.

However, it is to be remembered that the individual anticyclones are made up of different types of air masses at differenttimes. Therefore the weather associated with them always shows different characteristics.

But one characteristic is always shared by all the anticyclones, i.e. they are never affected by advection from extraneoussources. The weather produced by any anticyclone is very much regional and diurnal in character.

Anticyclone circulation is characterized by subsidence and surface divergence. Anticyclone wind system is not so welldeveloped as is the case with a cyclonic circulation. In the eastern part of a moving anticyclone, there are north-westerlywinds, while on the westward side or on the rear the southeasterly winds prevail.

Pressure gradient is never so steep and the wind-velocities are never as high as in a cyclone. On the other hand, anticycloneshave always high winds. The front part of cold-core anticyclones is always marked by cold waves and blizzards in the middlelatitudes.

Unlike cyclones, the anticyclones are always associated with scanty rainfall. Subsidence and divergent wind system within ananticyclone do not favour condensation and cloud formation.
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But in case the southeasterly air is moist, there may be some precipitation on the rear of an anticyclone.

On occasions, the cold northwesterly winds may produce snowfall. Whatever uncertainty in weather is produced, it isbecause the anticyclones are often capped by cyclonic circulation aloft.

The surface temperature conditions in an anticyclone depend upon temperature of the air masses involved, humidity of air,and season of the year.

In winter, the cold anticyclones originating in the snow-covered sub-polar legions always bring with them very lowtemperatures and blizzards which render the winter chill unbearable. The middle-latitude anticyclones always produce thelowest temperatures of the season.

In summer, the stagnant type of warm anticyclones associated with the air of subtropical or tropical origin produceextremely high temperatures, called 'heat waves'. Clear weather allows the maximum receipts of solar radiation during theday. Tropical air masses carry heat to the north as the high pressure system moves into the sub-polar regions.

Since the anticyclone conditions favour clear weather, the diurnal range of temperature is bound to be large.

Distribution:

The regions of origin and paths of movement of the cold and warm anticyclones are different. Sub-polar regions give birth tocold anticyclones which always move towards the south.

The warm anticyclones generally move from west to east. However, the source regions as well as the tracks followed byanticyclones tend to shift towards the north in summer and south in winter.

In winter, there are two regions of high frequency of cold anticyclones: the extensive plateau of the Rocky Mountains innorthwestern Canada and east central Siberia. The states of Nevada, Utah, and Idaho have the largest number ofanticyclones.

The area extending from Alaska to the Great Plains has high frequency of high pressure systems. These anticyclones are coldand shallow highs comprising the polar continental air (cP).

The cold Canadian anticyclones, which travel from their centers of origin to the Middle Atlantic States, bring with them coldwaves, blizzards or snow storms and lowest temperatures to the Mississippi Valley. Some of these anticyclones push theirway to the Gulf States where they are called 'norther', the most dreaded weather phenomenon.

Cold anticyclones originating in east central Siberia travel towards northern China and reach the mouth of the Yangtze River.They sometimes cross over to Japan.

In Europe, there are only a few cold anticyclones moving southward from the Peninsula of Scandinavia.

In summer, as stated earlier, the storm paths and their centers of maximum frequency shift towards the north. The GreatLake region has a maximum of anticyclone frequency in summer, whereas the cold anticyclones of the winter months avoidthis region because of intense cyclonic development there.

In eastern Asia too, the number of anticyclones is greatly reduced. Some of the feeble anticyclones move across China insummer. Now, the subtropical anticyclones follow a more northerly route.

Their frequency over the eastern Pacific is high, and there are only a few high pressure systems in the western part.

This is so because in this part of the Pacific the summer monsoon dominates the weather drama. A number of warmsubtropical anticyclones pass over the Mediterranean Sea.

Characteristics:

It may be noted that in winter the anticyclones form with a great regularity in the higher latitudes of the continents. Since

these anticyclones result from radiational cooling of the earth's surface, they are also called thermal anticyclones.

In the upper troposphere they either disappear or shift towards the lower latitudes. On the contrary, the anticyclones thatform over the ocean surface have warm air in their upper parts. Such anticyclones are called dynamic anticyclones. Theseanticyclones maintain their vigour up to considerable heights.

The warm season anticyclones are invariably associated with clear weather, but some of the winter highs produce cumulus orcumulonimbus clouds. In winter, the anticyclonic conditions are conducive to the formation of radiation fogs during night.

On the rear of these anticyclones warm and moist air currents from over the oceans produce advection fogs. On certainoccasions, the day-time surface heating causes the dissipation of fog at the surface, but the remaining fog still persists athigher levels.


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When looked at from the surface of the earth, these upper-level fogs appear as low stratus clouds. These foggy layers do notallow the light rays to reach the surface in toto.

In the middle-latitude regions this phenomenon of subdued day-light is termed the 'anticyclonic gloom'.

Brief notes on the Classification of Fronts

As a result of the observations of atmospheric conditions at the surface and aloft, the following types of fronts are identified:(1) cold front, (2) warm front, (3) occluded front, and (4) stationary front.

The frontal symbols used on weather maps. Here the structure and some of the sal ient features of the various. Frontalsymbols used on weather maps, types of fronts have been discussed in detail.

It should be remembered that fronts are differentiated by determining whether the colder air mass is moving on the warmerair mass or vice versa. However, it is the aggressor air mass that, to a large extent, determines the type of weather that will beproduced along a front.

(1) Cold front:

A cold front is defined as a front along which cold air is invading the warm- air zone. Since the colder air mass is denser, itremains at the ground and forcibly uplifts the warmer and lighter air mass.

In fact, when pressure distribution is such as to force the cold air to advance and the warm air to retreat, the zone oftransition is called a cold front.

The vertical structure of warm air that is forced upward by an advancing wedge of cold air determines the type of weatherproduced along the cold front.

The effect of friction retards the air motion near the ground, while the free air aloft has a higher velocity. This causes the coldfront to become much steeper than the warm front. The steepness of the front is closely related with its velocity.

Thus, higher velocity results in the steeper slope, while lower velocity makes the slope of the front rather gentle, sometimeswere approaching that of a warm front. The slope of a cold front varies from 1 : 50 to 1 : 100.

In other words, the wedge of cold air has a slope of 1 km of rise for 50 or 100 km of distance. When a cold front movesrapidly, warm air can be forced to rise ahead of the front. Depending on the instability of the overrunning warm air,convective clouds or even thunderstorms may occur along the leading edge of the cold front.

This type of front slopes backward instead of forward, so there is no warning far in advance of an approaching cold front andno preceding cloudiness until the front is near. The cold front in general is associated with a narrow band of cloudiness and

precipitation.

The cold front passes more rapidly. The sky becomes clear soon after the passage of the front. However, the weatherproduced along the cold front is more violent.

When the cold front moves over a rough terrain, the lower air is retarded by the effect of friction at the ground. This causesthe air aloft to run ahead of the surface air and a bulge or squall head is formed.

The lapse rate steepens and the convective overturning takes place resulting in heavy showers in a line ahead of the surfaceposition of the front.

In meteorology this is called the squall line. However, precipitation depends on the moisture and temperature conditions ofthe warm air lying above.

With the approach of the cold front there is some increase of wind in the warm sector. Cirrus and cirrostratus clouds appearin the sky. These cloud types are quickly followed by lower and denser altocumulus and altostratus clouds.

At the actual front, the clouds are of nimbostratus and cumulonimbus type which produce heavy showers. In certain casesprecipitation falls ahead of the front, while on occasions it is behind the same.

However, there are departures from this typical condition depending on the physical characteristics of both the air masses.

If the cold air moves over a warm water surface, the lower layers absorb heat and moisture which results in heavy rain orsnowfall. Such a precipitation occurs in the cold air.

This phenomenon is characteristic of late fall and early winter when there is a considerable difference between thetemperatures of air and water. On occasions, secondary cold fronts develop some distance behind the rapidly moving coldfront.
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With the passage of a cold front, the sky becomes rapidly clear and the weather improves. There is a sudden drop intemperature. A wind shift from south to west or northwest generally accompanies the frontal passage. There is a markeddecrease in the specific and relative humidity.

The weather after a cold front has passed is dominated by subsiding and relatively cold air mass. In winter, the passage of acold front is followed by a cold wave which further reduces the surface temperature.

(2) Warm front:

A warm front is defined as a gently sloping frontal surface in which there is active movement of warm air over cold air. As thesurface position of a warm front moves, the warm air occupies territory formerly covered by cooler air. Because of friction,advance of the surface position of the front is slowed down so that the front has a small slope.

The average slope of a warm front is from 1 : 100 to 1 : 200. As the warm air gradually ascends the gently sloping surface ofthe wedge of cold air lying ahead, it cools adiabatically. This cooling leads to the cloudy condensation and precipitation.Unlike the cold front, the changes in temperature and wind direction are gradual.

The sequence of clouds precedes a warm front. The appearance of cirrus clouds heralds the approach of a warm front. Thesehigh-altitude clouds form some 1000 kilometers or more ahead of the surface front indicating the ascent of overrunningwarm air over the retreating wedge of cold air.

The cirrostratus clouds that form ahead of the front produce halos around the sun and the moon. In case there is instabilityin the overrunning warm air, mackerel sky is produced by cirrocumulus clouds.

As the front draws closer to the observer, the clouds become lower and thicker. About 300 kilometers in advance of thesurface position of the front thicker stratus and nimbostratus clouds appear and precipitation starts falling from them.

Thus, as the warm front approaches, the clouds show a sequence of cirrus, cirrostratus, altostratus, stratus andnimbostratus, and finally nimbus. The thick cloud sheet overlying the surface position of the front gives steady precipitationextending over a long distance ahead of the front.

Warm fronts usually yield moderate to gentle precipitation over a relatively larger area for several hours. This is inconformity with the gentle slope of the front. Convective activity is generally absent along a warm front.

But there are occasions when cumulonimbus clouds and the associated thunderstorms are produced along the warm fronts.But this is exception rather than the rule.

Sometimes the rains falling through the cold air mass below evaporate. This causes the air below the cloud base to becomesaturated and stratus clouds form. These clouds make atmospheric visibility poor causing much hardship to pilots of thesmall aeroplanes.

During the winter, an inversion of temperature is produced along the warm front which is situated near the surface. Theinversion layer may produce during the cold season freezing rain or sleet in the very cold air ahead of a warm front.

The passage of a warm front is marked by a rise in temperature and pressure. There is a small shift of about 45 in thedirection of wind.

The specific humidity rises, and there is usually a change in the weather. The weather in the warm sector, of course, dependson physical properties of the air mass and the season.

(3) Occluded front:

An occluded front is defined as a front formed when a cold front overtakes a warm front. The cold front moves more rapidlythan the warm front with the result that the warm sector is progressively reduced in size.

Ultimately the cold front overtakes the warm front and completely displaces the warm air at the ground. Ultimately the coldand warm fronts combine into one. Thus, a long and backward swinging occluded front comes into existence.

There are two types of occlusion: (a) cold front type occlusion and (b) warm front type occlusion.

(a) Cold front occlusion:

It occurs when the cold air which overtakes the warm air is colder than the retreating cold air. It is illustrated. In the initialstages of the cold front type occlusion, the weather system of the warm front still persists.

Later on, when the warm front has been pushed further upward it has little effect on weather conditions. At the later stagesthe weather conditions resemble those of the cold front. Cold front type occlusion is the common type.

(b) Warm front occlusion:


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The warm front type occlusion occurs when the retreating cold air mass is colder than the advancing cold air mass. In thiscase the advancing cold air being relatively less dense overrides the retreating cold air mass.

This type of occlusion generally takes place when the retreating cold air becomes progressively colder by radiation, and theadvancing cold air mass is of the maritime polar type.

Weather produced at an occluded front is usually very complex depending to a large extent on the nature of warm air beingforced aloft.

As a matter of fact, in either type of occlusion it is the uplifting of the warm air mass which results in cooling, condensationand precipitation.

The weather that is produced along an occluded front is usually a combination of the cold front and the warm front weather.

(4) Stationary front:

There are situations in which the surface position of a front does not move. Therefore such a front is called a stationary front.

The wind motion on either side of such a boundary is nearly parallel to the position of the front. Whenever someoverrunning of warm air occurs along a stationary front, warm front type precipitation is likely to be produced.

Brief notes on Extra tropical Cyclones (Wave Cyclones)

Much of the highly variable and cloudy weather we come across in the temperate zone is the direct result of travellingcyclones. The terms extra tropical cyclones, temperate cyclones, or depressions are interchangeably used to denote thesemoving cyclones in the mid-latitude zone.

Since the middle latitudes are an area of convergence where contrasting air masses generally meet, it is there that thecyclones and anticyclones travel with varying regularity along with the prevailing westerly winds.

As centers for converging and rising air these moving cyclones produce cloudiness and precipitation. They also bring aboutchanges in temperature and air- pressure.

Extra tropical cyclones develop in regions lying between 30 and 65 north and south latitudes in both the hemispheres. It isin these latitude zones that the polar and tropical air masses meet and form what is known as the polar fronts.

Most of these cyclones form at a wavelike twist or perturbation on these fronts. Since a cyclone on a weather map is shown asa low pressure area enclosed by a number of isobars circular or elliptical in shape, it is also referred to as a low or adepression.

When the isobars take an elongated shape, the pressure system is called a trough. Depicts the general lay-out of cold andwarm fronts in an extra tropical cyclone as shown on a surface weather map.

Shape and size:

There is a great degree of variation in the shape and size of middle-latitude cyclonic storm. No temperate cyclone is everexactly like any other. Generally the isobars are almost circular or elliptical.

However, in certain depressions, the isobars take the shape of the letter V. Such storms are called a V- shaped depression. Attimes, the cyclones become so broad and shallow that they are referred to as troughs of low pressure.

There are occasions when these storms become greatly elongated and lose some of the common characteristics of anordinary temperate cyclone.

The V-shaped depressions are generally oval-shaped with one part relatively wider than the other. The long axis of this type

of depression is aligned in the south-west to north-east direction with its wider part towards the north.

The short axis is arranged in the north-west to south-east direction. The long axis is often twice the short axis in length.These storms vary in size, intensity and other characteristics such as speed, strength of winds, and amount and type of cloudcover.

The diameter of the temperate cyclones may vary from 160 km to 3,200 km. But most of the cyclones have diametersmeasuring 300 to 1500 km. The average length of extra tropical cyclones in the United States of America is about 1600 km.

The estimated area covered by an average cyclone is about 1.6 million sq. km. The vertical extent of an average-sized cycloneis estimated to be 10 to 12 km.
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The air pressure in a cyclone is lowest at the centre and increases towards its margins. The pressure at the centre varies fromone storm to another.

A strong cyclonic circulation may have as low as 940 to 930 mb pressure at its centre, while a moderate cyclonic storm mayhave about 1000 mb pressure.

The pressure difference between the centre and the outer margin of a low may vary from 10 to 20 mb. In a very large andintense cyclone, this pressure difference may be as much as 35 mb.

Freeessay on Atmospheric Stability and Lapse Rate

Atmospheric stability is defined as that condition in the atmosphere in which vertical motions are absent or definitelyrestricted; and, conversely, instability is defined as the state wherein vertical movement is prevalent."

According to Trewartha, air is said to be stable, and consequently antagonistic to precipitation, if it is non-buoyant andresists vertical displacement.

Voluntary vertical motions are largely absent in stable air. On the other hand, if displacement results in buoyancy and atendency for further movement away from the original position, the air is unstable".

The stability of air is determined by the distribution of temperature in the atmosphere at various heights. This measure ofthe change of temperature is called the lapse rate which is altogether different form the adiabatic lapse rates.

As we know, the lapse rates always vary with time and place. The dry-adiabatic lapse rate is always the same. By noting atany level the difference in temperature between an air parcel moving upward and the surrounding atmosphere, stability orinstability can be ascertained.

In other words, the environmental lapse rate prevailing in the atmosphere makes it stable or unstable. If the lapse rateexceeds the dry-adiabatic lapse rate, the air is bound to be in the state of unstable equilibrium, and it will tend to rise further.

On the other hand, if the lapse rate is lower than the dry-adiabatic lapse rate, there will be stability in the air. Such an airparcel, even if pushed up strongly, tends to return to its original position. Such a state of equilibrium resists vertical motionsin the atmosphere.

The interrelationship between atmospheric stability and lapse rates has been illustrated ill Figure 32.2. In the left hand sidediagram the surface air is at a temperature of 35"C with a lapse rate of 6"C per kilometer.

Imagine that a parcel of air with 35C temperature at the ground is forced upward as shown in the Figure. After the air hasreached a height of 1 kilometer, its temperature has come down to 25C, while the temperature of the surrounding air isabout 29C.

Obviously the ascending air is colder than the environment at the same level and must sink downward. This parcel of airwould tend to come back to its original position unless some outside force is applied to it, because further ascent would causeit to become colder and heavier than the surrounding air.

The relationship between the actual lapse rate and the dry-adiabatic lapse rate is such as to resist vertical movement. Suchair is said to be in stable equilibrium. It is to be noted that in this case the existing lapse rate is lower than the dry-adiabaticrate of cooling.

The right hand side drawing is a diagrammatic representation of the state of unstable equilibrium. In this case the ascendingair parcel at the height of 1 kilometer has cooled down to 25C, while the temperature of the surrounding air at the samelevel is only about 24 C.

The rising air is warmer and lighter than the surrounding air. In such a situation, the rising air will continue to rise andexpand.

Here the rate of cooling of the ascending air is lower than that of the surrounding air, because the lapse rate is higher thanthe dry-adiabatic lapse rate. Such an air is considered to be unstable. This case illustrates the behaviour of the atmospherewhen unstable equilibrium conditions prevail.

Thus, to examine whether an air mass is stable or unstable a comparison should be made between its lapse rate and the dry-adiabatic rate of cooling.

There are occasions when the lapse rate in a certain layer of the atmosphere is found to be about 4.6C per 1000 meters.Under this situation, when the lapse rate is less than the wet adiabatic rate, even at the point of condensation no verticalmotions develop in the atmosphere. In this case the air is dead to be absolutely stable.
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Temperature inversion is the typical example of absolute stability. The inversion layer present in the atmosphere acts as a lidto the ascending currents of air. Just beneath the base of the inversion layer the upward rising smoke is forced to spread outin horizontal plane.

In winter, it is a common sight at about sunset near human settlements where rising columns of smoke from domesticchimneys are not allowed to move upward beyond a certain level. This level is provided by the base of the inversion layer.

What are the Characteristics of tropical atmosphere?

The tropical atmosphere should be considered as a heat sink of the radiant energy obtained through short-wave solarradiation and terrestrial radiation. Vast expanse of the tropical oceans plays a significant role in the supply of atmosphericheat.

Now, the data supplied by weather satellites indicate that our estimates of the depletion of solar radiation because of albedoand cloud cover were far in excess of the actual amount.

The amount of insulation received in the tropics is more than what it was previously considered to be. The ocean currentsthat originate in the oceans of the tropical region also contribute a lot to the transference of heat to the higher latitudes.

The rate of exchange of energy between the oceans and the atmosphere is greater in the tropics than in any other regions.

Transfer of sensible heat to the lower layers of the atmosphere lying close to the oceans and the latent heat obtained there

from are two such meteorological facts which more than compensate the loss of radiant energy in the atmosphere.

In the warm and humid atmosphere of this region the latent heat of condensation is an important source of energy for theinnumerable atmospheric disturbances and tropical cyclones of varying magnitudes.

Another very important characteristic of the tropical atmosphere is that there is no random precipitation; rather it isconcentrated in various atmospheric disturbances which are small in size.

Of various factors which produce an element of instability in the tropical weather the following are more important: thermalconvection; convergence; and orographic lifting of air.

Why the rainfall decreases from east to west in theNorthern plain while it increases in thePeninsular India?

The rainfall decreases from east to west in the Northern plain while it increases in the Peninsular Indiadue to the following reasons:

Northern plains receive rains by South West Monsoons. These Monsoons being the branch of Bay ofBengal Monsoon move westwards along the Himalayas.

These monsoon winds on moving away to western part of country gradually loose moisture causing lessrainfall. Hence rainfall decreases from east to west.

In the Peninsular India, the rain is received by the Arabian Sea branch of South West Monsoons. TheSouth West Monsoon winds cause heavy rainfall on the western slopes of Western Ghats as they passthrough the rain bearing area of the region.

The moment, these winds cross the Western Ghats towards east, they become dry owing to the rainshadow area and therefore rainfall starts decreasing.

What are the functions of Oceans ?

The important functions performed by the oceans are given below :
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The oceans regulate the temperature of land (of our globe).

The oceans act as reservoir of resources like fossil fuels, sea-foods, metals and salts.

The oceans dissolve out excess carbon dioxide from the atmosphere and hence prevent the excessiveheating of earth by decreasing the green-house effect.

The oceans acted as a cradle for the origin (birth) of primitive life.

The oceans act as a medium of transport by boats, ships, etc.

The oceans act as a dust-bin for throwing unwanted waste materials of the land.

What are the main ingredients of modern industries ?

Main ingredients of modern industries :

Raw material

Availability of skilled labour

Capital

Organisation and management by efficient hands

Means of transport and communication

Market for the products.

Let us discuss each of them in some detail:

Raw material. Availability of raw material is the first and the foremost pre-requisite of any industry. This is more true incase of modem industries which is characterised by the production on a mass scale.

Skilled labour.Well qualified and efficient labour is a 'must' for processing raw material and transforming it into thefinished product.

Capital.Purchasing raw material, employing labour on a large scale and setting up huge power-driven machines for quickand mass scale production, in turn, call for huge capital.

Organization and management.Efficient and enterprising organisation and management is yet another characteristicof the successful modem industry.

Market.Production on a large scale presupposes a potentially big market or demand for the finished products.

Means of transport and communication.The collection of raw materials and the distribution of the finished productsdemand an efficient network of the means of transport and communication, including facilities for financial transactions.

All these factors put together provide the necessary set-up for developing modem industry.

Indian Land Resources and Crop Pattern

India has a geographical area of about 329 million hectares but statistical information is available only for about 93 percentof the area (viz., for 305 million hectares). More than half of the area (51 percent) is under cultivation compared to 11 percentof world's average. Our farmer is very hard-working and raises two crops in a year instead of one being the normal practicein the other countries.

According to state of forest Report, 2003, Forests cover about 20.6 percent of land area for which data is available. Another30.3 percent of area is not available for cultivation because it either comprises fallow lands, residential or commercial areasor is otherwise not fit for cultivation. Consequently, cultivation is done only on about 50 percent of the total reporting area inthe country.

Soil Types

Soil quality is an important factor in crop-yield. The soil provides nourishment and water to the plant life. It consists ofminerals, organic matter, water, air, etc., all of which determine its characteristics, fertility, depth, texture and structure and,thus, govern the type and quality of plants and crops that can be grown in any region of the country. India, with its vast landsurface and diverse relief features, possesses a large variety of soils, which, according to the National Council of AgriculturalResearch, are classified into the following eight categories.

(i) Alluvial Soil
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Alluvial soil covers almost a quarter of India's land surface and provides the base for the largest share of country'sagricultural production. This type of soil is composed of sediments deposited by the mighty rivers in the interior parts of theIndia and by the sea wave in the coastal areas of the country. The Great Plains of India running from Punjab to Assampossess rich alluvial soil which is also found in Narmada and Tapti valleys in Madhya Pradesh and Gujarat, Mahanadi Valleyin Chhattisgarh and Orissa, Godavari Valley in Andhra Pradesh and Cauvery Valley in Tamil Nadu. It also occurs in thedeltas of Mahanadi, Godavari, Krishna and Cauvery rivers. Alluvial soils are generally deficient in nitrogen and humus andthus necessitate repeated fertilisation. Such soils are suitable for growing all types of cereals, pulses, sugarcane, vegetables,oilseeds, etc.

(ii) Black Soil

Black soil is found largely in the Deccan Plateau. It is eminently suitable for cotton cultivation and is, therefore, also calledblack cotton soil. In some areas, it is known as 'regur'. The black color of the soil is attributed to the presence of compound ofiron and aluminum. This soil is generally deficient in nitrogen, phosphates, and organic matter but is quite rich in potash,lime, aluminum, calcium and magnesium. The black soil exists in many areas of Madhya Pradesh, Maharashtra, Gujarat,Karnataka, Andhra Pradesh and Tamil Nadu. Cotton, cereals, some oilseeds and a variety of vegetables are grown in areas ofblack soil.

(iii) Red Soil

The red soil occurs mostly in the southern peninsula and extends up to Jhansi (Uttar Pradesh) in the north, Kutch (Gujarat)in the west and Rajmahal Hills in the east. This soil is made up of crystalline and metamorphic rocks and is rich inferromanganese minerals and soluble salts but is deficient in nitrogen and humus and thus needs fertilization. It has a lighttexture and a porous structure. Red soil is most suited to the growth of rice, ragi, tobacco and vegetables.

(iv) Laterite Soil

This type of soil is found in areas of high rainfall and temperature with alternate dry and wet periods. The so il contains highcontent of iron oxides. It is deficient in nitrogen, phosphorus, potash and magnesium. Such soil is found in the high reachesof Sahyadris, Western Ghats, Rajmahal Hills and the hilly tracts of the eastern region. It is also found in parts of Karnataka,Andhra Pradesh, Kerala, Orissa and West Bengal. This type of soil is suitable for rice, ragi and sugarcane cultivation.

(v) Forest Soil

Forest soil is rich in organic matter and humus. It is found in the Himalayas and other mountain regions of the north, highersummits of the Sahyadris, Eastern Ghats, Karnataka, Tamil Nadu, Kerala, Manipur, Jammu and Kashmir and HimachalPradesh. Crops like tea, coffee, spices and tropical fruits are grown on this type of soil.

(vi) Arid and Desert Soils

The arid and semi-arid regions of north-west India have this type of soil which is generally deficient in nitrogen and humus.It is largely found in the areas west of Arvalli Ranges and covers Rajasthan, parts of Haryana and Punjab and extends up tothe Rann of Kutch. Generally desert soil is infertile but its fertility improves with proper irrigation and fertilisation.

(vii) Saline and Alkaline Soils

Saline and alkaline soils are found in the arid and semi-arid parts of Rajasthan, Punjab, Haryana, Uttar Pradesh and Bihar.These soils, variously called 'reb', 'usar' or 'kallar' are largely infertile. However, they can be improved through propertreatment and reclamation measures.

(viii) Peaty and other Organic Soils

Peaty soils contain large accumulations of humus, organic matter and soluble salts. These soils are highly saline and aredeficient in phosphorus and potash. Marshy soils occur in regions of Orissa, West Bengal and Tamil Nadu. They are alsofound in central and north Bihar and in Almora district of Uttarachal.

Crop Pattern

Crop Seasons

There are three major corp seasons in India, viz., Kharif, Rabi and Zaid. The Kharif crops are associated with the monsoons.They are sown in the months of June and July and are harvested in autumn months, viz., in September and October.Important among the Kharif corps are rice, jowar, bajra, ragi, maize, sugarcane, cotton and jute.

The Rabi crops are sown in the period between October and December and harvested in April and May. Important amongthe Rabi crops are wheat, barley, peas, rabi pulses, linseed, rapeseed and mustard.

The Zaid is the summer season crop. Rice, maize, vegetables, sunflower and groundnut are grown during this season. Again,areas, which are extensively irrigated, grow three to four crops per year and, thus, fall out of the purview of the distinction


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between the Kharif and Rabi crops. Similarly, in southern half of the Peninsular India where temperatures are sufficientlyhigh and rainfall is extensive in winter months, rice, jowar, coffee, etc., are sown, thus again blurring this categorizationunder Kharif and Rabi crops. However, for most of India, Kharif and Rabi remain the distinct crop seasons with the specificvariety of crops grown therein.

Major Crops

Agricultural crops can be broadly divided into two categories, viz., food crops and non-food crops. Food grains consist of

cereals and pulses. Among the cereals are included rice, wheat, jowar, bajra, maize, etc. Pulses include gram, moong, masur,athar, etc. The non-food crops comprise a number of cash crops such as sugarcane, cotton, jute, tobacco, etc. Tea, coffee,rubber are included among the plantation crops. Besides these, we have the horticulture crops like fruits, vegetables ,coconut, cashew, etc.

India is the largest producer and consumer of tea in the world and accounts for around 27 percent of world production and13 percent of world trade in tea. In coffee, India contributes 4 percent of the global production. Rubber is primarily producedin the State of Kerala and adjoining Kanyakumari district of Tamil Nadu.

India is the third largest producer of fish and second largest producer of inland fist in the world. As per Economic survey,fish production from marine and inland sources has been at 2.8 million tonnes and 3.5 million tonnes, respectively andmarine products worth Rs. 6188 Crore were exported in the last year.

Why Working Conditions in the Tropical Forests are Difficult?

Working conditions in the tropical forests are extremely difficult due to the following reasons:

(i) Numerous Species: Heterogeneous characters of forests and the occurrence many different species makes the extractionand location of valuable trees difficult and expensive.

(ii) Hostile Environment: Unfavourable climatic conditions like high temperature and heavy rainfall greatly hinderedlumbering in the tropical forest areas.

(iii) Lack of steady demand for Hardwood: While demand for some of the tropical hardwood is great, they are little use inpulp and papermaking. In contrast to tropical forest temperate hardwood forest are both more accessible and more easilyextracted, therefore, the timbers are more readily exploitable.

(iv) Non-replacement of species: In comparison to the coniferous trees, the tropical hardwood trees are not only large butalso take a long time to mature. Thus, many of the tropical forest areas are being replaced not with original species withgrowing conifers. This process may make the forests less valuable.

(v) Transportation: The transportation imposes a great difficulty in most of the tropical forest regions because of the fact that

tropical forests are difficult to approach and the logs are too heavy to transport.

(vi) Shifting Cultivation: the activity of shifting cultivation restrict exploitation of tropical forest by degenerating forests interms of species and also initiates soil erosion by wantion destruction of forests.

(vii) Soil erosion: In most of the tropical areas where the rainfall is usually high and the unscientific exploitation of trees fortimber leads to very rapid soil erosion which, in turn, native species.

In spite of the difficulties associated with the lumbering in tropical forests, the tropical woods are gaining importance as anexport item of international trade; this is because of poor and incompetent substitution by the timber of coniferous forests.

What are the differences between a galaxy and a constellation?

Difference between a Galaxy and a Constellation are :

We know that a galaxy consists of stars and a constellation also consists of stars. So, let us find out the difference between thetwo.

(i)The first difference is that a galaxy is a collection of billions of stars whereas a constellation is a collection of only a veryfew stars.(ii)The second difference is that a galaxy does not form a definite pattern which resembles the shape of an animal or ahuman being but a constellation appears to resemble an animal or human being in its shape.

(iii)The third difference is that the billions of galaxies in this universe but only about 88 constellations are known atpresent.
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What are the difference between folding and faulting ?

The difference between folding and faulting are discussed bellow:

Folding

The horizontal movement of the earths crust results in folding.

In shallow seas and lakes, deposited sediments (sedimentary rocks) generally get so compressed that they take the form offolds at many places resulting in complex structure. Called fold mountains. The process is known as folding.

Examples. Himalayas in Asia and Rockeys in North America.

Faulting

The vertical movement of the earths crust involves uplift or subsidence of crust along the lines ofweakness and is calledfaulting.

The process of uplift and subsidence along the line of weakness is called faulting. The uplifted position may become BlockMountain and the subsided area may form deep Rift Valleys.

Examples: Rift Valleys in East Africa. In India Narmada Valley is a Rift Valley.

Essay on Migration in the World

i. Ancient migrations encompassed relatively small numbers, but they were extremely important in the development and

spread of civilisation. Greek colonisation resulted in the gradual extension of their people and their culture throughout theMediterranean basin and the Near East;

ii. During the early Middle Ages (A.D. 200 to 800) the Germanic people of northern Europe began a series of greatmigrations that took them to almost all parts of western Europe as well as a portion of North Africa.

Wave after wave of Asiatic people entered Europe from the east during the first fifteen centuries of the Christian (A.D.) era.

This great movement of Asians displaced large numbers of earlier European cultures, causing the relocation of people in akind of chain-reaction series of migrations.

iii. In the process, noConly people but also cultural concepts and practices diffused throughout what later Europeansreferred to as the "known world."

iv. Regardless of the importance of the cultural impact that resulted from these smaller, early movements, the migration ofgreat number of people is a more recent phenomenon.

This great transfer of humanity from one portion of the globe to another intensified with time; between 1820 and 1980. Morethan 50 million migrants entered the United States alone.

In addition, some 6 million migrants entered Brazil, 4 million became permanent residents of Argentina, and over 1.5million came to Cuba and nearly a million to Uruguay during the same time period.

While the cases mentioned are predominantly associated with the colonization of new agricultural areas or the supply oflabour to the (then) emerging industrial states.

Countless millions of other Europeans and Asians have migrated within or between the countries of those continentsbecause of changes in political borders or governments and the destruction wrought by civil and international wars.

What is the difference between Igneous Rocks andMetamorphic Rocks ?

The difference between Igneous Rocks and Metamorphic Rocks:

Igneous Rocks

These rocks are formed by the cooling and solidification of molten magma flowing from the interior of earth during volcaniceruption.

These rocks often contain crystals of different minerals.

Granite and basalt are examples of Igneous Rocks.

Metamorphic Rocks

Metamorphic rocks are formed out of Sedimentary and Igneous Rocks under extreme heat and pressure conditions.
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Thus, the Metamorphic Rocks are the altered forms of Igneous and Sedimentary Rocks.

Granite for example changes into Gneiss and Coal into Diamond.

What are the Characteristics of the Monsoon Climate?

The word monsoon has been derived from an Arabic word 'mausim' which means season. It denotes a season in which thewinds are completely reversed. In short, reversal of winds is called monsoon.

Characteristics of the monsoon climate of India are

Monsoons are not certain. Their onset is sometimes very early and sometimes very late.

Secondly, there is great variation in the amount of rainfall from year to year.

Monsoons do not reach in equal amount all around the country. They vary from region to region.

Continuous heavy spell of rainfall is sometimes followed by dry spell.

What is Soil-forming Processes by Translocation?

Also called Transfer processes it involves internal reorganisation of matter and redistribution of energy, but involvingmovement, e.g., translocation of iron, clay, humus, and hydrated ions, diffusion of gases, ion exchange, and mass-movementand through flow, capillary rise, mixing by soil fauna, cryoturbation.

The various types of translocation processes are

Leaching

The process by which water is percolating downwards through a soil, removes humus in solution, soluble bases andsesquioxides from the upper horizon or A-horizon. The upper layer of a leached soil becomes increasingly acidic and mineraldeficient. It is most prounced in humid areas than in dry areas.

Podzolization

The formation in organic acids of soluble chelates (organic-metallic complexes of Fe, Al), and the dissociation of clay humuscolloids, susceptible to leaching

The Process of Pedogenesis

Laterization

(Now called Ferralization) It occurs in the humid tropics where heavy rain and uninterrupted warmth give rise to a deeplyweathered layer.

Dense forests produce a heavy leaf fall, but bacteria break this down at one: the circulation or mineral nutrients areparticularly rapid.

Leaching is heavy, but silica is removed rather than iron or aluminium, which accumulate at the surface. The removal of thesilica leaves a porous and firm soil, rather than a soft and sticky one.

In regions of more marked dry season, the alternation of wet and dry conditions gives rise to increased movement in to soil,and the formation of iron crusts.

Calcification

Used by some to refer to the processes of calcium carbonate accumulation. This term is not specific. It leads to the formationof pedocals, e.g., chernozem chestnut soil slightly alkaline (basic). Pedocals have:

i. A Horizon: humus-rich. Bases abundant and brought to soil surface by grasses

ii. B Horizon: nodules and slabs of calcium brought up from parent rock by capillary action and evaporated out.

iii. Climatic Types: temperate continental; tropical wet-dry.

iv. Climate: dry enough (600 mm) to inhibit leaching. Dry season necessary warm enough in summer (20C) for evaporationto act

Gleyisation
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The reduction of iron in an anaerobic or water logged environment leading to the formation of grey or blue colours. Not avery good term because it includes a very large number of individual processes.

Salinization

It involves the accumulation of highly soluble sodium, magnesium and potassium salts in a soil. Salinisation usually occursin arid and semi-arid areas where evaporation rates exceed those of precipitation, especially in coastal regions and areas withunderlying evaporate deposits.

High air and ground temperatures cause evaporation and the deposition of salts from the groundwater. Salinisation can alsoresult from the excessive and wrongly timed application of irrigation water.

Irrigation followed by a lengthy hot, dry phase can result in a substantial upward movement of salts, which accumulate as asalt pan.

One example of salinisation is found in northwestjndia particularly in Punjab, Haryana and western Uttar Pradesh wheresurface irrigation has led to a rise in the water table.

The process of salinization causes the formation of Solonchak soils, i.e., the accumulation of soluble salts in the soil(sulphates and chlorides of sodium and calcium).

What are the uses of Manganese?

It is used as a ferro-alloy. The purpose of the input is to neutralize the negative effects of sulphur on the high temperature

strength of steel and to act as a cleanser in the manufacture of steel.

Percentage of manganese up to 14% give steel a hard surface but tough core, needed in rock crushers and railroad switches.

Manganese is also used in the manufacture of bricks, glazed pottery, plastics, floor tile, glass, varnish and dry- cell batteries.

Manganese compounds are used in making disinfecting liquids; as a decolorize in glass making; and for the manufacture ofbleaching powder, used in the textile industry.

Mangnese is mixed with copper to produce manganese-bronze, and with nickel to produce 'manganin' which is highlyresistant to corrosion.

Brazil-Near Mecapa in Amapa, Minas Gerais, and Urucum near Corumba in western Mato Grosso

Others-Deposits as nodules especially in the Pacific Ocean

Essay on Inland Waterways of Europe and North AmericaInland waterways are best developed in two continents, Europe and North America.

Europe

A number of countries in Europe, e.g. France, Germany, Belgium, Netherlands and the erstwhile USSR, have very extensiveinland waterways including both rivers and canals.

France

i. The second largest country in Europe after the CIS has 5600 km (3,500 miles) of navigable rivers and another 4800 km(3,000 miles) of canals.

ii. The major French rivers, e.g. Loire, Garonne, Seine, Rhone, Meuse and Moselle have been modified and improved and arelinked by canal systems such as the Canal du Midi, Canal du Centre, Burgundy Canal, Maine and Rhine Canal and Rhone

Rhine Canal.

iii. Though France has a great length of waterways the traffic is not as great as in Germany or the Netherlands because manyof the older canals are only capable of taking small barges with a low carrying capacity.

iv. Germany and other central European countries have many canals.

(a)The Rhine Waterways.

i. The Rhine flows through Switzerland, West Germany and the Netherlands and forms the eastern border of France.

ii. It is navigable as far as Basel and is the most important waterway in Europe.
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iii. It is linked to the River Rhone and the Mediterranean by the Rhone-Rhine Canal and is joined by many tributaries, someof which, including the Main and Moselle, have been canalized.

iv. The river has been dredged, straightened and improved over much of its navigable length; it suffers little seasonalfluctuation, seldom floods and is rarely frozen.

v. The Rhine and the Rhone, to which it is linked by a large modern canal, are so important for transport that they havebecome the axis on which trade hinges in the whole of the Common Market.

(b) Waterways of the Germanic-Baltic Lowlands

i. An extensive network of waterways consisting of east-west canals joining the north-south flowing rivers crosses the NorthGerman Plain.

ii. The Mittelland Canal, joins the three major rivers of Ems, Weser and Elbe, and continues eastwards to Berlin and intoPoland.

iii. Near Hamburg another canal the Kiel Canal, 96 km (60 miles) long and 14 metres (45 ft) deep, links the Elbe estuary tothe Baltic Sea, improving access to the Scandinavian countries.

iv. The Dortmund-Ems Canal runs north-south and links the Rhine with the ports of Bremen and Emden.

(c) Waterways of Southern Germany

i. The region is served mainly by the Danube which flows through seven different countries- Germany, Austria,Czechoslovakia, Hungary, Yugoslavia, Romania and Bulgaria-before draining into the Black Sea.

ii. The Ludwig Canal links the Main, a tributary of the Rhine, to the Danube and allows waterborne traffic from the Black Seato reach the Mediterranean Sea through the Rhone- Rhine Canal or the Atlantic via the Rhine.

Waterways in Netherland

The low-lying Netherlands, at the mouth of the Rhine, is criss-crossed by its distributaries and also has extensive man-madewaterways.

The densest network is at the Rhine delta, where the Lek and Waal distributaries meet the Maas (or Meuse).

Inland

Rotterdam, linked to the North Sea by the deep New Waterway, serves a vast hinterland stretching up the Rhine to Germany,

Switzerland, France and Belgium.

Amsterdam is joined by the North Sea Canal to the port of Ijmuiden.

CIS

i. The CIS has immense systems of navigable waterways the most important of which are in European Russia.

ii. More outstanding canals are the Baltic and White Sea Canal, the Moscow-Volga Canal and the Volga-Don Shipping Canal.

iii. The vast Volga system links five seas: the Baltic, White, Caspian, Black and the Sea of Azov, Inland Waterways NorthAmerica

Great Lakes - St. Lawrence Waterways

i. In North America, the most important waterways is the Great Lakes-St. Lawrence Waterways shared by Canada and the

U.S.A.

ii. It stretches from Duluth on Lake Superior to the estuary of the St. Lawrence below Quebec.

iii. Its natural barriers such as rapids, waterfalls, gradient differences and shallow stretches of rivers have been overcome bythe construction of locks and canals and by constant dredging to maintain a depth of over 7.5 metres the U.S. and Canadiangovernments constructed the St. Lawrence Seaway which (27 ft), has many locks and dams which, apart from improvingnavigation, generate H.E.P.

iv. Below Montreal the St. Lawrence is sufficiently deep for navigation all the way to the Atlantic.


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v. Silting is tackled by constant dredging, but in winter from December to March the St. Lawrence is frozen and navigationcomes to a standstill.

vi. The main traffic on the waterways includes trade in iron ore, coal, grains (in particular whet from the Prairies), timber,furs, dairy products, metallic ores (nickel, copper, gold) and a whole range of manufactured goods.

vii. Important cities linked to the Great Lakes-St. Lawrence waterways by smaller canals are-Carillion and Grenville Canalsfrom Montreal to Ottawa.

viii. By the Rideau Canal to Kingston; and

ix. By the Erie Canal from Buffalo via the Mohawk Gap and the Hudson River to New York.

x. Despite the fact that the Great Lakes-St. Lawrence Waterway is ice-bound for three to four months in a year, the amountof traffic it handless is greater than any other commercial waterway.

This is partly because of the brisk trade on the waterway an the large number of vessels engaged, and partly because theships are large and can carry huge quantities of goods.

xi. In Canada, many of the north-bound rivers are navigable in summer, Examples

(a) The River Mackenzie from the Great Slave Lake to the Arctic,

(b) The Yukon from Whitehorse in

(c) The Yukon Territory through Alaska to the Bering Sea

(d) The Nelson and Albany rivers.

These rivers have little commercial importance, however, because of their northerly position. U.S.A.

The most important inland waterway is formed by the Mississippi and its many tributaries.

Why in India the long distance routes are connected byrailways whereas shorter distances are connected by road?

In India the long distance routes are connected by railways whereas shorter distances are connected by road due to thefollowing advantages and dis-advantages:

I. Two advantages of railways for long distance routes:

Railway is a cheap and convenient mode of transport for long distance journeys.

It carries in bulk non-perishable goods like machines, raw material like iron-ore, coal etc and other heavy goods.

Two disadvantages of railways for long distance routes :

It is highly expensive to construct and maintain railway tracks. It requires huge investment

Railways are not fit to transport perishable and valuable goods for long distance.

II. Two advantages of road transport:

Roads can negotiate higher gradients of slopes and can traverse mountains. They can be made to pass through forests,deserts and difficult terrain.

Roads provide 'door stop' service to the people. They are the only means to connect the vast rural areas of our country withtowns and cities.

Two disadvantages of road transport:

They are unsuitable for transporting heavy goods and raw material.

The long distance journey by road transport is tiring and inconvenient.

Distribution and Characteristics of Brown SoilsDistribution

Arid margin of chernozem belt

Characteristics

(a) Less humus content in comparison to chernozem.
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(b) Formation of CaCo3nodule in B. horizon.

(c) Lighter colour than chernozem

(d) It has prismatic and cloddy structure

(e) It is less fertile than black-Earth

(f) It is productive if proper irrigation is available

What are the Major Fishing Grounds of the World?

(a) There are five major fishing grounds of world. These are: (a) The North West Pacific Region.

i. Extends southward from the outer Aleutian Islands in the north to the central Pacific, north of the Philippine Islands.

ii. Salmon, King crab, Herring, Halibut, Alaskan pollock and Cod are the most important catch.

iii. Japan: Commercial fishing is best developed because of highly organised industry with modern fishing methods.

(b)The North East Atlantic and adjacent waters of the Arctic

i. Extending from Iceland to Mediterranean shores including the European countries especially Norway, Denmark, SpainIceland and the United Kingdom.

ii. Shallow waters of the North Sea especially the most exploited Dogger bank are important areas where fishing is carriedout all round the year.

(c) The North West Atlantic includes

i. It includes Grand Bank and the Georges Bank area of the Northwest Atlantic.

ii. The convergence of the Gulf Stream and the Labrador Current in that region enhances productivity. The major fish is thecod but halibut, squid, flounder and redfish are also important and herring andMtiackerel are caught on the surface water.

(d) The North - East Pacific

i. Extending from Alaska to California along the western shores of North America form the fourth large fishing area of theworld.

ii. Salmon is the most valuabfe fish of this region but tuna, halibut and sardines also important.

iii. This fishing ground comprises the world's best cod fishing ground along with herring and haddock.

(e) The South East Pacific

i. Lying off the coast of South America is known for the anchovy harvest off the coast of Peru.

ii. The northward flowing Peru Current provides an ideal environment for the anchovy culture because it is associated with acoastal upwelling of nutrient rich colder water laden with plankton on which the anchovy feeds.

(f) The West Central Pacific

i. Extends from the Philippines and Indonesia southward to the Australian coast.

ii. A wide variety of fish flourish in this extensive region including redfish, bass, mullet, mackeral, oyster, crabs and tuna.

iii. This area, together with the Indian Ocean, comprises a major marine environment not being fished at a maximum level.

Facts on Indian Geography

Facts on Indian GeographyIndian Geography : Learn the most important facts and factors about Indian Geography. This article includes significantinformation on various Geographical terms and projects. Waiting for some more information on Indian Geography fromyour side. Please share your comments below.

Geographical Terms :Irrigation :Water is very important for the survival of all forms of life plants as well as animal. India, by virtue of itspeculiar placement in the foothills of the Himalayas and having the ranges of the Satpura, Arvalli and the Deccan Plateau
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running through it, has vast water resource which have been very meagerly tapped. Conventional and recognized means ofirrigation are tanks, wells and canals.

Wells : Well irrigation is an important type of irrigation in India. Wells are particularly suitable for small farms. Theimportant well-irrigated States are Uttar Pradesh, Punjab, Tamil Nadu and Maharashtra. In these States water-table is high,soil is soft and, therefore, wells are easily sunk. Tubewells are an important development in India. They are worked byelectricity or diesel oil and thus, they relieve our cattle of much of the strain. They are being quickly developed in Uttar

Pradesh, Bihar, Haryana and Punjab. This is because these have ample sub-soil water.

Tanks : Tanks are also important and ancient source of irrigation. They are of considerable importance in central andsouthern India, specially in Andhra Pradesh and Tamil Nadu. About 8 percent of the total irrigated area is irrigated by tanks.Canals :Canals are the most important means of irrigation in the country. Some canals were constructed by the early Hindiand Mohammedan kings. Most of the canals, however, are the product of the British rule. At present, canals irrigated about39 percent of total irrigated area of India. Most of the canals of the country are found in Uttar Pradesh and Punjab. Storagecanals have been constructed in Deccan and Madhya Pradesh.Major, Medium and Minor Irrigation Projects :The methods of irrigation used in India can be broadly classified intomajor, medium and minor irrigation schemes. Irrigation project having Culturable Command Area (CCA) of more than10,000 hectares each are classified as major projects. Those having a CCA between 2,000 hectares and 10,000 hectares fallunder the category of medium irrigation projects. And the projects which have a CCA of less than 2,000 hectares areclassified as minor irrigation schemes. For the purpose of analysis the major and the medium irrigation projects aregenerally grouped together. These projects comprise a network of dams, buns, canals and other such schemes. Such projectsrequire substantial financial outlay and are, therefore, constructed by the government or any other agency which may drawfinancial assistance from the government and financial institutions. The minor irrigation projects, on the other hand,comprise all ground water development schemes such as dug wells, private shallow tubewells, deep public tubewells, boring

and deepening of dugwells, and small surface water development works such as stroage tanks, lift irrigation projects, etc.Minor irrigation projects or the groundwater development schemes are essentially people's programmes implementedprimarily through individual and co-operative efforts with finances obtained mainly through institutional sources.

Before 1951, the total irrigated area in India was only 22.6 million hectares of which 9.7 million hectare land was irrigatedthrough major and medium irrigation projects and 12.9 million hectares through minor irrigation schemes. This has nowgone up to 94.37 million hectares at the end of 1999-2000.

Some Irrigation and Multipurpose Projects In IndiaBargi Project : (Madhya Pradesh) : It is a multipurpose project consisting of masonry dam across Bargi river in theJabalpur district and a left bank canal.Beas Project :(Joint venture of Haryana, Punjab and Rajasthan) : It consists of Beas-Sutlej Link and Beas Dam at Pong.Bhadra Project :(Karnataka) : A multi-purpose project across the river Bhadra.Bhakra Nangal Project : ( Joint project of Haryana, Punjab and Rajashtan : India's biggest, multipurpose river valleyproject comprises a straight gravity dam across the Sutlej river at Bhakra, the Nangal dam, the Nangal hydel channel, twopower houses at Bhakra dam and two power stations at Ganguwal and Kotla.

Bhima Project(Maharashtra) : Comprises two dams, one on the Pawana river near Phagne in Pune district and the otheracross the Krishna river near Ujjaini in Sholapur district.

Chambal Project : (Joint project of Madhya Pradesh and Rajasthan ) : The project comprises Gandhi Sagar dam, RanaPratap Sagar dam and Jawahar Sagar dam.Damodar Valley Project ( West bengal and bihar) : A multipurpose project for the unified development of irrigation,flood control and power generation in West Bengal and Bihar. It comprises multipurpose dams at Konar, Tilaiya, Maithonand Panchet; hydro power stations at Tilaiya, Konar, Maithon and Panchet; barrage at Durgapur; and thermal power housesat Bokaro, Chandrapura and Durgapur. The project is administrated by the Damodar valley Corporation.Dulhasti Power Project( Jammu & Kashmir ) : It is a 390 MW power project in Kishtwar region of Jammu & Kashmir onChenab river. Work for this project started in 1981. The foundation stone was laid on April 15,, 1983 by the ten PrimeMinister, Mrs. Indira Gandhi. work on this project was suspended due to threats of kidnapping and killings by Kashmirimilitants resulting in long delay in completion of project.Gandak Project(Joint project of Bihar and Uttar Pradesh) : Nepal also dervies irrigation and power benefits from thisproject.

Hirakuad(Orissa) : World's longest dam, is located on the Mahanadi River.

Jayakwadi Project(Maharashtra) : A masonry spi

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