Geography of Earth Mountains

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Geography of Earth Mountains

{tab=Mountains, Plateaus & Plains}

Mountains

Mountains come under the second order of relief features. This is a portion of land surface rising considerably above the surrounding country either as a single eminence or in a range or chain.

Types of Mountains

  1. Fold Mountains :
    • These mountains have originated due to compressional tectonic forces and have been thrown up to form fold mountains e.g. Himalayas, Andes, Alps etc.
    • The folds consist of two inclined parts called limbs, the upward portion is called “anticline” and the downward portion is called “syncline”.
    • All the young folded mountains have originated from geosynclines. Gepsynclines are long but narrow and shallow water depressions characterised by sedimentation and the subsequent subsidence.
  2. New or Young Fold Mountains :
    • Example: The Alps, the Himalayas, the Circum-Pacific oceanic Mountains, etc.
    • The main features of these mountains are the complex folding of the rocks, faulting, volcanic activities, the erosion & weathering caused by running water, ice, winds, etc.
  3. Old Fold Mountains :
    • Example : The Caledonion and Hercynian mountains of Central Europe, the Pennines, the Highland of Scotland, etc.
    • These mountains were folded in very ancient times, then subjected to denudation and uplift; many faults were formed and the layers of the rock were wrapped. Many mountains exist as relicts due to erosion.
  4. Block Mountains :
    • They are originated by tensile forces leading to formation of rift valleys.
    • They are also called horst mountains e.g. Black Forest, Vosges, Vindhya, Satpura, Sierra Navada etc.
    • When the earth’s crust cracks due to tension or compression, faulting takes place. A section ‘of the land – form may subside or rise above the surrounding level giving rise to Block Mountains or Horst or Rift valley or Graben. The block mountains have a steep slope towards the rift valley but the slope on the other side is long and gentle.
  5. Dome Mountains :
    • They are originated by magmatic intrusions and upwarping of crustal surface e.g. lava domes, botholith domes etc.

Mountains of Accumulation :

  • They are originated by accumulation of volcanic material e.g. cinder cones, composite cones etc. These are formed by the emission and deposition of lava and so they are also called volcanic mountains. The slope of the mountains becomes steep and the height increases due to the development of the cones of various types like Cinder cones, Composite cones, Acid lava cones, Basic lava cones, etc. Some of the examples of this type are Popocatepetle of Mexico, Mount Reineer of Washington, Lessen Peak of California, the Vesuvious of Italy, the Fujiyama in Japan, the Aconcagua in Chile etc.

Circum – erosional or Relict mountain :

  • e.g. Vindhyachal ranges, Aravallis, Satpura, Eastern and Western ghats Nilgiris, Parasnath, Girnar, Rajmahal.These mountains have been subjected to weathering and erosion for a long time and lowered down. They represent the old stage of mountain life cycle.

Mountain – Building Period

  • Pre – Cambrian Mountain : Rocks of ages older than the Cambrian era, such as Laurentia Shields, Fennos Candia ( Europe ), Angora land ( Asia ), Gondwanaland ( Asia ) etc.
  • Caledonian Mountain : ( 820 m. year ) : Mountain of Scandinavia, Scotland, N. America, Brazil of South America, Aravallis, Mahadeo and Satpura falls under this category.
  • Horeqnian Mountain : ( 240 m. years ) : These mountains were formed during Permian and Permo – Carboniferous period. This mountain in Europe extends from Meseta in Spain through Britanny, South Wales England, South West Cornwell etc.
  • Alpine Mountains : ( 30 m. years ) : It was formed by the end of Mesozoic and continued into the tertiary period. These mountain, are the highest mountains of the world.

Important Facts
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  • Nilgiri mountain of India is an example of block mountain.
  • Ojas Del Saldo, situated in the Andes is the highest active volcanic mountain of the world.
  • The western Ghats of India is not a true mountain range. It is infact a fault scarp whose western part has been displaced and subsided to the west.
  • Andes, the fold mountains of South America, is the longest one ( 7000 km ) in the world.
  • Fold mountains are made up chiefly of the sedimentary rocks but their core is characterised by the massive granitic intrusions.
  • Fold mountains are generally found in arc shape and they extend for greater lengths but their widths are far smaller.
  • Marine fossils found in the rocks of fold mountains are of those marine organisms which can survive only in shallow water. All these things indicate that sedimentary rocks of fold mountains were deposited in long shallow seas called Geosynclines.
  • Great Dividing Range of Australia is an old fold mountain.
  • Fold mountains are generally found along the margins of the continents either in north – south direction ( Rockies & Andes ) or in East – West direction (Alps in Europe, Atlas in Africa, Himalayas etc ).

Plateaus

Plateau is an extensive landform with a plain area and is sufficiently high at least on one side of its land or water surroundings. The great Deccan plateau with its slope towards east is tilted plateau in our country.

  • Plateaus formed by running water : Many ports of the Deccan of India ( Kaimur Plateaus, Kewa plateau, Rohtas plateaus, Bhander plateau and the Brazilian plateaus ).
  • Plateaus formed by Glaciers : By erosion – plateau of Greenland and Antarctica, Garhwal plateau. By deposition – Russian plateau, Finland, and Marg of Kashmir.
  • Plateaus formed by wind / Aeolian Plateaus : Loess plateau of China, Potwar, plateau of Rawalpindi in Pakistan.
  • Intermontane Plateau : Tibetan plateau, Bolivian plateau, Peruvian plateau, Columbian plateau, Mexican plateaus.
  • Piedmont Plateau : Appalacian plateaus, Patagonia ( USA ) Malwa plateau, Colorado plateaus.
  • Dome Plateau : Ozark Massif ( USA ) Chhotanagpur plateaus.
  • Lava Plateau : Plateau of Columbia, Mahabaleshwar plateaus, Panehgani Tableland.
  • Intermountain Plateaus : Tibetan plateaus, Bolivian plateau, Peru plateaus, Columbian plateaus, Mexican plateaus, Iranian plateaus, Anatolian plateaus etc.
  • Piedmont Plateaus : Appalacian plateaus, Patagonian plateaus and Colorado plateaus.
  • Continental Plateaus : Deccan plateaus of India, Ranchi plateau, Shillong plateaus, Columbian plateaus, Mexican plateaus, Arab plateaus, plateaus of Spain and Australia etc.
  • Coastal Plateau : Coromandal coastal upland of India.
  • Young Plateaus : Colorado plateaus, Idaho plateaus ( U.S.A. ) Mahabaleshwar plateaus, Khandala upland ( Maharashtra ).
  • Matures Plateaus : Appalachian plateau, Ranchi plateau, Hazaribag plateau.
  • Old Plateaus : Plateaus are eroded to base level and take the form of plains, Manadnocks appear in the plateaus on account of the erosion.
  • Rejuvinated Plateau : Missouri plateau ( USA ).

Economic Importance
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  • Plateaus and Minerals : The plateaus of France, the Deccan plateaus of India, Western Australian plateaus and Brazilian plateau are very good sources of minerals like Iron, copper, gold, diamond, magnese, coal etc.
  • Plateaus and Climate : Plateaus have cooler climate and those of plains. The new colonies have developed on the plateaus in tropics. The plateaus are desert in temperate latitude. The people live a migratory life.
  • Plateaus and Agriculture : Generally plateaus are not very useful from agricultural point of view but agriculture is promoted where lava soils have developed as fou: J on the terraced slope of Indonesia and Deccan lava plateau. Grasses are the common vegetation on plateaus and various types of animals are reared on it. The plateaus of Australia, Patagonia and South Africa ( Welds ) are well known for rearing of goats and sheeps.

Plains

Plain is an extensive tract of flat land or a gently undulating terrain without prominent hills or depressions. Plains are major centres of population concentration in the world. Their categories are :

  • Diastrophic Plains
    • It must be born in mind that plains are seldom formed by a single process. Hence categorisation of plains is done on the basis of dominant process.
    • Diastrophic forces have played a dominant role in the evolution of Great Plains of USA, hence they are called diastrophic plains.
  • Erosional Plains
    • River Eroded Plains : Peneplains are regarded as the end – product of normal cycle of erosion ( Fluvial cycle of erosion ). A peneplain is an undulating surface of low relief, interspersed, with occasional residual hills, known as Monadnocks.
    • Glaciated Plains : Plains of northern part of North America and western Europe are dominated by the imprints of glacial features. Laddakh plain of India in the east of Shyok river is also a glacial – eroded plain.
    • Wind – Eroded Plain : Wind – eroded plains of Sahara ( Africa ).
    • Karst Plains : Plains of Yugoslavia ( Karst region ), Chitrakoot ( India ).
  • Depositional Plains
  • River – Deposited Plains : These include Piedmont Alluvial Plains formed in the foot hill zones ( e.g. Bhabar & Tarai of Ganga – Yamuna plain ), flood plains formed due to deposition of fine sediments in the flood affected areas and Delta plains at the end of the river course (e.g. Ganga – Brahmaputra delta).
  • Lacustrine Plains : Harmed by the filling up of lakes with sediments. Kashmir valley is regarded as a lacustrine plain.
  • Lava Plains : Formed of thin sheets of lava coming through fissure eruption, e.g. lava plains of Iceland, Argentina, New Zealand, etc.
  • Wind – Deposited Plains : They include sandy desert plains and loess plains, e.g. Thar desert plain, Sahara desert, Loess plain of China.
  • Glacially – Deposited Plains : Plains of North Germany, N.W. Russia, etc. Imphal Basin is an example of Lacustrine plain; Uplifted Peneplains are found in the Applachian region ( USA ) and Chhotanagpur region of Jharkhand ( India ).

Atmosphere

  • Atmosphere : Envelop of gases Surrounding the earth held by gravity.
  • Thickness of Atmosphere : About 480 km ( 300 miles ).
  • Major Gases : Nitrogen – 78.084 %, Oxygen – 20.947 %, Argon – 0.934 %, Co2 – 0.0314 %.

Troposphere

  • Contains 90% gases.
  • Temp deas Tropopause is about – 57°C.
  • 18km at Equator & 13 km at Poles.
  • Vertical decease in temp at tne rate of 6.4°C / 1000m. All weathers phenomena confined to troposphere.

Stratosphere

  • It lies on Tropopause.
  • It has ozone layes which absorbs UV rays.
  • Temp ranges between 57°C & 0°C.
  • Little water vapors.
  • Presence of Jet stream.

Mesosphere

  • 50 to 80 km.
  • Temp falls with elevation.

Thermosphere

  • Above 80km.
  • Temperature increases with height.
  • 100 to 300km – Ionosphere, beyond 300 km is Exosphere.

Inversion of Temperature

  • In the troposphere, temp decreases at the rate of 6.4°C / 1000m this is known as lapse – rate.
  • Contrary to the normal lapse – rate, if the temp increases with the increase in height that is known as inversion of temperature.
  • Inversion of temperature generally occurs in valleys.

Conditions for the Inversion of Temperatures :

  • In winter on calm & clear nigh to.
  • When the sky is clear & anti – cyclone condition prevails.
  • When Callused consider are cooling.
  • When the earth surface is coverlid with ice snow & frost.

High Altitude Invasion : It occurs because of frontal convergence.

Surface Inversions : Localized dependent on terrain. It frequently occurs in winter season, especially in valleys.
General Studies Question Bank CD
{tab=Wind Systems}
Wind Systems

  • On an ideal earth, there is a close relationship between the pressure distribution & wind system.
  • Equatorial low pressure Best ( ITCZ ) : This is known as doldrums N.E & S.E Trade Winds converge on Doldrums.
  • In this Zone, strong heating calluses surface air to expand & rise.
  • The humid, rising – expanding air loses moisture as conventional rainfall ( tropical rain forests ).
  • Doldrums migrates ale out 5°N & 5°S.
  • Subtropical high pressure belts lie adjacent to that outside the Tropic of cancer & Tropic of Caysricon . ( 40°N & 40°S ).
  • They are the regions of anticyclones.
  • The subtropical high pressure belts are however not contiguous. They are lest developed over oceans.
  • In these belts, the are descends. The descending air is generally arid.
  • The great hot deserts are found in both the hemispheres in the subtropical thigh pressure belts.
  • They are called as horse – latitudes.

Low – Pressure Belts

  • The sub – poles low pressure belts lie between 60° & 65° latitudes.
  • They are dynamically produced by the rotation of earth on its axis.
  • The Sub – Poles low – pressure belt is more developed in the Southern Hemisphere.
  • In the Northern Hemisphere, it is more developed on the Aleutian Is & Iceland.

Polar High – Pressure Belts

  • Fbles regions are cold throughout the year.
  • They are the areas of high pressure.
  • The poles winds move outward.
  • Mare developed in caudal & Salsas.
  • The Pressure belts are the bas is for Wind Systems.

Permanent winds or Trade winds

  • The trade winds are the surface winds of the Hadley cell as they move from horse latitudes to the Dol drums.
  • In the Northern Hemisphere, they blow from NE to SW & in the Southern Hemisphere from S.E to NW.
  • Trade winds blow with great regularity on Oceans.
  • Trade winds help in maintaining the global heat balance.
  • With the change in season, the Trade winds move 5°C latitudes.
  • Between the two trade winds, lie the Doldrums.

Westerlies

  • Blow from the subtropical high pressure towards the Poles.
  • In the N. Hemisphere, they blow from SW to N.E & in the S. Hemisphere from NW to SE.
  • In winter, they move southward & in summer north – ward affecting the Mediterranean region.
  • They blow throughout the year.
  • Cyclonic weathers is characteristic.
  • In the S. Hemisphere, they blow with greater strait.
  • Roaring Forties ( between 40°S to 50°S ).

Polar Easterlies

  • They blow from poles arras towards the mid – latitudes.
  • They all more pronounced in S. Hemisphere.
  • In N. Hemisphere they blow from NE to SW & in the S. Hemisphere from NW to SE.

Shifting of Pressure Belts

Summer Solistice ( 21st June ) :

  • The pressure belts move northward ( equator up to 10°N ).
  • Autumn Equator ( 23rd sep ).

Winter solistice ( 23rd Dec ) :

  • The pressure belts move southward.
  • Spring equinox ( 21st march ).
  • The Occurrence of the Mediterranean & Monsoon Climates, are closely influenced by the shift in pressure belts.

Monsoon
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  • Monsoon – An Arabic Word means Mausam ( season ).
  • There is a complete reversal of wind dissection after every six – month.
  • Monsoons are permanents within the tropics on the eastern sides of the continent. But it occurs, too, outside the Tropic in Eastern Asia ( up to 600N in Asia ). S.W. Monsoon moves forward & arrives at each place at approximately the same date, every year.
  • The first sudden rain of Monsoon is known as ‘the burst of the Monsoon’.
  • The relief of the land controls the monsoon.
  • The Monsoon regions of the World : S. E Asia, E. Africa, Central America, Southern Parts of Brazil & Northern coast of South America.

El – Nino Concept

Recent studies have revealed that these seems to be a link between meteorological even to which are separated by long distances & large intervals of time. El Nino is a narrow warm Current which appears off the coast of Pesu in December. In Some years this warm current is more intense than usual. When the surface temp goes up in the southern Pacific Ocean, India received deficient rainfall.

  • Southern Osculation :
    • When the Pressure Was high over equatorial south Pacific, it was lower over the equatorial south Indian Ocean & vise – versa.
    • The Pattern of low & high pressure over Indian & Pacific ocean, gives .. to vertical circulation along the equator with it using limb over low pressure area & descending limb over high pressure area.
    • This is known as walker calculation. The location of low pressure over Indian ocean is considered good for Indian monsoon.
  • Jet Stream
    • Jet Stream is a strong wind blowing from west to east at high altitudes usually near the level of Tropopause ( 12,000 m ).
    • The speed of the jet stream raises between 110km / hr to 190km / hr.
  • Polar Front Jet Stream :
    • Found in the Middle latitudes. It is less steady owing to the transitory thermal contrasts in these latitudes.
  • Arctic Jet Stream :
    • In the N. Hemisphere, the Jet – stream moving equator wed adopts a cryonics curvature ( anti – clockwise ) & clockwise in the S. Hemisphere.
    • The subtropical Jet Stream Presents throughout the year.
    • Jet stream are more pronounced above the Rockies, Andes, Plateaus of central Asia & S. Africa.
    • Jet stream have great effect on the travel time of, air crafts.
    • They influence the development of temperate & topical cyclones & the intensity & failure’ of the monsoon.

Atmospheric Circulation
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  • The Movement of air in the atmosphere is known as atmospheric circulation.
  • Air mass is a distinctive, homogeneous body of air in terms of temperature & humidity that takes on the moisture & temperature Characteristics of its source region.
  • The horizontal extent of an air – mars may be several thousand km & extends upward to the top of the troposphere.
  • Homogeneous temperature & humidity means that the changes over a distance of a distance of about 100 to 200km within the air-mass are very much smaller than the changes we experience where we” go through the border between two ad jaunt masses.
  • The border region is called as frontal zone or front.
  • The temp of air mare may vary from hot to icy cold.
  • The physical characteristics of an air – mass depends on source region.
  • The longer an air – mass remains stationary over a region, the more definite its physical attributes become.
  • In source region air moves slowly or stagnates, which allows the air to acquire temperature & moisture characteristics from the surface.

Local Wind

  • Generated by the variations in local temp., Pressure & humility.
  • Local periodic winds on a diurnal basis which change their direction after every 12 hours.
  • They result when a differential heating takes place within a short distance near the sea – coast.
  • Their air movement is caused either by heating or cooling of a particular area.

Mountain Winds

  • A down fall wind usually cold which blows down valleys at straight & outward from large ice – caps such as Antarctica & Greenland.
  • Since it blows from the mountain, this is termed as mountain breeze.
  • As these winds are cold by morning, they may produce temperature inversion in the valley i.e. the valley becomes colder than hill tops & ridges.

Valley Breeze

  • On warm Sunny days, the heating of mountain, slopes result in the development of low pressure on the peak, ridges & highest slopes.
  • The wind in the day blows from valley to mountains.
  • As the cool valley wind moves upward, it moderates the surface temperatures.
  • In general, mountain winds all strongest than valley winds.

Drainage Winds

  • There local winds blow in the temperate latitudes during the winter season.
  • Brick fielder : Blows from deserts of Australia in Summers.
  • Chili : A hot dry wind which blows from the Sahara Desert to Mediterranean sea.
  • Gibli : Sahara to Mediterranean sea. 38°C to 45″C.
  • Harmattan ( Mali & Niger ) Blows from Sahara towards the Gulf of Guinea. It is hot wind. It provides relief from moist heat. It is known as “Doctor”.
  • Karabuen ( Tarim basin of China ) Blows from March to July. Hazy weathers, helps in loess deposits of china.
  • Khamsin : ( Egypt ) : hot wind blows for 50 days ( April to June ).
  • Loo ( N.W India ) : Blows from Sahara desert towards Malta & Sicily April to July. It becomes hot & humid.
  • Zonda ( Argentina & Uruguay ) : A warm & dry wind.
  • Blizzard ( Greenland, Canada, Antarctica ) : Intensely cold, high wind, accompanied by following show, visibility reduced.
  • Pampers ( Pampas of Argentina ) : It is a cold wind.
  • Descending Winds
  • Berg ( Germany, descends from Aips Mts. ) : hot & dry, leads to irritation & impact.
  • Fohn : Blows northward from the Aips Mts, in the Upper Rhine Valley.
  • Chinook ( Show & Ice eater ) : blows in USA & Canada.
  • Period : Dec to April. Warm & dry. It melt snow & Ice.
  • Samoon ( Iran & Kurdistan ) : Hot. & Dry.
  • Anadhi ( Dust Storm ) : N.W. India.
  • Haboob ( Sudan ) : Hot Wind.
  • Simoom ( S. Arabia ) : Hot Wind.

Rainfall
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The meteorologists & Climatologic have classified the rainfall into 3 categories.

I. Conventional Rainfall

  • When the surface layer of the troposphere is heated, the moisture ladu air rises in convection current. While ascending, it is cooled the deuce – point, therelry forming clouds which generate heavy torrential rainfall.
  • Conventional rainfall generally occurs in the equatorial region.
  • Occasionally, it may occur in the temperate regions in the afternoon of summer season.
  • Convectional rainfall is associated with thunders & lightening.
  • It occurs throughout the yeas.

II. Orographic Rainfall

  • Rainfall which is caused by the mountain standing in the path of moisture laden air is orographic rainfall. The moisture laden air is forced to sise which gets cool idealistically.
  • There is a pronounced difference in the amount of rainfall on the windward & leeward rider.
  • The Monsoonic rainfall is of this type.
  • It is highly erratic & variable.
  • In developing countries, agriculture is largely controlled by orographic rainfall.

III. Cyclonic Rainfall

  • It generally occurs in the temperate latitudes.
  • Rainfall, generally, in the form of drizzle from warm front, heavies from cold front.
  • Hydrological cycle
  • This cycle is a simplified model of the flow of movement exchange & storage of the earth’s free water in gaseous state, liquid state & solid state.
  • More than 97% of the earth’s water is in ocean.
  • Precipitation on Ocean – 78 %.
  • Precipitation on land – 22 %.
  • Evaporation from ocean including water moving from the soil into plants moots & passing through their leaves ( transpiration ) – 86 %.
  • Evaporation from land – 14 %.
  • Global average evaporation – 86 % + 14 % = 100 % Equals all precipitation ( 78 % + 22 % = 100 % ).
  • Hydrological cycle is on intricate combination of evaporation, transpiration, air mass movements, condensation, precipitation, nin – off & groundwater movement.

Cyclones Types

  • Temperate Cyclones
  • Tropical cyclones
  • Temperate cyclones ( low pressure systems of the temperate latitudes ).
  • Isobars are queasily dongated or oval shaped.
  • The size ( diameter ) may be 150 – 300 km ( 100 – 200 miles ) & even more..
  • Speed : it may be practically stationary or moving at a speed of 900 – 1000 km per day.
  • They originate where warm tropical air – mass meets cold polar air.
  • General direction of movement is from west to East.

Fogginess & Poor Visibility

  • Feue house after the front has passed, clean weather ( anti – cyclone ) prevails.
  • Weather Associated with Temperate Cyclones.
  • Appearance of cirrus in western horizon.
  • As the front approach the cloud lower & thicker to cirro – stratus, then nimbo – stratus.
  • Rainfall occurs in drizzle, which may continue for two to three days.
  • At the advent of cold front, there is rapid fall in temperature, rainfall occurs in heavy showers & the wind blows from north to east or westerly.
  • Thunder & lightening are indications of the end of cyclone.
  • Geographical Distribution of Temperate Cyclones.

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