Geography(Part i)

8/3/2019 Geography(Part i)

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IAS OUR DREAM

Authored by: NISHA DOLAS

GEOGRAPHY

TOPICTOPICSTOPICTOPICS

----------------------- Branches Of GeographyBranches Of GeographyBranches Of GeographyBranches Of Geography

Earth In UniverseEarth In UniverseEarth In UniverseEarth In Universe

Structure Of The Atmosphere

Physiographic Of India

Ocean AndOcean AndOcean AndOcean And OceanographyOceanographyOceanographyOceanography


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APPROACHES

A Greek scholars Eratosthenes is considered to have been the first to use theterm geography.

According to Hartshorne, geography is concerned with providing accurate,orderly and rational description and interpretation of variable character of earthsurface.

Three essential characteristics of geographical work, acc to Haggett1. Emphasis on location, cartography (making maps) is an imp tools

2. Emphasis on society- land relations, environmental effects on humans,changes of environment brought about by human intervention3. Regional analysis, involving identification of regions, analysis of their internalmorphology

Regional Geography- a region at different scales a continent, a country, a localarea is studied in all its geographical aspects.

Systematic Geography- in the other aspect, any particular theme or element ofthe system is chosen, say climate and analyzed systematically6 over the earthsurface or a large part of it -with the idea of identifying the general law of itsprevalence over the globe.

The two approaches are complementary.


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BRANCHESBRANCHESBRANCHESBRANCHESOFOFOFOFGEOGRAPHYGEOGRAPHYGEOGRAPHYGEOGRAPHY

PHYSICAL GEOGRAPHY: concerned with natural features such as

land, water and climate, these features are and in relationship with one anotheras well as with human activities.Subdivided into

I. Geomorphology- concerned with landforms, their distribution andorigin : studies the relationship between landforms and human activities

II. Climatology : making of weather and climate, changes in climate ndhow climate is affected by human activity

III. Hydrology :earths water- ocean, rivers, glaciersIV. IV. Oceanography: study of ocean ,study of shape, depth and

distribution of ocean, life forms, ecology and currents, besides the legalstatus of ocean

V. V. Soil geography: deals with kinds of soils, their evolution andDistribution

HUMAN GEOGRAPHY: concerned with the earth features created byhuman action in the course of contriving to build and improve habitats to live incomfort and security.Subfields of human geomorphology

I. Cultural Geography: deals with the location and diffusion of beliefs,customs and other cultural traits.

II. Social Geography: close to cultural Geography, examines relationshipamong groups of people

III. Economic geography: deals with the location and distribution of economic

activitiesIV. Population geography: concerned with pattern of population and the reasonsfor a change in those patterns.V. urban geography: concerned with cities and other urban areas examining theimp of location; study the distribution of various groups within a city


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VI. Political geography: concerned with relations between independent states,frontiers, boundaries, problems of political instability, pattern of voting andregional planningVII. Historical Geography: concerned with the geography forces that have caused

the changesVIII. Anthrogeography: distribution of human communities on earth in relationto their geographical environmentIX. Agricultural Geography: studies the development of different kinds of farmsand farming systems in particular areas and compares them with the farms andfarming systems of other areas

Other two imp branches

MATHEMATICAL GEOGRAPHY: study of earths shape and size, of

time zones and of the motion of earth

CARTOGRAPHY: study of maps and charts, responsible for geodetic and

topographical surveys and the preparation of maps on certain selected scales


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EEEEARTH INARTH INARTH INARTH IN

Earth, the planet on whichlying with its satellite betwtaking into account an 18-depression at the South Polsize among the nine planets

HEHEHEHE UUUUNIVERSENIVERSENIVERSENIVERSE

e live, is the third planet outward froen Venus and Mars. The earth is an obletre rise at the North Pole and a 26-me

e, it may be called pear-shaped. It is fift.

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the sun,ate spheroid;trein order of


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EEEEARTHARTHARTHARTH DDDDATAATAATAATA

Age: At least 4.5 billion years

Motion: Rotation (spinning motion around an imaginary line connecting theNorth and South Pole) once every 23hours, 56 minutes. 4.09seconds. revolution(motion around the sun) once every 365days 6hours, 9minutes, 9.54 seconds.

Size: polar diameters (distance through the Earth from North Pole to SouthPole) 12713.54 kms. Equatorial diameter (distance through the earth at theequator) 12756.32kms. Polar circumference (distance around the earththrough Poles) 40008.00kms. Equatorial circumference (distance around theearth along the equator) 40075.16kms

Area: Total surface area 509,700,000square kms. Land area approximately148,400,000 square kms, about 29per cent of total surface area. Water area approximately 361,300,000 square kms, about 71 per cent of total surface area.

Mass: 5.882____tonnes

Mean density: 5.517

Surface features: Highest Land- Mount Everest, 8848 metres above sealevel. Lowest Land- shore of Dead Sea, about 399 metres below the sea level

Ocean depths: Deepest part of ocean area of the Marina Trench in PacificOcean southwest of Guam, 11033 metres below surface. Average ocean depth 3730 metres.

Temperature: Highest more than 99 %of the atmosphere is less than 80kms above the earths surface, but particles of the atmosphere are 1600 kmsabove the surface. Regions of atmosphere troposphere (up to 10or 16 kmsabove surface ); stratosphere( from about 48 to about 80kms); thermosphere(from 80kms into outer space)

Chemical make-up of atmosphere about 78 % nitrogen, 21 %oxygen, 1 % argon, and small amounts of other gases.

Chemical make-up of earths crust( in per cent of the crusts weight) :oxygen 46.6; silicon 27.7; aluminum 8.1; iron 5.0; calcium 3.6; sodium 2.8;magnesium 2.0; and other elements totaling 1.6


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IIIINTERIOR OF THENTERIOR OF THENTERIOR OF THENTERIOR OF THE EEEEARTHARTHARTHARTH

Layer Chemical composition Physical property

Crust or Lithosphere

I. Outer or upperpart

SIAL( silica and alumina) sedimentary andgranitic rocks Silica

Solid

II. Inner or outerpart

Silica Partly molten

Mantle or Mesosphere

I. Inner orsilicate layer

Partly SIMA( silica andmagnesium) basic rocks

Some properties of asolid and some like those

of plastic materialII. Transitionalzone of mixedmetal and silicates

Wholly SIMA( ultra-basicrocks )

Core or Barysphere

I. Outer metalliccore

NIFE nickel (NI)andiron(Fe)

Liquid or in plastic state

II. Inner metallic

core

Barysphere (heavy

metallic rocks )


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SSSSTRUCTURE OF THE ATMOTRUCTURE OF THE ATMOTRUCTURE OF THE ATMOTRUCTURE OF THE ATMOSPHERESPHERESPHERESPHERE

Principal layers

Earth's atmosphere can be divided into five main layers. These layers are mainlydetermined by whether temperature increases or decrease with altitude. From

highest to lowest, these layers are:

ExosphereThe outermost layer of Earth's atmosphere extends from the exobase upward. Here

the particles are so far apart that they can travel hundreds of km without collidingwith one another. Since the particles rarely collide, the atmosphere no longerbehaves like a fluid. These free-moving particles follow ballistic trajectories and

may migrate into and out of the magnetosphere or the solar wind. The exosphere ismainly composed of hydrogen and helium.

ThermosphereTemperature increases with height in the thermosphere from the mesopause bup tothe thermopause then is constant with height. The temperature of this layer can rise

to 1,500 C (2,730 F), though the gas molecules are so far apart that temperaturein the usual sense is not well defined. The International Space Station orbits in this

layer, between 320 and 380 km (200 and 240 mi). The top of the thermosphere isthe bottom of the exosphere, called the exobase. Its height varies with solar activity

and ranges from about 350800 km (220500 mi; 1,100,0002,600,000 ft).

MesosphereThe mesosphere extends from the stratopause to 8085 km (5053 mi; 260,000

280,000 ft). It is the layer where most meteors burn up upon entering the

atmosphere. Temperature decreases with height in the mesosphere. Themesopause, the temperature minimum that marks the top of the mesosphere, is the

coldest place on Earth and has an average temperature around 100 C (148.0 F;173.1 K).

StratosphereThe stratosphere extends from the tropopause to about 51 km (32 mi; 170,000 ft).Temperature increases with height, which restricts turbulence and mixing. The

stratopause, which is the boundary between the stratosphere and mesosphere,typically is at 50 to 55 km (31 to 34 mi; 160,000 to 180,000 ft). The pressure here

is 1/1000th sea level.


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TroposphereThe troposphere begins at the surface and extends to between 7 km (23,000 ft) atthe poles and 17 km (56,000 ft) at the equator, with some variation due to weather.

The troposphere is mostly heated by transfer of energy from the surface, so onaverage the lowest part of the troposphere is warmest and temperature decreases

with altitude. This promotes vertical mixing (hence the origin of its name in theGreek word "", trope, meaning turn or overturn). The troposphere containsroughly 80% of the mass of the atmosphere. The tropopause is the boundarybetween the troposphere and stratosphere.

Other layersWithin the five principal layers determined by temperature are several layersdetermined by other properties.

The ozone layer is contained within the stratosphere. In this layer ozoneconcentrations are about 2 to 8 parts per million, which is much higher than in the

lower atmosphere but still very small compared to the main components of theatmosphere. It is mainly located in the lower portion of the stratosphere from about

1535 km (9.322 mi; 49,000110,000 ft), though the thickness varies seasonallyand geographically. About 90% of the ozone in our atmosphere is contained in the

stratosphere.

The ionosphere, the part of the atmosphere that is ionized by solar radiation,stretches from 50 to 1,000 km (31 to 620 mi; 160,000 to 3,300,000 ft) and typically

overlaps both the exosphere and the thermosphere. It forms the inner edge of themagnetosphere. It has practical importance because it influences, for example,

radio propagation on the Earth. It is responsible for auroras.

The homosphere and heterosphere are defined by whether the atmospheric gases

are well mixed. In the homosphere the chemical composition of the atmospheredoes not depend on molecular weight because the gases are mixed by turbulence.[3]The homosphere includes the troposphere, stratosphere, and mesosphere. Above

the turbopause at about 100 km (62 mi; 330,000 ft) (essentially corresponding tothe mesopause), the composition varies with altitude. This is because the distancethat particles can move without colliding with one another is large compared with

the size of motions that cause mixing. This allows the gases to stratify bymolecular weight, with the heavier ones such as oxygen and nitrogen present only

near the bottom of the heterosphere. The upper part of the heterosphere iscomposed almost completely of hydrogen, the lightest element.


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The planetary boundary laEarth's surface and is directl

During the day the planetarbecomes stably stratified wi

planetary boundary layer rato 3000 m or more during th

er is the part of the troposphere that is ny affected by it, mainly through turbulen

boundary layer usually is well mixed,h weak or intermittent mixing. The dept

ges from as little as about 100 m on cleae afternoon in dry regions.

arest thediffusion.

hile at night itof the

r, calm nights


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PPPPHYSIOGRAPHIC OFHYSIOGRAPHIC OFHYSIOGRAPHIC OFHYSIOGRAPHIC OF IIIINDIANDIANDIANDIA

India is a land of diversities. Great mountains, rivers, wide plateaus and plains,

lengthy coastlines etc., constitute the topography of our country. It has a monsoonclimate with local and seasonal climatic diversities. We shall look at thetopography, rivers and climate of our country. Physiographically, India can be

classified into four divisions.

_ The Northern mountain region_ The Great Plains of the north_ The Peninsular plateau_ The Coastal plains and Islands

The Northern mountain regionThis is the great wall like physiographic unit, which stretches from Kashmir in the

North West to the Indian border in the east. This region is formed by theKarakoram, Ladakh, Zaskar and the Himalayan range of mountains and the eastern

highlands. These mountain ranges are subdivided into three divisions namely,Trans Himalayas, Himalayas and the Eastern Highlands. The Trans Himalayas

comprises the Karakoram, Ladakh and Zaskar ranges that originate from the Pamir

Knot. The highest peak in India, Mount K2 (Mt. Godwin Austin, 8611m) is in theKarakoram Range. The Trans Himalayas, in which there are several gorges and

mountain passes, has an average height of above 6000m.


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THE ROOF OF THE WORLD

The Pamir plateau with the Pamir Knot in the central Asian country ofTajikisthan is known as the roof of the world. Mountain ranges such as theHindukush, Sulaiman, Tienshan, Kunlun and Karakoram run to different

directions from the Pamir Knot. The Kailas range in Tibet is an extension ofthe Karakoram Range.

The Himalayas, a part of the Northern mountain region, which trend in NW-SE

direction for a length of about 2400km is an arc shaped mountain range. Thismountain region with an area of about 5 lakh km2 is the highest region in the

world. The width of this mountain range is about 400km in Kashmir, and it shrinksto 150 km in Arunachal Pradesh. There are three parallel mountain ranges in this

physical division, which is composed of many deep valleys and extensive plateaus.

The Himalayas, still growing!

Himalaya means the abode of snow. It is the youngest fold mountainsystem of the world. These mountain ranges are formed due to theintensive folding of the floor of an ancient sea called Tethys. The fossils ofdifferent marine organisms, found at various locations on the mountainranges support the fact that the region was covered by sea in the past.

The height of the mountain ranges gradually decreases as they approach the eastern

parts of the Northern mountainous regions. This region with an average height of

500m to 3000m above MSL is known as the Eastern highlands (Purvachal). Thethickly forested Khasi-Jaintia hills in this region are the worlds rainiest (wettest)spots.

Greater/InnerHimalayas

Lesser/MiddleHimalayas

Outer/Lower Himalayas

*The highest mountain

range of the Himalayas.

*Under perpetual snow,

these ranges have anaverage height of about

6000m.

*Mountain peaks with aheight of more than

8000m are situated in

this

*Situated to the south of

the Himadri

*Average height is

above 3000m*Many health resortsare

situated on the southern

slope of the mountain

range, eg: Shimla,

Darjeeling.

*This is the outer mostrange, situated on the

south of the lesser

Himalayas.*These discontinuousranges join the lesser

Himalayas in the

extreme east.

*Its average height isabout 1200m


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mountain range. (Eg:

Kanchenjunga- 8595 m,

Nangaparbat- 8126m)

*The source of Ganges

and Yamuna

*There are severalelongated and flat

valleys running parallel

to the mountain ranges.

They are called duns.(Eg:

Dehradun)

Himalayan Rivers

The snow clad peaks and glaciers are excellent sources of fresh water. Severalgreat river systems originate from the melt waters of these glaciers. Abundant rain

fall in the valleys enriches the flow of these rivers.

Tributaries and distributariesTributaries are those small and big streams that join a river. Upon reachinga plain the rivers branch out and join the sea. These branches are calleddistributaries.

River IndusOriginating at a height of about 5180m from the Manasarowar in Tibet, RiverIndus flows northwest through Tibet and enters Jammu and Kashmir. Flowing

through the deep valleys of Ladakh, Baltistan and Gilgit, River Indus crosses the

Indian border and reaches the plains through Attok in Pakistan. Having a length ofabout 2880 km, it is one of the longest rivers of the world. Only a length of 709 kmof the river is in India. Flowing through the plains of Pakistan, Indus branches out

into many distributaries and merges with the Arabian sea to the south of Karachi.Jhelum, Chenab, Ravi, Beas and Sutlej are the important tributaries of the Indus.

River GangaThe river Bhagirathi, which originates from the Gaumukh caves of the GangotriGlacier and the river Alaknanda, which originates from the Alakpuri glacier meet

at Devaprayag and flows further as the Ganga. Flowing through the snow-cladvalleys, it enters the plains at Hardwar and becomes sluggish. After flowing

through different states the river flows southeast and enters Bangladesh at

Farrakkain West Bengal. The Ganga, with a length of more than 2500 km is theriver with the largest number of tributaries in India. Important tributaries of the

Ganga are Yamuna Son Ghaghara Kosi Gandak.


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Hooghly is an important distributary of the river Ganga. Kolkata city issituated on the banks of the river Hooghly. The river Damodar is atributary of the river Hooghly.

The river Damodar is known as "Sorrow of Bengal". This is because of thesevere threat it posed to the life and property due to the frequent floods andchange in river course. The construction of dams across the river Damodarhas mitigated this havoc to a considerable extent. The Ganga is known asPadma in Bangladesh.The river Padma joins the Brahmaputra near Chandpur inBangladesh and isknown as Meghna and Jamuna. Later it flows as a number ofdistributaries andbuilds an extensive delta. It then merges into the Bay of Bengal.

Farrakka Barrage

It was with the aim of developing water transport in Hooghly river that

the Government of India decided to construct a barrage across theriver Ganga. The barrage, which was completed in May 1986, has alength of 2240 m. The barrage is bridged with rail and road. Therailway that connects the Eastern states with Kolkata passes over thisbarrage. Travelling by train over the roaring greatness of the riverGanga is an unforgettable experience.

River BrahmaputraThe Chemayungdung glacier (5150m) on the Kailas range about 100 km from the

Manasarowar Lake in Tibet is the source of the river Brahmaputra. Having a lengthof 2900 km, the Brahmaputra is one of the longest rivers of the world. This river,

which is known by different names in Tibet and Bangladesh, has a length of 725km in India. The river Tista, river Manas, river Luhit and river Subansiri are the

major tributaries. With the maximum discharge among the Himalayan Rivers,Brahmaputra causes severe floods in Assam and Bangladesh

THE RED RIVER OF INDIA

The Brahmaputra is also known as the red river of India. It's red colour isdue to the suspension of red soils of Assam. Brahmaputra is known as

Tsangpo in Tibet and Jamuna in Bangladesh.

The disappeared River Saraswathi


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Saraswathi was an ancient river, which originated from Himachal Pradeshand flowed to the south and then to the southwest direction. The riverwhich is mentioned in the Rig Veda remains totally disappeared. Studies,with the

help of satellite imageries indicate that the river still flows, beneath theground!

Water way on mountains!

Ferries and boats of bamboo and leather are in use at a height of 3658 mabove MSL. This is a spectacular scene in Brahmaputra River in theTibetan region. This waterway has a length of670 km.

In the mountainous zone, deep valleys have been formed due to soil erosion forcenturies by rivers that originate from the Himalayas. These valleys break the

continuity of the Himalayas. The Himalayas are divided into different divisions.The regions from one river bank to other have different names too.

From River Indus to River Sutlej Punjab Himalaya

From River Sutlej to River Kali Kumaon Himalaya

From River Kali to River Tista Nepal Himalaya

From River Tista to River Brahmaputra-Assam Himalaya

Northern Great PlainsExtensive plains have been formed due to the continuous depositional activity ofthe Himalayan Rivers. With several thousand kilometers of thickness, the Northern

Great Plains spread out to about 7 lakhs km2. This plain is one of the world's mostextensive alluvial plains.

Northern mountain zone Northern Great Plains*Stands as a natural barrier in the northern part ofIndia

*Prevents foreign invasion to a certain extent

*Supports an indigenous culture* Protects India from the cold winds blowingfrom the northern parts of Asia

*Obstruct south western monsoon winds andprovides rain throughout India

* Forms the source of several rivers*This region has a remarkable role in the

*This is the birth place ofIndian culture

*It forms the backbone of

Indian agriculture* One of the worlds mostdensely populated regions

* Many metropolitan cities andindustrial Centres are situated

in this zone.

*There is an extensive network


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formation of the Northern Great Plains, which is

the food bowl of India

*It is the abode of diverse animal n plant species.*This region with cool climate and serene natureis a heaven for tourists

of rail and road system in this

zone

Peninsular PlateauThe peninsular plateau is a landmass believed to have got separated from theancient Gondwanaland. This zone is built of stable rocks and is the most extensive

physiographic division of India. Note the characteristic features of the peninsularplateau given below.

This physiographic division has an area of about 15 lakh km2

It has a diverse topography of mountains, plateaus and valleys

The plateaus of this physiographic division has an average altitude of above

400m from mean sea level. Anamudi with a height of 2695m is the highest peak in this zone

Most of the rivers that originate from this zone flow towards the east

There are large deposits of different minerals occur in this zone

Based on the uniqueness of the different regions, the peninsular plateau hasbeen divided into nine subdivisions. The Aravalli hills, Malwa plateau,Vindhya ranges,

Satpura ranges, the Chotta Nagpur plateau, the Deccan plateau, the WesternGhats, the Eastern Ghats, the Kachchh and Kathiawar of Gujarat are these

subdivisions. Many small and large hills and plateaus are also included inthese subdivisions

Deccan Trap RegionThe northwestern part of the Deccan plateau was formed due to thecooling down of lava from volcanic eruption hat occurred millions ofyears ago. Formed out of igneous rocks, this region is known as theDeccan Trap. Black soils have developed as a result of weathering ofrocks in the lava plateau, one of the largest in the world. This black

soil, also known as regur (black cotton soil) is most suitable forcotton cultivation.


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Rann of Kachchh

The brackish swampy region in the northwestern part of Gujarat is calledthe Rann of Kachchh. High tides from the Arabian Sea and the rivers Luniand Banas, inundate this region. There are two different divisions in the

Rann of Kachchh, namely the Great Rann and the Little Rann. The GreatRann which is situated to the north of the Kachchh peninsula is a regionfilled by black sedimentary deposits and salts.

Peninsular RiversOriginating from the Peninsular Plateau, rivers Chambal, Betwa,Kenand Sind flow towards the north and join the Yamuna and theriver Son joins the River Ganga. When compared to other peninsularrivers, these rivers are comparatively smaller in length.

River Source Length Majortributaries

The sea towhich itmerges

Mahanadi Maikala Ranges(Madhya

Pradesh)

857 km Ib, Tel Bay ofBengal

Godavari Western Ghats(Nasik district of

Maharashtra)

1465 km Indravati,Sabari

Bay ofBengal

Krishna Western Ghats (aspring to the northof Mahabaleshwar

in Maharashtra)

1400 km Bhima,Tungabhadra

Bay of

Bengal

Cauvery Western Ghats(Brahmagiri hills in

Coorg district ofKarnataka)

800 km Kabani,Amaravati

Bay ofBengal

Narmada Maikalaranges(Chhattisgarh) 1312 km Hiran, Bajan Arabian Sea

Tapti Multai plateau(Betul district of

Madhya Pradesh)

724 km Aanar, Girna Arabian Sea


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Himalayan Rivers Peninsular Rivers* Extensive catchment area* Rain fed and snow fed

* High erosive capability* Develop gorges in the mountains andMeanders in the plains

*Inland navigation is possible in theplains.

*Comparatively small catchment area

* Rainfed

* Low erosive capability* Deep valleys are not produced as theyFlow through hard crystalline rocks

*Less chances for inland navigation

Coasts and IslandsExtending from the Rann of Kachchh in Gujarat to the Ganga-Brahmaputra delta,it has a length of about 6083 km and lies divided into the west and the east coasts.

West Coast East Coast*Between Arabian Sea and WesternGhats

*Stretches from Rann of Kachchh toKanyakumari.

*Comparatively narrow* Divided into Gujarat coastal plain,Konkan coast and Malabar coast

* Lagoons and estuaries are formed in

the west coast* Highly influenced by the south westmonsoon

*Between Eastern Ghats and Bay ofBengal

* Stretches from Sundarbans toKanyakumari.

* Comparatively wider*Divided into Coromondel coast andNorth Sircar coastal plains

*Deltas are formed in this coastal

stretch*Influenced by north east monsoons

IslandsThere are many islands situated in the Indian Ocean, which form part of ourcountry. These are distributed in the Bay of Bengal, Arabian Sea and in the Gulf of

Mannar, between India and Sri Lanka. Lakshadweep means a hundred thousand

islands. But, there are only 36 coral islands present in this group of islands. Onlyten islands in the group have been inhabited. This group of islands is situated about300 km away from the Kerala coast. Kavarati is the capital of Lakshadweep.

Known as Bay Islands, the Andaman and Nicobar islands are located in the Bay ofBengal. There are about 200 islands, in this group the majority of which are

uninhibited. The Barren volcano is situated in the Barren Island of this islandgroup.=


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OCEANOCEANOCEANOCEANANDANDANDANDOCEANOGRAPHYOCEANOGRAPHYOCEANOGRAPHYOCEANOGRAPHY

The ocean floor can be divided into four major divisions.

Continental Shelf: the continental shelf is gently sloping part of continent that lie

submerged below the sea.

Average width: 70km and Average Depth: 200mIn all, the continental shelves cover about 7.5 % of total area of the oceanNorth Sea and The Baltic Sea - lie on the continental shelf, known as epicontinentalor shelf seas

About 20% of the world production of petroleum and gas comes from shelves.

Continental Slope: that descends from the edge of the continental shelf to the deep

sea platform.

Continental Rise: where the continental slopes ends, the rise Continental begins.Continental Rise has an average slope of between 0.5 to1 and its general relief is low.

Abyssal Plain: are the areas of deep ocean floor found at depth of 3000 to6000metres. they occupy about 40% of the ocean floor.

Ocean Facts

Pacific Ocean- name was coined by Ferdinand Magellan.Shape: roughly triangular with the apex in the north at the Bering StraitDeepest part: North PacificDeepest trench: the Mariana off the Guam Islands; most of the islands are of volcanic orcoral origin.

Atlantic OceanShape: resembles the latter SStriking feature: presence of Mid- Atlantic Ridge which divides the Atlantic into two deeperbasins on either side.The Atlantic Ocean has less troughs and trenches than the Pacific Ocean.Of all the oceans, the Atlantic Ocean has longest coastlines.


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Indian Ocean: considered half ocean, because, unlike the Pacific Ocean andAtlantic Ocean, it does not open out northward into Arctic Ocean. Most of theislands in the Indian Ocean represent detached parts of the continental blocks.The Lakshadweep and Maldives Islands in the Indian Ocean are coral Islands, while

the Mauritius and Reunion Island to the east of Madagascar is of volcanic origin.

MAJOR OCEAN CURRENTSName Types Description

PACIFIC OCEANNORTHEQUATORIALCURRENT

warm current flows westwards in north of theequator ,produced by north east trades

SOUTHEQUATORIALCURRENT

warm current flows westwards in south of the

equator south east tradesKURO SIWACURRENT

/KUROSHIO/JAPANCURRENT

warm current north east trades winds blow the northequatorial current off the coasts of thePhilippines and Formosa into EastChina sea as Kuro Siwa Current

NORTH PACIFICCURRENT

warm current from the south-east coast of Japan thecurrent flows right across the oceanfrom west to east

ALASKA CURRENT cold current flows anti-clock wise along the coast of

British Columbia and Alaska , branchof north Pacific current

CALIFORNIANCURRENT

cold current flows southwards along the Pacificcoastline , caused by upwelling g ofcolder water from greater depths dueto the southward deflection of thenorth Pacific current, joins northequatorial current

PERU/HUMBOLDTCURRENT

cold current reaching the south western coast of

South America, the South Pacificcurrents turns northward as Perucurrent

COUNTEREQUATORIALCURRENT

Between the north and south equatorial current, a currentflows from west to east

OYA SIWA OROYASHIO

The cold Alaska current/Bering strait current creeps


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INDIAN OCEANSOUTH WESTMONSOON DRIFT

in summer ,when the dominant wind is the south-westmonsoon

NORTH EASTMONSOON DRIFT in winter , when the dominant wind is the north-eastmonsoonWEST WINDDRIFT

cold current ;one of the branches of this current turns northwardsalong the west coast of Australia- known asAUSTRALIAN CURRENT

SOUTHEQUATORIALCURRENTS

include the Agulhas current and Mozambique current

Geography(Part i)

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