Alexander VonHumboldt, consideredto be the foundingfather of physicalgeography

Carl Ritter -considered to be oneof the founding fathersof modern geography

Physical geographyPhysical geography focuses ongeography as an Earth science(and is sometimes called EarthSystem Science).

The word 'geography' derivesfrom the greek words ‘geo’(meaning 'the earth') and“graphia” (meaning 'to write').Geography is the science thatdeals with the description ofEarth’s surface.

World Day of Water .................................................

March 22

World Environment Day ............................................... June 5

Earth Day ..................................................

................ April 22

World Meteorological Day ....................................... March 23

World Solar Energy Day ............................................... May 3

World Environment Day ............................................... June 5

World Food Day ..................................................

.. October 16

World Forestry Day .................................................

March 21

World Habitat Day ............................... Ist Monday in October

World Standard Day .............................................. October 14

World Animal Welfare Day ..................................... October 4

PHYSICAL GEOGRAPHY

For hundreds of millions of years, all theland of Earth was joined together in onelarge mass or super continent. Scientistscall it Pangaea (meaning "all lands" inGreek)..

Then about 200 million years ago theland began to drift apart. It broke intotwo pieces, and scientists have calledthe continent in the North Laurasia andthe continent in the SouthGondwanaland.

The two large continents continued tobreak apart into the smaller continents

Gondwanalandthat exist today. Scientists call this move-ment 'continental drift'.

It included most of the landmasses in today'ssouthern hemisphere, including Antarctica,South America, Africa, Madagascar, Austra-lia-New Guinea, and New Zealand, as well asArabia and the Indian subcontinent.

Gondwanaland was named by Eduard Suess,an Austrian geologist.

Gondwanaland was a hot and dry place withrainy seasons. The first tree ferns and conif-erous trees appeared there. Dinosaurs livedthere at one time too.

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Physical Geography

Geomorphology studies the Earth’sstructure, the rocks that make upthe earth, relief features likemountains and plains and theirevolution.

Hydrology is the study of themovement, distribution and qualityof water throughout the earth.

Oceanography is the study ofocean currents, waves and tides.

Climatology is the study of climaticfeatures such as temperature,precipitation and humidity.

Biogeography is the science thatdeals with the distribution of floraand fauna in different parts of theworld.

Pedology is the study of soils andsoil formation.

Paleontology is the study of fossils.

Cartography: Deals with the pro-duction and study of maps andcharts.

Chorology : Study of geographi-cal areas, plants and animal distri-bution.

Demography : Described as popu-lation geography, it examines thestructure of human populations andtheir dynamic aspects.

Lithology: Deals with the charac-teristics of rocks.

Geology: Study of the chemicalcomposition of earth’s crust.

Potamology: Study of rivers.

Orology: Study of mountains.

Petrology: Study of the origin, com-position and structure of rocks.

The Origin of theEarth

Most of the theories concerned withthe origin of the earth emphasise thatthe planet originated as a hot gaseousmass, which on cooling, turned firstinto a liquid and then into a solid mass.

Continental drift theoryContinental Drift Theory was put for-ward by the German scientist AlfredWegner in 1915. According to the Con-tinental Drift Theory, part of the crustare capable of horizontal movementround the globe causing the conti-nents to slowly change their positionsin relation to one another.

The fact that South America is amirror image of Africa is presented asa proof of the continental drift theory.

Plate Tectonics TheoryPlate tectonics theory was put forward by A.Holmes. According tothis theory the lithosphere of earth is considered to be divided intolithospheric plates. Each plate is capable of moving over theasthenosphere carrying oceanic or continental crust alike. At plateboundaries major landforms are created.

Most theories about the origin of the earth assumes that it began ina gaseous state.

Life appeared on earth only when the earth cooled from its gaseousstate to solid one.

Carbon dating is the most important method for estimating the age offossils found in the rocks of the earth's crust.

The age of the earth is estimated to be about 4.6 billion years.

Alfred Lothar Wegener(1880 – 1930)

Wegener was a German interdisciplinaryscientist and meteorologist, who becamefamous for his theory of continentaldrift.

Structure of Earth1. Crust :This is the outer layer of the Earth varying between 5 to 50 km in depth under the surface of the

earth.2. Mantle: This portion is made up of iron and magnesium silicates, with temperature ranging up to 16000

C and extends downwords to a depth of about 1000 km. The thickness of the lower mantle is about 1900km.

3. Core: The outer core, approximately 2100 km thick, consists of molten iron and nickel with temperaturesranging between 20000 C and 50000 C. Below this is the solid inner core which has diameter of 2,740 km.

Crust is the outermost andthinnest layer of the earth’ssurface.

The crust comprises about 5%of the earth body.

Thickness of the crust is moreunder the continents and lesserunder oceans.

The outermost layer of thecrust is composed of lightersilicates termed as sial (Silica+ Aluminium).

Moho or Mohorovicic discon-tinuity separates crust frommantle.

The average density of thislayer is 2.7

The Mantle a layer betweencrust and the core.

Mantle contains 83% of thetotal volume and 68% of thetotal mass of the earth. Aver-age density of this layer is 5.68.

Place of the Earth in the UniverseTwo theories have been given to locate the earth’s position in

the universe. These are Geocentric theory and Helio centric theory.Geocentric TheoryThis theory prevailed in ancient and middle ages. According tothis theory, the earth is located in the centre of the universe andall the planets revolves around it.Heliocentric theory

This theory states that the sun is the centre and all the planetsincluding the earth revolves around it.

Mantle is separated from thecore by Gutenberg discontinu-ity.

It is largely composed of sili-con and magnesium calledsima.

The rocks in this layer may bein the glassy state.

Core is the central region ofthe earth.

It is 3475 km in radius.

By volume, it is 16% of theearth body .

By mass, it constitutes 32%of the mass of the earth.

The temperature of the innercore is 60000 C - 70000 C

The inner core is composed ofNiFe (Ni for Nickel Fe for Iron.).

Density of this part is 17.2. Average density of earth is

5.53.

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The EarthAge : 4.6 billion yearsMass : 5.976 ×1024 kg.Volume : 1.083 × 1024 litresMean Density : 5.518 kg/litresShape : An oblate spheroid or a geoid.Size : Polar diameter 12,713.54 km;

Equatorial diameter 12,756,32 km;Polar circumference 40,008.00 km andEquatorial circumference 40,075.16 km.

Area : Total surface area 509,7000,000 sq. km; Land area about 148,400,000 km (about 29per cent of the total area); Water area about 361,300,000 sq. km. (about 71 per centof the total surface area).

Motions : (i) Rotation (spinning motion on polar axis), once every 23 hours 56 minutes and4.09 seconds

(ii) Revolution (around the sun), once every 365 days, 6 hours, 9 minutes and 9.54seconds.

Surface Features : Highest point on land - Mt Everest 8,848 m above the sea level. Lowest area on land-shore of Dead Sea (399 m below sea level). Mean height of land 756 m.

Ocean Depths : Deepest area - Mariana Trench in Pacific Ocean south-west of Guam (11,033 mbelow the sea surface). Average depth of oceans 3,730 m.

Chemicalmake up of theEarth’s Crust : (percent by weight): oxygen 46.6, silicon 27.7, aluminium 8.1, iron 5.0, calcium 3.6,

sodium 2.8, potassium 2.6, magnesium 2.0 and other elements 1.6.Mean SurfaceTemperature : 14°C, Highest temperature 58°C at Al Aziziyah, Libya and the lowest temperature

-89.6°C at Vostok Station in Antarctica.Inclination of thePolar Axis to theOrbital Plane : 23 deg. 26 min. 59 second.Orbital Speed : 29.8 km/sAbout the SunMean DistanceFrom the Sun : 149,598,500 km (one astronomical unit). The maximum distance at the time of

aphelion between July 2 and 5 is about 152 million km and the minimum distanceat perihelion between January 2 and 5 is about 147 million km.

The rotation of the earth causes day and night and the revolution of theearth results in the change of the seasons. Since the path of the earthabout the sun is elliptical, the distance between the two keeps changing.

Earth is lyingbetween the Venus

and Mars. It is the thirdplanet of the solar system.It ranks fifth in size with a

mean radius of 6371 kilome-ters. The shape of the earth is

oblate spheroid, ie, almostspherical, but flattened alittle at the poles with a

slight bulge at thecentre (equator).

Geographic InformationSystems (GIS) GIS uses computers for storing

and processing informationabout the Earth's surface andland use.

Geographic Information Sys-tems or GIS is a technology thatattaches a database to an elec-tronic map.

GIS technology can be used forscientific investigations, re-source management and devel-opment planning.

GIS is used to calculate the emer-gency response in the event ofa natural disaster.

GIS can help to pinpoint wet-lands that need protection frompollution.

The map gives detailed data, i.e.,every asset in a municipality,town or even a park, primaryschool, hospital, housing can beshown on the map.

The National Geographic Society The National Geographic Society (NGS) is one of the largest non-

profit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, the

promotion of environmental and historical conservation, and the studyof world culture and history.

It is located in Washington D.C. The National Geographic magazine is currently published in 32 lan-

guage editions in many countries around the world. National Geographic Channel, is a television channel that airs non-

fiction television programs produced by the NGS.

Lithosphere,Asthenosphere &

Centrosphere The earth is divided into

lithosphere, asthenosphere andcentrosphere.

Lithosphere is the outer por-tion of the earth, including thecrust and the upper mantle.

Asthenosphere is the upperpart of the mantle which is about250 km thick. The rocks con-tained in the asthenosphere arepartially molten.

Centrosphere is the centralpart of the earth which inspiteof having a very high tempera-ture behaves like solid due toimmense pressure of the over-lying rocks.

Composition of theEarth's Crust

Most abundant element in at-mosphere is Nitrogen (78%)then Oxygen (21%). But themost abundant element in theuniverse is hydrogen.

The crust is made up of rocks.The rocks are made up of min-erals in a consolidated form.

The process of rock formation,consolidation of mineral parti-cles is called lithification.

A rock can be defined as anaggregate of minerals.

The ratio between the totalamount of light reflected froman object in space and the to-tal amount of light falling onan object is called albedo.

A perfect reflector has analbedo of 1 and earth has analbedo of 0.34 (34%).

Position, Shape andSize of Earth

Earth moves around the sun inan elliptical orbit. The spinning(rotation) of the earth at a highspeed has caused its mass tobulge at the equator and sinkin at the poles.

The bulging of central part(equatorial region) is due tocentrifugal force.

The plane passing through theEarth's orbit is called orbitalplane. The Earth's axis is in-clined and makes an angle66½0 with the orbital plane.

The difference between theequatorial diameter (12,755 km)and the polar diameter (12, 712km) of earth is 43 km.

71% of the total surface areaof earth is water and 29% island.

Earth has 40,005 km polar cir-

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cumference and 40,077 kmequatorial circumference.

Motions of the Earth andtheir Consequences

The movement of earth can bemainly divided into two as, ro-tation and revolution.

Rotation is the spinning ofearth on its own axis.

Earth spins on its axis at anangle of 66½0 to the plane ofearth from west to east.

Earth’s rotation takes 23 hours,56 minutes and 4.091 secondsto complete one rotation.

Rotation results in the forma-tion of day and night, changesin the direction of wind andocean currents. The daily oc-currence of tides twice is alsoresulted by the rotation ofearth.

Day and night are not of equalduration throughout the yearbecause of the tilt of earth’saxis.

Earth rotates 10 in 4 minutes.Therefore earth rotates 150 inone hour. It takes 24 hours(one day) to complete one ro-tation (3600).

Day and night are equal at theequator throughout the year,because the circle of illumina-tion always divides the equa-tor into two equal parts.

The duration of day and nightat the poles is six months each.

Rotation also causes coriolisforces (named after the Frenchmathematician Gaspard deCoriolis who first explainedthem mathematically) which arerelated to the decreasing rota-tional velocity with increasinglatitude and tend to deflect any-thing which is moving over theearth’s surface.

Coriolis force is zero at theequator and increases progres-sively towards either poles.

Revolution is the movement ofearth in its orbit around thesun, along an almost circularpath (elliptical) called its orbit.The earth revolves approxi-mately one degree in one day.The speed of revolution ofearth is 29 km/second.

The earth’s revolution causesa change in seasons. Seasonsare classified into four called theSpring, Summer, Autumn andWinter. The earth’s axis is in-clined at an angle of 66 ½0 tothe plane of its orbit.

Equinoxes are dates when thenight and days are equal. Dur-ing these days the sun shinesvertically on the equator. Thisoccurs twice a year. March 21is called the vernal equinox orSpring equinox and September23 is called autumnal equinox.

Solstice is the time of the yearwhen the difference between

The movement of earth can be mainly divided into two as,

rotation and revolution. Rotation is the spinning of earth

on its own axis. Earth takes 365 days, 5 hours, 48 minutes

and 45.51 seconds for one revolution around the sun. It is

called one solar year. Earth has to cover 938 million kilometers

along its elliptical orbit to complete one revolution.

Earth’s Plates The Earth's rocky outer crust

solidified billions of years ago,soon after the Earth formed.

The top layer of the Earth'ssurface is called the crust (itlies on top of the plates). Oce-anic crust (the thin crust un-der the oceans) is thinner anddenser than continental crust.Crust is constantly being cre-ated and destroyed; oceaniccrust is more active than con-tinental crust.

The plates are made of rock anddrift all over the globe; theymove both horizontally (side-ways) and vertically (up anddown). Over long periods oftime, the plates also change insize as their margins are addedto, crushed together, or pushedback into the Earth's mantle.These plates are from 50 to 250miles (80 to 400 km) thick.

The current continental andoceanic plates include: theEurasian plate, Australian-In-dian plate, Philippine plate,Pacific plate, Juan de Fucaplate, Nazca plate, Cocos plate,North American plate, Carib-bean plate, South Americanplate, African plate, Arabianplate, the Antarctic plate, andthe Scotia plate. These platesconsist of smaller sub-plates.

Type of Plate Movement: Di-vergence, Convergence, andLateral Slipping.

When two continental platescollide, mountain ranges arecreated as the colliding crustis compressed and pushedupwards.

the length of days and thelength of nights is the largest.During these days, the sunshines vertically over thetropic.

On or around June 21, theNorth pole tilts towards the sunand the sun shines directlyover the tropic of cancer. Thisis called Summer Solstice. Onor around December 22, theearth is at the end of its orbit.The South pole tilts towardsthe sun and the North poleaway from it, which is called asWinter Solstice.

Tropics are the regions circlingthe earth between the Tropicof Cancer (230 27'N) and theTropic of Capricorn (230 27'S).These imaginary lines of lati-tude, mark the farthest pointsreached by the sun’s verticalrays. The 23½0 North parallelis termed as Tropic of Cancerand the 23½0 South parallel istermed as Tropic of Capricorn.

Sun rays fall vertically at theTropic of Cancer on June 21and they fall vertically at theTropic of Capricorn on Decem-ber 22.

Aphelion is the point in theearth’s or other planets orbit

which is farthest from the sun.Earth is at its aphelion on July4 every year at a distance of152 million kilometers.

Perihelion is a point in the or-bit of a planet or any other ce-lestial body at which it passesclosest to the sun. Earth willbe at its peri helion on January3 every year at a distance of147 million kilometres.

Perigee is the point in the or-bit of the moon at which it isclosest to the earth. Apogee isthe point in the orbit of themoon at which it is farthestfrom the earth.

Location of Place andTime on the Earth's

Surface Equator is an imaginary line

passing round the earth mid-way between the north andsouth poles, dividing the earthinto two equal halves.

Latitude is the angular dis-tance in degrees on the earth’ssurface measured north andsouth of the equator. The lati-tude of any point on the earthis most precisely expressed indegrees, minutes and seconds.

There are about 180 parallellatitudes. The distance be-tween any two parallel lati-tudes is always equal. One de-gree of latitude is approximatelyequal to 111 km.

A meridian is an imaginary lineextending from the north poleto the south pole at right an-gles to the equator.

Prime Meridian is the 00 merid-ian which passes throughGreenwich,a place near Lon-

Longest day (shortest night) in the north-

ern hemisphere is June 21and shortest day (longestnight) is December 21. Long-est day in the southern hemi-

sphere is Dec. 22 and shortest day is June 21.

don. It is also known as theGreenwich meridian.

Longitudes are equi-distantlines drawn east and west ofthe Greenwich meridian. Theydenote the angular distancesof a place due east or west ofthe Greenwich meridian. Thereare 360 meridians oflongitudes.

One hour is equal to 150 of lon-gitude.

Longitude is an important fac-tor in determining the time inall parts of the world. Localtime of a place is calculatedwith respect to the mid dayposition of the sun at thatplace.

Local time varies from Green-wich time (London) at the rateof four minutes / degree of lon-gitude.

Standard time is the uniformtime fixed by each country.

Standard time in India is thelocal time of a place nearAllahabad at 82 ½oE longitude.

Greenwich Mean Time is thestandard time of U.K. It isbased on the local time of themeridian passing throughGreenwich near London.

If a person going east of Green-wich for 1800, he would put hisclock forward by 12 hours. Atthe same time if another per-son is going to west of Green-wich for 1800, he would put hisclock backward by 12 hours.When they meet on the Inter-national Date Line, there wouldbe one day’s difference be-tween them.

Earth is divided into 23 full timezones and two half time zones

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each having longitudinal widthof 150 and 7½0 respectively.

The International Date Line issituated at 1800 meridian fromGreenwich. It runs down the midPacific Ocean, veering to keepall of the islands in a group.

When one crosses the Inter-national Date Line from east towest the date is to be advancedby one day (loses one day).Similarly when one crosses theDate Line from west to east, thedate is to be set back by oneday (gains one day).

A ship while crossing the DateLine eastwards gains a day,while it loses a day crossingwestwards.

The local time of ArunachalPradesh is two hoursahead of that of Gujarat be-cause Arunachal Pradesh is300 east of Gujarat.

Russia, the largest country inthe world, extends 1650 fromEast to West. Therefore it isdivided into eleven time zones,each differing in one hour.

The distance between any twomeridians is not equal. Theyget closer from the equator topoles.

Since earth rotates 150 in onehour, there is a difference ofone hour in local time to every150.

Sidereal day is the time be-tween two observed passagesof a star over the same merid-ian of longitude.

Sidereal day = 23 hrs. 56 min.4.09 seconds.

Solar day is the time betweentwo successive transits of thesun over the same meridian.

Mean solar day = 24 hrs.

Volcanoes A volcano is formed when the

molten magma in the earth’s in-terior escapes through the crustby vents and fissures accom-panied by steam gases (hydro-gen sulphide, sulphur dioxide,hydrogen chloride, carbon di-oxide etc) and pyroclastic ma-terials.

The molten rock material is themost common form of volcanicmatter ejected during volcanicactivity. This material is calledMagma. Upon reaching thesurface of the earth, it is calledLava.

Volcanic activity is an impor-tant process of construction onthe earth’s surface.

Crater is a funnel shaped de-pression having a circular plan

The difference between the

Greenwich Mean Time and In-

dian Standard Time is 5 ½

hours. Greenwich Mean Time

is the standard time of United

Kingdom. Indian Standard time

is the local time of a place near

Allahabad at 82 ½oE longitude.

and a neck at the centre. Cra-ters are formed by explosion orsubsidence.

Some times, the volcanic ma-terial may not be able to reachthe surface and it may get de-posited in the layers of thecrustal rocks. This type of ac-tivity is called intrusive vol-canic activity.

Lava that is rich in silica andpoor in metallic minerals iscalled acid lava.

Lava that is rich in metallic min-erals has a low melting pointand remains liquid for a longertime even with some loss ofheat. Therefore such lava ismore likely to reach the surface,is called basic lava.

Circular deposit of lava mayremain higher than the areassurrounding it. Such a featureis called a volcanic plug.

Concave Saucer shaped de-posits of lava in the crustalrocks are called lopoliths.

There are three types of volca-noes - active, dormant and ex-tinct.

An active volcano erupts oc-casionallyeg: Mount Stromboli in Italy,Barren Islands in India (Theonly active volcano in India).Mt. Etna in Sicily and Cotopaxiin Ecuador.

Mt. Stromboli whose frequenteruptions that resulted in morelike a summit glow, haveearned it a crown title 'Lighthouse of the Mediterranean.'

A dormant volcano has notbeen seen to erupt, but itshows evidence of recent ac-tivity.

Pinatubo ash plume reaching a heightof 19 km, 3 days before the climac-tic eruption of 15 June 1991.

Mt. Vesuvius and Mt.Krakatau are examples of dor-mant volcano.

An extinct volcano shows nosign of life.Eg: Mt. Kilimanjaro

Fumaroles are fissures in theground of volcanic areasthrough which gases includingnitrogen, ammonia, carbon mon-oxide and methane are given off.

The Pacific belt is known asthe Ring of fire because of thelargest number of active vol-canoes along the coasts ofAmerica and Asia on theocean.

Batholiths are a large mass ofmagma which often forms theroot of a mountain and is madeup of granite.

Famous volcanoes of theworld: Cotopaxi (Ecuador), Mt.Kilimanjaro (Tanzania), Mt.Etna (Italy), Mt. Vesuvius(Italy), Mt. Popa (Myanmar),Mauna Lao, Mt. Kenya, Mt.Stromboli (Italy).

The volcanic islands of Hawaiin the mid pacific, the famoushot water geycers of the Yel-low Stone region of NorthAmerica are examples ofinplate volcanoes.

Surtsey, is an island born froma series of volcanic explosionsfrom deep within the earth'score culminated in the creationof a barren crest of rock thatjutted from the Atlantic Ocean.

Earthquakes An earthquake (also known as

a quake, tremor or temblor) isthe result of a sudden releaseof energy in the Earth's crust

that creates seismic waves. Earthquakes which originates

naturally below the surfacesending out a series of shockwaves.

Earthquakes are frequently as-sociated with faults. The placeof origin of an earthquake in-side the earth is called its fo-cus.

Epicentre is the point on theearth’s surface vertically abovethe focus. On the earth’s sur-face the maximum damage iscaused at the epicentre.

Most of the earthquakes origi-nate at a depth of about 60 kmbelow the surface of the earth.The point of origin of an earth-quake in the interior of the earthis called the seismic focus.

Seismology is the study ofearthquakes and their impact.There are two correspondingmeasures of the severity of anearthquake : intensity and mag-nitude.

Intensity is the measure of thelocal effect which varies ac-cording to both the distancefrom the source of the earth-quake and the intr insicstrength of the earthquake.The intensity is expressed inPoints.

About 68% of all earthquakesare observed in the vast region

of the Pacific ocean as a 'Ringof fire'.

Some earthquakes are causedby the movement of lava be-neath the surface of earth dur-ing volcanic activity.

The Kutch earthquake (1819),the Assam earthquake (1897),the Kangra earthquake (1905),the Bihar earthquake (1934),the Lathur, Maharashtra earth-quake (1993) and the Gujarat(Kutch) earthquake (2001) arethe well known examples ofearthquakes in India.

Tsunami Tsunamis (tidal waves) are

long-wave length, long-periodsea waves produced by thesudden or abrupt movement oflarge volumes of water.

The Japanese word for a greatsea wave, 'tsunami', has cameinto general use to identify aseismically generated seawave.

Earthquakes, volcanic erup-

The Aravallis is the oldestmountain range in India.

The Himalayas are theyoungest fold mountains in

India. The Himalayas, theAlps, the Andes, the

Rockies etc. are examplesof fold mountains or young

mountains. The Pyrenees(Europe), Appalachians

(America) and the Aravallis(India) are examples of old

mountains. They wereformed in the pre-drift

area.

Earthquakes aremeasured with a seismo

meter; a device which alsorecords is known as a

seismograph.

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Ritcher Scale & Seismograph An earthquake is measured by its Magnitude and Intensity. Magnitude is a measure of the strength of the earthquake at its source (focus). It is assessed in Richter scale. Seismometers are instruments that measure motions of the ground, including those of seismic waves gener-

ated by earthquakes, nuclear explosions, and other seismic sources. It is also used to measure the strength(intensity) and location of earthquakes.

Richter Magnitude Scale was developed in 1935 by Charles F Richter of the California Institute of Technol-ogy as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake isdetermined from the logarithm of the the amplitude of waves recorded by seismographs.

On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. The Richter magnitudesare based on a logarithmic scale (base 10). What this means is that for each whole number you go up on theRichter scale, the amplitude of the ground motion recorded by a seismograph goes up ten times.

The Richter Scale has no upper limit. Recently, another scale called the Moment Magnitude Scale has beendevised for more precise study of great earthquakes.

Earthquakes with magnitude of about 2.0 or less are usually called microearthquakes; they are not com-monly felt by people. A magnitude 5.3 might be computed for a moderate earthquake, and a strong earth-quake might be rated as magnitude 6.3. The magnitude ranging ‘7’ is severe and magnitude ranging ‘8’ isdevastating.

Petrology is the study of theorigin, composition andstructure of rocks, while

Lithology is the study of thecharacteristics of rocks.

tions and other underwater ex-plosions (including detona-tions of underwater nuclear de-vices), landslides and othermass movements, meteoriteocean impacts or similar impactevents, and other disturbancesabove or below water all havethe potential to generate a tsu-nami.

Tsunamis can also travel thou-sands of kilometers acrossopen ocean and wreak destruc-tion on far shores hours afterthe earthquake that generatedthem. Most destructive tsuna-mis are caused by earthquakesof magnitude 7.5 or more.

Rocks and Minerals Rocks and minerals mainly

constitute the upper part of theearth’s crust. Minerals arenatural substances havingcharacteristic properties and

more or less specific chemicalcompositions.

Rocks are solid materials thatmakes up the earth’s crust. Onthe basis of texture, structureand composition, rocks maybe classified into igneous, sedi-mentary and metamorphic.

Igneous rocks are formed bythe solidification of moltenmagma from the interior of theearth. About 95% of the earth’scrust is made up of this type ofrocks generally do not occurin layers. Most of them arecrystalline.eg: Granite, Volcanic rocks andBasalt.

Also called primary rocks; theyare generally hard, massive,crystalline and contain no fos-sils.

Intrusive igneous rocksformed due to solidification oflava under the surface of theearth. They have content ofsilica and poor in metallic min-erals. Also called acid lavarocks.

If the lava has very high melt-ing point it may get solidifiedat great depths. Rocks thusformed are called plutonicrocks. Granite is a common plu-tonic rock.

Extrusive igneous rocks areformed when the lava reach thesurface of the earth and thensolidify. It is also called basiclava rocks. e.g., Rhyolite, basaltetc.

Sedimentary rocks are formedfrom the sediments depositedon the ocean beds. They com-

prise only about 5% of theearth’s crust, but covers about75% of the total land surface.Sedimentary rocks are gener-ally softer, fossils are com-monly found in these rocks.These rocks are also calledstratified rocks.eg: Sandstone, Limestone etc.

Shale is the most abundant ofall sedimentary rocks which iscomposed of silt and clay.

Sandstone is a common sedi-mentary rock which is formedmainly of quartz particles ce-mented together by silica, limeor iron oxide.

Metamorphic rocks areformed when pre-existing sedi-mentary or igneous rock is al-tered as a result of changes inphysical or chemical condi-tions.eg : Quartzite and Marble

The process which producesmetamorphic rocks is calledmetamorphism.

Quartzite is the metamorphicform of the sedimentary rock,sandstone.

Slate is formed by the com-pression of sedimentary rockslike shale and mudstone.Gneiss is formed by the meta-morphosis of igneous rockslike granite.

Chalk is a calcareous rock madeup of microscopic skeletal ele-ments from a variety of limesecreting organisms.

Coal and Peat represents theaccumulation of vegetationwhich originated in swamps.Peat is the first stage in the trans-formation of vegetable matterinto coal.

'Black Twins' is the name givento iron and coal. 'Black lead' isgraphite. Anthracite is themost superior type of coal.

Classification ofLandforms

There are three major landforms -mountains, plateaus and plains.Mountains: An uplifted portion of the

earth’s surface is called a hillor a mountain.

In our country, a mountain isdifferentiated from a hill, whenits summit or top rises to morethan 900 metres above thebase.

Those with less than thiselevation are called hills.

On the basis of their origin ormode of formation, themountains are classified asstructural or tectonic, residualor dissected and volcanic.

Structural mountains: All great mountain systems of

the earth are of this type. Such systems are hundreds of

kilometres wide and thousandsof kilometres long.

Many of them lie near or parallelto continental coastlines.

Both the fold and the blockmountains are included in thistype.

(1) Fold mountains: The major mountains of the

present day including the Alpsin Europe, the Rockies of NorthAmerica, the Andes of SouthAmerica and the Himalayas ofAsia are structural foldmountains.

The granitic core of suchmountains is surrounded by

metamorphic rocks, mergingwith sedimentary layers alongthe margins.

These young fold mountainsare still r ising under theinfluence of the earth’stectonic force.

The Aravallis are considered tobe one of the oldest mountainson the earth.

(2) Block mountains: These mountains are formed

when great blocks of the earth’scrust may be raised or loweredduring the late stages ofmountain building.

The land between the twoparallel faults, either risesforming block mountains orhorsts, or subsides into adepression termed as a riftvalley or graben.

An old fold mountain may alsobe left as block mountains dueto continuous denudation.

The Vosges in France, Blackforest mountains in Germanyand Salt Range in Pakistan arecited as typical examples ofblock mountains.

River Rhine in Europe flowsthrough a rift valley.

(3) Volcanic mountains: As these are formed by the

accumulation of volcanicmaterial, they are also knownas mountains of accumulation.

The matter is thrown out anddeposited around the crater toform a mountain.If the lava is thin and basic inits composition, it spreads along distance forming a flattercone of gentler slope and oflowe elevtation

If it is thick and of acid

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composition a small volcaniccone sharply pointing out isthe result.

Sometimes lava is thrown outalong with ash and cinders.Such a volcanic cone is termedas ash and cinder cone.

(4) Residual or DissectedMountains:

They owe their present formdue to erosion by differentagencies.

That is why they are alsoknown as relict mountains ormountains of circumdenu-dation.

Hills like the Nilgiris, theyParsanath, the Girnar andRajmahal in India are examplesof this type.

Plateaus A plateau is an elevated area

generally in contrast to thenearby areas.

It has a large area on its topunlike a mountain and has anextensively even or undulatingsurface.

The rocks of the plateau arelayered with sandstones,shales and limestones.

But an inclined or a tilted stratamany also become flat throughcontinuous wearing down.The great Deccan Plateau withits slope towards east is a tiltedplateau in our country.

Very often, rivers and streamscut out deep valleys andcanyons in a plateau regions.The plateaus are of four typeson the basis of their situation.(1) intermontane plateaus(2) continental plateaus(3) piedmont plateaus(4) lava plateaus

(1) Intermontane plateaus: The plateaus which are partly

or fully enclosed by mountainsare known as intermontane.Plateaus.

The highest and extensiveplateaus of the world suchasTibet, Bolivia and Mexicoare of this category.

These are the results of themountain-building processwhich was accompanied by avertical uplift of the adjoiningenclosed lands.

(2) Piedmont Plateaus: Situated at the foot of a

mountain, they are boundedon the opposite side by a plainor an ocean.

The plateau of Malwa in India,Those of Patagonia in Argen-tina and the Appalachian in USare some of the examples

(3) Continental plateaus: They rise abruptly from the

lowlands or from the sea. They are the result of a

continental uplift producinglarge tablelands like theplateaus of Brazil, South Africa,West Australia, Chotanagpurand Shillong. Their heightsvary from 600-1500 metres.

Sometimes a plain or a low-lying area is vertically upliftedand gives rise to a plateau.

In India plateaus of Kaimur,Rohtas, Ranchi and Karnatakaare of this type.

(4) Lava plateaus: When lava spreads out to

cover the pre-existing landsurface, a lava plateau isformed which is also called aplateau of accumulation.

The horizontal sheets of lavaflow have trapped the originaltopography varying in depth

from 1200-1500 metres overlarge parts of Maharashtra andthe adjoining areas in Deccan.

Plains A relatively flat and a low-lying

land surface with least differe-nce between its highest andlowest points is called a plain.

The plains are usuallylowlands.

Plains can be placed accordingto their position and surfacerelief but are better classifiedon the basis of their mode offormation.

They are sub-divided intostructural, erosional anddepositional plains.Structrural plains: These plains are fomed by the

uplift of a part of the sea floorusually bordering a continent,that is the continental shelf.

On the other hand, there arestructurally depressed areaswhich make up very extensivelowlands on the earth.

Erosional plains: These are formed when an

elevated tract of land, forinstance, a mountain, a hill or aplateau is worn down to a plainby the process of erosion.

Over long ages, the higher landis levelled down into a sort ofplain.

The surface is hardly smoothand forms almost a plaintermed as a peneplain.

These are found in river, iceand wind eroded regions.

Depositional plains: These plains are formed by the

filling up of sediments intodepressions along the foothills, lakes and seas.

The deposition at sediments,eroded and brought down bylarge rivers, forms riverinealluvial plains.

The Indo-Ganga plains in theIndian subcontinent is anexample of alluvial plain.

Peneplains are formed by thewearing down of land due toweathering and erosion.

Coastal plains are those partsof the continental shelf whichhave been uplifted.

Glacial plains are formedthrough glacial erosion anddeposition.

Lacustrine plains are old lakebeds and are made up of sedi-ments deposited by rivers etc.

Karst plains are formed inlimestone areas mainly by theagency of underground water.

Flood plains, delta plains andalluvial plains are all formedthrough the deposition oferoded material by rivers.

Movements of theEarth's Crust

Warping and Isostasy consti-tute vertical movements, whilefolding, faulting and continen-tal drift constitutes horizontalmovement.

Folding is the process wherebythe rock strata are bent into aseries of arches (anticlines) andtroughs (synclines) as a resultof the horizontal earth move-ments which cause compres-sion within the crust.

Fold mountains are formed bythe crumbling or folding ofrocks.

The Himalayas, the Alps, the

Andes, the Rockies etc. areexamples of fold mountains.

Faulting is the process bywhich the tensional earthmovements under the effect ofconsiderable pressure createsa fracture in the earth’s crust.

Faulting gives rise to relief fea-tures such as block mountainsand rift valleys.

Block mountains are formed bythe lifting up of land betweenfaults or by the sinking of landoutside the faults. They areusually steep sidedeg: The Vosges.

A Rift valley is a long, relativelynarrow depression formed bythe sinking of a block of landbetween two or more or lessparallel faults.eg: East African Rift Valley.

Warping is the deformation ofearth’s crust which affects verylarge areas on the earth’s sur-face. It results in the formationof domes, shields and depres-sions.

Isostasy is a condition of gravi-tational balance between thecrustal segments of differentthickness.

Continental drift refers to thehorizontal movements of thecontinents on a vast scale.

The Himalayas, The Andes,The Rockies and The Alps areexamples of young mountains.They came into being after thecontinental drift.

The Pyrenees (Europe), Appa-lachians (America) and theAravallis (India) are examplesof old mountains. They wereformed in the pre-drift area.

The Rockies are North Ameri-can mountain ranges while theAlps are European, the Andesbelongs to South Americanrange. Mt. Blanc is the highestpeak in the Alps.

The Vindhyas separatesSouthern India from NorthernIndia.

Satpuras lies in betweenNarmada and Tapti andNarmada lies in betweenVindhya and Satpura.

The southernmost tip of West-ern Ghats is calledCardamom Hills. Sahyadri andNilgiri are parts of the WesternGhats. Western Ghats and East-ern Ghats meet at Nilgiri Hills.

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Earth’sRotation

Earth's rotation is the rotationof the solid Earth around its ownaxis. The Earth rotates towardsthe east. As viewed from theNorth Star Polaris, the Earthturns counter-clockwise.

Earth's rotation period relativeto the Sun (true noon to truenoon) is its true solar day orapparent solar day.

The velocity of the rotation ofEarth has had various effectsover time, including the Earth'sshape (an oblate spheroid), cli-mate, ocean depth and currents,and tectonic forces.

Earth’s rotation results in the de-flection of all moving objects onthe earth’s surface.

The primary effect of Earth's ro-

tation is the phenomenon of dayand night.

Due to the rotation of the earth,the stars, the planets, the moonand the sun appear to move inthe opposite direction viz., fromeast to west (e.g. the sun risesin the east in the morning, movesoverhead at noon and sets in thewest in the evening.)

If there is no rotation, one sideof the earth will always be fac-ing the sun and be excessivelyhot. The other side will havedarkness always and be exces-sively cold.

Another effect of spin or rota-tion placed on weather systemsby what is called Coriolis effect.

The rotation of the Earth also

Moment Magnitude

Scale (MMS)MMS was developed in the

1970s to succeed Richter Scale.

The magnitude is based on the

moment of the earthquake. The

MMS is used to estimate

magnitudes for all modern large

earthquakes by the United

States Geological Survey.

Mercalli ScaleThe intensity ofearthquake is measuredusing Mercalli Scale. TheMercalli scale quantifiesthe effects of anearthquake on the Earth’ssurface, humans, objectsof nature, and man-madestructures on a scale of 1through 12. This wasdeveloped by Italianvolcanologist GiuseppiMercalli in 1902.

The Atmosphere Atmosphere is defined as an

envelope of gaseous mixturescovering the earth held to it bygravitational forces. Atmos-phere is essential for the lifeon earth.

The principal constituents ofthe lower atmosphere areNitrogen (78.08% by volume)Oxygen (20.94%)Argon (0.93%)Carbondioxide (0.033%)Besides, there are minute pro-portions of other gases.

Oxygen is the most importantcomponent among atmosphericgases.

Nitrogen which is an importantconstituent of all organic com-pounds is relatively inert.

The main function of nitrogenis to control combustion by di-luting oxygen, thus it acts as adilutant.

contributes to the shift of theshape of our home planet.Earth's shape has actually beenmodified by its rotation, and wedescribe its shape as that of anoblate spheroid.

The most celebrated test ofEarth's rotation is the Foucaultpendulum first built by physi-cist Léon Foucault in 1851.

The amount of carbondioxidevaries from place to place, be-ing greatest around the citiesand smallest in the countryside. Green plants during pho-tosynthesis absorb carbondio-xide from the atmosphere anduse it to manufacture food andkeep other bio-physical proc-esses going.

Ozone (O3) consisting of threeoxygen atoms chemicallylinked is another variable con-stituent of the atmosphere. Inthe lowest layers, the propor-tion of ozone is very low (lessthan 0.00005 by volume of at-mosphere).

Between 20km and 40 km al-titude greater concentrationsof ozone are found. At levelsabove 32 km, it increases form-ing what is known as the ozonebelt. It plays a crucial role inblocking the harmful ultravio-let radiation from the sun.

Water vapour is one of themost variable gaseous sub-stances present in the atmos-phere, constituting between0.02% and 4% of the totalvolume in cold dry and hu-mid tropical climates respec-tively. 90% of moisture con-tent in the atmosphere existswithin 6km on the surface ofearth.

Atmosphere also containshuge numbers of solid and liq-uid particles called aerosols. Inaddition, negligible quantitiesof other gases such as argon,neon, helium, hydrogen, xe-non, krypton, methane etc arepresent in the atmosphere.

Structure ofAtmosphere

The earth’s atmosphere ismade up of a series oflayers on the basis of the ver-tical distribution of tempera-tures.

Troposphere is the lowest layerof the atmosphere and extendsroughly to a height of 7 to 8km near the poles to some 16kmover the equator. The thicknessis greater at the equator, be-cause the heated air rises togreater heights.

Stratosphere is a region ofuniform temperature extendingfrom an altitude of about 11kmabove the earth to a height ofnearly 50km. It is free from wa-ter vapour, clouds and dust.

The upper part of the strato-sphere has plenty of ozonewhich affords protection tohuman beings on the earthagainst the fatal effects of ul-traviolet radiations.

The Stratosphere also pro-vides ideal conditions for fly-ing aeroplanes. The upper limitof this layer is calledstratopause.

Mesosphere is a very cold re-

gion above the stratospherewhich extends from 50 or 80kmabove the earth’s surface.

Within the mesosphere thetemperature decreases with al-titude from about 0oC atstratopause to about –100oC atmesopause. Mesopause is theboundary line between iono-sphere and mesophere.

Thermosphere is the upper-most layer of the atmosphere

The Atmosphere is divided into layersaccording to major changes in temperature. 99% of

the total mass of the atmosphere is below 32 kilometers.Atmosphere can be classified into five main layers. troposphere,stratosphere, mesosphere, thermosphere (Ionosphere) and the

Magnetosphere. Troposphere - 0 to 12 km, Stratosphere - 12 to50 km, Mesophere - 50 to 80 km, Thermosphere - 80 km

and up. Thermosphere contains Ionosphereand Exosphere.

MagnetosphereMagnetosphere is the area

around the earth that extendsbeyond the atmosphere. The

earth's magnetic field operateshere. It begins at about 1000

km. It is made up of positivelycharged protons and nega-

tively charged electrons. Thistraps the particles that are

given off by the sun. They areconcentrated into belts orlayers called the Van Allen

radiation belts. The Van Allenbelts trap deadly radiation.

When large amounts are givenoff during a solar flare, theparticles collide with each

other causing the auroraborealis or the northern lights.

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extending from the mesopauseat an altitude of about 85 kmsto the outer limits of atmos-phere.

Ionosphere is that part of thethermosphere which extendsabove the mesosphere from 65km to nearly 400 km above theearth’s surface. It is an electri-cally charged layer character-ised by the ionisation of atoms.

Due to the presence of electriccharge in the Ionosphere, ra-dio waves transmitted from theearth are reflected back to theearth by this layer.

Exosphere is the uppermostregion of the atmosphere. Itextends beyond the iono-sphere above a height of about400km. The air is extremely rar-efied and the temperaturegradually increases throughthe layer. Here the gravity ofearth is exceedingly weak.

The lowest temperature of airis recorded just before sunrise,because of the predominanceof land over water in the north,the northern hemisphere iswarmer.

The pressure exerted by at-mosphere as a result of itsweight above a unit area of theearth’s surface is called the at-mospheric pressure.

Atmospheric pressure is ex-pressed in millibars (mb) andis measured with a mercurybarometer.

Two principal types of barom-eter used are mercury barom-eter and aneroid barometer.

One millibar of atmosphericpressure is equal to the forceof one gram on a square centi-metre.

The normal pressure at sealevel is taken to be about 76centimetres (1013.25 millibars).

Aurora are produced bycharged particles from the suncaptured by earth’s magneticfield at a height of about 100km.

Aurora Borealis is a luminousphenomenon in the northernhemisphere and AuroraAustralias is a luminous phe-nomenon in the southern hemi-sphere.

Insolation is the radiant energythat reaches the surface of theearth from the sun. Insolationis the most important singlesource of atmospheric heat.

Winds A wind can be defined as a

stream of air in a fairly well-defined direction. Winds aregenerated due to differences inpressure from one place to theother.

Wind is ‘air in motion’ andplays an important role in cli-matic variations on the earth.

Air always moves from a re-gion of high pressure to a re-gion of low pressure. The chiefcause of winds is the differencein pressures.

Winds can be classified into Regular winds (Primary)

eg: tradewinds and westerlies. Periodical winds (Secondary)

eg: monsoon winds. Variable winds (Tertiary)

eg: cyclones and other localwinds

Trade winds refers to thewinds that blows from thesub-tropical belts of highpressure towards the equato-rial region of low pressure.

The effect of rotation of earth

on the direction of winds is

called the Coriollis effect. This

effect causes deflection in the

direction of winds.

International Date LineThis line is a zig-zag line and roughly coincides with the 180th merid-ian.

When the date line is crossed from the east to the west, the date mustbe advanced by one day, when the line is crossed from the west to theeast, the date must be set back by one day.

The International Date Line (the meridian 180°) was chosen becauseit passes through the mid-Pacific, where there are no land masses.

It goes zig-zag in some places to avoid land and leaves some islandgroups wholly on the same side of the line.

It deflects to the east of 180° the Bering Strait, between Siberia andAlaska.

It deflects to the West of 180° to leave the Hawaiian group of islandson the East of the line.

It deflects again to the East, South of the equator to avoid the Fiji andTonga islands, on the same side as New Zealand. If the date line isdrawn exactly North and South, it will cut inhabited islands makingwhat is Tuesday to one man, a Wednesday his next door neighbour.

The twenty-four hour time is increasingly used by railways, airlinesetc. for dispensing with the suffix a.m. and p.m.

The day begins at midnight, the zero hour and the following hoursare numbered from 0 to 23 hours.

Trade winds blow towards theequator between 50 and 300

north and south latitude. The word ‘trade’ comes from

the saxon word ‘tredon’ whichmeans 'to tread and follow aregular path.'

Trade winds are also calledtropical easterlies.

Trade winds are called so be-cause prior to the steamage;sailing ships carrying goods oftrade and cargo depended onthese winds.

Westerlies or Anti-Tradewinds are regular winds whichblows outside the tropics in thetemperate zone. These windsblow from the sub-tropical highpressure areas to sub-polar lowpressure areas and between350 and 600 North and Southlatitudes.

Polar Easterlies constitute thewind system characteristic ofthe arctic and polar zones.They extend from about 600

north and 600 south latitude tothe poles.

Monsoon winds are seasonalwinds which blow briefly overIndia, Sri Lanka, China andnorth-west Australia.

Monsoon climate is marked bysummer rains and winterdroughts.

The word 'monsoon' derivedits name from the Arabic word‘mausin’ meaning seasonalwinds. Traditionally monsoonhas been considered as a re-sult of the differential heatingof land and sea.

According to dynamic theory,monsoon are a result of the shiftof the Inter Tropical Conver-gence Zone (ITCZ) under theinfluence of the vertical sun.

Polar winds are winds whichblow from the high pressurearea around the poles towardsthe temperate regions.

Planetary winds are permanentwinds which blow throughoutthe year from one latitude to theother in response to the latitudi-nal differences in air pressure.They blow over the vast areasof continents and oceans.

Horse Latitudes are sub-tropi-cal belts of variable winds andcolumns that lie between thelatitudes of 250 and 350 Northand South. They coincide withthe sub-tropical high pressurebelts.

Horse Latitude winds are weakand shifting. In early days, thesailing vessels with a cargo ofhorses found it difficult to sailunder such calm conditions.They used to throw horses intothe sea to save valuable drink-ing water and this part there-fore came to be called as HorseLatitudes.

A gale is a strong wind having the speed between 56 and 72 kmper hour.

A storm refers to a strong wind whose speed exceeds 72 to 121km/hr.

Doldrums are equatorial beltsof low pressure where thenorth-east and south-easttrade winds converge on andmeet each other approximatelybetween 50 south and 50 northlatitude. The belt is character-ised by extremely low pressurewith calm conditions.

Roaring Forties are powerfulwesterly winds that blowthroughout the year over theoceans of the southern hemi-sphere between 400 and 600

south latitudes. They arecalled Best brave winds andbring storms and heavy rain-fall.

The winds which developedbetween 450

and 550 are calledFurious Fifties and that devel-oped between 550 and 650 arecalled Shrieking sixties. Theseare the dreaded terms used bysailors.

Local winds develop as a re-sult of the local differences intemperature and pressure.They affect the smaller areasand are restricted to the low-est levels of the troposphere.

Local winds includes hot, cold,convectional and slope winds.

The most famous local coldwinds that blow from Alps overFrance towards the Mediterra-nean sea is the mistral.

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Loos are very hot and dry lo-cal winds that blows from thewest in the months of May andJune, usually in afternoons inthe plains of Northern Indiaand Pakistan. Its temperatureinvariably varies between 450Cand 500C. It may cause sun-stroke to people.

Local convectional winds areof two types - Land breeze andsea breeze.

Land breeze is defined as theprocess by which cold windsblows from the land to sea dur-ing night. Land breeze is notas strong as the sea breeze.

During the day time, the landget warmer than the sea pro-ducing low pressure over theland into which cooler airmoves from over the sea. Thelocal winds that blows from seato land during the day time iscalled Sea breeze.

Valley breeze and mountainbreeze are the counterparts ofland and sea breeze. During theday time the slopes of themountain gets heated morethan the valley floor. As suchthe air from the valley flows upthe slope. This is called theValley breeze. After sunset theprocess is reversed. Rapid lossof heat through terrestrial ra-diation along the mountainslopes results in the sliding ofcold dense air from higher el-evations to valleys. This iscalled the mountain breeze.

Jet streams are narrow con-centrated bands ofmeandering high velocitygeotrophic streams boundedby low speed winds and is apart of upper level westerlies.

The Jet streams have an averagevelocity of 120 km per hour in win-ter and 50km per hour in summer.

A hurricane is a strong windwhose speed exceeds 121 km/hr.

Cyclones are irregular windmovements involving closedair circulation around a lowpressure centre. Cyclones areassociated with destructiveand violent disturbances suchas heavy squalls and torren-tial rainfall.

Cyclones are called hurri-canes in the South-eastCarribean region.

In the Philippines islands,eastern China and Japan, cy-clones are called Typhoons.

Around South-east Africancoast, Madagascar, Mauritiusislands and North-west Aus-tralia they are called WillieWillies.

If the speed of cyclone isgreater than 250 km/hr, it isknown as Super Cyclone.

Tornadoes are violently rotat-ing storms, characterised by afunnel shaped cloud in whichwinds whirl around a small areaof extremely low pressure. Theyare generally accompanied bytorrential rains.

Water Spout is a tornado occur-ring in the sea usually in tropicaland sub-tropical regions whichconnects a whirling cone ofdense cloud with a cone of

spray raised from sea and thusraises a huge column of water.

Anti–cyclone is a high pressurewind blowing outwards from thecentre, clockwise in the North-ern Hemisphere and anti-clock-wise in the Southern Hemi-sphere.

Coriolis force is a ‘fictious’force needed to relate themovement of air masses overthe earth’s surface to its rotat-ing co-ordinate system (thegrid). It was named after theFrench mathematician Gaspardde Coriolis, who first describedit in 1835.

Coriolis force is absent at theequator and increases towardsthe poles. The force is respon-sible for the formation and di-rection of movement of anti-cy-clones and whirlpools.

Clouds Clouds are a visible mass of

small water drops or ice crys-tals formed by the condensa-tion of water vapour in the at-mosphere, usually at a consid-erable height above the earth’ssurface.

Clouds are caused mainly bythe adiabatic cooling of air be-low, its dew point.

On the basis of appearance, theclouds can be identified as(i) Cirrus clouds are high,white & thin. They are com-posed of ice crystals. They

Wind Wane : Instrument for knowing the direction of wind. Anemometer : Measures the velocity of the wind. Beaufort wind scale is an internationally accepted wind scale

which consists of a series of number devised by Sir FrancisBeaufort in 1805 to indicate different wind strengths.

Instruments to Measure Wind

form delicate patches and givea fibrous and feathery appear-ance.(ii) Cumulous clouds : have aflat base and have the appear-ance of rising domes. Theseclouds are often described ashaving cauliflower structure.(iii) Stratus clouds : as sheetsof layer that covers much or allof the sky.

Stratiform clouds - Theseclouds are fairly thin and blan-ket like. Subdivided into highclouds, medium clouds andlow clouds.

Alto and Nimbo are the twoprefixes which refer to middlelevel clouds and low clouds ofconsiderable thickness withdark grey appearance respec-tively.For eg:- (1) Low clouds includestratocumulus, stratus,nimbostratus, cumulus andcumulo nimbus. (2) Mediumclouds include alto cumulusand alto stratus. (3) Highclouds include cirrus, cirro stra-tus and cirro cumulus.

Precipitation is the formationof water particles or ice withinthe cloud that falls towards theearth’s surface. It occurs whencondensation takes placerapidly within the cloud.

Precipitation in the form of ice-pellets (hail stones) that devel-ops in and fall from cumulonimbus clouds, either at a coldfront or where intense heatingof the surface causes rapidlyascending convection cur-rents called Hails.

Climatic zonesof the Earth

Equator is the biggest circledrawn on the globe.

The regions between 5o northand 50 south of the equator iscalled the Equatorial region.Here the temperature is veryhigh and rainfall is very heavy.

Torrid zone which is the hot-test zone lies between 23½0

North and 23½0 South. ie., be-tween the Tropic of Cancerand Tropic of Capricorn.

Temperate zone: Lies between23½o north and 66 ½o northNorth Temperate zone andSouth Temperate zone lies be-tween 23½o south and 66½o

south. This zone has a markedannual range of temperature.

Frigid zone lies between 66½0

north and 900N in the case ofnorth frigid zone and 66½o

south and 900 south in the caseof south frigid zone. They areextremely cold regions.

Climatic Conditionsof Earth

The world climate can beclassified into Tropical Climate,

Dry Climate, Humid MesothermalClimate, Humid Microthermal

Climate, Polar Climate andHighlands Climate.

Tropical Climate Major subtypes of tropical cli-

mate are the tropical rainforest,tropical monsoon and tropicalsavanna climates.

Occurs in the tropical zonewhere the mean monthly tem-perature remains generallyabove 22°C.

Dry Climate This climate is characterised by

a general water deficit. It can be classified into-tropi-

cal and substropical desert,and tropical and subtropicalsteppes.

Humid Mesothermal Climate It is subdivided into - Mediter-

ranean type, China type andWest European type.

Humid Microthermal Climate Based on the type of forests

growing in the region, this cli-mate is also known as ‘taiga’.The summer temperature ishigher than 10°C, but the tem-peratures in the winter seasongo below the freezing point andremain so for eight months.

This type of climate is experi-enced in North America andEurasia.

Polar Climate This climate is also known as

the tundra and is experiencedin the polar regions.

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Fog-Smog-Mist

Fog is made up of droplets of water suspended in the lower layers

of atmosphere resulting from the condensation of water vapour

around nuclei of floating dust or smoke particles.

Smog also called smoke fog, is a form of fog that occurs in areas

where the air contains a large amount of smoke.

Mist is the term given for a reduction of visibility between 1 -

2km caused by the condensation, producing water droplets

within the lower layers of atmosphere. It is the intermediate be-

tween fog and haze.

Mist and fog are identical and are formed in the same way. The

only difference is that in a fog, the particles of water are smaller

and visibility is poorer than in a mist.

Haze is formed by water particles that have condensed around

the nuclei in the atmosphere but may also be a result of particles

of smoke, dust or salt in the air.

It is experienced in Arctic mar-gins of North America andEurasia and the Antarctic con-tinent.

Highland Climate It is significantly modified by

the altitude and the aspect ofthe slope and these regionshave a variable climate.

This climate is experienced inthe mountainous regions ofHimalaya, Tibetan Plateau,Rockies, Andes and Alps.

Weather is a condition of theatmosphere at a certain placeand time, with reference to tem-perature and the presence ofrain, sunshine, wind etc.

Climate is the regular patternof weather conditions of a par-ticular region.

Humidity is the degree of watervapour present in the air. For anyspecified temperature, there is adefinite limit to the maximumquantity of moisture that canbe held by the air. This limit isknown as the saturation point.

Humidity can be measured bymeans of a hygrometer.

Relative humidity is the ratiobetween the amount of watervapour actually present in anair mass and the maximumamount that the air mass canhold at that temperature. It isexpressed in terms of percent-age.

Vapour Pressure - The amountof pressure exerted by a givencolumn of air differs accordingto the varying amounts of wa-ter vapour present in it. Thatpart of barometric pressure dueto water vapour alone is knownas vapour pressure.

Vapour pressure is maximum at

the equator (about 30 mb) anddecreases towards the poles(less than 10 mb).

Dew is the moisture depositedin the form of water dropletson the earth’s surface or on ob-jects near the earth’s surface.

Dew point is the temperatureat which air is fully saturatedand below which condensa-tion normally occurs.

Condensation is the physicalprocess of transformation fromthe vapour to liquid state. Con-densation occurs when tem-perature reaches the dew point.

Frost is a weather conditionthat occurs when the air tem-perature is at or below 0oC. Themoisture on the ground sur-face and objects, freezes toform an icy deposit.

Global warming andclimate

Global warming refers to anaverage increase in the Earth’stemperature, which in turn,

causes changes in climate. Awarmer earth may lead tochanges in rainfall patterns, arise in sea level and a widerange of impacts on plants,wildlife and humans.

Average global temperatureshave risen (0.6+ 0.2°C) sincethe late 19 th century. Thescientific consensus is that asignificant proportion of thispast rise, particularly in the last25-50 years, is due tohumanity’s emission of greenhouse gases such as carbondioxide. (CO2)

The impact of climate change.Carbon dioxide emitted mainlyby the burning of fossil fuelsand the emission of methane,nitrous oxide, CFC’s and othergreen house gases thickens theblanket of greenhouse gasesover the earth’s atmosphereupsetting the natural flow ofenergy from the sun.

Deforestation acceleratesglobal warming by reducing theabsortption of carbon dioxidein the atmosphere.

Based on current emissionlevels, it is estimated that theglobal tremperature will rise bybetween 1°C and 3.5°C by theyear 2100.

The mean sea level may riseupto 100 cm by the year 2100,causing flooding andsubmergence of many islandsand coastal cities.

Ozone depletion The Ozone layer is found in the

atmosphere between 20-50 kmfrom the Earth’s surface.

The Ozone layer is region ofconcentration of the allotropeof an oxygen molecule knownas Ozone (O3) which isproduced by the action of Solarradiation on ordinary Oxygenatoms.

It filters sunlight and preventsthe harmful ultravioletradiation from reaching theEarth’s surface by absorbingmost of the ultra violetradiation.

If these ultraviolet rays wereto reach the Earth’s surface infull intensity all exposedbacteria would be destroyedand animal tissues damagedseverely.In this protective role, thepresence of the Ozone layer isan essential factor in the lifeenvironment.

There are certain householdand industr ial chemicals,having widespread applicationin refrigeration, air conditi-oning, fire extinguishing anddry cleaning, that are knownto deplete this life-saving layer.These chemical are calledOzone-Depleting substances

and include primarily theChlorofluoro Carbons (CFCs),Carbon Tetrachloride (CCl4)and Hydro Chloro fluorocarbons (HCFCs)

Molecules of thesesubstances drift upwardthrough the troposphere andeventually reach thestratosphere.

As these compounds absorbultra violet radiation they aredecomposed and chlorine isreleased.

The Chlorine in turn attacksmolecules of Ozone, conver-ting them in large numbers intoordinary oxygen molecules.

In this way, the Ozone concen-tration within the stratosphericozone layer can be reduced.With less ozone in theatmosphere, more ultravioletradiation reaches the earth,leading to a higher incidenceof skin cancer (or melanomia)catarats, destru-ction ofcertain forms of aquatic life,reduction in crop yields anddamage to the immune system.

Oceanography It deals with the study of

oceans and is concerned withelucidation of the physical andbiological characteristics of theoceans.

Pacific Ocean This is the largest ocean in the

world. One-third of the earth is

covered by this ocean. Itcovers an area of 166 millionsq.km. and has a volume of 696million cubic km.

The outer boundary of the

There are five majoroceans each encompassingwithin it a large number ofseas, bays and gulfs. Theyare the Pacific, theAtlantic, the Indian, theArctic and the Antarcticor the Southern Ocean.

deep ocean-type structure iscalled the andesite line, sonamed after the andesite rockthat is found only in the oceanbottoms and not on thecontinents.

The name ‘Pacific’ was givenby Magellan who was the fistEuropean to cross it in 1521 toreach Philippines.

The Mariana Trench in theChallenger Deep of the PacificOcean is the deepest point onthe earth.

In shape, it resembles a broadtriangle with its apex in thenorth at the Bering Strait andthe base to the south.

Atlantic Ocean This is the second largest

ocean in the world. It is the busiest ocean route in

the world. The Atlantic Ocean separates

American continents fromEurope and Africa.

The greatest depth in theAtlantic is Milwaukee depth inthe Puerto Rico Trench.

Bermuda Triangle is located inthe Atlantic Ocean.

Indian Ocean Indian Ocean is the third

largest ocean in the world andthe only ocean named after acountry, India.

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The days and years are based on solar (sun) time. One day equals to the length of time it takes for the earth to make one complete revolution in its

own axis. One year is the approximate time taken by the earth to make one complete revolution around the sun. The Sumerians, Babylonians and ancient Egyptians had calendars based on the lunar month. The

original Roman calendar apparently covers only agricultural months. A calendar instituted in 1582 by Pope Gregory XIII has now been used in most of the world. Its

distinguishing feature is that, in it a century year is a leap year. Leap year is an year which is exactly divisible by four. But the last year of a century will be a leap

year only if it is exactly divisible by 400. Thus 1700, 1800, 1900 are not leap years but 1600, 2000,2400 etc are leap years. This correction was made by Pope Gregory XIII in AD 1582.

A year with 366 days is called a leap year. In a leap year, February will have 29 days. The concept of leap year was introduced in the Roman calendar by Julius Ceasar in

46 BC, on the advice of his astronomer Sosigenes. Britain introduced the Gregorian calendar in 1752.

Years, Months & Calendars

The greatest depth in theIndian Ocean is the JavaTrench (7,725 m).

Madagascar is the largestisland in the Indian Ocean.

Indian Ocean is mostlyconfined to the SouthernHemisphere while in theNorthern Hemisphere, itextends only to a few degreesof latitude. Due to this fact, theIndian Ocean is often calledhalf an ocean.

Arctic Ocean The Arctic Ocean is connected

to the Pacific Ocean throughthe narrow Bering Strait and tothe Atlantic Ocean throughlarge openings of the BarentsSea, Greenland Sea andnumerous straits in theCanadian archipelago.

This ocean is roughly circularin shape and it surrounds theNorth Pole.

Antartic Ocean (Southern Ocean) The Antarctic Ocean flows in

the eastern direction. The Antarctica Ocean is the

fourth largest among the fivemain oceans .

The current, popularly knownas West Wind Drift moves theocean from west to east allaround Antarctica. Thiscurrent mixes the ends of thePacific, the Southern ends ofthe Atlantic, and the IndianOcean.Ocean MovementsThere are three types of

motions in the oceans viz., thetides, the waves and the

currents. Tides imply a rhythmic rise and

fall in the level of water in theoceans and seas. They arecaused by the gravitationalpull of the moon and the sunon the surface of the earth.

An earthquake originating onthe sea bottom may give rise

to very high magnitude wavescalled tsunamis.

Both the tides and the wavesdo not involve large scalemovement of water from oneregion to the other.

SubmarineTopography

Ocean Currents General movement of a mass

of surface water in a fairlydefined direction is known asan ocean current.

Ocean currents are of twokinds:(i) Warm Currents(ii) Cold Currents

Warm currents which flowsfrom a warmer region to acolder region (equatorial to thepolar regions).

Cold currents which flow froma colder to a warmer region (po-lar region to the equatorial re-gion).

Ocean currents are caused by

several interacting forces. Oneof the prime causes, particu-larly of surface currents iswind.

Florida current and Brazil cur-rent are warm currents of theAtlantic ocean.

Kuroshio current is in the Pa-cific Ocean.

Agulhas current is a majorwarm current of Indian Ocean.

Ocean currents change theirdirection annually in the IndianOcean.

Labrador, Canaries, Beneguelaand Falkland are cold currentsof Atlantic Ocean.

Alaska, Peruvian or Humboldtand California are cold cur-rents of the Pacific Ocean.

Ocean currents influence theclimate of the regions they passthrough.

Tides Tide is the periodic rise and

fall of sea water. The tides arecaused by gravitational pull ofthe moon and sun on earth’ssea water.

The time period between ahigh tide and a low tide is ap-proximately six hours. Each ofthem happens twice a day.

Highest tidal amplitude andrange was found in Bay ofFundy.

Highest tides recorded in In-dia is at Okha, Gujarat.

Generally, tides occur twice aday. But in Southampton, alongthe southern coast of England,experiences tides 4 times a day.

A rise in the water level iscalled high tide and a fall iscalled low or ebb tide. Tidesare of two types, Spring Tidesand Neap Tides.

Spring Tides are caused as aresult of the moon and sunpulling the earth gravitationallyin the same direction. Theyoccur twice a month around thefull moon and new moon. It isthe tide of maximum rise.

Neap Tides are caused whenthe moon and the sun pull theearth gravitationally in oppo-site directions. These tides areproduced when the moon andthe sun are at right angles tothe earth. It is the tide of mini-mum rise, occuring twice amonth. They occur on halfmoon days.

Waves A wave is an undulation that

moves across the surface ofthe sea caused by the transferof energy from the wind to thesea.

Standing waves or stationarywaves are caused by storm orsudden disturbances in wateror atmosphere.

Tidal waves or seismic wavesor tsunamis are waves whichare formed by underwaterearthquakes in volcanic erup-tions at the sea bottom. Theyhave a long tidal period and avery high speed.

A canyon is a deep narrow val-ley with almost upright sidesformed by the denudation ofsoft rocks by rivers and rainwater.eg : Grand canyon on the Colo-rado River in U.S.A

Coral reef is a ridge of rock inthe sea that is composedchiefly of the skeletons of smallanimals called reef - buildingcoral polyps.

The most extensive of all thebarrier reefs is the Great Bar-rier Reef of Australia.

Atoll is a circular or horse–shoe shaped coral reef sur-rounding a lagoon either hav-ing an island or submergedplateau in it. They are foundchiefly in the Pacific Ocean.

Lagoon is a shallow stretch ofwater separated completely orpartly from the sea by a nar-row strip of land.

Isthmus is a narrow strip ofland joining two larger areas ofland that would otherwise beseparated by water. The isth-mus of Panama joins North andSouth America.

Strait is a narrow passage ofwater connecting two seas ortwo large areas of water.

A bay is a part of the sea or ofa large lake enclosed by a widecurve of the shore.

Gulf is a part of the sea almostsurrounded by land. Gulfstreams are warm currentsflowing across the AtlanticOcean from the gulf of Mexicotowards Europe.

High seas are the open seas oroceans outside any territorialwaters of countries. They arealso known as Internationalwaters.

The laws binding the territo-rial right over the sea has beenfixed by the UN and have beenaccepted since 1974. Withinthe Exclusive Economic Zone(EEZ) the coastal state has theright to exploit all economicresources - fish, minerals, oiland gas and energy produc-tion.

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An estuary is the single v-shaped mouth of a river whenit merges into the sea. It is wid-est near the sea.

A delta is a triangular tract ofalluvium, usually fan shaped atthe mouth of a river where itdeposits more material thancan be carried away. The rivergets divided into two or morechannels (distr ibutaries),which may further divide andrejoin to form a network ofchannels.The world’s largest deltaSunderbans, is formed bythe Ganges and theBrahmaputra in Indiaand Bangladesh. Its areais nearly 75,000 sq.km.

Beach is the shore of a sea,consisting of a strip of pebbles,sand or mud lying between lowand high water marks.

Shoal is a shallow region in asea, river or lake.

Waterbodies Hydrosphere - The mass of

water that covers about 71%of the earth's surface. Oceansare the largest single constitu-ent unit of the hydrosphere.

Average depth of the ocean isabout 4 km.

Oceans contains more than97% of the total water on theearth.

The study of various aspectsof oceans is called oceanogra-phy.

Oceans predominate over landareas in southern hemisphere.

The greatest depth in Indianocean is the DiamentinaTrench.

Arctic ocean is the smallest

ocean in the world. The two most abundant ele-

ments in sea water are chlorineand sodium.

Peninsula is a piece of landalmost surrounded by water.Southern India is a peninsula.

The sea with the highest de-gree of salinity is the Dead Sea.No fish live in this sea, henceit is called Dead Sea.The Panama Canal links

the Pacific Ocean with the At-lantic Ocean. The length ofPanama Canal is 82 km (50miles). It was built by the USAduring 1904-14. Now the con-trol of the canal is with Panama.

Kiel canal, an internationalcanal linking the North Seawith the Baltic sea was built bythe Germans in the years be-fore first world war. It is 96 kmlong. It was declared an inter-national waterway by theTreaty of Versailles in 1919.

Berring Strait connects thePacific Ocean and the ArcticOcean in the north, which sepa-rates Asia and North America.The International Date Linepasses through the BerringStrait.

Baffin Bay lies in betweenGreenland and Canada.

The Grand Banks are the fa-mous fishing grounds in theNorth-West Atlantic.

Abyssal Plain - The deepestand most extensive part of theocean floor and it accounts forthe largest proportion of thetotal area of the oceans.

A waterfall is simply the fall ofan enormous volume of waterfrom a great height. Jog orGersoppa Falls on Sharavati (atributary of Cauvery) inKarnataka is the highest wa-terfall in India.

A glacier is a moving mass ofice at a speed averaging be-tween 30 to 40 cm and 15 to 18metres per day. It originates athigh altitudes due to low tem-peratures and high orographicprecipitation.

Rivers The Nile (6670 km) which is the

longest river in the worlddrains into the MediterraneanSea.

The Amazon, flowing into theSouth Atlantic, is the largestriver in terms of size and vol-ume of water discharged. It is

The Suez Canal

The Suez Canal is an artificial sea-level waterway in Egypt, con-

necting the Mediterranean Sea and the Red Sea.

Opened in November 1869, it allows water transportation be-

tween Europe and Asia without navigating around Africa.

The canal was nationalised by Col. Nasser on July 26, 1956.

Suez Canal is an artificial water way from Port Said to Suez. It is

169 km long (105 mile). It separates Asia from Africa. It was

opened in 1869 and nationalised in 1956. Suez Canal has short-

ened the distance between Southampton and Mumbai by about

6500 km.

Ferdinand de Lesseps, the French architect designed it.

6437 km long. It makes the larg-est river basin in the worldcovering an area of 7,045,000sq.km.

The longest river in Europe isthe Volga, 3690km.

The longest river of Oceania isthe Murray in Australia(3220km).

The Indus (2900km) is the long-est river of the Indian subcon-tinent. The longest river of In-dia is the Ganges (2640km).

Indus river system is the mostextensive river system in theIndian subcontinent. It in-cludes - Indus, Ravi, Beas,Sutlej, Jhelum, Chenab.

The Brahmaputra (2688km) isbigger than the Ganges; butonly a small part of it flowsthrough India. It originatesfrom Manasarovar Lake in Ti-bet. In Tibet, its name isTsangpo.

The only river that crosses theequator twice is river Congo.

Victoria falls are in river Zam-bezi.

The only river to cross theTropic of Capricon twice isriver Limpopo in South Africa.

City at the confluence of Blueand White Nile is Khartoum,capital of Sudan.

DesertAntartic Deserts, Arctic,

Sahara (Africa), ArabianDesert (Middle East), GobiDesert (Asia), Kalahari Desert(Africa), Pantago nian Desert(South America), Great Victo-ria Desert (Australia), SyrianDesert (Middle East), GreatBasin Desert (North America)are the ten largest deserts inthe world .

Hot deserts have sparse veg-etation often found in clumpsover small patches of land.

Cacti are the most typical plant.In some places, dwarf trees likeAccacia, Date palms etc are alsofound.

June 17 : World day to com-bat desertification

The Takla Makan (32,000 sq.km)is the largest desert in China; Gobi(Mongolia) is the coldest desertin the world. Largest Desert inIndia is Thar Desert.

Camel is known as the ship ofthe desert.

Atacama Desert in NorthernChile is the driest place onEarth. It is virtually sterile be-

Longest river of Asia ................................ Yangtze (Chang Jiang) Longest river of Europe ..................................................... Volga Longest river of North America ...................... Missisipi-Missouri Longest river of South America ..................................... Amazon Longest river of Australia ............................................... Murray Longest river of Africa ......................................................... Nile Longest river of South East Asia ................................... Mekong Longest river of South West Asia ............................... Euphrates Longest river of Russia ......................................................... Ob Longest river of Sri Lanka ................................ Mahaweli Ganga World's longest rivers in descending order of length are Nile, Ama-zon, Chang Jiang and Missisipi-Missouri.

Lakes Lake Superior (North America) is the largest freshwater lake in the

world. The Caspian Sea is the largest salt water lake. It borders with Russia,

Kazakhistan, Azerbaijan, Iran and Turkmenistan. Lake Baikal (Russia) is the deepest freshwater lake (depth 1620 m). The highest navigable lake in the world: Lake Titicaca in Peru and

Bolivia. The saltiest lake in the world : Lake Van (Turkey) Great lakes arranged from west to east are Lake Superior, Lake Michi-

gan, Lake Huron, Lake Erie, Lake Ontario. Great lake lying entirely in USA is Lake Michigan.

cause it is blocked from mois-ture on both sides by the An-des mountains and by the Chil-ean Coast Range.

Kalahari Desert lies in South-ern Africa. The Bushmen arethe aborigines of Kalahari.

Hottest Place - Denakit Depres-sion, Ethiopia, 34.4oC

Hottest inhabited place - DjiButi.

Islands Greenland (Kalaait Nunait),

which is the largest island inthe world, is in North Atlantic(2, 176,000 sq.km). It is a terri-tory of Denmark.

Archipelago is a group of is-

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lands. Indonesia is the largestarchipelago in the world.

Ireland is known as the Emer-ald Island. Baharain is knownas the Pearl Island.

The second largest island isNew Guinea.

Malagasy (Madagascar) is thelargest island in the IndianOcean (588,000 sq.km).

Andaman and Nicobar Islandsis the biggest union territoryin India. It lies in the Bay ofBengal. Its capital is at PortBlair. There are 223 islands inthe group.

Lakshadweep is in the ArabianSea. There are 27 coral islandsin the group.

Japanese archipelago of over4000 islands.

Japan comprises 4 islands -Honshu, Hokkaido, Kyshu,Shikoko. Among this Honshuis the biggest island.

The Sahara (8,400,000 sq.km) is the largest desert inthe world. It spreads over nearly 6% of world’s total

land area and 28% of the land area of Africa.

Ten Degree Channel -----Little Andaman and NicobarDuncan passage ----------South Andaman and Little AndamanCape of Good Hope ------Located at the southern tip of African continent.Cape of Horn ---------------Located at the southern tip of South America.Strait of Malaca ------------Between Malaysia and SumatraBarents Strait --------------Between Scandinavian countries and Arctic Ocean.Palk Strait --------------------Between India and Sri LankaEnglish Channel ----------Between England and FranceBerring Strait ---------------Russia and the USAFlorida Strait----------------Cuba and USAStrait of Gibralter ---------Spain and MoroccoStrait of Magellan ---------Tip of South AmericaBass strait -------------------Separates Australia from Tasmania

Important Straits

Types of Island1. Continental Islands2. Oceanic Islands3. Tropical Islands4. Desert Islands

Greenland is the example ofContinental Island.

Natural Vegetation Natural vegetation refers to a

plant community that has beenleft undisturbed over long time.

Flora denotes the plants of aparticular country or region.

Fauna denotes the animal king-dom found in a particular geo-graphical region.

The world climate types havebeen classified on the world'sclimatic / temperate zones.

The major climatic types of theworld have been classified as(i) Equatorial(ii) Tropical Monsoon(iii) Tropical Desert

(iv) Mediterranean type(v) Cool Temperate (Continental or Ocean)

Teak is the most valuable tim-ber, which is used for furnituremaking and is found in tropi-cal monsoon climate.

Savannah is a region which lieson both sides of the equatorroughly between 5 degrees andthe tropics. Here summers arehot and moist and winters arewarm and dry.

Deciduous forests are forestswith trees which shed theirleaves seasonally.

Tundras is the belt of treeless,cold desert which remains un-der heavy snow during mostof the year. Eskimos live there.Igloos are dome shaped hutsof Eskimos which are dug halfunderground and coveredwith blocks of ice. Eskimos arealso called Inuits.

Natural resources are classifiedinto biotic and abiotic re-sources.

Biotic resources are renew-able resources consisting ofliving things such as forestsand their products, agriculturalcrops, fodders, wild and do-mestic animals etc.

Abiotic resources consists ofnon-living things like mineralsand fuels which are mostly non-renewable.

Reserved forests are forestsreserved for commercial exploi-tation.

Wettest place - MawsynramIndia - 1187 cm.

Valley of moon is the Atacamadesert.

Tropical monsoon forest is thetypical vegetation of monsoonland, like that of India.