INDIAN GEOGRAPHY AT A GLANCE

Indian Geography At a Glance

CHAPTER1

(I) INDIAPHYSICAL FEATURES

Geographical Set Up:

India takes its standard time from themeridian of 82 30 E, which is 5 ½ hoursahead of Greenwich Mean time ( 0 longitude).Pakistan time is 5 hours ahead ofGMT and Bangladesh time is 6 hours ahead of GMT.

Significance of Location:

Barring the plateau of Baluchistan (which form partof Pakistan), the two great ranges of Sulaiman and Kirthar cutit off from the west. Along the north, the great mountain wall formed by theHindukush, Karakoram and the Himalayas, which is difficult to cross, cuts it off from therest of the continent. Similarly, the southward of-shoots of the Eastern Himalayas separate it from Russia. The tropical monsoon climate of India, which ensures a fair supply of moisture and formsthe basis of farming in India, is also a result of its location in the southernpart of Asia. Since the opening of Suez Canal (1867) India’s distance from Europe has been reduced by 7,000km. It thus bridges thespace between the highly industrialized nation of the west and the semi-arid,and south-western Asia and the most fertile and populated regions in thesouth-east and far-east countries.

PHYSIOGRAPHICUNITS OF INDIA

S.NO	UNITS	AREA KM (Sq) (appro)	% OF TOTAL AREA
01	Northern mountains	578,000	17.9
02	Great Plains	550,000	17.1
03	Thar Desert	175,000	5.4
04	Central Highlands	336,000	10.4
05	Peninsular Plateaus	1,241,000	38.5
06	Coastal Plains	335,000	10.4
07	Islands	8,300	0.3

The Trans Himalayas orTibetan Himalayas: The largest glaciers are Hispar and Batura (over 57km long) of Hunza Valley and Biafo and Baltaro (60 km long) of Shigar Valley. The Siachen of Nubra Valley is the longest with a length of over 72km.The Purvachal or the Eastern Hills: In the east after crossing the Cihanggorge the Himalayas bend towards south forming a series of hills runningthrough Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura and easternAssam and form the boundary between India and Burma. Brahmaputra rivers divide Himalayas into three sections: themain Himalayas, the northwest Himalayas and the southeast Himalayas. The main Himalayas running from the PamirPlateau in the northwest to Arunachal Pradesh in the southeast are the youngestmountains in the world. The highest peakof the word, the Mount Everst(8,884m, named after SirGeorge Everst). There are about 140peaks in the Himalayas whose elevation is morethan the Mount Blanc (4,810m),the highest peakof the Alps. The three mountain ranges: the Himadri in the north(thegreater Himalayas)the Himachal in the middle(the lesser Himalayas) and the Siwalik(the Outer Himalayas),facing thrpalins of India. The Himadri is of grat elevations (6,000m)which remains covered with everlasting snows. The Siwalik have some flat-floored structural valleys knowns asduns. Dehradun is well-known. Betweenthe Himadri and the Himachal are some broad synclincal valleys. We alsoclassify them as Punjab Himalayas, Kumayun, Assam Nepal and Northern.

Significance of Himalayas:

(i) Physical Barriers (ii) Birthplace ofRivers (iii) Influence on climate (iv) Flora and Fauna (v) Mineral Resources(vi) Economic Resources (vii) Tourist

II The GreatNorthern Plains:

Lies between the great Himalayas in the North and the plateau of Peninsular India in the south. Nearly2400 km long around 250-320 km broad, the most extensive plan indeed. It issaid that this region was once a vast depression, filled with silt – broughtdown by the three Himalayas River, namely the Indus, the Ganga and the Brahmaputra andtheir numerous tributaries. It contains some of the richest soils. The bhangarrefers to the upland formed by deposition of older alluvium in the river bedsand the Khadar are lowlands formed by deposition of detritus of new alluvium inthe river beds.

Bhabar and Terai:

Includes those regions where the Himalayas and other hilly regions join the plains. Coarse sand and pebbles aredeposited. Bhabar lands are narrower in the east and extensive in the western andnorth-western hilly. Water converts large areas along the river into swampsknown as Terai.

The Western or Rajasthan Plains:

are known as Marusthali ofThar and the adjoining Bagar areas to the west of Aravalli. Luni whose water issweet in the upper reaches and saltish by the time is reaches the sea. Theseveral salt lakes in the region such as the Sambhar, Degana, Kuchaman andDidwana; from which table salt is obtained. In most of the region shifting sanddunes occur.

The Punjab-Haryana Plain:

These plains owe their formation to the Sutlej, the Beas and the Ravi rivers. Manylow lying flood plains (called bets) are found here. The Bari Doab between Ravi and Beas rivers, the Bist Doab between the Beas and Sutlej and the Malwa plain are relatively more fertileplain.

The Ganga Plain:

The Ganga-Yamuna Doab comprising theRohilkhand and the Avadh Plain is the tile area that is drained by thetributaries of Ganga.

The North Bengal Plains: thePlains extending from the foot of Eastern Himalayas tothe northern limb of Bengal basin cover an area of 23,000km2.

Brahmaputra Plains:

This is a low level plain,rarely more than 80km broad, surround by High Mountain on all sides except on the west.

Significance of the Great Plains: Riverine region, Fertile soil, favorable climate, flatsurface, constructions of roads, extensive system of irrigation.

The Peninsular Plateau:

oldest structure of theIndian subcontinent whose slow and steady movement towards north and north-easthas been responsible for creation of the Himalayas and the Northern Plains in place of the Tethys sea of geological time.It is marked of from the Indo-Gangetic plain by the mountain and hill rangessuch as the Vindhyas, the satpura, and Mahadeo, Maikal, and Sarguja ranges withthe average height is usually divided into two major subdivisions with the Narmada valley as the line of demarcation. The region north of the Narmada valley is known as the Central Highlands and in south of the Narmada valley lies the Deccan Plateau.

III The Central Highlands:

Old Aravalli Mountain on the west and the Vindhyas on the south. Thisregion lopes northward to the Ganga plains. The western part of the Central highlands isknown as the Malwa Plateau. The Central part has a number of small plateauslike those of Rewa, Baghelkhand and Bundlekhand. The eastern part of theCentral Highlands comprises the Chotanagpur plateau.

The Deccan Plateau:

The Deccan Plateau extendsfrom the vindhyas to the southern tip of the Peninsula. This triangle plateau is at its widest in the north. The Vindhya Range and its eastern extension namely Mahadev hillsKaimuir Hills and Maikal Range from its northern edge. Western Ghats are known by different regional names such as theSahyadris in Maharastra and Karnataka, the niligris in Tamil Nadu and Annamalaiand the Cardamon hill along the Kerala and Tamil nadu border. The elevation ofthe ghats increases towards the south. The highest peak, Anaimudi (2,695 m) isin Kerala. The most important gap in the Western Ghats is the Palghat gap which links Tamil Nadu withKerala. The Bhorghat and the Thalghat are other gaps lying in Maharastra state.

Eastern Ghats:

These hills rise steeplyfrom the Coromandel coastal plain. The Eastern Ghats are well developed in the region between the Godavari and Mahanadi rivers. The Eastern Ghats and Western Ghats converge in theNilgiri hills. Dodda Betta (2,637 m) is the highest peak in the Nilgiri hills.

Significance of Peninsular Plateau: (i) Geological richness (ii) Sources of Irrigationand hydroelectricity (iii) Agricultural Resources (iv) Forest Resources (v)Rich Fauna

(vi) Cultural Influences.

IV THE COASTALPLAINS AND ISLANDS

The Coastal plains:

The Peninsular plateau isbounded by coastal plains on the east and west. There is wide difference betweenthe eastern and western coastal plain. The west coast is narrower but wet. Eastcoast much wider but relatively dry. A number of river deltas occur on the eastcoast. The deltas of east coast from the ‘granary’ of the five southern states-Andhra Pradesh, Tamil Nadu, Karnataka, Kerala and Pondicherry. The western coastal strips which have a large number of lagoons and back waters on otherhand are noted for spices, areca nuts, coconuts palms etc.

Western coastal Plain:

These lies between the Western Ghats and the Arabian seas and stretch from Kutch in the north to Kanyakumari in the south. The Gujarat plain is a broad and flat plain. The Kutch Peninsula, Gulf of Kutch, and the Gulf of Cambay. The Kathiawar Peninsula, also known as Saurashtra which lies to the south of Kutch, is also a plain level area except for some hills rising into Mount Girnar. Sun-divided regionally into the Konkan coast inMaharastra Canara coast in Karnataka and Malabar Coast in Kerala.

Eastern Coastal Plain:

The eastern coastal low lands extend from themouth of the Ganga to Kanyakumari. The northern half is called Northern Circars or Kalinga coast, while the southern half is knownas the Coromandal coast. The border part is the Carnatic region, which is about480 km wide. They are not suitable for harbours as their mouths being full ofsit.

Significance of Coastal plains:

(i) Harbours (ii) Specialized crops (iii)Fisheries and Navigation (iv) Economic Influence (v) Historical Importance

V ISLANDS

1.Bay of Bengal Islands:

The Andaman & Nicobar group of islands areseparated by 10 Degree channel. These islands have been formed by extension oftertiary mountain chain of Arakan Yoma. The Andaman group of island is dividedinto 3 major groups’ viz., North Andaman, Middle Andaman and south Andaman,collectively called Great Andamans. Little Andaman is separated from GreatAndamans by Duncan passage. The Nicobar group of islands of which GreatNicobar is largest and southern most one. Saddle peak situated in Andaman Islands is the highest peak of Andaman & Nicobar group.

The Dhuliar peak is thehighest peak of Nicobar group of islands.More habitable and different origin thanofArabian seaislands. Barran island is dormant volcano and Narcondam island is extinctvolcano.

2) Lakshwadeep islands: Coral- More Muslim population and have fringingreefs. They are 25 small island groups. The island’s north is known as Amindiviand spot is Cannonore island. Extreme south is Minicoy islands which islargest.

CHAPTER 2

CLIMATE REGIONS

1. Tropical Rainy climate Region:

This region has consistently even temperature,which stays above 18 C even in December, April, and May are the hottest months,the temperature varying from 18 C to 27 C. July and August are the coolestmonths, which copious rainfall. The average rainfall exceeds 250cm, whichencourages wet evergreen forests. The western coastal strip, Western Ghats, south of Bombay, Meghalaya, western Nagaland and Tripura come inthis climatic region.

2. Tropical Savanna Region: The chieffeature of this climate is the long dry period. Temperature even in winter stayabove 18 C, and in summer may even go up to 46 c. Rainfall, except in thesoutheastern parts, is in summer and averages about 100cm. In the south easternparts, the retreating monsoons bring sufficient rains. A major part of thesouthern peninsula, except the arid tract lying east of the Western Ghats,northeastern Gujarat, south Bihar, major parts of Madhya Pradesh, Orissa,northern Andhra Pradesh, eastern Maharastra, and eastern TamilNadu coast comeunder this region.

3. Tropical Steppe Region: The average temperature is over 27 C, the lowesttemperature being about 23 C April and May are the hottest months, whentemperature may rise over 30 C. Average rainfall being less than 75cm, the regioncomprises a part of the famine zone of the country. The southwest monsoonsbring rain to this region. The region comprises the rain shadow areas lyingeast of the Western Ghats and covers Karnataka, interior TamilNadu, westernAndhra Pradesh and central Maharastra,

4. Sub-Tropical Steppe Region: The average temperature rises over 27 C and as high48 C is recorded during summer. Rainfall from the southwest monsoon averagesbetween 50 to 75 cm. It often fails, leading to widespread drought conditions.This region comprises tracts stretching and encompassing western Rajasthan andnorthern Gujarat.

5. Tropical Desert Region: The summer Temperature rises over 48 C, while inwinter it goes down to 1 C. May and June are the hottest months. Averagerainfall is 12.5 cm and very unreliable. Excessive evaporation during summerand intense cold during winter hinder crop production except through riverirrigation. Western Rajasthan and parts of Kutch, which are purely sandy plains, come in this region.

6. Humid Sub-Tropical Region: Summer temperatures are 46 C to 48 C. Averagerainfall, mostly from summer monsoons, is about 62.5 cm, which increases toover 250cm in the east. Winters are virtually dry. This region is spread overthe foothills of the Himalayas, eastern Rajasthan, plains of U.P, Bihar, northern Bengal, part of Assam and Arunachal Pradesh.

7. Mountain Region: Average temperature in June is 15 C to 17 C, inwinter it goes below 8 C. On the northern slopes of the Himalayas, the rainfall is scanty, about 8-10 cm, but the western slopes enjoy aheavy rainfall of over 250 cm. The entire Himalayan belt comprising both thetrans-Himalayas and the main Himalayas come under this region.

CHAPTER 3

THE PENINSULAR PLATEAU

The Peninsula plateau is roughly triangular in shape with base coinciding withsouthern edge of the great edge of the Great Plains. It covers a total area of 160,000km 2. (About halfof total land area of the country)

The Plateaus of Peninsular India

1. The Marwara Upland: It lies east of Aravali range made up of standstone, shales and limestone of Vindhayan period. The upland is drained by Banas River originating in Aravali range.

2. The Central Highland: Also called the Madhya Bharat Pathar, lying in theeast of Marwara upland and drained by Chambal and its tributaries.

3. The Bundelkhand Upland: To south of Yamuna river between Madhya BharatPathar and the Vindhyan scarap lands consists of granites and gneiss.

4. Malwa Plateau: Bonded by Aravali range in the west and Bundlekhandin east and Vindhayas in south. It is an extensive lava plateau in M.P. withblack soil drained by a number of north flowing rivers like Betwa, Parbati,Kali Sindh, Chambal and Mahi.

5. Baghelkhand: East of Makal range and bounded by Son River on the north.

6. Chhotanagpur Plateau: It covers mostly Jharkhand adjoining eastern MadhyaPradesh and Purulia of West Bengal. This Plateau is composed mainly of Gondwanarocks with patches of granites ad gneisses and Deccan lavas. The highest general elevation is in the Midwest portion known as patlands (high level laterite plateau e.g. Netarhat).The Plateau is drained by numerous rives in a radial pattern such as Damodar,Subarnrekha, North Koel, South Koel and Barakar river.

7. Meghalaya Plateau: This Plateau has been separated from main block ofthe peninsular plateau by a gap called Ganu-Raj Mahal gap. From east to westthe plateau comprises Gana, Khasi and Jaintia hills and Mikir hills. Shilong isthe highest point of the plateau.

8. The Deccan Plateau: This is the largest unit covering an area of 5 lakhsq.km. It comprises Maharastra Plateau, Karnataka plateau and the Telenganaplateau (Andhra Pradesh). The general slope is form west to east. Indicated byflow of major rivers like Mahanadi, Godwari, Krishna and Cauveri.

9. The Chhattisgarh Plain: It is the only plain worth the name in the vaststretch of plateau drained by upper course of Mahanadi. This saucer shaped depression lies between Makal range and Orissahills.

HILL RANGE OF THE PENINSULA 1. Aravali Range: Aravalis are the world’s oldest fold mountainrunning in north east to southwest direction from Delhi to Palampur in Gujarat. Gurushikhar is the highest peak situated in Mount Abu. Barr, Piplighat, Dewair and Desuri passes allowmovements by roads and railways.

2. Vindhyan Range: It raises as an escarpment flauting the northernedge of the Naramada, Son-trough. The Vindhyas are continued eastward as theBharner and Kaimur hills. This range acts a s a water divided between Ganga system and river system of South India. TheMakal range forms a connecting link between Vindhyan and Satpuras.

3. Satpura Range: It is a series of seven (Sat) mountains running ineast-west direction south of vindhyas and in between the Narmada and Tapi. Commencing from Rajpipla hills in the west through theMahadeo hills it extends to Makal range in the east. Dhupgarh near Panchmarhion Mahadeo hills is highest peak of Satpuras.

4. Western Ghats(Sahyadris): The western Ghatrun in north-south direction from Tapi valley to north of Kanyakumari. Alongthe Arabian sea-coast for about 1600 Km. these are Block Mountains due to the down warping of the land to the Arabian Sea. Sahyadris form the real water divide of thepeninsula. All the important rivers rise from these hills and flow eastward.The Sayadris up to 16 north latitude are mainly composed of basalt. In thisportion Kalsubai is the highest peak. South of Goa Sahyadris are composed ofgranites and Gneisses. In the Nilgiri hills, Eastern Ghats join the Sahyadris to form a mountain knot whose highestpoint is Doddabetta (2637 m). South of it is Palghat gap connecting Tamil Naduwith Kerala. South of Palghat there is mountain knot comprising Annamalai hillsin north. Patni hills in the north-east and the Cardamon hills in the south.Anaimudi (2695 m ) situated in the Annamalai hills is the highest peak of Sahyadri. Kodaikanal hill station is located on the Patnihills. There are 3 important passes in the Sahyadris:

(a) Thalghat (b) Bhorghat(c) Palghat

5. Eastern Ghat: It is a chain of highly broken and detached hillsstarting from Mahanadi in Orissa to Vaigai in Tamil Nadu. These are part ofthe very old fold mountains. It is only in the northern part between Mahanadi and Godavari that Eastern Ghatsexhibit true mountain character comprising Maliya and Maduguala konda ranges,South of Godawari the broken hill ranges are Nallamalai, Palkonda, and Javadi,Shavroy and Biligiri Rangan hills. Mahendragiri is the tallest peak of easternGhat.

CHAPTER 4

SOILS

1. COMPOSITION OF SOIL: Soil isthe loose material which forms the upper layer of the mantel rock, i.e., thelayer of loose fragments which covers most of the earth’s land area. It hasdefinite and constant composition. It contains both decayed plants and animalssubstances. The four main constituents of soils are;

(i) Silica: The chief constituent of sand

(ii) Clay: is a mixture of silicates and contains severalminerals such as iron, potassium, calcium, sodium and aluminum. Particles ofclay absorb water and swell.

(iii) Chalk: (calcium carbonate) provides calcium, the mostimportant element for the growth of plants.

(iv) Humus: is not a mineral, it is an organic matter. It isformed by decomposed plant remains, animal manure and dead animals and is themost important element in the fertility of the soil. It helps retain moisturein the soil and helps the plant in absorbing materials from the soil forbuilding its body. A soil looks dark on account of the presence of humus.

2. TOP SOIL AND SUB SOIL: Twolayers namely top soil and sub soil. Top soil(the upper layer) is of greaterimportance. Good top soil means good crops. It varies considerably in depth andalso in character and ability to grow crops. It is only a few meters deep.Million of bacteria, insects and worms live in it. Top soils develop veryslowly. It may take years to form top soil suitable for plants, but it can bewashed away in a few years if proper precautions are not taken. Sub soilsconsist of the parent material from which soil is formed. It also containsplant food and moisture but it is not a s productive as top soil. It has to beconverted into soil and it may take years to convert sub soil into soil. Belowthe sub soil generally there is solid rock.

3. FORMATION OF SOIL: The natural processes involved in the formation ofsoil are

(i) Weathering: process of disintegration of rocks into soil.

(ii) Deposition: process of progressive lying down of rock particlescarried by rivers, ice, marine, currents wind or tides.

(iii) Biochemical processes

Soilformation depends upon the following factors;

*Natureof the parent rock, * Climate, * Natural Vegetation, * Topography, * Time

4. GENERAL CHARACTERISTICS OFDIFFERENT SOILS

a) Sandy Soil (light soil): It contains more than 60% sand and les than 10%clay. It is easy to cultivate and is favoured for fruits and vegetables.

b) Clayey Soil: It has high proportion of clay. It becomes stickywhen mixed with water. A soil very rich in clay is called ‘heavy’,

c) Loam: is rich soil and consist of a mixture of sand andclay. All loamy soils are good for farming and general gardening.

5. MAJOR SOIL TYPES

TheIndian Council of Agricultural Research (ICAR) classifies the soils of India into eight categories.

6.ALLUVIAL SOIL: This is the mostimportant and widespread group of soils. It covers about 15 lakh sq.km of theland area in Great Plains from Punjab to Assam and also in the valleys of the Narmada and Tapi, Mahanadi, Godavari, Krishna and Cauvery. These soils have been brought down anddeposited by three great Himalayan rivers Sutlej, Ganga and Brahmaputra. These soils consist of varying proportions of san,silt and clay. Khadar is the newer alluvium which is sandy, light coloured andoccurs near river beds where deposition takes place regularly and bhangar orolder alluvium. Alluvial soils as a whole are very fertile and therefore thebest agricultural soils of the country. The regions of these of these soilsconstitute the’ wheat and rice bowls’ of India.

7. BLACK SOIL: As the name indicates these soils are black inColour and since they are ideal for growing cotton, they are also called cottonsoil. These soils, covering an area of 5.46 lakh sq.km, are most typical of theDeccan trap (Basalt). The black Colour of regur isvariously attributed to the presence of titaniferrous magnetite, compounds ofiron and aluminum-Unsuitable for heavy irrigation. Ideally suited to dryfarming. Suitable for cotton, cereals, oilseeds like linseed, castor andsafflower, many kinds of vegetables and citrus fruits.

8. RED SOIL: These soil occupy about 5-18 lakh sq.km over thepeninsula reaching up to Rajmahal Hills in the east, Jhansi in the north andKutch in the West. In North western peninsula is covered by the black soils andthe remaining south-eastern half is covered by red soils- Entire black soil inthe eastern part of Peninsula comprising of Chhotanagpur plateau, Orissa, eastMadhya Pradesh, Telengana, the Niligris, Tamilnadu plateau and Karnataka. Thesoil have reddish colour due to iron compounds. It is suitable for rice, ragi,tobacco and vegetables.

9. LATERITE SOILS: These soils occupying an area of 1.26 lakh sq.km-Found capping the flat uplands, and are spread in western coastal regionreceiving very heavy rainfall – Poor in nitrogen, phosphoric acid, potash, lime– suitable for rice, ragi, tapioca and cashewnuts.

10. FOREST AND MOUNTAIN SOIL: These soils occupy about 2.85 lakh sq.km in thehilly regions of the country – described as soils in the making – found in theHimalayas and the other ranges in the north and high hill summits in theSahyadris, Eastern Ghats and Peninsula – poor in potash, phosphorous –Temperate fruits, maize, wheat and barley are grown in Jammu and Kashmir andHimachal Pradesh where soils are mostly podzols which are acidic in re-action.

11. ARID AND DESERT SOILS: Northwestern parts of the country and occupy about1.42 sq. km area in Rajasthan, south Haryana, north Punjab and Rann of Kutch. Thar Desert alone occupies anarea of 1.06 sq. km. It contains high percentage of soluble salts and a low tovery low organic matter.

12. SALINE AND ALKALINE SOILS: These soils occupy about 170 lakh sq. km of arid andsemi-arid areas of Rajasthan, Punjab, Haryana, Uttar Pradesh, Bihar and whole of Maharastra. Textually they are sandy to loamy sand. Salinesoils contain free sodium. Crops grown on these soils include rice, wheat,cotton, sugarcane and tobacco.

13. PEATY AND MARSHY SOILS: These soils cover an area of about 150 sq. km in theKottayam and Allepey districts of Kerala. They are suitable for paddycultivation.

14. SOIL FERTILITY: The factor responsible for deficiency of Indiansoils are: (i) loss of nutrients, largely brought about through the removal ofharvested crops, (ii) leaching which occurs under heavy monsoonal rains, causesloss of nutrients, sandy soils are more subject to leaching than the heavierones and bare soils are more than thosecovered by plants. Indian soils are mainly deficient in nitrogen, phosphorusand potash. These can be supplied to the soils by application of organic manuresand fertilizers.

15. SOIL EROSION: Soil erosion is the removal of soil particles bynatural agencies such as water and wind and also as a result of human andanimal interference.

16. TYPES OF SOIL EROSION: Two types of soil erosion:

(i) Water Erosion: The important types of this erosion are sheet, rilland gully. In sheet erosion thin layer of soil is removed by the water duringheavy rains. If the erosion continues unchecked, numerous finger-shaped groovesmay develop all over the area as a result of the silt-landen run-off. This iscalled rill erosion. The rills may deepen and enlarge into gullies.

(ii) Wind Erosion: Wind erosion is mainly confined to arid andsemi-arid areas devoid of vegetation. Wind, particularly during sand-storms,lifts and carries away soil particles leaving behind a depression devoid of topfertile soil. Rajasthan and the adjoining areas of Haryana, Uttar Pradesh and Gujarat show this type of soil erosion.

17. CONSEQUENCES OF SOIL EROSION: (i) heavy floods in rivers, (ii) lowering down ofsub soil water level, (iii) reduction of soil fertility, (iv) silting ofstreams and water courses, (v) disappearance and downfall of civilizations.

8 a) SOIL CONVERSATION: Soil conservation is an effort made by man toprevent soil erosion to retain the fertility of soil. It may not be possible tostop soil erosion entirely.

b) Measures for Soil Conservation: (i) Planting cover crops, (ii) Adoption of correctfarming techniques, (iii) Terracing the practice of cutting steps in hillside,to create level land for cultivation, (iv) Construction of check dams, (v)Creation of wind break, (vi) Controlling of grazing of pastures, (vii)Suspending cultivation for one season and more so as to help the soil recoverits fertility.

CHAPTER 5

THE EARTH’S CRUST

Theearth is made up of several concentric layers. The outer layer of the earth’scrust is called lithosphere, which comprises two distinct parts. The upperparts consist of granitic rocks and form the continents. Its main mineralconstituents are silica and alumina knows as Sial. It has an average density of2.7. The lower part is a continuous zoneof densers, basaltic rocks forming the ocean’s floors. Comprising mainlysilica, iron and magnesium known as Sima and has an average density of 3.0. TheSial and the Sima together form the earth’s crust which varies in thickness 4.8to 6.4 km, beneath the oceans and about 48 km under some o continents. Beneaththe lithosphere is the mantle known as the mesosphere about 2880 kms thick.Composed mainly very dense rock rich in Olivine. The interior layer is the coreknown as baryshpere about 2456 km in radius is made up mainly iron (Fe) and nickel (ni) known as nife. Thetemperature of core is as high as 2000 C and subject to extremely highpressure. The crust forms only 0.5% of the volume of the earth, 83% consist ofthe mantle and 16% makes the core that of the earth. The mean radius of theearth is 6400 km. the average rate of increase temp 1 C for every 32 meters ofdescent. But in upper 100 kms, the increase is estimated at 12 C/kms. It is 2C/Km in next 300 kms and 1 C/kms below it.

Name of the layer	Chemical Composition	Volume (Earth)	Mars (Earth)	Density	Physical Properties
CRUST (A) (i) Outer-part of lithosphere (ii) Inner part of Lithosphere	Sial	1% of the earth	10%	2.75 to 2.90	Solid
MANTLE (B) (i) Outer part of mantle (ii) Inner part of mantel	Silica with Sima Wholly Sima	83%	68%	3.10 to 4.75 4.75 to 5.00	Partly molten Close to melting point
CORE (C) (i) Outer part of Core (ii) Inner part of Core	NiFe	16%	32%	5.1 to 13	Plastic state Solid and rigid because of tremendous overlying pressure.

Composition of Earth’s Crust

1)oxygen: 46.6% 2) Silicon- 27.27% 3)Aluminium: 8.13% 4) Iron- 5% 5) Calcium-3.63%

6)Sodium- 2.83% 7)Pottasium- 2.59% 8) Magnesium- 2.09% 9)Others- 1,41%

CHAPTER 6

CLASSIFICATION OF ROCKS ACCORDING TOORIGIN

1. IGNEOUS ROCKS: Igneous rocks are formed by the cooling andsolidification of molten rock (magna) from beneath the earth’s crust. They onenormally crystalline in structure. They do not occur in layers and not containfossils. Some rocks can form a high percentage of silica are said to beacid. E.g., Granite. Other rocks such asBasalt contain a high percentage of iron or Aluminium or magnesium oxides arecalled basic rocks. There are two main groups:

(i) Volcanic Rocks: These are mole nocks poured out of volcanoes aslavas. They solidify rapidly on the earth’s surface and the crystals are small.E.g. basalt.

(ii) Plutonic Rocks: These are igneous rocks solidified deep in theearth’s crust and they reach the surface only by being exposed by erosion.E.g., granite, diorite and gabbros etc.,

2. SEDIMENTARY ROCKS:Sedimentary rocks are formed from sediment accumulated over long periods, usuallyunder water and deposited usually in layers by water, wind or moving ice. Theyare non-crystalline and often contain fossils of animals, plants and othermicro-organisms. There are three main groups;

(i) Mechanically-formed: (a) Wind-deposited e.g loess, (b) River-depositede.g., clays, gravels, and alluviums, (c) Glaciers-deposited e.g., morains,sands and gravels and boulder clay, (d) Sea-deposited.

(ii) Organically formed: (a) From animals e.g., chalk and coral, (b) Fromplants e.g., Peat, lignite, coal.

(iii) Chemically formed: e.g., rock slat, borax, gypsum, nitrates, potash andcertain limestone.

3. METAMORPHIC ROCKS: All thoserocks whose structure and appearance have been changed by great heat or greatpressure or both. Any rock can be changed into a metamorphic rock. In thesesmanner (a) State (from clay), (b) Marble (from limestone), (c) Quartzite (fromsandstone), (d) Graphite (from coal), (e) Gneiss (from granite), (f) Schist(from shale).

CHAPTER 7

STRUCTURE OF ATMOSPHERE

Accordingto Petterssen, the atmosphere is divided into the following five layers:

1.TROPOSPHERE:

The lowermostlayer of the atmosphere is known as Troposphere and is the most important layerbecause almost all of the weather phenomena is occurred in this layer. E.g., Fog,cloud. Thunder, lightning, etc., occurs in this layer. It extends roughly to aheight of eight kilometers near the poles and about 18 kilometers at theEquator. The thickness of the troposphere at the equator is the greater heightsby strong conventional currents. Temperature decreases with increasing heightat the rate of 6.5 C per 1000m. This rate of decrease of temperature is callednormal lapse rate. This layer contains dust particles and over 90% of theearth’s water vapour. The upper limit of the tropopause is called tropospherewhich is about 1.5km. Thick. Temperature ceases to fall with the airtemperature at the troposphere is about-80 C over the equator and about -45covers the poles. The word troposphere literally means zone or region of mixingwhereas the word tropopause means where the mixing stops.

2. STRATOSPHERE: The Stratosphere begins at the tropopause which forms its lower boundary. The lower stratosphere is isothermal in character, i.e, the temperature in the lower part of this layer does not change with altitude. The stratosphere extends up to a height of 50 km. Afterwards it gradually increases up to a height of 50 km because of the presence of ozone layer which absorbs the Sun’s Ultra-Violet Rays. Clouds are almost absent and there is very little dust or water Vapours. The air movement is almost horizontal. The upper boundary of the stratosphere is called Statopause. Above this level there is a steep rise in temperature.

3. MESOSPHERE: Over the stratopause there exists the third layer knownas mesosphere. It extends up to a height of 80 kms. Temperature decreases withheight again and reaches up to – 100 C at the height of 80 kms.

4. IONOSPHERE: Ionosphere is located between 80 km to 400 kms. Itis electrically charged layer. Radio waves transmitted from the earth arereflected back to the earth by this layer. Temperature again starts increasingwith height because of radiation from the sun. The ionosphere consists of thefollowing ionized layers:

D – Layer: 60 -99 km

E – Layer: 90 – 130 km

Sporadic Layer: 110 km

E2 Layer: 150 km

F1 Layer, F2 Layer: 130 -1890 km

G Layer: 400 km and above.

5. EXOSPHERE: The outermost layer of the earth’s atmosphere isknown as the exosphere which lies between 400 and 1000kms. The atmosphere inthis region is so rarefied that it resembles a nebula-hydrogen and helium gasespredominates in this outermost region. The temperature becomes 5568 C at itsouter limit but this temperature is entirely different from the air temperatureof the earth’s surface.

CHAPTER 8

LATITUDE, LONGITUDE AND TIME

1. INTRODUCTION: The earth is nearly a sphere and it has no edges. Itpresents some difficulties in positioning its surface features. To over comethis problem, a network of imaginary lines is drawn on a globe or a map to helpus locate places. The spinning of the earth on its axis provides – the NorthPole and South Pole. They form the basis for the geographical grid. The grid consists of two sets of lines –horizontal and vertical. The horizontal lines, running eat-west, are circularand parallel to each other. The line drawn midway between the North Pole andthe South Pole is called the equator.It is the largest circle and hence, is called a great circle. All other parallels get smaller in size in proportionto their distances form the equator towards the Poles. These imaginary linesrunning east-west are commonly known as parallels of latitude. The vertical lines, running north-south are halves of thegreat circle and join the two Poles. They are called meridians of longitude. The latitudes and longitudes are commonlyreferred to as coordinates because they provide systematic network of linesupon which position of various surface features of the earth can berepresented.

2. LATITUDES: The latitude of a place onthe earth’s surface its distance north to south of the equator measured alongthe meridian of that places as an angle from the centre of the earth. Linesjoining places with the same latitudes are called parallels. The value ofequator is 0 and the latitude of the poles are 90 N and 90 S. If the parallelsof latitude are drawn at an interval of one degree, ther will be 90 parallelsin the northern and southern hemisphere each. The total number of parallels thus drawn including the equator, theletter N or S is written along with the value of latitude. If the earth were aperfect sphere – 23 ½ N –Tropic Cancer, 23 ½ S – Tropic of Capricorn, 60 ½ N –Artic, 60 ½ S – Antarctic, 1 of latitude (a one- degree arc of a meridian)would be a constant value i.e., 111 km – a degree of latitude changes slightlyin length from the equator it is 110.6 km, at the poles it is 111.7 km.Latitude of a place may be determined with the help of the altitude of the sunor the Polar Star.

3. LONGITUDE: Unlike the parallels of latitude, which are full circles, the meridiansof longitude are semi-circles touching the poles. Meridians intersect theequator at right angles. The meridian of longitude passing through the Greenwich observatory (near London) has been adopted as the Prime Meridian by aninternational agreement and has been given the value of 0 degree. The numericalvalue of a longitude varies form 0 degree to 180 degree East or West – be 360degree meridians.

4. LONGITUDE ANDTIME: While rotating on its axis, the earth completes onecircle (360 degree) in approximately 24 hours time. In other words, it move 15degree longitudes per hour. As such the sun appears to be traversing 15 degreeof longitude from east to west every hour or 1 degree of longitude in every 4minutes. Thus, when it is 12 noon at Greenwich(Prime meridian), the time at 30 degree east of Greenwichwill be 30*4= 120 minutes or 2 hours ahead of Greenwich time. In order tomaintain uniformity of time as far as possible within the territorial limits ofa country us taken as the standard meridian and its local time is taken as thestandard time for the whole country. The standard meridian is selected in amanner that it is divisible by 15 degree or 7 degree 30’ so that the differencebetween its standard time and the Greenwich Mean Time may be expressed asmultiples of an hour or half an hour. The Standard meridian of India is82degree30’ E and the standard time is 5 ½ hours a head of Greenwich Mean Time.