Earth's Crust

CHAPTER – II

THE EARTH’S CRUST

The outer part of the earth what we see is the Lithosphere.  The word lith means Rock.  Rocks are made of individual substances which are called minerals.  Each mineral usually contains two or more simple substances called elements.  The major element in the earth’s crust is the Silicates.  Quartz, for example has two elements silica and oxygen, united together form a compound known as carbonate of lime. 

Classification of the Rocks

On the basis of the mode of formation rocks are usually classified into three major types.

1.       Igneous rocks

2.       Sedimentary rocks

3.       Metamorphic rocks

Igneous rocks: All rock material at one time are hot, liquid and a sticky thing called Magma.  This rock forming material generally moves towards the surface from 60 – 100 km depths when steam pushes it up through cracks.  It hardens below or upon reaching the earth’s surface.  The hardened rock particle is called Igneous rocks.  Ignis in Latin means Fire.  Igneous rocks are the parent rocks of all other rocks and are known as primary rocks.  Broadly  these are divided into two 1. Extrusive and 2. Intrusive.  Extrusive rocks is the name given to the magma erupting and solidifying of lava on reaching the surface of the earth, the lave cools down rapidly on coming out of the earth’s hot interior, the mineral crystals change their structure and are very small, making them looked fine grained.  These rocks have glassy appearance.  The best example for such a rock is Basalt.  These are extensively found in the northwest of peninsular India called as Deccan Traps.  This material is used for building roads and yields a fertile black soil locally called Regur.  The intrusive rock is formed by solidification of magma at moderate depths beneath the earth’s surface.  The cooling is slow because of great heat at depths and crystals formed are large, best examples are Granite and Dolerite. 

Characteristics:

1.       They are massive having no layers

2.       They are hard and compact

3.       They are free from fossils

4.       They are dark as Basalt or light coloured as Granite depending on silica content

5.       They are crystalline rocks

6.       These rocks are of great economic value, they are associated with the minerals like gold, copper, nickel, zinc, chromite, manganese and rare metals like diamond and platinum.

The intrusive igneous rocks include two types, Plutonic and Hyper bassal.  The rocks solidified at greater depths are called Plutonic igneous rocks and the rocks solidified at intermediate depths are called hyper bassal rocks, these include, batholiths, dykes, sills, laccoliths.  Batholiths are the largest intrusive igneous rock bodies.  They may be 50 km across and hundred kilometers in length.  The batholiths covering smaller areas are called Stocks, having somewhat rounded form and same characteristics.  Laccoliths are huge masses of rocks in roughly mushroom shape or a loaf of bread.  Dykes are near vertical formations from a few meters to kilometers in length.  Sills are the thin sheets of magma in horizontal shape parallel to the layers of existing rocks.

Sedimentary rocks

These rocks occupy three fourth of earth’s crust.  These rocks are formed from sediment accumulation over a long period, usually under low lying areas, meaning, any rock on earth’s surface is exposed to weather changes and to the agents of erosion.  It thus gets broken into fragments, further reduced into small particles called sediments.  These are derived from igneous, metamorphic or even from older sedimentary rocks.  All the sediments are carried by running water, wind or ice.  These are left buried layer by layer at favourable sites, mostly settling down along silent water of a stream or a lake.  The sediments get sorted by the transporting agents like running water, wind, waves; the larger and the heavier particles being deposited first after moving for a relatively short distance.  The smaller and finer particles are carried far away.  But most of the material transported by moving ice are not sorted out and are all dropped together when the ice melts.  As sedimentation is favoured by water, most of the sedimentary rocks have been formed under water.  The Loess is one such example of fine sand carried by wind and deposited as wind borne sedimentary rocks as in northwestern China.  The organic matter derived from plants and animal remains is also the raw material for the formation of the sedimentary rocks in course of time.  Well known examples of sedimentary rocks of organic are coal and limestone.  Another category of sedimentary rocks is the direct precipitation of mineral from their solutions in water.   The rock salt, gypsum, and saltpeter are examples of such chemically formed sedimentary rocks.

Characteristics:  

1.       These rocks are stratified rocks

2.       They have fossils embedded into their layers   

3.       They may be hard like Limestone and soft like lime sandstone

4.       They are the sources of rich aquifers

5.       Most of the rocks have ripple marks left by the water.

Metamorphic rocks:

All rocks undergo changes, when the original character of the rocks- their colour, hardness, texture and mineral composition is partly or wholly changed, it gives rise to metamorphic rocks, under favourable  conditions of heat and pressure.  Metamorphic means change of form in Greeck language.  The process of metamorphism takes place at depths under the pressure of overlying rocks or as a result of contact with a hot igneous material.  The formation of metamorphic rock under the stress of pressure is called Dynamic metamorphism.  In this case the Granite is converted into Gnesis, Clay and Shale into Schist at great depths.  The change of form or re-crystallisation of minerals under the influence of high temperatures is known as Thermal or Contact metamorphism.  In areas of mountain building or volcanism, molten matter is injected into the existing layers of rocks near the surface.  Such a contact with heat turns the rocks into Metamorphic rock.  Here, Sandstone is changed into Quartize; clay and shale into Slate, Coal to graphite and limestone into Marble.

Charateristics:

1.       These rocks are of great hardness

2.       They have closely banded structures and interlocking of crystals

3.       They contains precious stones and minerals like Rubies, Gems & Sapphires.

ROCK CYCLE

All rock materials originating from beneath the earth’s surface form igneous rocks.  As soon as igneous rock is exposed to weather on the surface of earth, it is eroded by various agents.  The material changes into sedimentary rocks at some place and at some point of time. Either of the two rocks are likely to change into metamorphic rocks in course of time.  A change into sedimentary rock takes place at the earth’s surface and conversion into a metamorphic rock takes place within the crust of the earth.  The sedimentary rocks may again be buried so deep that they melt forming igneous rocks.  The change of one rock into another type under different conditions is known as rock cycle.  The matter of earth’s crust is not lost and the process changing one form to another becomes cyclic.

The sources of energy powering this cycle are two.  one, the heat inside the earth which is capable of melting the existing rock.  It may also bring about the changes within the remaining rock.  Second, is the solar energy responsible for breaking and decomposing the rocks on earth’s surface for converting them into sedimentary rocks.  Deep burial and strong compression during volcanism activity may also change the sedimentary into metamorphic or igneous rock.  The metamorphic rock can also furnish sediments to produce a sedimentary rock.  All known materials in the form of minerals and rocks are defined as mineral matter.  Throughout hundreds of millions of years, the rock cycle has been re-cycling the mineral matter of the earth’s crust.

GEOMORPHOLOGY

INTERIOR OF THE EARTH

Man with his technological up gradation had send the rovers like “Curiosity” to the other planets and even the instruments like “Voyeger-1 and voyager-2” to the areas beyond Neptune (area recently named as Magnetic Highway).  Exploring the earth beneath our feet is a more difficult task than mapping the moon.  The deepest drill on this earth till date is near the kola peninsular of just 12 kms deep.  Direct observation of the earth’s interior is not possible because of the tremendous heat energy inside the earth but there are certain indirect sources through which we can able to know what is there inside the earth.  The sources which provide the knowledge about the inside of the earth can be grouped into two.

1. Natural sources

2. Artificial sources

Natural sources like Volcanism, Seismology and evidence from meteorites, where as the artificial sources like Temperature, Densityof its different shells & the pressure inside the earth.  It is these sources which provide enough knowledge about the interior of the earth. By using seismograph a graphic recording of the earthquake waves or vibrations is made.  An earthquake occurs when ever a rock breaks inside the earth, this will release energy in the form of waves called seismic waves, Seismic waves are vibrations in Earth caused by the rupture and sudden movement of rock, they will travel all over the globe just like ripples in the well.  The seismic waves are of two types

1.       The Body waves

2.       The Surface waves.

  The body waves are those waves which travel through the earth’s interior and are of two types, Primary waves denoted by the letter P and the Secondary wave denoted by the letter S.  The surface waves are those waves which travel along the surface of the earth for long period waves and are denoted with the letter L, these are of two types, one Rayleigh waves denoted by R and the Love waves denoted by Q.

Primary waves: also called Longitudinal waves or compression waves which are analogous to the sound waves wherein particles move both to and fro in the line of the propagation of the wave.  These waves travel faster through solids, though, these also travels through liquids and gaseous but their speed is slowed down.

Secondary waves:   also called as transverse waves which are analogous to the light waves.  These can travel only through solid media couldn’t travel through liquid or gaseous media.

Surface waves:  also called Long period waves or simply L waves. These affect the surface of the earth and die out at smaller depths.  Though their speed is less than P and S waves but these are most violent and destructive.

There is a change in the course and velocity of the waves on crossing the boundaries of different zones inside the earth.  If the ground through which the wave travels is solid, they behave in one way.  If it is liquid, the waves behave in a different way.  Their velocity in both the cases differs for example the velocity of the P and S waves increases with depth but up to 2900kms.  Afterwards, S wave passing across the direction of their movement do not pass and the P waves travelling in the direction of their movement generally pass at a reduced velocity.  The long L waves do not pass and do not go deeper in the earth.  The S waves cannot pass through a liquid and are transmitted only through a rigid solid body.  The velocity of the P waves passing through inner core again increases as compared to their passage through the outer core.  This data briefly point out that the inner core of the earth is solid iron core and the outer core has probably the properties of a liquid.  It may be concluded that as a whole behaves like a solid even when the parts of its interior are reported to be in a plastic or semi- liquid state.  The rock samples from various depths have also provided the evidence of the density of the materials. 

    The Meteorites belonging to our solar system are another source of our information for a better understanding of the earth’s structure.  The meteors outer layered burnt during their fall to the earth, as the stony material of the meteorites are similar to those found on the earth’s surface, these are scarcely recognized.  But the composition of the heavier materials confirms the similar composition of inner core of the earth. 

Temperature and Pressure:  The evidence of the volcanic eruptions and the hot springs indicate that high temperatures prevail in the interior of the earth.  A progressive rise in the temperature with the increasing depth is recorded in mines and deep wells all over the world, the average rate of the increase being 1 degree for every 32 meters of descent.  Normally, at this rate of increase in temperature, the rocks at great depths should be in a liquid state.  At one time, on the basis of this view, it was accepted that thin solid crust of the earth was perhaps resting on a molten core.  But the behavior of the earthquake waves as hinted above has led us to revise our views.  The rate of increase in temperature is now considered to be variable and there is no uniform increase from the surface to the centre of the earth.  The rate of increase in the overlying pressure makes the melting point higher but only to a certain degree.  In upper 100kms, the increase is estimated at 12 degrees per km.  it is 2 degree centigrade per km in the next 300km and 1 degree per km below it.  By this calculation the temperature is actually 2000 degree centigrade at the core of the earth.  The heat or rise in temperature is the result of internal forces, automatic disintegration of radioactive substances, chemical reaction and other sources keeping the earth’s interior hot.  It indicates the liquid or perhaps the gaseous conditions prevailing at the greater depths.  But at the same time there is a tremendous increase in the pressure of overlying layers on earth’s interior.  Thus, even under extremely high temperature towards the central part of the earth, the liquid nature of its core has acquired the properties of a solid and is probably in a plastic state.  The earth is rigid and behaves mostly as a solid down to a depth of 2900 km because of such pressure conditions.  Wherever even a slight release of pressure occurs, the underlying matter escapes to the surface and becomes molten because of high temperatures prevailing there.  While solid material melts inside the earth, the liquid also takes up the properties of a solid as alluded above.

DENSITY: The velocity and the path followed by earthquake waves, temperature and pressure conditions inside the earth tell us of varying physical properties, density and composition prevailing there.  The structure of earth’s interior is therefore layered.  The arrangement of layers is comparable to onion with its shells, one inside another.  The inside of the earth has a shallow crust as thin as an eggshell which can be compared with the size of a ball.  Below the surface capped by the sedimentary material, upper layer of the crust is mainly composed of crystalline igneous and metamorphic rocks, acid in nature.  The lower layer of the crust has basaltic and ultra basic rocks.  The layer of heavier or inner silicate is not found beneath oceans.  The oceans are mostly under laid by a thick greenish and tremendously hot layer.  The continents are composed of silicates termed as SIMA or silica and Aluminium.  The oceans have heavier silicates named SIMA or silica and Magnesium.  The continents of lighter material are floating in a sea of heavier and denser material.  The central core has the heaviest mineral materials of highest density.  It is composed of NIFE or Nickel and Ferrous.  A zone of mixed heavy metals and silicates separates the core from the other layers.

Based on the chemical composition of the earth’s interior, different scientists have given different views about the interior of the earth.

1.       Edward Suess has identified three zones of different matter below the outer thin sedimentary layer.

SIAL : It is located just below the outer sedimentary cover.  It composed of Granite.  This layer is dominated by Silica and Aluminium – SIAL.  The average density is 2.9 whereas thickness ranges between 50 – 300 kms.  Continents have been formed by sialic layer.

SIMA : It is located just below the sialic layer.  This layer composed of basalt and is the source of Magma and Lava during the volcanic eruptions.  Silica and Magnesium are the dominating materials in this layer.  Average density of this layer is 2.9 to 4.7 whereas the thickness varies from 1000km to 2000km.

NIFE :  It is located just below the SIMA layer.  This layer is composed of Nickel and Ferrium.  It is thus apparent that this layer made of heavy metals which are responsible for very high density.  The diameter of this zone is 6880 km.  The presence of the Iron (ferrium) indicates the magnetic property of the earth’s interior.  This property also indicates the rigidity if the earth.

2.       Van Der Gracht has identified 4 layer system of the composition of the earth.

Outer sialic crust : This layer varies in thickness, under the continents it is 60 km and under the oceans it is 20km esp Atlantic ocean, completely absent under the Pacific ocean. Density of this layer is between 2.75 to 2.9

Inner silicate mantle : it extends between 16km to 1140 km and has the density of 3.1 to 4.75.

Zone of mixed metals and silicates : the thickness of this layer from 1140km to 2900km where as the density of this layer varies between 4.75 to 5.0

Metallic nucleus : This layer thickness is from 2900km to 6371km and density is 11.0.

It appears that there are different opinions about the number, thickness and density of the layers.  In order to avoid the confusion a commonly accepted view has been brought by majority of the scientists.

     The scientific study and the analysis of various aspects of seismic waves – mainly its velocity and path of the waves, also the earthquakes have enabled the scientists to unravel the mystery of the earth’s interior.  Three zones of varying properties have been identified in the earth e.g. crust, mantle and the core.

CRUST:  The very first layer of the earth is the Crust, it extends up to a depth of 50 km on an average.  It is divided into two the Oceanic crust and the Continental crust, the oceanic crust is denser as it is made up of basalt rock which is denser than the granitic rock, with which the continental crust is made of.  The thickness of the crust is more under the continents the thickness is less under the oceans.  This crust based upon the depth is again divided into two, outer and lower crust.  The average density of the outer and lower crust is 2.8 and 3.0 respectively.  This difference in the density is because of the Pressure of superincumbent load.  The formation of the minerals of the upper crust was accomplished at relatively lower pressure than the minerals of the lower crust.

MANTLE: It is the second layer just below the crust, it extends up to a depth of 2900 km inside the earth.  This mantle is divided initially into two zones based on the changes in the velocity of seismic waves and density, the upper mantle and the lower mantle.  The upper mantle starts from 50 km and extends up to 1000km and the lower mantle from 1000km to 2900km but now the mantle is divided in to three based on the information received from the discovery of International Union of Geodesy and Geophysics.  (i) first zone extending from the crust to 200km depth. (ii) Second zone extends from 200km to 700km and  (iii) third zone extends from 700km to 2900km depth.  The velocity of the seismic waves relatively slows down in the upper most zone of the mantle for a depth of 100 to 200 km.  This zone is called the zone of low velocity, i.e the rocks here are in the semi molten or Gel like form, this layer is also called as Asthenosphere.   There is a sudden increase in the velocity of the seismic waves at the base of the lower crust and the upper mantle this trend of seismic waves denotes discontinuity.  This discontinuity was discovered by Mohorovicic in 1909 and thus it is called as Moho discontinuity. 

CORE:  The core, the deepest and the most inaccessible zone of the earth, extends from the lower boundary of the mantle at the depth of 2900km to the centre of the earth.  The mantle  - core boundary is determined by the “Weichert – Gutenberg Discontinuity” at the depth of 2900km there is a pronounced change in the density of the core from 5.5 to 10.0, this sudden change in the density is indicated by sudden increase in the velocity of P waves along the mantle core boundary i.e the Gutenberg discontinuity.  The density further increases from 10.0 to 13.0 with the increasing depth of the core.  Thus it appears that the density of the core is twice the density of the mantle.  The core is further divided into two zones the outer and the inner core, the dividing line being at the depth of 5150km.  S, waves disappears in this outer core indicating it as molten state.  The next layer is the inner core which extends from 5150km to 6371km i.e the centre of the earth.  The density of this layer is 13.0 where the P waves travel at greater velocity than that of the outer core indicating this layer as  a solid zone.  It is believed that the core is composed of Iron and Nickel and so it the most density part in the interior of the earth.

catastrophic theories

CATASTROPHIC THEORIES

Planetesimal Hypothesis :  Mr. Chamberlin along with an astronomer Moulton postulated this theory in 1905.  According to Chamberlin, our sun is a proto-star which was formed of solid particles and was cold and circular in shape.  There was another star, termed as intruding star which was destined to pass very close to the proto-sun.  when the intruding star came very close to the proto-sun infinite number of small particles were detached from the outer surface of the proto-sun due to the massive gravitational pull exerted by the giant intruding star.  Chamberlin called these detached small particles as planetesimals.  Initially, the detached particles were just like dust particles.  These particles are not of uniform size, the large particles attracted the smaller planetesimals thus numerous particles were added to the larger planetesimal called nuclei, around this nuclei remaining dust particles started accumulated to form other remaining planets.  With the passage of time, the remaining proto-sun changed into present day sun.  The satellites of the planets were created due to the repetition of the same processes and mechanism.

Tidal Hypothesis : Sir James Jeans, a British scientist propounded this theory in 1919 along with other scientist by name Harold Jeffery.  According to them initially the sun is a giant incandescent gaseous mass of matter, besides the sun, there was another star termed as intruding star.  There was a great impact of the tidal force of the intruding star on the surface of the primitive sun.  The intruding star was continuously moving along such a path that it was coming nearer to the primitive sun, its gravitational force went on increasing and became maximum, with the result a giant Cigar shaped tide of matter ejected from the primitive sun, thousands of kilometers in length was created.  This ejected cigar shaped matter Jeans called this as filament, which was thicker in the centre and thinner and sharper at the ends.  This shape is because, when the intruding star was at distant place, it could exert less pull and when it comes near to the primitive sun the force of attraction increased to maximum.  Therefore the shape of matter ejected is in the shape of a cigar.  The formed cigar or the filament later on cooled to get contract and broke into smaller pieces and each piece condensed to form one planet.

 Binary star Hypothesis: This theory is based on the dualistic concept in 1937 postulated by Mr. Russell.  According to him there were two stars neat the primitive sun, in the beginning the companion star was revolving around the primitive sun.  Later on one giant star, the third star approached the companion star but the direction of revolution of the approaching star was opposite to that of the companion star.  Thus, large amount of the matter from the companion star was attracted towards the giant approaching star because of the gravitational pull.  This ejected matter started revolving in the direction of the giant approaching star and thus opposite to the direction of the revolution of companion star.  Later on planets were formed from the ejected matter.  In the beginning the planets might have been nearer to each other and thus matter might have ejected out from these planets due to the mutual attraction and thus satellites might have been formed from the matter.

Super Novae Hypothesis: Propounded by Mr. Hoyle in 1946, this theory is based on the principles of Nuclear physics.  According to Hoyle initially there were two stars one primitive star and the two companion star.  This companion star later on became supernova due to the nuclear reaction.  It may be pointed out that every star will be emitting the energy in the form of light, heat, etc., is generated by the process known as Nuclear fusion, where in atoms of lighter elements combine under intense heat and pressure to form atoms of heavier elements, releasing a vast amount of energy.  The stars generally contain Hydrogen this slowly combine with each other to form Helium which is a heavier atom than hydrogen.  In this process vast amount of energy is also released. This same reaction was also going on in Hoyle’s primitive sun and companion sun but the rate of nuclear fusion was many times greater in the companion star. With the passage of time all the hydrogen of the companion star was consumed and got collapsed by exploding violently this Hoyle called as Supernova.  This explosion resulted in spread of enormous gaseous matter and mass of dust which started revolving around the primitive sun.  Thus the matter and dust became building material for the formation of future planets.

Non catastrophic theories

Non - Catastrophic theories

Gaseous Hypothesis :  Immanuel kant, the German philosopher, presented this hypothesis in 1755.  His theory is based on the Newton’s laws of gravitation and rotatory motion.  According to Kant, there was a primeval, slowly rotating cloud of gas, (now called nebula) and matter comprised of very cold, solid and motionless particles.  He further assumed that these particles began to collide against each other under their mutual gravitational attraction.  This collision generated random motion in the primordial matter along with the frictional force which generated heat energy as a result the primordial matter got heated up and started up rotating.  The rise in temperature also changed the state of matter from solid to gaseous, thereby the rotating matter started to move as a nebula.  With continuous rise in temperature and rate of rotatory motion the nebula started expanding in size. 

     According to Immanuel kant as the heat increased, the size of nebula increased and as the size of nebula increased, the angular velocity or rotatory speed further increased.  Due to continues increase in the size of nebula the speed of rotation become so fast that the centrifugal force exceeded the centripetal force.  The nebula started spinning so rapidly that an irregular ring was separated from the middle part of the nebula and was ultimately thrown off due to centrifugal force, by repetition of the same process eight concentric ring were separated from the nebula.  The residual central mass remained as the sun.  The irregularity of the rings caused the development of the cores for the formation of the corresponding planets. In other words, all the matters of the each ring were aggregated at a point to form and ultimately grew as planets in due course of time.

 Nebular Hypothesis : This was propounded by the French mathematician Laplace in 1796.  This hypothesis is just the modification of the kant’s hypothesis.  According to Laplace, there was a huge and hot gaseous nebula in the space and from the very beginning this huge and hot nebula was rotating on its axis, therefore because of the rotation the nebula continuously cooling due to loss of heat from its outer surface through the process of radiation and thus it was continuously reducing in size due to the contraction on cooling.  As the size of the nebula continued to reduce in size, the velocity of the rotatory motion continued to increase.  Thus nebula started spinning at very fast and consequently the centrifugal force became so great that it exceeded the centripetal force, when this stage was reached the material at the periphery  that is the outer layer cooled and contracted so it couldn’t rotate with the same velocity of that of nuclei and was separated from the remaining part of the nebula.  This separated ring of material started moving around the nebula.  This original ring further divided into eight rings and each ring moved away from each other.  All the materials of each ring condensed at a point in the form of hot gaseous agglomeration.  Each such agglomeration was later cooled and condensed to form planet.

INTRODUCTION

The word Universe is derived from French word “Univers”, which means “All turned into one”.  The Universe is everything that we can perceive.  In 1927, the Belgian priest Georges Lemaitre proposed that the Universe began with the explosion of a Primeval atom, which he called this as “BIG BANG THEORY”, his proposal came after observing the Red shift in distant nebulas.  The Red shift, in simple means, the displacement of spectrum lines towards the red end of the visible light.  Years later, Edwin Hubble found experimental evidence to help justify Lemaitre’s theory.  He found that distant galaxies in every direction are going away from us with speeds proportional to their distance.  Finally, the big bang theory received its strongest confirmation when Radiation was discovered in 1964 by Arno Penzias and Robert Wilson, who later won the Nobel prize for this discovery. 

    The Universe is the vast and infinite space having millions of galaxies.  It is estimated that the age of our universe is between 15 and 20 billion years old.  The three most common elements in the universe are: 1. Hydrogen 2. Helium and 3. Oxygen.  However, Hydrogen comprises around 90 percent of all matter in the universe.  About 70 percent of the universe has dark energy and 25 percent consists of dark matter.  It is only 5 percent of the universe is visible to us. 

The Origin of the Earth

Our solar system is a small part of the system of stars collectively called Milky way.  It consists of more that thousands million of stars.  Like other stars, the Sun with its solar system is revolving around the centre of the Milky way, there are several theories which explain the formation of the solar system, in which earth is a part.  These theories can be broadly classified under two groups called Catastrophic and Non catastrophic theories. 

The catastrophic theories like

Planetesimal Hypothesis of Chamberlin

Binary star Hypothesis of Russell and Littleton

Super Novae Hypothesis of Hoyle

Tidal Hypothesis of James Jeans

     The Non-catastrophic Hypothesis like
 Gaseous Hypothesis of Immanuel Kant
 Nebular Hypothesis of Laplace.

content

CONTENTS

PART – I

INTRODUCTION

GEOMORPHOLOGY

• 1.       Interior of the Earth
• 2.       The Earth’s crust
• 3.       Vulcanism and Earthquake
• 4.       Weathering and mass movement
• 5.       Continental drift & Plate tectonics
• 6.       Landforms

 CLIMATOLOGY

• 1.       Atmosphere composition and structure
• 2.       Insolation and Heat budget
• 3.       Temperature Humidity and Precipitation
• 4.       Air pressure and Winds
• 5.       Air masses, Fronts and Cyclones
• 6.       World climate

OCEANOGRAPHY

• 1.       Relief of Ocean basins
• 2.       Salinity
• 3.       Ocean deposits
• 4.       Ocean currents
• 5.       Ocean tides and waves
• 6.       Coral reefs and Atolls
• 7.       Marine resources

BIO GEOGRAPHY

• 1.       Biosphere : an Eco system
• 2.       Soils of the world
• 3.       Biomes of the world

ENVIRONMENT GEOGRAPHY

• 1.       Man and Environment symbiosis
• 2.       Global warming
• 3.       Climate change and recent conventions
• 4.       The Cryosphere
• 5.       Bio-diversity & Hotspots, Biosphere reserve and wildlife           conservation
• 6.       Environmental Impact Assessment – EIA
• 7.       Disaster management

PART – II

INDIAN GEOGRAPHY

PHYSICAL GEOGRAPHY OF INDIA

• 1.       Origin of peninsular India
• 2.       The Himalaya
• 3.       The Great Northern Plains

DRAINAGE

• 1.       The Drainage pattern
• 2.       Indian river systems – Himalayan & Peninsular
• 3.       Interlinking of the rivers

CLIMATE

• 1.       Introduction to Indian climate
• 2.       Monsoons
• 3.       Jet streams and Tibetan plateau
• 4.       El-Nino, La-Nina and ENSO
• 5.       Seasons in India
• 6.       Rainfall in India and its variability
• 7.       Climatic regions of India
• 8.       Drought and Floods

NATURAL VEGETATION

• 1.       Distribution of the natural vegetation
• 2.       Classification of forests
• 3.       Endemic species
• 4.       Social forestry and conservation
• 5.       Wildlife and conservation
• 6.       Mangroves

SOILS

• 1.       Characteristics of the Indian soils
• 2.       Classification of soils
• 3.       Problems and conservation

ECONOMIC GEOGRAPHY

RESOURCES

• 1.       Mineral resources
• 2.       Energy resources

AGRICULTURE

• 1.       Land reforms
• 2.       Characteristics of Indian agriculture
• 3.       Green revolution
• 4.       Problems in Indian agriculture
• 5.       Cropping patterns
• 6.       Agro climatic regions of India

INDUSTRIES

• 1.       Industrial development in India
• 2.       Industrial clusters, Industrial policy and Globalization
• 3.       Iron and steel industry
• 4.       Textile industry
• 5.       Fertilizer industry
• 6.       Pharmaceutical industry
• 7.       Special economic zones

TRANSPORT & TRADE

• 1.       Land , water and air transport
• 2.       Trade policy, Balance of Trade

SOCIAL GEOGRAPHY

CULTURAL SETTINGS

• 1.       Races in India
• 2.       Demographic features
• 3.       Literacy
• 4.       Age composition
• 5.       Sex ratio
• 6.       Migration
• 7.       Human development index
• 8.       Urbanization

General studies GEOGRAPHY

PREFACE

Dear Friends,

     Once you decide to start the preparation for India’s toughest and the most desired exam, the first and the foremost thing you come across is to find a good material where you could find all the related information at one source.  Unfortunately most of the material available in the market is providing a part of the syllabus.  As a student I faced the same problem and the problem still persist, therefore I decided at least for my beloved subject Geography I shall do something for the benefit of the student community. 

     Frequently, I come across the questions from the students like, “which books are sufficient for the preparation, is there any one such book which can have all the content” the answer is unfortunately NO as each book is specialized in one chapter eg: for Geomorphology Savinder singh & Strahler are the good book and for climatology D.S.Lal book is good.  If I keep on giving all the list of books the student will end up reading Geography alone.

         After referring many a books and materials available in the market and going through the syllabus of the Union Public Service Commission, Special care has been taken to ensure quality and excellence in this material.  This has been prepared keeping the preliminary part of the examination as well as Mains part of the examination. 

      I am very happy to upload this GEOGRAPHY material in my blog which can help IAS aspirants all over the country.  I feel delighted by your positive feedback.  Any suggestion for alteration or addition is welcome.  Lastly, this material is exclusively for General Studies purpose only and not for optional, I keep on updating the material as and now I find time. 

                                                                                                                              - JAYAKRISHNA.S

Free lance IAS Faculty

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