CBSE i

CLASS XI, GEOGRAPHY

STUDENTS’ MANUAL

CBSE i

CLASS XI, GEOGRAPHY

STUDENTS’ MANUAL

CBSE i

CLASS XI, GEOGRAPHY

STUDENTS’ MANUAL

The CBSE-International is grateful for permission to reproduce

and/or translate copyright material used in this publication. The

acknowledgements have been included wherever appropriate and

sources from where the material may be taken are duly mentioned.

In case any thing has been missed out, the Board will be pleased to

rectify the error at the earliest possible opportunity.

All Rights of these documents are reserved. No part of this

publication may be reproduced, printed or transmitted in any form

without the prior permission of the CBSE-i . This material is meant

for the use of schools who are a part of the CBSE-International

only.

CBSE i

CLASS XI, GEOGRAPHY

STUDENTS’ MANUAL

Preface

Education plays the most important role in acquiring professional and social skills and a positive attitude

to face the challenges of life. Curriculum is a comprehensive plan of any educational programme. It is also

one of the means of bringing about qualitative improvement in an educational system. The Curriculum

initiated by Central Board of Secondary Education -International (CBSE-i) is a progressive step in making

the educational content responsive to global needs. It signifies the emergence of a fresh thought process in

imparting a curriculum which would restore the independence of the learner to pursue the learning process

in harmony with the existing personal, social and cultural ethos.

The CBSE introduced the CBSE-i curriculum as a pilot project in few schools situated outside India in

2010 in classes I and IX and extended the programme to classes II, VI and X in the session 2011-12. It is

going to be introduced in classes III, VII and for Senior Secondary classes with class XI in the session

2012-13.

The Senior Secondary stage of education decides the course of life of any student. At this stage it becomes

extremely important for students to develop the right attitude, a willingness to learn and an understanding

of the world around them to be able to take right decisions for their future. The senior secondary

curriculum is expected to provide necessary base for the growth of knowledge and skills and thereby

enhance a student’s potential to face the challenges of global competitiveness. The CBSE-i Senior

Secondary Curriculum aims at developing desired professional, managerial and communication skills as

per the requirement of the world of work. CBSE-i is for the current session offering curriculum in ten

subjects i.e. Physics Chemistry, Biology, Accountancy, Business-Studies, Economics, Geography, ICT,

English, Mathematics I and Mathematics II. Mathematics at two levels caters to the differing needs of

students of pure sciences or commerce.

The Curriculum has been designed to nurture multiple intelligences like linguistic or verbal intelligence,

logical-mathematical intelligence, spatial intelligence, sports intelligence, musical intelligence, inter-

personal intelligence and intra-personal intelligence.

The Core skills are the most significant aspects of a learner's holistic growth and learning curve. The

objective of this part of the core of curriculum is to scaffold the learning experiences and to relate tacit

knowledge with formal knowledge. This involves trans-disciplinary linkages that would form the core of

the learning process. Perspectives, SEWA (Social Empowerment through Work and Action), Life Skills

and Research would be the constituents of this 'Core'.

The CBSE-i Curriculum evolves by building on learning experiences inside the classroom over a period of

time. The Board while addressing the issues of empowerment with the help of the schools' administering

this system strongly recommends that practicing teachers become skilful and lifelong learners and also

transfer their learning experiences to their peers through the interactive platforms provided by the Board.

The success of this curriculum depends upon its effective implementation and it is expected that the

teachers will make efforts to create better facilities, develop linkages with the world of work and foster

conducive environment as per recommendations made in the curriculum document.

I appreciate the effort of Dr. Sadhana Parashar, Director (Training), CBSE, Dr. Srijata Das, Education

Officer, CBSE and their teams involved in the development of this document.

The CBSE-i website enables all stakeholders to participate in this initiative through the discussion forums.

Any further suggestions on improving the portal are always welcome.

Vineet Joshi

Chairman, CBSE

CBSE i

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STUDENTS’ MANUAL

Acknowledgements

Advisory

Shri Vineet Joshi, Chairman, CBSE

Dr. Sadhana Parashar, Director (Training),

CBSE

Conceptual Framework

Shri G. Balasubramanian, Former Director

(Acad), CBSE

Ms. Abha Adams, Consultant, Step-by-Step

School, Noida

Dr. Sadhana Parashar, Director (Training), CBSE

Ideators: Classes XI and XII Prof. A K Bakshi Ms. P Rajeshwari Dr. Niti Nandini Chatnani Ms. Neeta Rastogi

Dr. N K Sehgal Ms Gayatri Khanna Dr. Anil K Bali Dr. Anshu

Prof. Kapil Kapoor Mrs. Anita Makkar Dr. Preeti Tewari Dr Rajesh Hassija

Ms. Renu Anand Prof. Biswajit Nag Dr. Deeksha Bajpai Mr. Mukesh Kumar

Dr. Barkatullah Khan Dr. Jacqueline Symss Mr. S K Agarwala Dr. Om Vikas

Ms. Avnita Bir Ms. Usha Sharma

Material Production Groups: Classes XI and XII

English :

Ms Gayatri Khanna

Ms Renu Anand

Ms. P Rajeshwary

Ms. Sandhya

Awasthi

Ms. Manna Barua

Ms. Veena Bhasin

Ms. Urmil Guliani

Ms. Sudha Ravi

Mr. Anil Kumar

Ms. Vijaylaxmi

Raman

Ms. Neerada Suresh

Ms. Himaal Handoo

Chemistry :

Dr. G S Sodhi

Dr. Vimal Rarh

Dr. Shalini Baxi

Dr. Vinita Arora

Dr. Vandana Soni

Ms. Charu Maini

Ms. Rashmi Sharma

Ms. Kavita Kapoor

Biology :

Dr. Ranjana Saxena

Dr. Neeraja Sood

Dr. P Chitralekha

Ms. Mridula Arora

Ms. Lucy Jad

Ms. Priyanka Choudhury

Ms. Prerna Gosain

Ms. Malini Sridhar

Physics :

Dr. B. Biswal

Ms. Namrata Alwadhi

Mr. Dhirender Sharma

Ms. Vandana Banga

Mr. Vivek

Mathematics :

Dr. Sushil Kumar

Mrs. Monica Talwar

Mrs. Charu Dureja

Mrs. Seema Juneja

Dr. H K Bhatia

Geography:

Dr. Preeti Tewari

Ms. Rupa Das

Mr. S Fazal Daoud

Firdausi

Ms. Neena Phogat

Ms. Sujata Sharma

Ms. Deepa Kapoor

Ms. Bharti Malhotra

Ms. Isha Kaushik

Mr. Riyaz Khan

Economics :

Mr. S K Agarwala

Ms. Ambika Gulati

Ms. Nidhi Singh

Ms. Malti Modi

Ms. Sapna Das

Ms. Ingur Agarwal

Ms. Shankar Kulkarni

Accountancy :

Mr. S S Sehrawat

Dr. K Mohna

Dr. Balbir Singh

Mr. Bhupendra Kriplani

Dr. Shipra Vaidya

Mr. Sandeep Sethi

Business Studies :

Dr. S K Bhatia

Ms. Meenu Ranjan

Arora

Mrs. Shegorika

Mr. Sandeep Sethi

Ms. Usha Sharma

Ms. Komal Bhatia

Ms. Ravisha Aggarwal

ICT :

Mr. Mukesh Kumar

Ms. Nancy Sehgal

Ms. Purvi Srivastava

Ms. Gurpreet Kaur

Chief Co-ordinator: Dr. Srijata Das, E. O.

Coordinators:

Ms. Sugandh

Sharma, E O

Dr Rashmi Sethi, E O Ms. S. Radha

Mahalakshmi,

E O

Ms. Madhu Chanda, R

O (Inn)

Mr. Navin Maini, R

O (Tech)

Ms. Neelima Sharma,

Consultant (English)

Shri R. P. Sharma,

Consultant (Science) Shri Al Hilal Ahmed,

AEO

Shri R.P Singh, AEO Ms. Anjali Chhabra, AEO Ms Reema Arora

Consultant (Chemistry)

Mr. Sanjay Sachdeva, S

O

CBSE i

CLASS XI, GEOGRAPHY

STUDENTS’ MANUAL

CBSE ‐ i CLASS -XI

GEOGRAPHY

UNIT – 2

THE EARTH

STUDENTS’ MANUAL

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CONTENT

Stages in formation of Earth,

interior of Earth

Continental drift and Plate tectonics

o Concept of Plate movement

o Boundaries / margins

Earth Movements

o Folds

o Faults

Earthquakes

Tsunamis and

Volcanic eruptions

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THE ORIGIN AND EVOLUTION OF THE EARTH

In the following section, we shall be curious to find the answers to the numerous questions

that come to our mind regarding the origin and evolution of the Earth and the universe.

Questions such as

What is the universe? How did it come into being? What was it created out of? What is its composition? When was it created, what is its current

state and what is its future?

Next, we shall look at the planet Earth. How was it formed? What is it made up of?

How does it support life?

ORIGIN OF THE EARTH: Early hypotheses

Different philosophers and scientists have put forward various hypotheses regarding the formation of the universe and planets. A German philosopher named Emanuel Kant provided the world with what is known as the Nebular Hypothesis. Laplace, a mathematician, revised this theory further in 1796. The hypothesis postulated that a cloud of material belonging to an early star was rotating slowly. The planets were formed out of this cloud. Chamberlain and Moulton, in 1900, suggested that another wandering star could have approached the Sun during the early periods of its life. Material was separated from the solar surface as a result. This material started to revolve around the Sun and as time passed, condensed into planets.

This theory was supported by Sir James Jeans and later by Sir Harold Jeffrey.

Simultaneously, theories suggesting the existence of a companion to the Sun were also put

forth. These are referred to as Binary Theories.

1950 saw the revision of the Nebular Hypothesis. Otto Schmidt and Carl Weizascar

suggested that a solar nebula surrounded the Sun. This nebula was made up of hydrogen and

helium, and also some cosmic dust. These particles collided to form a disc-shaped cloud out

of which planets were formed through what is called the process of accretion.

Modern hypotheses Modern day scientists have tried to explain the origin of the universe, rather than just the

origin of the planets. The most popular explanation of the origin of the universe is what is

called the Big Bang Theory. Edwin Hubble studied the movement of the galaxies and

proposed what is commonly known as the Expanding Universe Hypothesis. This hypothesis

states that galaxies in the universe are constantly moving away from one another. The

universe started as a tiny ball with an incredibly small volume, infinite temperature, and

infinite density. This tiny ball exploded violently (The Big Bang) perhaps more than 13

billion years ago, and continues to expand since then. In the process, some energy was

converted into matter. Matter was distributed unevenly within the universe. The greater

accumulation of matter in certain places favoured the formation of galaxies, each containing

many stars thousands of light years apart. Available evidence seems to support Hubble’s

hypothesis, though Hoyle’s Steady State Theory has been suggested as an alternative.

The Solar System

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The solar system is said to consist of eight planets. A ninth planet 2003 UB313 has also been

discovered recently. The Sun, 8 planets, 63 satellites, millions of smaller bodies like asteroids

and comets and a huge quantity of dust make up our solar system. The inner planets consist

of Mercury, Venus, Earth and Mars. These planets have an Earth like structure and are called

terrestrial planets since they are made up of rock and have relatively higher density. The

other planets, Jupiter, Saturn, Uranus and Neptune, are called Jovian or Gas Giant planets.

These planets are much larger than the inner planets and have relatively lower density. They

have a thick atmosphere comprising hydrogen and helium. These planets were formed about

4.6 billion years ago.

FIGURE 2.1. THE SOLAR SYSTEM1

Evolution of the Earth

At the time of its formation, the Earth was a hot object, completely barren and rocky. The

very thin atmosphere that existed consisted mostly of hydrogen and helium. As we can see

today, the Earth today is very different. In the last 4.6 billion years the Earth has transformed

into a beautiful planet with ample amount of water and an atmosphere that allow it to harbour

life. The Earth today consists of the Lithosphere, the Atmosphere the hydrosphere and the

Biosphere. The different layers of the Earth have their distinct characteristics – the

atmosphere or the outermost layer, is the least dense of them all.

In the early stages of its development, the Earth was volatile. With a gradual increase in its

density, the temperature in its interior also increase .This resulted in the sinking of the heavier

materials towards the centre of the Earth while lighter material moved to the surface. The

outer crustal layer was thus formed of lighter materials. Subsequently other layers emerged

through the process of differentiation. The density of the layers increases as one goes

from the surface to the interior i.e. through the crust, mantle and core. The progressive

cooling of the Earth was accompanied by a reduction in its size.

The Earth’s atmosphere has evolved in three stages. It is believed that it in the first stage, the

primordial atmosphere was lost, perhaps under the influence of strong solar winds that blew

away the Hydrogen and Helium. In the second stage, its formation was influenced by the hot

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interior of the Earth which released into it gases like water vapour, nitrogen, carbon

dioxide, methane and ammonia as it cooled. This process is known as degassing. Volcanic

eruptions added water vapour and gases to the atmosphere. With the lowering of temperature ,

the released water vapour started cooling , which led to condensation. The rain water

dissolved the carbon dioxide present in the atmosphere, which led to further cooling and

more rain. This rain water collected in the vast depressions on the surface of the Earth giving

birth to oceans. The oceans formed about 500 million years after the formation of the

Earth. It is believed on the basis of different evidences that life evolved around 3800 million

years ago. The process of photosynthesis started about 2500 to 3000 million years ago. It is

believed that life originated in the oceans. The process of photosynthesis added oxygen to

oceans. Around 2000 million years ago, after the ocean waters were saturated with oxygen,

oxygen started moving into the atmosphere. Thus in the final stage of its evolution, the

composition of the atmosphere was influenced by the biosphere.

INTERIOR STRUCTURE OF THE EARTH:

It is known to us that the shape of the Earth is round – to be precise it is ‘Geoid’, i.e. ‘Earth shaped’-

with flattened polar regions. The surface features of the Earth are very significant to a geographer, but

it is equally necessary for us to know about the interior of the Earth that lies beneath the crust or

lithosphere .It is also intriguing to know about the internal forces that affect us.

Introductory Activity: Have you ever thought of the feeling of going inside the earth? .... The way we love to climb up

the mountains? -

Think, visualise and compare the facts -as one moves up the mountains and goes inside the earth’s

interior – (from the point of view of surroundings, temperature, pressure, resources,

etc.) - jot them down…..

If you were to go down a deep mine or cave, you would find that it gets warmer on an average

of about 1oC for every 33m of descent unlike a decrease of 1

oC for every 165m of ascent in the

mountains.

So one can imagine that at this rate of increase in temperature, the Earth’s interior gets very hot, hot

enough to even melt the rocks of which it is made up.

The density of the Earth increases as one goes inside the Earth’s interior towards the centre. The

average density is 5.5 g/cc while at the centre it may increase up to 10-15 g/cc.

The temperature in the core is higher than at the Sun's surface. This intense heat from the inner core

causes material in the outer core and mantle to move around.

Earth has a diameter of about 12,756 km and a radius of about 6370 km. The Earth's interior

consists of rocks and metals.

Sources of information

You may be wondering as to how scientists have got this information. It is not possible for anyone to

go inside to study or collect information about the Earth’s interior due to unfavourable conditions.

Most of the information about the Earth’s interior is based on inferences drawn from different sources

– both direct and indirect.

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Mines are one of the direct sources of information about the Earth’s interior. They give us evidence

about its composition – but only to a very limited extent- as it is not possible to go beyond 3 to 4 km

due to the rising temperature.

Apart from mining, the other source of direct information is the various drilling projects. Analysis of

material collected through drilling does throw light on the interior of the Earth. But this too, is limited

to only a certain depth.

Volcanoes are yet another major source of direct information – they tell us about the composition and

characteristics of the materials found inside the Earth.

Scientists have also gathered information from indirect sources like the behaviour of seismic waves

(the waves generated by Earthquakes). As these waves move through the different layers of the

interior their behaviour changes – pointing to a change in composition and density.

Meteors are another source of indirect information as they share many characteristics with the Earth.

After gathering information from various sources, scientists have concluded that the structure

of the Earth’s interior is as follows:

1. The Crust:

It is the outermost and thinnest layer of the Earth’s structure. Its thickness varies from 5 to 40 km. It is

about 40 km thick under the continents and about 5 km beneath the oceans. It is formed of igneous,

metamorphic and sedimentary rocks.

FIGURE 2.3. STRUCTURE OF EARTH3

The sudden change in the behaviour of Earthquake waves has defined the separation zone between the

crust and the mantle. The transitional (separation) zone between the crust and the mantle is known as

Mohorovicic discontinuity or simply ‘Moho” after the name of the scientist who discovered it.

Seismologists have concluded from the behaviour of Earthquake waves that the crust beneath

the continents has more granitic rock while the crust under the oceans is basaltic.

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Sial and Sima

The Earth’s crust – which has an average thickness of 32 km – is formed of two layers – Sial and

Sima. The continents are formed of comparatively lighter rocks – which the geologists call Sial

(from Silica and Aluminium) and the ocean beds are termed as Sima (Silica and Magnesium).

Scientists suggest that large slabs of lighter Sial rest or float on a layer of heavier Sima.

FIGURE 2.4. OUTER LAYERS OF THE EARTH42.

The Mantle: In between the crust and the core lies the mantle – which is about 2900 Km thick. It

extends from the Moho discontinuity to a depth of about 2895 km. The minerals here are in a solid

state. Seismologic evidence suggests that the mantle is composed largely of the mineral olivine

(magnesium iron silicate). Peridotite is the main component of the upper mantle.

New evidence from Earthquake waves shows that in the upper mantle the rock is at melting point

temperature. It is a soft layer. This soft layer is at an average depth of about 80 km under continental

crust and about 40 km under oceanic crust. The soft layer of the upper mantle is referred to as

Asthenosphere (the word astheno means weak) and the rigid layer above it is the Lithosphere.

According to geologists, lithosphere means the outer rock layer, but it is also referred to as the solid

Earth realm. The lithosphere is about 10 to 200 km thick. The lower mantle, which is in a solid

state, extends beyond the asthenosphere. The asthenosphere extends to a depth of about 300 km.

The rigid lithosphere is broken into large plates, which bodily move around, independent of each other,

over the asthenosphere.

3. Core

The core is the centre of the Earth’s interior. It is a spherical zone, approximately 3500 km in radius.

The change in behaviour of Earthquake waves upon reaching this zone suggests that the outer core has

the properties of a liquid- in abrupt contrast to the solid state of the rock above it. The innermost part

of the core is thought to be in a solid state. It has a radius of about 1255 km.

The core is made up of heavy materials - Iron and Nickel are the two main constituents of the core.

On the basis of its composition, it is also referred to as Nife .The temperature here may go up from

2200oC to 2750

oC. Similarly the pressure inside is also a million times more than the atmospheric

pressure at sea level.

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CONTINENTAL DRIFT AND PLATE TECTONICS As soon as information about the outlines of continents came into the hands of scholars, they

pointed at the close correspondence between the western coast of Africa and the eastern coast of

South America. As early as in 1668, it was suggested by a Frenchman that the two landmasses had

been joined together at some point in the past. In 1858, Antonio Sneider Pelligrini produced a map

and supported this view with evidence pointing towards a similarity between rocks types in Europe and

North America.

But the strongest case for continental drift was made in 1912 by the German meteorologist and

geophysicist, Alfred Wegener. He presented various geologic evidences to support his idea that the

continents were once joined together. According to him, about 300 million years ago (in the

Carboniferous Period) there was a super continent which was named as Pangaea. The super

continent of Pangaea was surrounded by a super ocean called Panthalasa. He believed that the

Americas, Africa and Europe were fitted together, while the continents of Antarctica and Australia,

along with India and Madagascar, were grouped together near the south eastern side of Africa.

Around 200 million years ago the Americas moved away from Pangaea, thereby creating the Atlantic

Ocean in between the Americas and Africa. Gradually the other parts also started drifting apart from

each other, creating various seas and oceans as they moved apart. He suggested that the less dense

continental layer had floated like a raft over the denser oceanic crustal layer. The evidence that

Wegener had put forward in support of his theory has been validated by recent research. The

evidence is as follows:

1. The jigsaw fit between the continents of Africa and South America:

In 1964 Bullard, produced a computer generated map of the Atlantic margins and it proved that the

two continents were once together.

2. Rocks of the same age: Recent radiometric dating of rocks suggests that the same belt of ancient

rocks (about 2000 million years old) extends on both the sides of the Atlantic Ocean. The earliest

marine deposits found along the coasts of America and Africa belong to the Jurassic Period, suggesting

an absence of ocean before that.

3. The presence of Tillite in six different land masses of the southern hemisphere suggests prolonged

glaciation. Remarkably similar Gondwana -type sediments have been found in all these landmasses,

indicating that they were once together and experienced similar historical evolution. The occurrence

of placer deposits of gold in Africa without a source rock is intriguing. Its counterparts have been

found in Brazil, suggesting their closeness once upon a time.

4. Fossil Distribution: The study of fossils has indicated that identical species of plants and animals had

once dominated land masses which are today separated by water bodies. For example –the fossils of

Mesosaurus are found in only South Africa and Brazil – they are separated by an ocean now !

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FIGURE 2.5. GEOGRAPHIC BASIS FOR WEGNER’S CONTINENTAL DRIFT5

The solid geologic evidence presented by Wegener in the early 20th

century strongly supported

the existence of the Pangaea. Wegener suggested that a pole fleeing force and tidal force were the

forces behind the drifting of continents. According to him, over millions of years, these forces were

effective in moving the continents. But his entire hypothesis lost support over this issue. The forces

that he proposed were considered too feeble to move such huge landmasses. Subsequently, a number

of new discoveries were made, and new dimensions were added to Wegener’s hypothesis.

In the 1930s Arthur Holmes came up with the theory of ‘convection currents in the mantle’ to explain

the drifting of continents. According to him, these currents are caused by radioactive elements which

induce thermal differences in the mantle.

The mapping of the ocean floor and paleomagnetic study of rocks revealed some new facts, like:

• Regular volcanic eruptions along the mid oceanic ridges that add large amounts of lava.

• Great similarities in age, chemical composition, and magnetic properties of rocks on either side of

mid oceanic ridges.

• Increase in age of rocks with increasing distance from the crest of the ridge.

• The ocean crust being only 200 million years old as compared to the continental rocks which are

more than 3000 million years old.

• Occurrence of deep-seated Earthquakes in deep oceanic trenches and shallow focus Earthquakes in

other areas.

Based on these observations, Hess proposed his hypothesis on sea floor spreading. He maintained that

eruptions along the oceanic ridges caused the oceanic crust to rupture and lava to well up, thereby

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pushing the oceanic crust on both sides. This resulted in the spreading of the ocean floor. But it was

observed that spreading and creation of new oceanic crust did not lead to a change in the size of the

Earth. This led him to think about the consumption of ocean crust. Hess concluded that the ocean

floor that gets pushed due to the oozing of lava sinks at the oceanic trenches and gets consumed.

Plate Tectonics:

In the second half of the twentieth century, Wegener’s theory was interpreted in a new way and a new

concept emerged in. It is hypothesised that as the lithospheric plate is lifted to a higher elevation

above the rising the 1960s in the form of plate tectonics. This scientific seeks to explain the slow

movement of large segments of the Earth’s outer layers. Tectonics is a noun meaning the study of

tectonic activity. Tectonic activity refers to all forms of breaking and bending of the entire

lithosphere, including the crust. In 1967, McKenzie and Parker came out with the theory of plate

tectonics. According to this modern interpretation, continental drift involves the movement of large

lithospheric plates. (You may recall that the lithosphere consists of the crust and upper mantle and is

about 100 km in thickness.) Scientists recognise six or seven major plates and several minor ones.

The plates move over a soft plastic layer called the asthenosphere at rates varying between 2

and 15 cm/year.

It is generally believed that radioactivity is the source of energy that sets plates in motion.

Radioactive elements give off heat, causing rocks in the mantle to expand. A convective motion is

set up with the upward movement of the hot, less dense material. The mantle rock rises beneath the

spreading plate boundaries mantle, it tends to move horizontally away from the spreading axis under

the influence of gravity.

At the other end of the plate subduction takes place. As the oceanic plate is denser than the

continental plate, it bends and sinks into the aesthenosphere. Being cooler, and therefore

denser, than the asthenosphere, the descending lithospheric plate sinks easily. A part of it melts and

becomes magma which rises to the Earth’s surface to form a chain of volcanoes parallel to the deep

trench that marks the zone of subduction.

The lithosphere is divided into seven major plates and a number of smaller plates. The larger

plates are bordered by young mountains, oceanic ridges and trenches.

The seven major plates are as under:

1. The Pacific plate (the largest plate and covers about 20%of the Earth’s surface and is almost

entirely formed of oceanic crust).

2. Eurasian plate

3. Indo Australian plate

4. African plate

5. North American plate

6. South American plate

7. Antarctic plate. Since most of the tectonic activities take place along the plate boundaries , so they are now the focal

point of research for the geologists and other scientists.

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FIGURE 2.6. MAJOR LITHOSPHERIC PLATES WITH THEIR DIRECTION OF

MOVEMENTS 6

FIGURE 2.7. TYPES OF PLATE BOUNDARIES – DIVERGENT, CONVERGENT AND

TRANSFORM7

As plates move relative to one another, they interact along their common boundaries. There are three

major kinds of plate boundaries:

a) Spreading boundaries of diverging plates – where new lithosphere is being formed by accretion.

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b) Converging boundary of converging plates – where lithosphere is being consumed due to

seduction

c)Transform Boundaries – where plates just slide past each other along a transform fault – with

no motion that would cause the plates to either separate or to converge.

Converging plates where seduction is in progress are zones of intense tectonic and volcanic

activity.

The rate of the plate movement is not the same and varies considerably. The East Pacific rise in the

south Pacific moves at the fastest rate of 15 centimeters per year as compared to the Arctic Ridge

which has the slowest rate of movement at 2.5 centimeters per year.

FIGURE 2.8 SUBDUCTION UNDER CONTINENTAL PLATE8

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FIGURE 2.9. CONVERGING PLATE BOUNDARY SHOWING OCEAN‐CONTINENT

PLATE COLLISION. THIS TYPE OF COLLISION HAS CONTRIBUTED TO

DEVELOPMENT OF THE ANDES AND A DEEP OCEAN TRENCH9

FIGURE. 2.10. CONVERGING PLATE BOUNDARY SHOWING CONTINENT‐CONTINENT

COLLISION. FORMATION OF HIMALAYAN MOUNTAINS – FOLD MOUNTAINS, TOOK

PLACE WHEN INDIAN PLATE DRIFTED NORTHWARD TO COLLIDE WITH ASIAN

PLATE10

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News Paper : Times of India

Date: 11, February 2012

WASHINGTON: In the coming 50 to 200 million years, Australia may merge with India while all the

continents may collide each other to form one massive supercontinent, scientists have claimed.

Geologists at Yale University in the US predicted that the Americas and Asia will drift northward,

closing off the Arctic Ocean and Caribbean Sea to merge around the Pole and form

a supercontinent called Amasia.

The research, published on Thursday in the journal Nature, is a vivid reminder that the plates of the

Earth's crust are always moving and that one very far-off day, the world will be a very different place.

"This would lead to a collision with Europe and Asia, more or less at the present day North Pole,"

Yale geologist Ross Mitchell was quoted as saying by the National Post. "Australia would also most

likely continue its northward motion and snuggle up next to India."

The geologists believe that supercontinents — massive continents formed by other continents

squishing together over millions of years — form at 90 degrees from each other.

Mitchell and his colleagues analyzed ancient rocks to create a map of their locations around the globe

and used it to map how the Earth's mantle causes continents to move over time.

They found that formation of supercontinents follow a pattern. The last supercontinent Pangea —

formed 300 million years ago — was preceded by three others, Mitchell said. Pangaea, where giant

reptiles and dinosaurs arose, formed at 90 degrees to the Rodinia, the supercontinent before it, which

in turn formed at 90 degrees to the supercontinent before it, Nuna.

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FIGURE 2.11. CONTINENTAL DRIFT AND PLATE TECTONICS. EARTH’S TECTONIC HISTORY OVER THE LAST 250 MILLION YEARS

OF GEOLOGIC TIME11

EARTH MOVEMENTS You have learnt about the presence of irregularities on the surface of the Earth. Some of these

irregularities are in the form of very large features such as continents, oceans, mountains and

plateaus. There are smaller features too, such as valleys, terraces, caves and sand dunes. The forces

that shape the surface of the Earth can be endogenetic or exogenetic. Endogenetic or endogenic

forces are those that originate within the Earth. Exogenetic or exogenic forces are those that operate at

or near the surface of the Earth, shaping its features from outside rather than inside. We shall

discuss endogenetic forces first.

Over millions of years the internal forces of the Earth have been continuously affecting the Earth’s

crust. They have caused rapid movements like Earthquakes as also the extremely slow and wide scale

mountain and continent building movements. These movements have caused some areas to break and

subside while other areas have been uplifted. Some movements were so powerful that strata of rock

were squeezed and compressed to form long chains of mountains.

The forces generating these movements are known as diastrophic forces and the process is known as

diastrophism. All processes that involve movement, elevation or building of portions of the

Earth’s crust are included in diastrophism.

Classification of Earth movements: On the basis of their structural results diastrophic movements are classified into two categories:

Epeirogenic (continent building) and Orogenic (mountain building).

Epeirogenic movements are caused by vertical forces which act radially, causing uplift or depression

of the Earth’s crust. These movements are generally on a very large scale, like a continent (Epeiros in

Greek means continent) and so are referred to as Epeirogenic. Sometimes these movements occur at a

local level as well. For example, epeirogenic movements along a coast can result in changes in the

relative levels of land and sea.

Orogenic movements are caused by horizontal forces which act tangentially to the surface of the

Earth, resulting in both compression and tension of the crust and ultimately causing stress in rocks.

These movements formed the great fold mountains of the world. In fact the word ‘Orogenic’ has been

derived from the Greek word ‘Oros’, which means mountains.

Effects of Earth’s movement on Crust:

The shape and volume of rocks change due to stress induced by orogenic and eprierogenic forces..

Tensional forces cause the crust to stretch and move apart, resulting in extension of the Earth’s surface

and production of joints and normal faults. Compressional forces act towards each other- leading to

contraction of the surface and resulting in the formation of folds. Folding and faulting are now

discussed in detail.

FOLDS

Compressional forces can cause bending of sections of the Earth’s crust. This flexure of rock layers is

known as folding. Folding can lead to the formation of wrinkles a few centimetres in length and width

or it can lead to the formation of mountains covering thousands of square kilometres. Folding leads to

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a shortening of the Earth’s crust and the formation of waves. The simplest fold is symmetrical - upfold

(anticline) and downfold (Syncline). The central line of either fold is axis and the sides are the limbs.

When one side is steeper than the other the folds become asymmetrical. Depending upon the degree

of folding there are different types folds;

An over fold is formed when the crest of a fold is pushed too far due to complexity of compressional

forces. If it is pushed still further it is termed a recumbent fold. In case of extreme force, fractures

may occur in the crust – generally along the axis -so that the upper limb of the recumbent fold slides

forward over the lower limb along a thrust plain, giving rise to an overthrust fold. The overriding

portion of a Thrust fold is called a Nappe. These mountains are closely associated with volcanic

activity.

FIGURE 2.12 TYPES OF FOLDS12

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FIGURE 2.13 FORMATION OF

OVERTHRUST FAULT13

FAULTS Forces operating in the interior of the Earth cause rocks to crack or fracture. When there is no

displacement of rock on either side of the fracture, the crack is called a joint. When rock on one side

of the fracture moves in relation to the other side, it is known as a Fault. This movement is known as

Shift. The relative movement along the fault is known as slip while the vertical change in the level

of the strata is called Throw. Some fault lines may be small but some are several kilometres in

length. For example the San Andreas Fault running through San Francisco and Los Angeles is about

500 km long. Earthquakes commonly occur along active faults.

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FIGURE 2.14 TYPES OF FAULTS14

Fault Blocks: Sometimes areas of the crust may be divided into individual elevated or subsided

masses by faults – known as block faulting. When an individual block fault is sharply defined it

is known as Horst or Block mountain. These are formed between a pair of faults when the block

enclosed by the faults remains as it is or rises and the land on both sides subsides. The faulted edges

form very steep vertical walls while the top remains flat. The Vosges, Black forest, Sinai and Korea

are examples of Horsts.

Sometimes the central portion between two adjacent faults may subside and form a Rift valley or

Graben. It is the fault trough between two parallel faults with throws in opposite directions. It is the

reverse of a Horst. The river Rhine flows through the rift valley between the Vosges and Black forest.

Some prominent relief features of the Earth have been formed by the upliftment and

subsidence of the Earth’s crust. The crust may warp on a large scale, forming an arch or a basin, or

strata may be fractured to form uplands and troughs. In Central Asia, fold mountains enclose

plateaus (intermontane plateau) like the Tarim Basin and the Plateau of Mongolia.

FIGURE 2.15 LANDFORMS CAUSED BY FAULTING15

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FIGURE 2.15 LANDFORMS CAUSED BY FAULTING15

EARTHQUAKES: Earthquakes are vibrations or shake of the Earth’s crust.

The ‘shallow’ ones are caused by sudden diastrophic

movements but the majority of them are triggered by

localized energy release in the upper mantle. These

vibrations traveling different directions from the point of

energy release in the form of waves. The point from which

they originate is termed as the seismic focus or

hypocentre. The point on the Earth’s surface

perpendicular to the focus is referred to as the epicentre.

The epicenter experiences the first and most intense

energy waves. The effect of the Earthquake decreases as

one move away from the epicenter.

Do you know? Maximum Earthquakes occur in the

upper part of the crust. (upto 20 Km).

A Seismograph records any movement in

the crustal layer.

Scientists rank Earthquakes on the

bases of their magnitude or intensity.

The magnitude reflects the energy

released during the quake and is

expressed in absolute numbers from 0 to

10. It is known as Richter’s scale. The

intensity scale is based on the visible

damage caused by the Earthquake and it

ranges from 1-12. The intensity scale is

known as Mercalli scale.

Earthquakes occur regularly in the

Earth’s crust but most go unnoticed.

Though there are some stable areas on

the Earth where Earthquakes rarely strike, there are few places fully free of Earthquakes.

As mentioned earlier, scientists have been able to gather knowledge about the Earth’s interior

from the analysis of Earthquake waves. Data recorded by seismographs reveals three types of

vibrations in the strata, caused by three sets of waves. The behaviour of the first type of waves is

similar to sound waves – here each particle is displaced by the wave in the direction of movement

i.e. longitudinally. This type is referred to as ‘P’ or Primary (compressive) waves.

Figure 2.16

Earthquakes Epicente

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The second type is similar to light waves – where each particle is displaced by the wave at right angle

to its direction of movement. This type of wave is referred to as the ‘S’ or Secondary (transverse)

waves. The third type of wave travels along the surface of the ground – and is known as the L

waves. These waves are propagated in all directions from the epicentre. The P waves are the fastest

(8km/sec), followed by S waves (4.5km/sec). The velocity of waves increases as far as the Gutenberg

discontinuity that separates the mantle from the core. This indicates that the speed of the waves

increases with density. Seismologists have observed that S waves disappear at the discontinuity while

P waves get refracted but travel through the layer deeper inside. They have also observed that

seismographs located upto a distance of 105 degrees from the epicentre record both P and S waves.

Beyond that distance only P waves are recorded, and at a distance of between 105 and 145 degrees

of the epicentre, neither P nor S waves are recorded. This zone is referred to as a ‘shadow’ zone. This

also indicates that the S waves can only travel through solids and that the Earth’s outer core is liquid in

nature.

FIGURE 2.16 EARTHQUAKE SHADOW ZONES16

EFFECTS OF EARTHQUAKES: The sudden nature of Earthquakes has a great impact on landforms and life and property in the region

where it occurs. Though an Earthquake lasts only for a few seconds, its effects can be widespread

and devastating if the magnitude is more than 5 on the Richter scale. Minor Earthquakes occur very

frequently but major ones are rare. Some of the immediate hazards of Earthquakes are shaking of

ground, ground displacement, landslides and mudslides, soil liquefaction, avalanches, floods due to

breaking of dams, fires, tsunamis, structural damage to buildings, bridges and roads etc.

When an Earthquake originates beneath the ocean floor, huge sea waves may be generated.

They are known as Tsunami (Japanese term: Tsu – Harbour, Nami-Waves) . The waves spread

outwards in all directions at a great speed (300-800 km/h) and cause great damage to coastal areas.

We are all aware of the disastrous tsunami that occurred in March 2011 in Japan that took away many

lives and destroyed property worth millions.

Negative Effects of Earthquakes: Earthquakes produce various damaging effects to the areas they act

upon. This includes damage to buildings and in worst cases the loss of human life. The effects of the

rumbling produced by earthquakes usually lead to the destruction of structures such as buildings,

bridges, and dams. They can also trigger landslides. An example of how an earthquake can lead to

even more destruction is the 1959 earthquake near Hebgen, Montana. It caused a land slide that killed

several people and blocked the Madison River. Due to the fact that the Madison River was blocked, a

lake was created which later flooded the nearby town of Ennis.

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Positive Effects of Earthquakes:

Positive effects of Earthquakes explore that,

People come to know about the structure of the earth, for example, magma chambers, and P-waves

and S-Waves. scientists to monitor volcanoes and the threat of eruption. Earthquakes can also access

about the internal structure of the Earth. By measuring the time it takes the seismic waves to travel

through the Earth we can map out the structure of the Earth down to the core.

On a global scale, earthquakes are just a symptom of the movements of the plates going on all the

time, and they occur because the material at the surface at the earth is changing due to convection

within the Earth’s mantle – mountains are being created, minerals from below are being brought up

and new sea floors are being made. Tectonic activity is essential to sustaining life on Earth.

Matter is constantly being recycled between the atmosphere and the crust. We have continents because

of tectonic activity. Mid ocean ridges support a huge amount of life, and may have been important in

the origin of life, and the atmosphere is reliant on volcanic eruptions for its composition.

DISTRIBUTION OF EARTHQUAKES

Although Earthquakes occur in many parts of the world, they are more common in certain areas.

There is a belt around the Pacific Ocean and another one that extends eastwards from the

Mediterranean Sea, through Asia Minor, the Middle East to the northern part of India. These are

unstable areas with young fold mountains at the margins of plates. The Pacific coast is also dotted

with volcanoes and is also referred to as the ‘Pacific Ring of Fire’.

VOLCANOES: A volcano is an opening in the Earth’s crust through which magma and other materials come out to the

surface. Volcanoes are generally conical or dome shaped structures built by the emission of lava and

other volcanic materials from a vent in the Earth’s surface. The magma comes out through a pipe like

structure called conduit. The opening on the surface is termed as a crater. The conduit reaches the

magma chamber inside the Earth and connects it with the crater. The nature of the volcanic eruption

depends on the type of magma. When the magma reaches the Earth’s surface, it is termed as Lava.

The molten material is apparently in a state of solidity inside the Earth due to high pressure. Volcanic

activity occurs when pressure is released by Earth movements. Vulcanicity is the process by which

solid, liquid and gaseous materials are brought up to the Earth’s surface. Sometimes the material

remains within the crust as intrusive rocks. The material that reaches the surface and solidifies

there forms extrusive rocks.

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FIGURE 2.17 CROSS‐SECTION OF A VOLCANO17

VOLCANIC FEATURES: Volcanic activity leads to the formation of a number of features. The type of feature formed depends

on a number of factors – such as the strength and fluidity of magma, the types of cracks, faults and

joints that it penetrates, place of solidification, and the manner in which it escapes to the surface.

Viscous lava causes explosive eruptions, while less viscous lava causes quiet eruptions and flows

further, giving rise to flatter landforms. Volcanic features may be classified as Intrusive or extrusive.

Magma sometimes cools and solidifies within the crust as plutonic rocks and gives rise to intrusive

landforms. When magma solidifies and cools after reaching the surface it forms Volcanic rocks and

gives rise to extrusive landforms. Rocks formed by plutonic or volcanic activities are called igneous

rocks.

Landforms of Igneous intrusion

Sills and dykes are the commonest forms of intrusive landforms. When an intrusion of molten

magma occurs horizontally along the bedding plane of sedimentary rocks, it forms sills. When it is

injected vertically as a narrow wall within the sedimentary layer, it is called a dyke. Igneous intrusions

on a larger scale form a number of features such as Laccoliths, Lopoliths, Phacoliths and

Batholiths. A Laccolith is a large dome shaped igneous mound with a level base. A Lopolith is a

saucer shaped igneous intrusion that forms a shallow basin. A Phacolith is found at the crest of an

anticline or at the bottom of a syncline .A Batholith is a large mass of igneous rock that generally

develops at greater depth and forms a large dome. All these features generally have granitic bodies

and are exposed after the forces of denudation remove the overlying surface material..

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FIGURE 2.18 MAJOR INTRUSIVE FEATURES OF A VOLCANO18

Extrusive Landforms:

Based on the type of eruption, two major forms are identified. A central eruption takes place from a

single vent or a group of close vents. A linear or fissure eruption is one in which lava wells up from a

zone of weakness on the Earth’s surface. The resultant features depend on the nature of eruption and

the characteristic of ejected materials

Lava plains and basalt plateaus are formed by the more fluid basic lava. The highly fluid lava builds up

shield volcanoes with gently rising slopes and broad flat tops. The accumulation and solidification

of magma around a central vent leads to the formation of a cone, typically with a funnel-shaped basin

called a crater, surrounding the vent. When lava solidifies as it flies through the air, the cone is

formed of cinders and other pyroclastic material (fragmented rock material ejected by a volcano),

and is known as a cinder cone. The most common volcanoes are composite cones that are built of

alternating layers of lava and cinders. Sometimes during an eruption, material from the top of the

cone is blown off or it collapses into the vent, creating a large crater. Sometimes they may give rise to

large depressions called calderas that have a diameter many times that of the original vent.

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FIGURE 2.19 TYPES OF VOLCANOES (a) Shield Volcano (b) Cinder Cone, (c)

Composite Cone or Stratovolcano, and (d) Plug Dome19

According to the frequency of eruption, volcanoes may be classified as Active, Dormant and Extinct.

Active volcanoes are the ones which frequently erupt or have erupted in the historical past.

Dormant volcanoes show signs of eruption but have not erupted in the recent past though they might

erupt in future. Extinct volcanoes have not erupted in the historical past.

FIGURE 2.20 Location of the Pacific Ring of Fire20

There are over five hundred active volcanoes and thousands of dormant and extinct ones. They are

located in a distinct pattern along the coastal mountain ranges, islands and in the middle o f o c e a n -

commonly a round c o n ve r g i n g p la te b o u n d a r i e s . Their ma x i mu m concentration is around

the circum- Pacific belt which is known as the “Pacific Ring of Fire”.

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Worksheets

UNIT II ‐ EARTH, WORKSHEET 1

ORIGIN AND EVOLUTION OF EARTH

I. MULTIPLE CHOICE QUESTIONS 1. Nebular hypothesis regarding formation of universe and planets was put forth by

a. Aristotle b. Holmes c. Christaller d. Hess

2. The hypothesis stating that galaxies in universe are constantly moving away from one

another is a. Steady state theory b. Expanding universe theory

c. Drift theory

d. Nebular hypothesis 3. The planets with earth like structure, that are made up of rock and are of relatively high

density are a. Gas planets b. Terrestrial planets

c. Aquatic planets

d. Solar planets 4. During evolution of earth, the primordial atmosphere was lost probably due to

a. Influence of strong winds that blew away hydrogen and helium

b. Release of water vapour and hydrogen c. Volcanic eruptions d. Solution of carbon‐di‐oxide 5. The tertiary period in which the major mountain systems were formed is part of

a. Cenozoic era

b. Mesozoic era

c. Paleozoic era

d. Proterozoic era

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II. MARK THE STATEMENTS AS CORRECT OR INCORRECT

1) Theories suggesting that earth originated due to existence of a companion to Sun are known as

Nebular theories.

2) Big Bang theory postulates that the earth started as a tiny ball and subsequently exploded violently.

3) Terrestrial and Jovian planets differ in their composition.

4) In the geological history of the earth, during the Proterozoic , deposits of coal developed world

wide.

5) Rocky mountains began to form in the Cretaceous period. III. FROM THE GEOLOGIC TIME SCALE GIVEN BELOW ANSWER THE QUESTIONS

1. In which geologic period did the young fold mountains begin to form? How many

years back?

2. The coal swamps developed world wide, how many years back?

3. For how many million years did the Ice Age last?

4. The earliest fossil records are of which eon?

5. Geomnemonic to learn the Geologic Time scale is given below. Make your

own geomnemonic for the time scale.

Camels Often Sit Down Carefully

Perhaps Their Joints Creek

Proper Early Oiling Might Prevent

Permanent Harassment

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic,

Cretaceous, Palaeocene, Eocene, Miocene, Pliocene, Pleistocene, Holocene

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WORKSHEET 2

INTERIOR STRUCTURE OF THE EARTH

I. MATCH THE FOLLOWING AND WRITE A BRIEF COMMENT

1.Discontinuity a. Rigid

2. Core b. 5.5g/c.c

3. Lithosphere c. Mohorovičić

4. Mantle d. NIFE

5. Density e. Olivine

II. MULTIPLE CHOICE QUESTIONS 1. The thickness of the mantle is

a. 2700 kilometers

b. 2800 kilometers

c. 2900 kilometers

d. 2950 kilometers

2. The temperature of the core core varies between

a. 2100oC to 2550

oC

b. 2200oC to 2750

oC

c. 2300oC to 2650

oC

d. 2300o

C to 2750o

C 3. The soft layer of upper mantle is termed as

a. Lithosphere

b. Mesosphere

c. Asthenosphere

d. Exosphere

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4. The density of the earth as we go down from crust to core

a. Increases

b. Decreases

c. Remains same

d. First increases then decreases

5. Indirect source of information regarding the earth’s interior is provided by

a. Mines

b. Volcanoes

c. Drilling

d. Seismic waves

III. Study the following diagram and mark the statements as Correct or Incorrect.

1. In the P‐wave shadow zone, the seismic P‐waves pass.

2. Beyond 103° S‐waves do not pass at all, therefore it is termed as S‐wave shadow zone

3. There is an area between 103° and 142° in which P‐waves and S‐waves do not pass.

4. When the P‐waves pass through the core they are deflected due to change in temperature.

5. Till 103° from the earthquakes epicentre only P‐waves can pass.

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IV. MARK THE VARIOUS LAYERS OF THE EARTHS INTERIOR

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WORKSHEET 3

CONTINENTAL DRIFT AND PLATE TECTONICS

I. FILL IN THE BLANKS 1. The German meteorologist and geophysicist who propounded the continental drift theory

in 1912 is ........................................... 2. Arthur Holmes in 1930 explained the drift of continents through the theory

of………………………… 3. The process through which the denser oceanic plate bends and sinks under the continental

plate in the asthenosphere is known as .................................. 4. On the spreading margins of the plate boundaries new crust is being............... 5. The plates slide past each other along the.................... faults.

II. MULTIPLE CHOICE QUESTIONS

1. According to the Jig‐Saw fit of the continents as proposed by Wegner, there is perfect fit

between the refined rocks of the now separated continents of

a. Australia‐Europe

b. South America‐Africa

c. Africa‐Australia

d. South America‐Australia

2. The concept of Sea‐floor spreading that explains the movement of sea floor as conveyor

belt away from crest of mid‐oceanic ridges was given by

a. Wegener

b. Arthur Holmes

c. Harry Hess

d. Strahler 3. The lithospheric plates continue to diverge widening the sea. An example of such a

diverging boundary on sea floor is located on

a. Mid‐oceanic ridge

b. Himalayan mountains

c. Andes Mountains

d. Mojave Desert 4. Young fold mountains are created when there is convergence of

a. Continent‐continent plate

b. Ocean‐continent plate

c. Ocean‐ocean plate

d. Pacific‐Australian plate

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5. Transform boundaries are areas where the lithospheric plates are

a. Converging

b. Diverging

c. Sliding past each other

d. Colliding

III. WITH THE HELP OF THE GIVEN CLUES SOLVE THE PUZZLE ON PLATE

TECTONICS

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Across 3. Largest lithospheric plate 7. Layer of indeterminant thickness and behaves plastically 9. Sea‐floor is spreading according to the scientist 10. Plates slide past each other on this boundary Down 1. Denser plate sinks under less dense plate through the process 2. Rigid outer shell of earth 4. According to him radioactive elements induce convection currents in mantle 5. Plates move away from each other in this process 6. Propounded Continental Drift Theory 8. Study of earths past magnetism

IV. LABEL AND EXPLAIN THE FOLLOWING DIAGRAM

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WORKSHEET 4

EARTH MOVEMENTS

I. MULTIPLE CHOICE QUESTIONS 1. Orogenic movements are more commonly referred to as movements that build

a. Mountains

b. Continents

c. Oceans

d. Seas 2. When the crest of a fold is pushed too far due to complexity of

compressional forces it forms an

a. Upfold

b. Over fold

c. Anticline

d. Syncline

3. Nappe is the overriding portion of

a. Thrust fold

b. Over fold

c. Recumbent fold

d. Anticlinorium

4. Rocks on one side of fracture moves in relation to the other side, to form

a. Fold

b. Joint

c. Nappe

d. Fault

5. When the portion between two adjacent faults subside it forms

a. Graben

b. Horst

c. Block

d. Synclinorium

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II. FILL IN THE BLANKS 1. San Andreas Fault, zone of frequently occurring earthquakes lies between San

Francisco and ............................... 2. An up raised block bounded by normal faults form ........................ 3. In the structure of folds, the central line of either fold is termed as ................... and the

sides are termed as .......................... 4. When the vertical forces act radially, causing uplift or depression of the earth’s crust,

taking place at a large scale are termed as ................................movements. 5. An example of Rift Valley between Vosges and Black Forest is ........................ III. MATCH THE FOLLOWING AND EXPLAIN BRIEFLY

1. Graben a. Tarim Basin

2. Intermontane b. Nappe

3. Thrust fold c. Rift

4. Epeiros d. Mountains

5. Oros e. Continent

IV. IN THE FOLLOWING DIAGRAM MARK DIFFERENT TYPES OF FOLDS AND

DISCUSS THEIR FORMATION

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WORKSHEET 5

EARTHQUAKES

I. MULTIPLE CHOICE QUESTIONS

1. Seismology is the science of study of

a. Cyclones

b. Earthquakes

c. Volcanoes

d. Landslides 2. Surface waves are also known as

a. S‐waves

b. L‐waves

c. P‐waves

d. W‐waves

3. The point on the earth’s surface perpendicular to the focus is referred to as

a. Epicentre

b. Hypocentre

c. Focus

d. Core

4. The discontinuity that separates mantle from the core is

a. Mohorovičić

b. Gutenberg

c. Weiss

d. Mercalli

5. The P‐waves also known as primary waves and compressional waves can travel through

a. Only solid

b. Solid and Gas

c. Liquid and solid

d. Solid, Liquid and Gas

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1.Tsunami a. S‐waves

2.Richter b. Harbour Wave

3. Transverse waves c. Discontinuity

4. Instrument d. Earthquake magnitude

5. Gutenberg e. Seismograph

II. MARK THE STAEMENTS AS CORRECT OR INCORRECT 1. The point from which the earthquake originates is termed as epicentre 2. The P‐waves and S‐waves can travel through crust, mantle and core. 3. The speed of P‐waves is greater than the S‐waves. 4. The intensity of earthquake is measured on Beufort Scale. 5. The P‐wave shadow zone lies between 103° to 145° of the epicentre. III. Study the given diagram and answer the questions given below

1. Which waves can penetrate through all the three layers – crust, mantle and core and why?

2. Why does the shadow zone for P‐waves develop?

3. The shadow zone for S‐waves is larger, why?

4. Draw conclusions from behaviour of the different types of waves. IV. MATCH THE

FOLLOWING AND GIVE A BRIEF EXPLANATION

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WORKSHEET 6

VOLCANOES I. Some information about Volcanoes is given below. Collect more information and then

give a brief answer.

Stromboli, a volcano off the coast of Italy erupts once every 20 minutes! It is known as the

‘Lighthouse of the Mediterranean’.

On an average between 20 to 30 volcanoes erupt each year.

Mauna Loa in Hawaii is the largest live volcano on earth. One eruption lasted for one and a

half years.

Scientists have developed ways of using the heat inside the earth’s volcanic areas. Houses in

Iceland are heated by hot water which is piped from underground heat source. Power stations

in New Zealand, Italy, USA, Japan, Mexico and Chile use steam from underground to help

generate electricity. Energy from these hot zones below the surface of the earth is known as

Geothermal energy.

1. What is geothermal energy and what are its uses?

2. Name some live volcanoes that have erupted recently. Which is the largest one on earth?

3. Mention difference between magma and lava.

4. Which volcano is known as the ‘Light house of the Mediterranean’ and why?

5. Why is major volcanic activity concentrated on the ‘Pacific Ring of Fire’? II. FILL IN THE BLANKS

1. Solidification of magma on the surface of earth leads to formation of ...................

landforms.

2. Large dome shape igneous mound with a level base that solidifies below the surface is a

.................

3. Fragmented solid rock material ejected by the volcano during eruption is termed as

........................... material.

4. ........................................ are large depressions that have a diameter much larger than that

of the original vent.

5. The volcanoes that show signs of eruption but have not erupted in the recent past,

though they might erupt in future are ............................ volcanoes.

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WORKSHEET: 7 Map Based Exercise

Q1. On the outline map of the world mark the following lithospheric plates.

a. Nazca Plate

b. Philippines Plate

c. Cocos Plate

d. Australian Plate

Q. 1. In the physical map of the world colour the region most conspicuous for volcanic

activity also known as Ring of Fire. Mark the fold mountain formed due to:

(a) Subduction of Nasca Plate under South American Plate (b) Movement of Indian plate towards Asian plate (c) Collision of African and Eurasian plate

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Reverences

1. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 79

2. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 79

3. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 77

4. http://www.bbc.co.uk/scotland/learning/bitesize/standard/physics/energy_matters/heat in_the_home_rev1.shtml

5. http://www.educationalelectronicsusa.com/p/heat‐IV.htm

6. http://www.physics.arizona.edu/~thews/reu/the_science_behind_it_all.html

7. http://www.aos.wisc.edu/~aalopez/aos101/wk5.html

8. Fundamental of Physical Geography CLASS XI, NCERT, p. 81

9. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 99

10. http://news4u.co.in/tag/shimla/

11. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 107

12. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 108

13. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 109

14. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 103

15. http://apollo.lsc.vsc.edu/classes/met130/notes/chapter8/p_measure.html

16. McKnight, T and Hess, D. 2005 Physical Geography: A Landscape Appreciation, Prentice Hall: London, p. 104 17. Fundamental of Physical Geography CLASS XI, NCERT, p. 89

18. Fundamental of Physical Geography CLASS XI, NCERT, p. 90

19. Strahler, A. 2011 Introduction to Physical Geography, John Wiley and Sons: New Jersey, p. 154

20. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 120

21. http://nsidc.org/arcticmet/factors/winds.html

22. http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/geos.rxml

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23. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 122

24. https://courseware.e‐education.psu.edu/courses/earth105new/content/lesson07/03.html

25. http://www.boqueteweather.com/climate_article.htm

26. McKnight, T and Hess, D. 2005 Physical Geography: A Landscape Appreciation, Prentice Hall: London, p. 117

27. Gabler, R.E, Peterson, J.F. and Trapasso, L.M. 2007 Essentials of Physical Geography, Thomson Books: Belmont, p. 126

28. https://www.brisbanehotairballooning.com.au/faqs/exam‐help/140‐sea‐land‐breezes.html

29. https://www.brisbanehotairballooning.com.au/faqs/exam‐help/140‐sea‐land‐breezes.html

30. http://www.kidsgeo.com/geography‐for‐kids/0099‐mountain‐valley‐breezes.php

31. http://okfirst.mesonet.org/train/meteorology/Fronts.html

32. http://www.siskiyous.edu/shasta/env/clouds/extra.htm

33. http://www.siskiyous.edu/shasta/env/clouds/extra.htm

34. http://tropic.ssec.wisc.edu/

35. http://tropic.ssec.wisc.edu/

36. http://tropic.ssec.wisc.edu/

37. http://www.aerospaceweb.org/question/atmosphere/q0242.shtml

38. http://www.toronto.ca/water/kids/story_of_water/html/3forms.htm

39. McKnight, T and Hess, D. 2005 Physical Geography: A Landscape Appreciation, Prentice Hall: London, p. 136 40. http://simple.wikipedia.org/wiki/File:Evaporation.png

41. http://en.wikipedia.org/wiki/Evapotranspiration

42. http://itistimetothinkformyself.blogspot.in/2011/04/morning‐dews‐evening‐duska‐z‐ challenge.html

43. McKnight, T and Hess, D. 2005 Physical Geography: A Landscape Appreciation, Prentice Hall: London, p. 145

44. http://www.sxc.hu/photo/689381

45. http://www.weatherreport.com/Local‐weather‐forecasts‐Cloud‐Reading.asp

46. http://www.scoutingresources.org.uk/weather/weather_clouds_cumulus.html

47. http://www.ratioconsultants.nl/?tag=clouds

48. McKnight, T and Hess, D. 2005 Physical Geography: A Landscape Appreciation, Prentice Hall: London, p. 157

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49. McKnight, T and Hess, D. 2005 Physical Geography: A Landscape Appreciation, Prentice Hall: London, p. 201

50. http://www.marathon.uwc.edu/geography/100/koppen_web/koppen_map.htm 51. http://www.seai.ie/Schools/Post_Primary/Subjects/Geography_LC/Greenhouse_Effect 52. http://www.wespeaknews.com/world/global‐warming‐to‐flood‐low‐lying‐areas‐more‐ frequently‐31268.html

53. www.buzzle.com/articles/maldives‐islands‐sinking.html

54. http://en.wikipedia.org/wiki/File:Kilimanjaro_glacier_retreat.jpg

55. http://junksciencearchive.com/Greenhouse/sea_level_calc.html

56. http://xaxor.com/bizarre/20609‐Extreme‐snowfall‐.html 57. Critchfield, H. General Climatology, Prentice Hall of India Pvt., Ltd. New Delhi, 1987 58. Trewartha G. T. and Horne L. H., An Introduction to Climate, McGraw‐Hill, 1980