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1Unit -1
UNDERSTANDING GEOGRAPHY
Unit Structure:
1.0.Objectives
1.1.Introduction.
1.2. Defining Geography
1.3. Nature and Scope of Geography
1.4. Branches of Geography
1.5.Spatial Distribution of Phenomenon
1.6.Importance of Physical Geography
1.7. Interior of th eE a r t h
1.8. Earthquake Waves
1.9. Distribution of Land and Water
1.10. Conclusion
1.11. Questions
1.0 OBJECTIVES :
Module 1 is on Understanding of Geography will help the student:
Will help them to understand through various definitions how
different scholars have perceived geography.
To realize the scope and importance of the Physical and Human
Geography.
To study various branches of physical, human and interface
geography.
To understand the spatial distribution of physical and human
phenomenon on t he earth’s surface.
To study various aspects of earth’s interior.
To know about earthquake and its waves.
To understand how and where the land and water is distributed
on the earth’s surface in the world.
1.1. INTRODUCTION:
Geography is a fundamental s cience that helps us to
understand our physical environment with its elements andmunotes.in
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2components forming a complex structure of the earth which is the
only habitable planet in the solar system. Geographers study the
factors responsible for spatial distribution and variation of people,
places with their locations. Physical geographers explain the
phenomenon of evolution of landforms, tectonic movements,
weather and climate, ocean characteristics and properties, flora
and fauna. Human geographers explain the inte rrelationship
between man and his physical environment. Interface geographers
study various physical and human aspects in the form of their
interaction and interrelation. The study of the earth system with
specific approaches by geographers has therefore developed
specialized branches of geography.
1.2.DEFINING GEOGRAPHY :
Geography is related to the distribution of various features
natural or man -made on the surface of the earth. A Greek scholar
Eratosthenes was the first to coin the term Geography derive df r o m
the two Greek words i.e. ‘Geo’ means ‘earth’ and ‘graphe’ means
description. Geography is thus a description of earth’s surface and
the entire phenomenon appearing on it. However different scholars
have defined geography as per their view point. So me of these are
as follows:
i)According to Richard Hartshorne ‘Geography is a discipline that
seeks to describe and interpret the variable character from
place to place of the earth as the world of man’.
ii)According to Bowman ‘Geography tells what i sw h e r e ,w h ya n d
what it is made of’.
iii)Vidal de la Blache defines Geography as the science of places.
iv)As per Griffith Taylor opinion ‘Geography is the correlative
science’.
v)According to David Harvey ‘Geography is concerned with the
descrip tion and explanation of the areal differentiation of the
earth’s surface’.
Check your progress:
Q.1) How is geography viewed by different geographers?munotes.in
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31.3.NATURE AND SCOPE OF GEOGRAPHY:
Geography is one of the important subjects of understanding
the spatial science of the earth in relation with the components of
physical and human aspects. Physical Geography as a science
studies the earth’s surface and its characteristics representing
spatial relationships and varying re gional patterns. It thus includes:
The land surface and its features (Lithosphere)
The water surface and its characteristics (Hydrosphere)
Gaseous envelop surrounding the earth (Atmosphere)
Living organisms in the environment (Biosphere)
Scope of Geogra phy: Maps form an important aspect of
explaining the spatial phenomenon of the earth. Geographical
Information System (GIS) is an advanced Computer Software
programme useful in almost all disciplines in the economy of the
world. Geography covers many of th e physical and human
branches in General knowledge and is one of the compulsory paper
in any competitive examination like MPSC, UPSC. Nearly 50 -60%
graduates, prefer Geography as special subject for these exams
because Geography it deals with physical and human phenomenon
of day to day to life and so relatively easy to understand and score
marks in these competitive examinations. Besides, Geography is
one of the popular subjects at B.Ed. Colleges. Geography students
can get better opportunities in Tourism, town planning, teaching
etc. Geography as a subject therefore offers wide and diverse
employment opportunities in their career.
Human geography studies the patterns of human activities in
an environment. It includes human, political, cultural, economic
aspects of social sciences. Human geography studies various
activities in relation to its physical components and involves
quantitative and qualitative data for analysis. Human geography is
studied with the help of thematic maps giving location and other
attributes of the phenomena under study. For example distribution
and pattern of rural and urban settlements transport and
communication lines etc. in any area (Figure 1.1)
Figure 1.1 Scope of Geographymunotes.in
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4Check your progress:
Q.2) Explain in brief the na ture and scope of geography?
Physical geography undertakes the study of the earth with its
four major components viz:
a)Lithosphere,
b)Hydrosphere,
c)Atmosphere, and
d)Biosphere.
All these four components with their varying spatial and
temporal aspects have produced different characteristics features
on the earth. This is well identified / observed by spatial distribution
of different phenomenon on the surface of the earth. For example
distribution of relief features natural vegetation, birds and animals ,
human population etc. However all these phenomenon are
unevenly distributed on the earth surface.
1.4.BRANCHES OF GEOGRAPHY
Branches of Geography
A. Physical Geography B. Human Geography C. Interface
Geography
1) Astronomical Geog .1) Population Geog . 1) Thematic Cartography
2) Geomorphology 2) Settlement Geog 2) Computer cartography
3) Climatology 3) Economic Geog 3) Remote Sensing
4) Oceanography 4) Regional Geog 4) Quantitative Geog
5) Hydrology 5) Cultural Geog 5) Geography of Health
6)Biogeography 6) Historical Geog 6) Environme ntal Geog .
7) Soil Geog 7) Political Geog7) G.I.S.(GeographicalInformation System
A.Physical Geography : Following are the branches of physical
geography.
1)Astronomical Geography :is the part of mathematical
geography that treats the earth in its relation to the other
celestial bodies in the solar system. Astronomical geographymunotes.in
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5thus studies the earth as a planet with its shape, size, imaginary
lines of latitude and longitude, time zones, and the earth's
diurnal and annual motions ( yearly calendar and seasons)
(Figure 1.1. a)
Figure 1.1a Importance / Relevance of Geography
2)Geomorphology : According to Bloom ‘Geomorphology is a
systematic description and analysis of landscapes and the
processes that change them (Figure 1.2 )
Figure 1.2 Geomorphology
3)Climatology: According to Miller ‘Climatology is the aggregate
study and analysis of climatic conditions with long term keen
observations’. Climatology is thus a e science which deals with
the atmosphere various changes that take place in the
atmosphere due to temperature, humidity and atmospheric
pressure and so the formation of various climatic zones on the
earth and their influence on the natural environment (Figure
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Figure 1.3
4)Oceanography : According to J. Proudman Oceanography
studies the fundamental principle of dynamics and
thermodynamics in relation to the physical and biological
properties of the sea water. It is related to the study of oceans
i.e. temperature, salinity of the ocean water, relief of the ocean
floor, movements of the ocean water, tides, ocean currents etc.
(F i g u r e 1 . 4 . )
Figure 1.4 : Oceanography
5)Hydrology : It is a study of earth’s surface and subsurface water
bodies found in the form of oceans, rivers, glaciers, lake sa n d
seas, underground water, water vapour in the atmosphere.
6)Biogeography: It is a study of factors responsible for evolution
and spatial uneven distribution of various species (plants and
animals / flora and fauna) found on the earth .(Figure 1.5 .)
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Figure 1.5 : Bio -geography
7)Soil Geography : It helps to understand the formation, its
nature (structure and texture), types and distribution on the
earth. Soil is the most important component of the earth that
determines the growth and distribution of natural vegetation and
thus the species associated with it (Figure 1.6 .)
Figure 1.6 : Soil Geography
B. Human Geography : Following are the branches of Human
Geography:
1) Population Geography: is a branch of geography that studies
factors respon sible for various patterns of spatial distribution and
location of population on the earth’s surface. It studies various
demographic aspects of human population explaining growth of
population, structure and occupation of population and other socio -
socio c ultural aspects.
2) Settlement Geography: Settlement geography explains the
evolution and growth of rural and urban settlements in relation tomunotes.in
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8their site and situation; their structure and pattern, nature of
functions .(Figure 1.7 )
Figure 1.7 : Settlement Geography
3) Economic Geography: This branch explains us about spatial
distribution and concentration of different types of economic
activities influenced by physical factors and practiced by man
based on their locational attributes. Acco rdingly they can be
classified as:
i) Primary activities : e.g. Food gathering and hunting, agriculture,
fishing, mining and quarrying.
ii) Secondary activities: e.g. Manufacturing and construction
activity.
iii) Tertiary activities: e.g. Trade, Transp ort and Communication.
iv) Quaternary activities: e.g. activities related to specialist service
providers such as banking and insurance, administrative and
educational, defense and security, legal and medical.
It is noticed that large population engage di np r i m a r y
activities are concentrated in underdeveloped countries while in
developed countries they are concentrated more in secondary and
tertiary activities, quaternary services.
4) Regional Geography: is a branch of geography that takes into
accoun t the homogeneous physical characteristics of an area to
designate it as a region. Thus various regions are formed by taking
into consideration its climate, relief, drainage, natural vegetation
and population that determines unique characteristics for form ing a
particular region. For example Monsoon region based on climate,
Himalayan mountainous region based on relief, coastal region
based on coastal location, river plain of Indus and Ganga river
basin, savanna region based on grassland, Amazon region based
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9on forest, demographic regions based on population characteristics
for example density of population etc.
5) Cultural Geography: studies various traditional customs and
traits of a community which is reflected in their life -style, dressing
pattern, food -habits, religious rituals and ceremonies, fairs and
festivals, arts and architecture, language, and the type of
occupation practiced by them and the nature of governance over
the space. For example in terms of festivals it can be said that
Christmas of C hristian community, Diwali of Hindus, Id of Muslims,
Buddha Jayanti of Buddhists, Mahavir jayanti of Jains etc. In case
of architecture Moghul architecture of Moghuls, Gothic architecture
of Britishers, Dravidian architectural style of south Indian, Hoysal a
architectural style of Indo -aryan, Stupas and Pagodas architecture
of Buddhist etc. This spatial distribution and variation of different
cultures are studied as cultural regions in this branch of geography
which have evolved over a period of time due to different
experiences, need and interactions. The culture of man has thus
changed with changing time and technology that can be identified
as a nomadic primitive man practicing hunting and food -gathering,
to a cultivator developing permanent rural settleme nts;
manufacturer, trader, transporter that developed urban settlements.
All this has influenced to some extent the traditional culture of each
society.
6) Historical Geography: is a branch of geography that takes into
account the geographical and human factors and processes
responsible for the happening of different historical acts and events
in the space over a period of time.
7) Political Geography: is a branch of geography that studies the
organization of political system in a country. It mainly de als with its
jurisdiction (boundaries and frontiers) and nature of relationship
with neighboring and other countries in the world. The functioning
of the political system determines the stability/ instability of the
government and its power within and outs ide the country in the
world.
C.Interface Geography : Following are the branches of Interface
Geography:
1)Thematic Cartography : is a science of preparing maps and
diagrams involving field survey with specific themes
representing the spatial distribution o ft h ep h e n o m e n o nu n d e r
study; for example spatial distribution of population density in
the world, distribution of rainfall etc.
2)Computer Cartography :T h e m a t i cm a p sa n dg r a p h sp r e p a r e d
by adopting quantitative and qualitative data analysis using
specializ ed software’s in a computer are called as computermunotes.in
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10cartography. Computer cartography has provided ease by
saving time, cost and energy while producing different spatial
dimension of maps / diagrams.
3)Remote Sensing : Remote sensing may be defined a collecti on
of data bout an object from a distance. For example aircraft
provides with aerial photographs, space satellites provide with
satellite imagery. These have specific uses such as information
about weather phenomenon, security purpose, identified the
areas affected with flood/ drought/ earthquake, landslide,
landuse, study of natural resource etc.
4)Quantitative Geography :The application of mathematical and
statistical concepts and methods to the study of geography.
Quantitative Geography is thus an empiric al study of spatial
phenomenon found on the earth surface that helps in
determining certain scientific principles and laws.
5)Geography of Health :Health geography is the application of
geographical information with spatial perspectives and methods
to the s tudy of health, disease, and health care of any area.
6)Environmental Geography : Is a branch of geography that
studies how physical and human environment are interacting
with each other to produce different landuse and its effect on the
nature environment and on living species (Figure 1.8)
Figure 1.8 : Environmental Geography
7)Geographical Information System (G.I.S.): G.I.S. is defined
as a system that facilitates storage and intelligent use of data
about land and water resources and human act ivities. An
essential feature of G.I.S. is the use of sophisticated computer
hardware and software to collect, store, operate and process
the geographic data. G.I.S. technology today is highly utilized in
the field of integrated development planning such a s, water
resource management, water -shed management, environmental
monitoring and assessment, landscape conservation,
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11telecommunication and network analysis, defence and military
planning operations.
Check your progress :
1)Discuss various branches of Physical Geography
2)Discuss various branches of Human Geography
3)Discuss various branches of Interface Geography
1.5. SPATIAL DISTRIBUTION OF PHENOMENON
All things or objects are not evenly distributed on the surface
of the earth. They are concentrated in some areas and absent in
the other areas for e.g. sand -dunes are found in hot deserts, sand
beaches near sea -coast, coal is sedimentary rocks, higher
educational institutions and medical services in urban areas
glaciers/snow in areas in minus degree temperatures, agriculture
and forest in area with favourable physical factors, mining in
mineralized zones etc.
Geographers study the pattern of distribution of a particular
phenomenon under study for e.g. population, where population is
concentrated and why? This geographical approach is also termed
as Spatial Analysis. Spatial means related to space.
Geographers use maps for representing various features
found on the earth. This pattern of distribution helps geographers to
understand th e areas of concentration and dispersion. It is a
geographer who finds the reasons for this uneven distribution of
various natural and man -made resources on the earth surface.
Maps help to understand the distribution of various
phenomenons at a glance.
The ability to analyse information given in the map provides
spatial analysis of the phenomena represented by the expertise of
the Geographer.
Our earth was formed about 4600 million years ago. Almost
all natural living features like plants, animals, birds, fish, and insectsmunotes.in
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12appeared on the earth much before the emergence of man. Radius
of the Earth is 6371 Kms.
Man appeared on the earth just about 2 million years ago.
Man has well developed thinking and reasoning ability. Hence he
developed science and technology and modified natural landscape.
Natural features modified by the man are known as Cultural
features. All the features found on the earth are therefore classified
as:
i)Natural features e.g. Mountains, rivers, trees, animals, plains,
ocean se t c . (F i g u r e 1 . 9.)
ii)Cultural/man -made features. e.g. production of primary goods,
rural and urban settlements, transport and communication,
manufacturing industries, trading houses, administration and
security etc .(F i g u r e 1 . 1 0.)
S:SUN Figure 1.10 Natural features
Figure 1.11 Cultural / Man -made/Anthropogenic Features
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131.6. IMPORTANCE OF PHYSICAL GEOGRAPHY:
Physical geography is that branch of natural science which
deals with the study of processes and patterns in t he natural
environment like the atmosphere, hydrosphere, biosphere, and
geosphere that shapes the Earth’s surface, the animals and plants
that inhabit it, and the spatial patterns they exhibit. The study of
Physical geography is well done with the help of field survey and
field visits for understanding various natural features .
1.7. INTERIOR OF THE EARTH:
INTERIOR OF THE EARTH: The changes that occur over the
earth’s surface are related with the deep existing internal forces
operating from within the earth. The interior parts of the earth can
be divided into 3 -4 zones as: a) crust b) mantle and c) Core
(Figure 1.12) . It is important to study the structure of the earth’s
interior as explained below:
Figure 1.12
a)Crust: This is the out ermost layer of the earth. Various landform
features like mountains, plateau and plains, rivers, lakes, sea,
oceans and human settlements are found on the crust. It is the
most significant zone of the solid earth with an average
thickness of 17 kilometer. The base of the crust is sharply
defined where it contacts the mantle. This surface of separation
between the crust and mantle is called ‘ Moho’ ( Mohorovicic
discontinuity). The crust varies greatly in thickness which is as
small as 5 km. thick in some plac es beneath the ocean and up
to 70 km. depth under the mountain ranges. It is composed of
silicon (27.7 %), aluminum (8.1%), Iron (5%), Calcium (3.6%)
and other elements (Figure 1.13 ).
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Figure 1.13 : Geomorphology
The layer of SIMA is found below the layer of SIAL. The
density of this layer is about 3.09/cm3. The silicates of magnesium,
calcium and iron are found in SIMA. SIMA (SI –Silica + MA –
Magnesium). The bottoms of ocean are composed of denser
material termed as SIMA (Figure 1.14) .
Figure 1.14 : Earths Crust
Magma is found in this layer which comes out on the earth’s
surface as lava during volcanic eruption.
a)The rocks of this layer are subdivided into:
i)Basaltic rocks underlying the ocean basins containing much of
iron and magnesium, and
ii)Granite rock: The rock that make the continents which are rich
in silicon and aluminum and are lighter in colour and density.
Boundary between the crust and next layer Mantle is termed
as Moho discontinuity or Mohorovicic discontinuity.munotes.in
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15b)Mantle: The m antle is a thick layer which lies below the crust of
the earth and extends up to a depth of 2900 km. and above the
core. Temperature and density increase with increase in depth
in this layer. The average density is 5.6 g cm3.I ti sm a i n l yo f
solid olivine rocks made up of silicates of magnesium and iron.
Silicate minerals rich in iron and magnesium are found in this
zone. Boundary between Mantle and core is termed as
Gutenberg discontinuity (Figure 1.15 ).
Figure 1.15 : Lines of Discontinuity and Core
c)Core: is the centre of the earth beyond a depth of 2900 km and
reaches up to 6371 km with a spherical zone and a radius of
3475 km. It is assumed that the core is subdivided into two
parts. Outer core and Inner core. The outer core extends from
mantle up to the depth of 5100 km. and the inner core extends
from 5100 km. to 6371 km. i.e. centre of the earth. Due to
extreme pressure the inner core is assumed to be in the solid
state. Temperature of the core is very high. As we move from
surface of th e earth towards it’s centre, there is a rise in
temperature i.e. 10cp e r3 2m e t r e so fd e p t h .T h et e m p e r a t u r eo f
the core is between 22000Celsius and 27500Cw i t ha t m o s p h e r i c
pressure as high as three to four million times found at sea level
and a density o f 13.5 g cm3. It is named as Barysphere and also
Nife. The central part is a liquid core consisting of small
proportion of nickel, ferrous (80%) and other elements. The
earth has a magnetic field. We are able to find out north
direction due to the earth’s magnetic field. This is possible due
to the presence of iron -rich core. The core of the earth is
composed of Nickel and Ferrous material. Hence it is termed as
NiFe. (Ni = Nickel and Fe=Ferrous)
From the diagram it is clear that the temperature at the cent re
will be more than 50000C. Metals such as iron, aluminium,
copper and even tungstone have lower melting points than
50000C. Hence we assume that the core is in liquid state (Figure
1.16).
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Figure 1.16 : Temperature towards the Core of the Earth
Chec k your progress:
Q.6) Explain with the help of suitable diagram various sections of
the earth’s interior.
1.8. EARTHQUAKE WAVES:
Earthquake waves provide useful information about interior
of the earth. Different types of waves are generated at the time of
earthquake i.e. ‘P’ Waves, ‘S’ Waves, ‘L’ Waves etc. These waves
have different wave motions, and so have different properties. e.g.
‘P’ waves are able to pass through liquid material but ‘S’ waves are
absorbed in the liquid material. These are : munotes.in
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Figure 1.17: Earthquake waves
i)P-Wave or Primary/ Longitudinal wave : These waves travel in
straight line and their speed is maximum i.e. up to 12 km. per
second. These waves can travel through solid as well as liquid part
of the interior of the ea rth.
ii)S-Wave / Secondary Wave or Transverse Wave .T h e ym o v e
with 60 % velocity of the ‘P’ waves. Theses waves are slower than
the P -Waves due to their zigzag wave motion. These can travel
through solid part but are absorbed in the liquid part of the e arth.
iii)L-Waves : Also known as Surface Waves or Love Waves (Love
is the name of the scientist who discovered these waves). These
waves cannot travel to a long distance and are restricted to the
surrounding surface region where earthquake occurs. Thes ea r e
the most destructive waves.
These earthquake waves are recorded all over the world
through the instrument called seismograph. Scientists used this
data/ information and on the basis of this data they visualised
internal structure of the earth .(Figure 1.17 )munotes.in
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18Check your progress:
1) Explain different types of earthquake waves.
1.8. DISTRIBUTION OF LAND AND WATER:
1) The distribution of landmasses and water -bodies on the surface
of the Earth is not uniform. The landmasses or continents occ upy
29 percent, while water -bodies or oceans cover 71 percent surface
area of the earth. The surface area of the Earth is 510 million km2
which has land surface of 149 million km2and water surface with
361 million km2(Figure 1.18 ).
Figure 1.18 :Distribution of land and water on the earth
2) The distribution of land and water in the northern hemisphere is
nearly equal but it is highly uneven in the southern hemisphere. Of
the total earth surface in the northern hemisphere 61 % is land and
39 % is wat er, while in southern hemisphere it is 19 % land and 81
% water surface. The proportion of water in the southern
hemisphere is nearly 15 times more than the amount of land in the
southern hemisphere is given in table 1.munotes.in
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19I. Land masses / continents Area in million sq. km. approximately
1. North America 24
2. South and Central America 18
3. Europe 10
4. Africa 30
5. Asia (including C.I.S.
Common wealth of
Independent States)44
6. Australia 7.8
7. Antarctica 13
II. Water bodies /Oceans
1. Paci fic Ocean 165
2. Atlantic 82
3. Indian 73
4. Arctic 14
Figure 1.19 :Antipodal locations
3)Water -bodies or oceans/seas are found at the antipodal
locations of landmasses or continents .(Figure 1.19 )
4) Land area is almost continuous in the tempera te belt (23 ½0N. to
66½0N.) of the northern hemisphere.
5) Water bodies or oceans form complete circle in the southern
hemisphere at550South latitude i.e . between the southern
continents and the continent of Antarctica.
6) Continents or land masses become narrow in the southern
hemisphere.
7) East -West trade and transport routes are more important in the
northern hemisphere while north –south routes are more important
in the southern hemisphere.
Major transport routes in the northern hemispheres like Trans -
Siberian railway, North Pacific routes, Trans -continental Americanmunotes.in
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20railways, North Atlantic route form complete of Transport network
around globe.
8) The landmass of Antarctica has three extended areas one
towards Australia second towards Sou th Africa and third towards
south America.
9) Australia is isolated from other major landmasses in the world.
10) About 90% of the world population is concentrated in the
northern hemisphere and hence transport and communication
network has developed mo re in the northern hemisphere.
11) Due to extensive landmasses in the northern hemisphere the
interior parts of the continents like Asia experience extreme
variation in summer and winter temperatures.
Figure:1.20:WORLD:Distribution of Continents (la nd) and
Oceans( Water)
The range of temperature (i.e. difference between maximum
and minimum temperature) increases as we move away from the
sea-coastal areas towards inside of the continents. This
phenomenon is termed as continentality of temperature is less in
these areas.
12) Landmasses in the southern hemisphere i.e. South America,
South Africa, part of Asia etc. have tapering southern tips so the
land area is narrow surrounded by the oceans and hence the range
of temperature is less. (Figure 1.20)munotes.in
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21Check you r progress:
1) Account for the distribution and location of landmasses and
water -bodies on the earth’s surface.
1.9. CONCLUSION
This module has thus explained the meaning, nature, scope,
importance and various branches wit h respect to physical, human
and interface geography. Various processes, features, facts,
locations and their distribution on the earth’s surface and
subsurface are well explained with supporting maps and diagrams.
1.10 QUESTIONS
1)Define and explain the nature and scope of Geography.
2)Describe various branches of geography.
3)With the help of suitable diagram explain the interior of the
earth.
4)Give an account of distribution of land and water on the earth’s
surface.
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Unit -2
ROCKS AND MINERALS
Unit Structure:
2.0.Objectives
2.1.Introduction
2.2.Rocks and Minerals: Classification, formation and types.
2.3.Folds and faults –Types.
2.4.Weathering and its types -Mass movements.
2.5.Conclusions.
2.6.Questions.
2.0 OBJECTIVES :
To understand different types of rocks and minerals and their
importance in human life.
To study different types of folds and faults and their impact on
determining the landform features.
To understand the factors responsible for weathering and its
types.
To understand the mass movement of weathered materials by
different agents and the resultant landforms.
2.1. INTRODUCTION :
The hard solid surface of the earth is called as lithosphere.
‘Lithos’ means rocks. Rock material may be soft or hard
constitut ing mud, clay, sand or stones and boulders. Rocks contain
different types of minerals and elements that play an important role
in the cycling movement of different geo -bio-chemical cycles
enabling ecosystem to function. These ecosystems thus supply
differe nt food elements to living species of the earth making it a
habitable (living) planet. The settlements, building structures,
different types of economic activities, transport and communication,
defense services etc. are developed only because of the presen ce
and utilization of these rocks and minerals in various forms.
2.2. ROCKS AND MINERALS :
Rocks and Minerals are found on the earth’s surface, and in
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Rocks: According to the geographer or geologists the term rock
is applied to any naturally occurring agglomeration of minerals
particles can be termed as rock. It can be soft materials as clay,
mud or sand as well as hard, massive boulders of stone.
Mineral sa re the chemical compounds of different elements. for
e.g. Silica ( Si O 2).
Some minerals contain only one element e.g. sulphur and
carbon (diamond).
Some minerals are crystalline because the atoms forming
the crystals are arranged in a definite manner e. g. quartz.
Some minerals are non -crystalline as the atoms forming
these minerals are not arranged in definite manner.
Rocks are formed due to the combination of minerals. Some
rocks may contain only one mineral but many rocks are composed
of different minerals.
Rocks are known by different names which are related to the
combination of minerals.
Some common minerals are found everywhere on the earth
and hence are termed as ‘Rock forming minerals’ , while some
minerals are scarce and are found only at particular location. These
minerals are costly and are termed as Economic minerals.
Metals are extracted from some minerals which are known
as ‘Ore’ of that metal e.g. Bauxite is an ore of Aluminum ( Figure
2.1).
Figure 2.1: Rocks: Ore: Mineralmunotes.in
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a) The Rock forming minerals:
Most of the rocks found on the earth are composed of following
major minerals.
(1) Feldspar (2) Quartz (3) Pyroxenes (4) Amphiboles (5) Mica (6)
Olivine
b) Economic minerals: Some of the important economic minerals
and their uses are as follows.
i) Apatite: It is red, brown or yellow phosphorous and Fluorine is
obtained from it.
ii) Barite: It is white or brown. It is used in glass, rubber, chemical
and other industries.
iii) Dolomite: It is white. It is used in cement and iron and steel
industries.
iv) Gypsum: It is soft, white. Used for the preparation of objects of
art, idols etc.
v) Pyrite: It is yellow. Sulphuric acid is obtained from it.
vi) Talc: It is white or brown. It is used in making paints, rubber,
crockery, paper, plastic, insecticides.
C) Ores: An economic mineral from which metal is extracted is
termed as an ore .S o m eo ft h em e t als extracted from ore are as
follows:
Ore Metal
Bauxite Aluminum
Cinnabar Mercury
Galena Lead
Haematite Iron
Magnetite Iron
Check your Progress:
1.Define mineral.
2.What is an ore?
3.State any four uses of rocks.
4.How is mineral different from the rock?
5.Which type of rock is associated with crude oil?munotes.in
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Rock Cycle:
Rocks are classified according to their mode of formation. Rocks
which are formed due to solidification of molten lava/magma are
termed as the I gneous Rocks. These rocks are disintegrated due to
various agencies and processes on the earth’s surface.
The weathered pieces of rocks are carried pieces of rocks
are carried by different agencies of erosion like river, glacier, wind,
sea waves etc. Whi ch are deposited in sea, lake or desert? These
weathered pieces of rocks are cemented together to form
sedimentary rocks.
Sedimentary rocks change their structure due to crustal
movements and heat and pressure inside the earth. The changed
rock is known as the metamorphic rock.
Metamorphic rocks go deep towards interior part of the earth
due to crustal movements and melt and become part of magam -
molten material inside earth. When magma comes out on the
earth’s surface it is termed as lava. Thus the rock cycle continues.
(Figure 2.2)
Figure 2.2: Rock Cycle
A) Igneous Rocks:
‘Magma’ is the molten material found below the crust. When
magma comes out on the earth’s, surface, it is termed as ‘Lava’ .
(Figure 2.3). The rocks which are formed due to solidification of
‘lava’ or ‘magma’ are termed as Igneous Rocks. (derived from the
Latin word ‘ignis’ means fire) Igneous rocks are formed first in the
Rock cycle and hence these rocks are also termed as pr imary
rocks.munotes.in
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Figure 2.3: Volcanic Eruption and formation of igneous
rocks
Igneous rocks are formed due to solidification of magma and
hence these rocks are also termed as ‘Magmatic rocks’ Igneous
rocks are classified according to the:
A) Place of formation
B) Composition
Classification of Igneous Rocks
A] According to the place of formation B] According to the composition
1) Intrusive 2) Extrusive 1) Acidic 2) Basic
a) Hypabyssal a)Volcanic More Percentage of More Percentage of
i) Sill Silica -Sticky Iron group of minerals
ii) Dyke -forms domes -Fluid
iii) Lacolith Forms platea u
iv) Stock
v) Phacolith
b) Plutonic
i) Batholith
1)Classification of the Igneous rocks according to their place
of formation (Location):
The igneous rocks which are formed on the earth’s surface
are termed as ‘Volcanic’ or ‘ Extrusive’ igneous rocks . The cooling
process of lava is more rapid on the earth’s surface and hence
different minerals in lava do not get opportunity to come together.munotes.in
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So we do not find large size crystals in the volcanic or extrusive
rocks. These are termed as ‘fi nd grained’ rocks.
On the other hand cooling process of magma below earth’s
surface is very slow hence different minerals in magma get
sufficient time to come together so we get large size crystals in the
intrusive igneous rocks . These rocks are also know n as ‘course
grain’ rock.
Intrusive igneous rocks are known by different shapes formed
by the solidification of magma into the cracks of the existing
rocks. These are:
a) Stock : Thick vertical formation like huge pillar.
b) Dyke : Vertical wall like f ormation.
c) Lacolith : Dome shaped formation.
d) Sill : Horizontal sheet like formation
e) Lapolith : Saucer type formation.
f) Phacolith : Wave like formation.
All these types of intrusive rocks are formed below earth’s
surface but not at very grea t depth. These are called as Hypabasal
rock.
The rocks which are formed at great depth e.g. Batholith are
known as Plutonic rock. These are coarse grained rocks. (Figure
2.4)
Figure.2.4:Classificaiton of igneous rocks according to their
location
2)Classification of the igneous rocks according to the
composition.
Igneous rocks are classified according to their composition
i.e. the type of magma/ lava. If lava/ magma contain more
proportion of silica it is termed as Acidic. Acidic lava being stickiermunotes.in
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(viscose) is not spread over large area, it forms domes. The
igneous rocks formed due to solidification of acidic lava have light
colours.
On the other hand if the lava contains mor e percentage of
iron group of minerals it is termed as basic lava. It is more fluid and
so it spreads over large area and forms plateau e.g. The Deccan
Plateau. The igneous rocks formed due to solidification of basic
lava are dark in colour. (Figure 2.5)
Figure.2.5: Classification of igneous rocks according to their
composition
Check your progress:
1.What are igneous rocks? How are they formed? Give examples.
2.Give a classification of igneous rocks.
3.Draw a neat diagram to represent intrusive igneous rocks.
B. Sedimentary Rocks:
Sedimentary rocks are also termed as ‘secondary rocks’
because these are formed after the formation of primary rocks (i.e.
igneous rocks). Igneous and other types of r ocks are weathered
and eroded by the denudation processes and agents of erosion
such as river, glacier, wind, etc.) The particles of these rocks are
transported and deposited in parallel layers, one upon the other.
Over a period of time, these layers becom e compact and cemented
together due to the Weight of the overlying layers and gradual
process of cementation develops hard, stratified layers termed as
sedimentary rocks. Of all the rocks that are found in the Earth’smunotes.in
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crust up to the depth of 16 kms from t he surface; about 95% are
non-sedimentary rocks.
However, on the surface of the Earth, about 80 per cent
rocks are sedimentary. These rocks are also known as stratified or
layered rocks.
Bedding plane:
The plane of separation between two layers of the
sedimentary rocks is termed as the Bedding plane. Sedimentary
rock can break easily along the bedding plane.
Characteristics of the Sedimentary Rocks:
These rocks are termed as layered or stratified rocks as they
display many layers in them.
Fossils of plants and animals are found in these rocks. As
the process of formation of sedimentary rock is long and slow (i.e.
heat or excessive pressure is not required), the imprints of the dead
organisms remain on the rock. Such remains are termed as fo ssils.
These fossils help us to identify the age or geological period of the
organisms through the process of carbon dating.
Mostly sedimentary rocks are porous.
About 80% of the rocks on the surface of the Earth are
sedimentary rocks.
Sedimentary roc ks contain fossil fuels such as coal, crude oil
etc.
Generally, these rocks are not crystalline as these are
formed due to compaction of the weathered material.
The sedimentary rocks are formed in extensive horizontal
layers. Therefore they form extens ive horizontal landforms. (Figure
2.6)munotes.in
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Figure 2.6. Sedimentary Rocks
Classification of Sedimentary Rocks: Sedimentary rocks can be
classified according to their components (composition) or according
to the place of forma tion.
1)Classification of sedimentary rocks according to the
composition: Sedimentary rocks have different chemical
composition, colour and size of particles.
a)Clastic rocks and their types : These sedimentary rocks are
composed of rock fragments. Clastic rocks are classified
according to the size of particles or grains of the sedimentary
rocks.
* Types of clastic sedimentary rocks
Clayey or argillaceous rocks: These rocks are composed of
very fine sediments, e.g. shale, mudstone, etc.
Sandy or arenaceous rocks: These rocks are composed of
sand particles, e.g. sandstone.
Conglomerate: The sedimentary rock composed of large
rounded pebbles is known as conglomerate.
Breccia: This sedimen tary rock is com -posed of large angular
fragments of rocks.
b)N o n -clastic rocks and their types: These sedimentary rocks
are composed of the remains of plants and animals.
*T y p e so fN o n -clastic Rocks:munotes.in
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Carbonaceous rocks: The sedimen tary rocks formed of the
remains of plants are known as carbonaceous rocks. This is
because these rocks contain carbon, e.g. lignite, coal, etc.
Formation of coal:
Calcareous rocks: The rocks formed of the remains of animals
are known as calcareous rocks. Calcium Carbonate (CaCO 3)i s
the main component of calcareous rocks. When fish and other
aquatic animals die their bodies are decomposed. The two main
components -(i) Bones and (ii) Flesh –are separately
decomposed. Bones contain calcium. The bones get
disintegrated into powder. This powder, which is deposited at
the bottom of the ocean, gradually becomes compact to form
layers of limestone.
Formation of limestone:
Limestone and dolomite are examples of calcareous
sedimentary rocks.
Formation of crude oil:
2)Classification of Sedimentary Rocks According to the Place
of Formation:
The process of sedimentation can take place at different
locations. Therefore sedimentary rocks are also class ified
according to the place of formation.
Marine sedimentary rocks –These are formed on the seabed.
i)Lacustrine sedimentary rocks –When the sedimentary rocks
are formed in a lake, they are termed as the Lacustrine
sedimentary rocks.
ii)Riverine or Fluviatile sedimentary rocks -Alluvium, i.e. the
disintegrated particles of rock with decomposed organic matter,
is deposited either on river bed or on flood plains during floods.
These layers of alluvium become compact to form the riverine
sedimentary rocks. The plains of North India, the Nile Delta of
Egypt, the Mississippi Delta, etc. are well known for such
sedimentary rocks.
iii)Aeolian sedimentary rocks –These rocks are formed in the
arid and semi -arid areas (i.e. desert areas) where the a ction of
wind is strong. These winds carry loose particles of the rocks
and deposit them elsewhere. Aeolian (related to wind) rocks are
formed due to compaction of these particles.
iv)Glacial sedimentary rocks: The weathered/ eroded material
carried down by the glacier is termed as moraine. When glaciersmunotes.in
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melt, the material brought by the glaciers is deposited on the
bed or in the surrounding region, which becomes compact to
form glacial sedimentary rocks. Many places in North America
and North Europe are kno wn for such rocks.
Check your progress:
1.What are sedimentary rocks. Give examples.
2.Which agents of erosion are responsible for the formation of
sedimentary rocks?
3.Name three types of sedimentary rocks according to their place
of formation.
C. Metamorphic Rocks:
The primary igneous rock or secondary sedimentary rock are
changed in their appearance or change in their mineral composition
and texture due to intense heat from below and pressure from
above. This process of change due to intense heat and pressure in
original rock structure and composition is called as metamorphism.
The word ‘Metamorphism’ means change of form. The process of
metamorphism brings change in the form of rocks in two ways :
a)Physical metamorphism causing changes in textural
composition of rocks, and
b)Chemical composition that changes che mical composition of
rocks.
v) Agents of Metamorphism: Three agents contribute to the
process of metamorphism:
1.Heat: is the fundamental agent that brings changes in the
parent rock to form metamorphi c rocks. Intense heat that is
received during the process when hot and molten magma from
the core tries to come out (vulcanicity) through the crustal rocks
beneath the earth surface changes entirely the composition of
minerals in the rock.
2.Compression :T h e endogenetic forces cause convergent
horizontal movement causing folding in rock beds. As a result
pressure from compressive forces and consequent folding ismunotes.in
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responsible for changing the form and composition of original
rock. This feature is mainly obser ved during mountain building
process.
3.Solution: During vulcanicity the chemically active hot gases
and water act as solution while moving out from the core
through the crustal rocks beneath the earth that changes the
chemical composition of the rock.
(F i g u r e2 . 7 ) .
Figure 2.7. Formation of Metamorphic rocks
vi) Types of metamorphism: is based on their process that is
characterized by the nature of the agent and the place and area
involved in metamorphism.
a)On the basis of the nature of agents:
Thermal metamorphism (due to intense heat): In this case,
the structure of rocks is changed due to heat caused by magma,
hot gases, geothermal energy, etc. Clay which changes into
shale is the best example of thermal metamorphism.
Dynamic metamorphism: (due to intense pressure): High
pressure due to crustal movements generates great heat and
pressure. This causes dynamic metamorphism.
Hydro -metamorphism (due to hydro -static pressure): Hydro -
static pressure is caused by a column of water. In the upper
crust of the Earth, there are enough fractures, cracks, and
porosity that the fluid within these voids is under hydrostatic
pressure.
Hydro -thermal pressure (due to pressure of water and
heat): Rocks t hat are altered at high temperatures and
moderate pressures by hydrothermal fluids are hydrothermally
metamorphosed. This is common in basaltic rocks that
generally lack hydrous minerals. Rich ore deposits are often
formed as a result of hydrothermal met amorphism.
Effect of high pressure and high temperature:
The interior of the Earth is very hot. Due to crustal
movements such as mountain building, rocks are subjected to highmunotes.in
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temperature and high pressure. As a result the structure of rocks is
altered, e .g. limestone is converted into marble.
Effects of basic change in the structure of rocks
Rocks are disintegrated due to chemical and mechanical
actions. These disintegrated pieces of rock are again assembled to
form hard rock, i.e. metamorphic rock.
b) On the basis of place or area:
Contact metamorphism (localized in area): The rocks which
come in contact with the hot molten magma are
metamorphosed and are converted into metamorphic rocks.
Regional metamorphism ( large area is involved): The layers
of sedimentary rocks covering large areas below the surface are
crumbled and compressed due to the pressure developed by
crustal movements. Metamorphic rocks formed by regional
metamorphism are found in the Himalayas, the Alps etc.
v)Formation of metamorphic rocks
Examples of the metamorphic rocks are given below:TypeOriginal rockMetamorphic
rock
Basalt SchistIgneous rocksGranite Gneiss
Limestone Marble
Sandstone Quartzite Sedimentary rocks
Shale Slate
Check Your Progress:
1.What are metamorphic rocks? Give examples.
2.Explain the process and agents of metamorphism.
3.Write a note on types of metamorphism.
2.3 FOLDS AND FAULTS -TYPESmunotes.in
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1. Introduction : It is a well known fact that our earth is dynamic
nature and undergoes constant changes caused by internal forces
that are sometimes sudden and some are very slow requiring
hundreds of years to view any significant changes in the earth.
Forces affecting the Earth’s Crust
Endogenetic forces Exogenetic forces
(Internal /Epeirogenetic forces) (External / orogenetic forces)
Weathering Mass wasting
Diastrophic Forces Sudden Forces
Upward movement
Slow c hanges Agencies of Erosion
River, Glacier
Wind, Sea -waves
Epeirogenetic Orogenetic Earthquakes Volcanic Underground water.
Eruption
Upward movement downward movement
(Emergence) (Submergence)
Continent /Mountain
Building
Tensional forces Compressional forces
Crustal fracture Crustal bending
Cracking Faulting Warping Folding
(Faults) (Folds)
Upwarping Downwarping
‘Endogeni c’ forces are the internal forces that produce
sudden movements in earth that are easily felt by man during his
existence. For example volcanic eruption and tremors produced by
earthquakes. (Figure 2.8 and Figure 2.9. figure 2.10).munotes.in
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Figure 2.8: Earthquake
Figure 2.9 : Volcanic Eruption
Figure 2.10: Volcano –Fissure eruption
This dynamism in earth through Endogenetic and
Exogenetic forces are explained as under:
a)Endogenic (Internal): These are diastrophic forces
classified as:
i) Epeirogenetic) Forces: The force coming from beneath the
earth is called as endogenetic force. These can be experienced
into two types:munotes.in
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Sudden movement in the form of volcanic eruption or
earthquake.
Slow development that may be horizontal (compressional and
tensional) and vertical (upward –uplift or downward -
subsidence).
As the submergence or emergence of the region affects very
large areas, these are also termed as the continent -building forces.
ii) Orogenic (Tensional and compressional) Forces: ‘Oros’
means mountain and genesis means to form. Hence, these forces
are termed as Orogenic or mountain forming forces. Orogenic
forces co nsist of fold and faults. Fault is caused by tensional forces
while fold is caused due to Compressional forces of the Earth.
Faults block mountains or rift valleys are formed due to the
horizontal tensional forces.
a)Exogenic (external) Forces: The force co ming from outside
the earth is called as exogenic force. They consist of all forces
that are actively engaged in levelling the relief of Earth. They
are doing all kind of erosional transportational and depositional
work. Exogenic forces on the Earth are wa ter (sea, river and
underground), wind, glaciers and cosmic forces.
Check Your Progress:
1.Differentiate between “vertical movement” and “horizontal
movement”.
2.Mention exogenetic forces.
3.State Endogenetic forces.
FOLDS :
Folds on the Earth’s surface are wave -like bends formed due
to tangential compressive force caused by the internal deep force
from within the earth to form folds. These forces acting on crustal
rocks give rise to a series of bends called as folds. The up-folds are
called as Anticlines and the down -folds as Synclines.munotes.in
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FIGURE: 2.11. Anticlines and Synclines:
The sides of a fold are termed as ‘limbs’. Folding mostly
occurs at the margins of the conti nental plates. Fold Mountains are
developed due to a series of parallel folds, e.g. the Alps or the
Himalayas. Different types of folds can be observed. These are:
a)Types of Folds:
The horizontal compressional forces acting towards each other are
sometimes equal but are unequal in most of the cases. This
inequality of the forces gives rise to various types of folds. These
are:
i)Symmetrical folds: These are simple folds in which both the
limbs of the fold incline uniformly. This is because the forces
exerted on both the sides of the limbs are equal.
FIGURE: 2.12.Symmetrical fold
ii)Asymmetrical folds: Asymmetrical folds are produced due to
exertion of unequal force on both the sides of the limbs.munotes.in
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FIGURE: 2.13.Assymmetrical fold
iii)Monoclinal / Vertical folds: In this case, one of the limbs is
moderately inclined and the other limb has a steeply inclined
slope at right angle indicating application of greater force in that
direction so as to develop monoclonal or vertical folds.
iv)Isoclinal folds: Here compressive forces are so strong that
both the limbs of the fold become parallel to each other but are
not horizontal.
FIGURE: 2.14 Isoclinal fold
v)Recumbent folds: Here compressive forces are so strong that
both th el i m b so ft h ef o l db e c o m ep a r a l l e la sw e l la sh o r i z o n t a l .munotes.in
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FIGURE: 2.15 Recumbent fold
vi)Overturned / thrust folds: In this case, as the force on one
side is extreme, the fold breaks and the upper part slides over
the lower part. Thus one limb of the fold is thrust upon another
fold due to intense compressive forces. Limbs her are seldom
horizontal.
FIGURE: 2.16 Overturned / thrust folds
I.FAULTS :A fracture in the crustal rock where the rocks get
displaced along a plane is called as a fault. In other words
displacement of crustal rocks caused tensional movement due
to internal force develops a fracture is called as a fault FIGURE:
2.16.1 .munotes.in
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FIGURE: 2.16.1 .Faulting
Horizontal tensional forces often develop cracks in the rock
strata. These cracks are called joints. The crustal blocks move
upward or in downward direction that develop faults. Faults also
developed in the horizontal direction.
FIGURE: 2.
a)Types of Faults Related to Gravitational Force. These are:
i)Normal faults: Here the rock strata move in the downward
direction due to the gravitational force. Hence, such faults are
also termed as gravity / normal faults’ FIGURE: 2.17 .F o r
example ‘Rift’ or ‘Graben’ Valley is formed due to the normal
fault. Rivers Tapti, Purna and Narmada of central part of India
flow through the rift valleys. Rift valleys generally have steep
sides or steep banks FIGURE: 2.18 .O t h e re x a m p les of rift
valley are:
Rhine rift valley in Europe;
Jordan River valley from Syria through Red Sea basin to
Zambezi valley is the longest rift valley with 6440 km.
Dead Sea in Asia
Narmada, Tapti rift valleys in India.
ii)Reverse / thrust faults: Here the rock strata are forced in the
upward direction due to the horizontal compressional forces.
Hence, the rock strata move up against the force of gravity.
Here the vertical stress is minimum and horizontal stress is
maximum. Therefore it is termed as revers e fault. Block
mountains or horsts are formed due to reverse fault. FIGURE:
2.17munotes.in
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FIGURE: 2.17 Normal Faults andReverse Fault
FIGURE: 2.18 Rift Valley
Block Mountain:
Faults also develop due to the horizontal displacement of the
rock blocks. This is termed as the ‘lateral’ or ‘strike -slip faults’
FIGURE: 2. 19.
FIGURE: 2.19 .Block Mountains or Horsts
Block mountains or horsts: Block Mo untains/‘horsts’ are
formed due to faulting and so they are also associated with rift
valleys. Block Mountains normally have steep sides and flat tops
that are developed due to faulting process. For example:munotes.in
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The Black Forest Mountain of Germany.
The Vosges in France.
The salt range in Pakistan.
The Flinders Mountains in Australia.
Check Your Progress:
1. What do you mean by “folding”?
2. Mention different types of folds.
3. What do you understand by the term “Faulting”?
2.4 CONCLUSIONS:
The present chapter has helped us to understand various
processes responsible for the formation of different types of rocks,
their location; structure; and physical and chemical composition.
These various processes involved in formation and change of
pare nt rock thus provide us with different types of rocks and
minerals. Different types of human settlements and his activities are
dependent upon the availability of these rocks and minerals.
2.5. QUESTIONS .
1.Explain any three differences between rocks and minerals.
2.How is igneous rock formed?
3.With the help of a neat diagram explain rock cycle.
4.Give major characteristics of the igneous rocks?
5.Give broad classifications of igneous rocks on the b asis of their
place of formation? Give two examples for each.
6.Give a classification of igneous rocks according to their
composition?
7.What are the four important characteristics of sedimentary
rocks?
8.Give a classification of sedimentary rocks?
9.How is metamorphic rock formed? Give four examples of
metamorphic rocks.munotes.in
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10.Explain with the help of suitable diagram the formation of crude
oil.
11.Explain the different types of folds with the help of suitable
diagrams.
12.Describe the major type s of faults with suitable diagrams.
13.Discuss the different types of forces affecting the earth’s crust.
References:
1.Savindra Singh (2003): ‘Physical Geography’, Prayag Pustak
Bhavan, Allahabad.
2.Savindra Singh (2011): ‘Geomorphology’ , Prayag Pustak
Bhavan, Allahabad.
3.Ahirrao W.R., Alizad S.S. and Dhapte C.S. ((1996): ‘Morphology
and Landscape’; Nirali Prakashan, Pune.
4.A.Das Gupta and A.N.Kapoor (1993): ‘Principles of Physical
Geography’, S.Chand and Co, Ltd. New Delhi.
5.Sutopa Mukherje e (1996): ‘Understanding Physical Geography
through Diagrams’, Orient Longman Publications, Calcutta.
6.Alan H. Strahler and Arthur N.Strahler (1992): ‘Modern Physical
Geography’ 4thedition, John Wiley and Sons, New York.
7.K.Siddhartha (2001) ‘The earth’s Dy namic Surface’, Kisalaya
Publications Pvt. Ltd. New Delhi.
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Unit -3
WORK OF RIVER
Unit Structure :
3.0 Objectives
3.1 Introduction
3.2 Importance of River
3.3 Processes of erosional w ork by river
3.4 Erosional Landforms of aRiver.
3.5 Depositional Landforms of aRiver
3.6 Conclusion
3.7 Questions
3.0OBJECTIVES
To know the origin/formation of river
To study the importance of river
To understand the work done by a river
To observe the erosional landforms developed by a river and
the underlying processes for its formation.
To observe the depositional la ndforms developed by a river and
the underlying processes for its formation.
3.1INTRODUCTION
Rain water that falls on the earth’s surface through
hydrological cycle starts running /flowing in the form of a river is
the most important agent of erosion ( Figure :3.1).It is manifested
by the flow stream sfrom uplands/highlands down the slope in the
lowlands as a main river that merge into a lake/inland sea or into
the sea in coastal areas. The main river receives water from
various streams that forms its tributaries in its catchment area .T h e
flow of water of Main River in the lowland is slowed down and at
times distributes its water through different channels as
distributaries before meetin gthe sea. These features are common
in the delta region of a rive r(Figure 3.2.) River action consisting of
weathering a nd mass wasting is responsible process forfluvial
denudation. It is most marked in semi -arid regions because theymunotes.in
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have little or no vegetation and the rains, though infrequent, are
torrential.
Figure :3.1.Hydrological Cycle.
Figure :3.2.Main River with its streams, tributaries and
distributaries.
3.2 IMPORTANCE OF RIVER
Availability of fresh water almost throughout the year from
the surface flow in the form of river, lake, pond or from the
subsurface through wells, springs captured through rain is possible
only because of these water flows from highland to lowlands
through river basins. They are the source of living for all living
organisms that sustains the ecosystem and our only living pl anet
‘the earth’ of this solar system.
3.3 PROCESSES OF EROSIONAL W ORK BY RIVER :
There are four processes of erosion through rivers or
streams water (Figure :3.3)such as:munotes.in
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1) Solution :It is a type of chemical weathering in which most of the
salts are removed from the bedrocks through process of chemical
action i.e. corrosion.
2) Abrasion: It involves the removal of loosened materials of the
valley walls and valley floors with the help of erosional tools.
3) Attrition :The wear and tear of the tran sported material
themselves when they roll and collide with each other.
4) Hydrolic Action :It involves the break down of the rocks of valley
sides due to the impact of water currents of the river channel.
Figure :3.3. Transportation of material by r iver
The river as an Energy system :
Energy of the river is the ability to do the work. The amount
of river energy to do the work determines whether the river can
effectively erode its valley and transport the material in the form of
deposition .
1) Three section of River :A well developed mature river can be
divided into the following three sections.
2) The upper course :The upper course of the river is that section
where most of the erosion takes place since the gradient of the
river channel is steep a nd river flow is very swift.
3) Middle course: In the middle course of river transportation of
weathered material is the dominant process.
4) Lower Course: This section of the river gradient low and hence
the river becomes sluggish. Therefore, depositi on of weathered
material is deposited on the bed of the river.
Ar i v e r ’ se n e r g y increases with its volume (erod ed material)
with its velocity and with its regime i.e. seasonal f low. It means amunotes.in
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large, fast -flowing will have more power to erode and when it sf l o w
becomes sluggish with little water.
One should not forget that all the energy in a river is used for
erosion. Some of it is necessary to overcome frictional resistance
along the bed and banks and internal turbulence and roll against
each other Ene rgy is also necessary to transport the bolders,
pebbles, sand, silt and dissolved chemicals and minerals in the
water.
The Development of a River valley
Energy of the river to erode, transport and deposit the load
(weathered material depends up on its si ze and its gradient and the
distance it has to travel before it reaches its base level. Base level
is the level or altitude, at which a river reaches the lake or sea or
another river. The river erodes down to this level.
The upper part of the river i.e. a bove the base level, because
it is high above the base level, will be able to deepen its channel
rapidly. However, a river cannot erode below its base level.
Life cycle of River: Like human beings the life cycle of a river is
divided into the following t hree parts (Figure 3.4) .
1) Stage of youth : In this stage the river flow is swift, in a narrow,
steep sided valley, whose floor is broken by pot holes, rapids and
water falls, and lowers its valley.
2) Mature sta ge:In this stage of the river denudati on widens the
river valley, gradient is reduced, the river has less energy to erode
and the river begins to take the initial curves because of the nature
of its valley floor.
3) Old stage : At this stage gradient is further reduced, the river
becomes slu ggish and deposition becomes the major work of the
river. Sediments brought down by the river are dropped by the river
and slowly spread over the entire floor of its valley, where it build up
a gently sloping plain known as a floor plain. Slowly river deve lops
great meanders across the plain. Deposition of very fine sediments
at the month of some rivers at the old stage, sometimes develop
triangular shaped land, is known as a delta.munotes.in
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Figure :3.4. Stages of River and its work in different st ages
Ar i v e r valley is deepened by vertical erosion and widen by
lateral erosion. When river gradient is steep i.e. young stage or
youth stage vertical erosion is dominant. When the river’s gradient
is very gentle i.e. old stage there is very little erosion but deposit ion
dominant. However, in a mature stage lateral erosion is dominant.
Check Your Progress:
1.Explain the importance of a river.
2.Which are the processes of erosion by river?
3.Explain the cycle of erosion of a river.
3.4EROSIONAL LANDFOR MS PRODUCED BY WORK
OF A RIVER
Different types of landforms features can be identified
produced because of erosion carried by the running water of a river
during its different stages from its source to its mouth. These
features are developed in the upper course (1st stage) of a river.
i) ‘V’ shaped valleys: Rivers flowing with strong water force in the
regions of heavy rainfall often leads to mass wasting that erodes its
bank and bed rapidly forming steeper slopes on its sides to develop
‘V’ shaped valley Figure 3.5.munotes.in
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Figure :3.5.‘V’ shaped Valley.
ii) Gorge :It often forms when a waterfall retreats up stream. Gorge
is formed in the mountains where vertical cutting is more rapid and
strong than lateral cutting to develop very steep and deep valley ,
forexample Ganga, Brahmaputra ,N a r m a d a . When they are large
in size they are called as Canyons for example Colorado of U.S.A. ,
figure 3.6.
Figure :3.6.Canyon
iii)Pot H oles: Pot Holes are commonly found along the upper
couse of the river, where flow s directly over solid bed rocks. Here,
the water of a fast flowing river swirls if the bed of the river is
uneven. The large and small pebbles carried by a swirling river cut
circular depression on the bed of the river. These depressions
gradully deepen th eb e da n da r ec a l l e dp o th o l e s ,Figure :3.6.1
Much larger than such depressions of pot holes some times from at
the base of a waterfall, known as Plunge pools.munotes.in
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Figure :3.6.1.Pot Holes
iv)Interlocking Spurs : When the river is in its youthful stage
vertical erosion rapidly deepens the river channel. The river twists
and turns around obstacles of hard rocks. There will be move
erosion on the concave banks of bends of the river and this
ultimately results into the formation of spurs, which are alternat eo n
each side of the river to interlock. On the other hand,tothe
opposite convex bank there is very little erosion. Thus, interlocking
spurs are one of a series of tapering ridges which alternately
project into a river valley and around which the river winds its
course Figure :3.7.
Figure :3.7.Interlocking Spurs
iii)Waterfalls :When a layer of hard and soft rock lies across a bed
of a river, the soft rocks on the down -stream side are more quickly
eroded than soft rocks. The river bed thus steepe ned where it
crosses and thus waterfall is developed. A waterfall develops when
the hard rock layer is horizontal, dips gently upstream or is vertical.
Continuous erosion causes waterfall to retreat upstream forming a
deep valley Figure :3.8.munotes.in
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Figure :3.8. Waterfall
iv) Rapids: These features are found in the mountain areas where
the under lying rock structure is composed of alternately hard and
soft composition. Thus the soft rock is eroded easily while the hard
resistant rock remains at its place to de velop rapids that appear as
step like structure Figure 3. 9.
Figure :3.9.R a p i d s
3.5.THE DEPOSITIONAL FEATURES DEVELOPED BY
THE RIVER WORK IN ITS MATURITY (2NDSTAGE)
ARE :
i)Alluvial fan : The force of the river slightly reduces due to
decrease in s lope that causes deposition of large materials in the
bed of a river. As a result its flow further slows down due to
obstruction causing more deposition. The river tries to find its way
by developing channels in its bed to flow downward. The shape
thus cre ated appears like a fan and since the deposited is fine soil it
is termed as alluvial fan figure 3.10.munotes.in
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Figure 3.10. Alluvial Fan
ii)Flood Plain and Natural Levee: Flood plain area of periodic
flooding that occurs inland along the course of river val leys. When
the river discharge exceeds the capacity of channel, water rises
over the channel banks and floods the adjacent low -lying area. As
water spills out of the channel some alluvium will be deposited on
the banks to form levees figure 3.1 1.This wate r will slowly seep
into flood plain, depositing a new layer of rich fertile alluvium. Many
important flood plains such as Ganga, Brahamaputra, Nile,
Mississippi are found in different parts of the world.
Levee is a naturally formed raised bank along the s ide of a
river channel. When river overflows its banks, the rate of in the
flood area is less than that in the channel and silt is deposited. After
water have withdrawn the sit is left on bank of the river, which
grows during successive floods. Slowly the height of levee
increases above the surrounding flood plain. Notable levees are
found on the lower reaches of the Mississippi river in U.S.A. and Po
river in Italy.
In times of sever floods, sometime, levees burst, through
which water spreads out over sur rounding flood plains; and
produce disastrous floods.
Figure 3.1 1.Flood Plain and Natural Levee
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Figure 11 A : Meandering River
Figure 11 B : Meandering River & Cross Section
3.6. DEPOSITIONAL LANDFORMS DEVELOPED DUE
TO WORK OF A RIVER:
Asflow of water becomes relatively slow and wide due to
the gently sloping land or lowland the large amount of material
carried and transported by a river from the uplands is thus
deposited in its different parts. This obstructs the flow of wat er and
over the time this continuous process gives rise to the formation of
different types of depositonal landforms. These are:
i)Meander and Oxbow Lake: A sweeping course of a river is
known as meander or the curves formed in the course of a river are
known as meanders . A meander usually has a steep slope on its
outer curve, where the velocity of the river is high and therefore,
erosion is greatest and a gentle on the inner curve, where the
velocity is slowest. Generally, meanders the gradient is gentle ,
discharge is fairly high steady and material carried is fine.
Oxbow lakes are curved lakes found on the flood plain of a
river. Oxbow lakes are cused by the loops of meanders being cut
off at times of flood and a river subsequ ently adopting a shorter
course figure 3.12munotes.in
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Figure 3.12 .Meander and Oxbow Lake
iii)Deltas :A large, roughly triangular shape body of s ediments
deposited at the mouth of a river is known as Delta figure 3.13
Figure :3.13 Deltas
Most of the eroded material is carried by ar i v e ri su l t i m a t e l y
deposited into the sea or a lake into which it flows. Such eroded
material sometimes is collecte di nt h em o u t ho far i v e r .T his
material builds up into low lying swampy or marshy plain. Such
plain is called delta.
As deposition of t he material brough by the river goes on
increasing in the mouth of the river, the river is forced to divide into
number of channels. Each channel is further divided into more and
more channels. All these channels are called distribu taries.munotes.in
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Figure: 3.1 4. shaped Delta
Types of Delts : There are three types of deltas :
a)Arcuate Delta b) Birds Foot Delta c) Estuarine Delta.
a) Arcute Delta :This is very common type of delta. This type of
delta is composed by course sediments, such as sand and gravels.
eg. Nile Delta. Such delta has a number of distributaries other
examples of this type of delta are Ganga, Indus, Irrawddy, Mekong
etc.
b) Bird’s Foot Delta :This type of delta is made up of very fine
sediments called silt. The river channels are divided into few
distributaries, clearly defined channels across the delta. The best
example of this type of delta is the delta of Mississippi river in
U.S.A. This type of delta develops in seas which have few ocean
currents and tides to disturb the deposited sed iments. Delta figure
3.14
c)Estuarine Delta : This type of delta develops in the mouth of a
submerged river such delta takes the shape of estuary figure
3.15. The best examples of this type of delta are Elbe river in
Germany, ob in Russia and Vistula river in Poland.
Figure 3.1 5.Estuarine Deltamunotes.in
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Necessary condit ions for the formation of Delta:
For the formation of delta the river must have large quantities of
eroded material. In order to have large quantities of eroded
material, the river must have acti ve erogen in its upper course of its
valley.
The material brought by river must be deposited at the faster
rate than it can be removed by the action of ocean currents and
tides.
Rejuvenation
The renewal of river’s power of downword erosion is known as
rejuvenation of a river. It may be caused by a fall in sea level or rise
in land level, its old flood plain perched upon the valley side to form
a river terrace. Meanders become deeper and their sides more
steep, forming incised meanders, waterfalls and ra pids become
more common.
Check Your Progress:
1.Explain with diagram the erosional landform features developed
by a river in its Youth Stage.
2.Explain with diagram the landform features developed by a river
in its Maturity Stage.
3.Which are the de positional landform features developed by a
river. Draw neat diagrams to explain them.
3.6.CONCLUSIONS :
It is thus important to note that rivers also play an important
role in determining and shaping the landscape features as well as
in the pr ovision of fresh water resources in different parts along its
course. Each type of landscape provides with some or the other
useful resource for the ecosystem and so to the mankind on this
earth.munotes.in
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3.7 QUESTIONS :
1.Describe the characteristic feat ures which commonly occur in
the river valley during its youth stage.
2.Describe the characteristic features which commonly occur in
the river valley during its old stage.
3.With the help of neat diagrams explain the following:
i)Flood plains a nd natural levee
ii)Delta may occur.
4.Write short notes on the following:
i)Interlocking spurs and waterfall.
ii)Flood plain and Natural Levee.
iii)Meander and Oxbow lake
iv)Delta.
munotes.in
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Unit -4
WORK OF GLACIER AND
WORK OF UNDERGROUND WATER
Unit Structure:
4.0.Introduction
4.1. Objectives
4.2.Work of Glacier
4.3.Erosional and Depositional Landforms of Glacier.
4.4.Work of Underground Water
4.5.Erosional and Depositional Landforms of Undergroun d
Water
4.6.Conclusions
4.7.Questions
4.0. INTRODUCTION
A Glacier is a moving mass of ice. It ca n be considered a
river of ice, but the velocity of movement in glacier is lesser than
that of a river. In fact the movement is very slow. When a lot gets
accumulated in slopy areas, the elower4 layers of accumulation
attain a momentum in the downward direction under the influence
of gravitational force. Movement in ice is possible in relatively flat
areas also. Glaciers originate in areas where the most of the
precip itation occurs in the form of snowfall. Polar ice caps and high
mountain areas are the major sources areas of formation of glacier.
Glaciers today, except in high latitudes and at high altitudes are of
minor importance in shaping of landforms. But those th atexisted
some 200 to 250 million years ago left their imprints up on millions
of squar e kilomet ers of the earth’s surface in Northern part of North
America, Europe ,Asia and Antarctica .T h o u s a n d so f glaciers
existed in mountains, but today there are eithe r no glaciers or are
only small ones .
Masses of ice which covers large areas of continents are
called Ice sheets and those which occupy mountains and valleys
are called Valley Glaciers. Today, ice sheets occur in Himalayas,
Andes, Alps and Rockies.
Glaciers play a crucial role in the lives of many people.
Glaciers store water which is slowly released through melting
process thus making it available during the dry season when theremunotes.in
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is almost no rain. Melting glaciers provide freshwater resources to
local communities settled at the base of these ice masses in the
temperate, polar and high altitude regions. For example, rivers
flowing in northern part of India from Himalayas are therefore
perennial and provide water to the northern plains of Indus, Ganga
and Brahmaputra river basins. The Gangotri Glacier, one of the
largest glaciers in the Himalayan Mountains, is the source of the
Ganga River . The Ganga is the most important source of
freshwater and electricity in India and Bangladesh. (Electricity is
create d by dams and hydroelectric power plants along the Ganga.)
Hence these regions are rich in agriculture with very high
population densities. Glaciers also play an essential role in
regulating weather systems .Glaciers areimportant indicators of
global warm ing and climate change in several ways. Melting ice
sheets contribute to rising sea levels. As ice sheets in Antarctica
and Greenland melt, they raise the level of the ocean. Tons of fresh
water is added to the ocean every day.
With increasing temperature due to global warming most of
the ice of the earth surface has melted. However, there are still
extensive areas around the poles and smaller areas in the high
mountain areas mentioned above, where glaciers are in existence.
4.1.OBJECTIVES :
To underst and the importance of glaciers
Tostudy the work of glaciers in the formation of different
landform features.
To study the spatial distribution and location of landforms
developed by glaciers.
To understand the importance of underground water
To study the work of underground water in the formation of
different landform features.
To study the spatial distribution and location of landforms
developed by underground water.
4.2.WORK OF GLACIER :
Glaciers erode and transport a lot of material from the
highla nds to the lowlands. Erosional work by glacier is carried
through abrasion (friction) and plucking (wearing and tearing of
frozen blocks of rocks at the base and of the path of glacier).munotes.in
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4.3. EROSIONAL AND DEPOSITIONAL LANDFORMS
DEVELOPED BY GLACIAL ACTION :
Erosional landforms:
i)U-shaped valley :‘U’ Shaped valley is developed because of
simultaneous plucking and abrasion of solid glacier flows.
Glacial valley is steep with wide base as top giving the shape of
‘U’(Figure 4.1.) .In U-shaped valley, sometimes waterfalls from
hanging valley build up alluvial fans of coarse material.
Figure 4.1 : U Shaped Valley
ii)Hanging valley :Hanging valley develops when v ertical erosion
of the main valley is much faster and greater than that of
tributary valley, which contain many small or no glaciers. After
glaciers has retreated the floor of the main valley lies far below
the floor of the tributary valley appearing ashanging valleys
(Figure 4.2.) . The streams of hanging valleys join the main
glacier via waterf alls, which may be several hundred meters
high.
Figure 4.2 : Hanging valleymunotes.in
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iii)Cirque :A cirque is a semi -circular steep sided depression
formed through glacial erosion. A cirque is formed at the head of
a valley glacier where snow accumulates and gets co mpacted in
thedepressions to form a cirque glacier that flows down the
slope to feed the valley glacier (Figure 4.3.) .
Figure 4.3 Cirque ,Arete and Horn Peak
iv)Giant Stairways :A series of small cirques formed one above
the other on an undulating slope is called as Giant stairways .
They are giant in size and appear like a series of steps on the
mountain slope.
v)Aretes and comb ridges :When cirques are formed on two
sides of a mountain range the mountain divide becomes narrow
due to cutting backwards by the glaciers on the opposite sides.
Such steep –edged ridges are called arêtes (Figure 4.3.) .
The edge of an arête appears like the blade of a knife from
distance. Some of the glaciers eating backward, cut through the
ridge passages that look like a serie s of narrow passes at high
altitude. The ridge thus attains the shape of a comb . Such a
discontinuous ridge is called a comb ridge (Figure 4.3.) ..
vi)Horn :When many glaciers develop cirques on the opposite
slope of a ridge, they cut across parts of the rid ge top forming
wide gaps. The consecutive gaps are separated by tall
remnants of ridge. These higher remnants of the ridge are
called horns .(Figure 4.3.)
vii)Col, pass, and saddle :When two glaciers develops cirques on
the opposite sides or slopes of a ridge , and they meet by cutting
across the ridge, a passage of sag is formed, leaving two horns
on the two sides or leaving arêtes on their sides. Such a sag or
gap in the ridge is called a ‘ Col’. When ‘Col’ islowered
sufficiently through erosion so that they are used regularmunotes.in
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crossing across the ridge, they are called as ‘passes’ .Av e r y
wide pass is known as a ‘ saddle’.
viii)Nunatak :ANunatak is a sol itary peak surrounded by ice an d
cirques on all sides which looks like an island in the snow.
These features are c ommon in tundra region where
mechanical and chemical weathering transform these
Nunataks to a lower ordinary rock.
ix)Crag and Tail :Differential erosion rate of hard and soft rock in
glacial region creates crag and trail topography by glaciers. The
area wh ich experiences glacier flow causes erosion to from a
steep slope forming Crag. Whereas the other sides are
protected from erosion and forms a long gentle tail (Figure
4.4.).
Figure 4.4 Crag and Tail
x)Truncated spurs / Kames and Roches M outonnees :In
general, glacial troughs are straighter than normal valleys.
Glacial troughs do conform to original valley course, but stream
of ice may straighten their troughs by abrasion of spur ends and
there by produce truncated spurs. A truncated spur is a steep
bluff on the side of glacial trough, protruding between tributary,
possibly hanging valley .Roches moutonnees are streamlined
asymmetric hillocks, mounds or hills having one side smoothly
moulded wit gentle slope and the other side with craggy steep
slope (Figure 4.5.). They are found in the glacier valleys of
Kashmir Himalaya.munotes.in
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Figure 4.5 Roches moutonnees
xi)Rock basins :Basins formed by abrasion glacial erosion in
snow covered areas are called as rock basins . These rock
basins are large in size and shallow in depth which are
developed in valleys and are filled with water. For example Five
Great Lakes of North America.
xii)Fiord :Glacial troughs occupied by the sea are called as
‘Fiords’. Fiords are deep near the coastal area and become
shallow at a dis tance towards the sea. For example they are
found in Norway, Finland, Sweden, Labrador, Alaska, and
British Columbia.
Depositional landforms: They are developed due to settling of
glacier sediments of varying size. They include moraines or
morainic ridges and drumlins.
i)Moraines :Amoraine is any glacially formed accumulation of
unconsolidated glacial debris ( soilandrock) that occurs in
glaciated regions. There are fourtypes of moraines classified on
the basis of their formation and location in the glacier region
(Figure 4.6.). These are:
Figure 4.6 Types of Morainesmunotes.in
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a)Terminal moraines: They are also known as end moraines
formed due to deposition of glacial till across the moving ice
sheets at th esnouts o fglaciers after ablation of ice.
b)Lateral moraines :These are parallel high ridges of debris that
are deposited along the sides on the top of the glacier that get
preserved .
c)Medial moraines : is a ridge of moraine running down the center
of a valley floor. Medial moraines are formed at the confluence
of two glaciers where the de bris on the edges of the adjacent
valleys sides join and are carried on top of the enlarged glacier.
After the melting of the glacier or its retreat the debris is
deposited and a ridge down the middle of the valley floor is
created. These are medial morain es.The Kaskawulsh glacier in
theKluane National Park ,Yukon ,Canada.
d)Ground moraines :Ground mor aines are till -covered areas with
irregular topography often forming gently rolling hills or plains
(Figure 4.7.). Ground moraines are formed when the till melts
out of the glacier in irregular heaps, forming rolling hills. They
are accumulated at the base of the ice as lodgment till ,b u tm a y
also be deposited as the glacier retreats. In alpi ne glaciers,
ground moraines are often found between the two lateral
moraines. Ground moraines may be modified into drumlins by
the overriding ice.
Figure 4.7 Types of Moraine
ii)Tillplains :Atill plain is an extensive flat plain ofglacial till that
forms when a sheet of icebecomes detached from the main
body of a glacier and melts in place, depositing the sediments it
carried. For example, Wisconsin glaciations covering much of
northern Ohio in Canada.
iii)Drumlins :are swarms of rounded hummocks resulting from the
deposition of glacial till are called as ‘drumlins’. They vary in
height from 10 to 70 metres or more and in length from a few
kilometers to several hundred kilometers. A typical drumlin ismunotes.in
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half ellipsoid in shape much like inverted spoon, but many
variations in shape are found. Generally, drumlins display a
striking parallelism. There are four major belts of drumlin in
North America: an area in New England, Southern New
Hampshire, Eastern Massach usetts, a belt in New York and
Ontario in southern and northern part
iv)Outwash Plain :The area beyond the margins of a glacier
where melt water deposit sand, gravel and mud washer out from
the glacier. The outwash plain becomes progressively finer
down vall ey and grades into silts and clays in the lower valley
courses.
v)Eskers: are common features in the areas of continental
glaciations when stagnation of ice takes place. These are
sinuous ridges that are stratified sand and gravel filling the
super glacial channels (Figure 4.9.).
Figure 4.9 Esker
vi)Erractics: Depos ition of rocks from upper and middle course to
the lower course from different regions by glaciations is called
as erractics (Figure 4.10 ).
Figure 4.10 Erraticsmunotes.in
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Check your progress:
1.Defin e Glacier.
2.Where do glaciers form?
3.What is the importance of glaciers?
4.What is the work of glacier?
4.4.WORK OF UNDERGROUND WATER (KARST
TOGORAPHY)
4.4.1.Introduction :
Rainwater that percolates underground reaches the surface
through springs or is extrac ted through artesian wells (Figure
4.11.).This is possible if the surface rocks are porous and the
underlying deep below is impervious. The subsurface water
(underground water) flows down the slope and oozes out as spring
along the hill/mountain slope as springs (Figure 4.1 2).A r e a s
lacking in surface water bodies extract subsurface water by digging
wells. However depending upon the amount of rainfall and amount
of water availability underground the water -table level keeps
fluctuating. Some wells have gone dry, some are seasonal while
others may be perennial (Figure 4.1 2).
Figure 4.11 Artesian Wellmunotes.in
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Figure 4.12 Springs and Wells
Karst topography is a landscape which is formed due to the
dissolution of soluble rocks including limestone, dolomit ea n d
gypsum. It is characterized by sinkholes, caves, and underground
drainage systems. Nearly all surface karst features are formed by
internal drainage, subsidence, and collapse triggered by the
development of underlying caves. Rainwater becomes acidic as it
comes in contact with carbon dioxide in the atmosphere and the
soil. As it drains into fractures in the rock, the water begins to
dissolve away the rock creating a network of passages. Over time,
water flowing through the network continues to erode a nd enlarge
the passages; this allows the plumbing system to transport
increasingly larger amounts of water. This process of dissolution
leads to the development of the caves, sinkholes, springs, and
sinking streams typical of a karst landscape.
4.4.2. Conditions Essential for the development of Kar st:
Development of Karst topography needs following four
conditions:
i)Soluble Surface Rocks :
The rocks at the surface need to be soluble that are preferably
limestone.
ii)Nature of soluble Rock :
Secondly, the soluble rock should be dense, highly jointed and
preferably thinly bedded.
iii)Existence of Entrenched Valley :
Third condition which favours excellent development of Karts is
the existence of entrenched valleys below uplands underlain by
soluble and wel l jointed rocks. This favours ready downward
movement of groundwater through rockmunotes.in
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iv)Moderate Rainfall Region :
Finally, the region must be of moderate rainfall. It is important to
note that all notable Karts regions are in areas of moderate
rainfall. In g eneral, arid and semiarid regions do not exhibit
marked development of Karts.
4.4.3. Characteristic of Limestone Region :
The most important characteristic of limestone region is the
almost complete absence of surface drainage. The permeability
of limes tone permits rain to soak into it very easily.
Erosional landforms:
i)Terra Rossa :In the gentle slope of limestone region the
descending solution of groundwater leaves behind a residue of
red, clayey soil on the surface which extends down upto the
opened joints. Under oxidizing conditions, when the soils are
above the water table ,iron oxide (rust) forms in th e clay. This
gives it a characteristic red to orange colour. This residual soil is
called as Terra Rossa. Terra R ossa is typically found in regions
with a Mediter ranean climate .
ii)Lapies / Karren / Bogaz: Limestone surface exposed at high
relief with running water across the surface of blocks forms
straight, grooved, pitted, etched, fluted, rugged surface called as
Lappies.
iii)Dolines and Uvala :When Swallow holes jo in together,
producers very large opening called a doline. Likewise dolines
may join up to give even larger openings are called Uvala.
iv)Swallow -holes or s ink holes: Rivers rising in a non -limestone
region sometimes flow into a limestone region. If this happens
such rivers disappear into swallow holes or sink holes in the
surface and continue to flow inside the limestone as
Underground River . Small vertical holes are known as Sinkhole
and larger holes are known as swallow holes.
v)Karst lake :Karst lake are f ormed due to clogging of doline
within washed clay that starts holding water above the regional
water table level.
vi)Karst window :They are formed due to the collapse of upper
surface of sink -holes or dolines.
vii)Polje :Most extensive and larger depressions for med in karst
topography are called Polje. For.eg. karst region of Jamaica
andYugoslavia .
vii)Blind valley :The valley of a surface stream in limestone
formation region disappears through a swallow hole or sink hole
is termed as blind valley.munotes.in
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viii) Underg round Caves and caverns :Caves are most
significant landforms produced by erosional works (mainly
corrosion, solution and abrasion) of groundwater in limestone
lithology. Some underground caves are of great size e.g. in
U.S.A and New Mexico State there is very large underground
cave known as Carlsbad and Mammoth caves. They are 1219
meters length, 190 meters wide and 300 meters depth
consisting of several chambers.
ix)Hums :Hums are residual hills that remain after the karst
landscape has been fully eroded .
Depositional landforms:
i)Dripstone :Some amount of water entering in the cave through
a fracture from ceiling gets evaporated and a small amount of
calcium carbonate is left behind. Such succeeding evaporation
adds more calcium carbonate to form a c ylindrical or cone
shaped protrusion built downward from the ceiling is called as
dripstone.
ii)Stalactites, Stalagmites and Pillars :There are a variety of
depositional features in the caves, which add to their beauty.
The most striking features are us ually accumulations of calcium
carbonate on the ceilings of the caves and floors of the caves.
Downward extending of the deposition of calcium carbonate is
known as Stalactites and the upward growing of the deposition
of calcium carbonate is known as Stala gmites. When stalactites
and stalagmites join each other, there is formation ofpillars
(Figure 4.13.). Sometimes the roof of an underground cave
collapses and gorge with almost vertical sides develops. Little
soil cover may occur in shallow patches, which support only a
few scrubs and grasses in the limestone region.
Figure 4.13 Karst Land form featuresmunotes.in
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iii)Drapes or curtains :They are formed in caves when rivulet of
underground water flows along an inclined roof. The curtain
attached to the ceiling hangs downwards. The continuous
dripping of water may be facilitated by roof joint, producing a
fluted curtain or drapes across the cave. Other depositional
features include Helictites, Globulites, etc.
Check your progress?
1.What is Karst topogaphy.
2.Wher e are karst topography formed?
3.What is the importance of Karst topography?
4.6CONCLUSION:
Glaciers thus play a crucial role in the host ile regions and
are a source of fresh water during summers that supports life in the
polar, temperate and high altitude regions. Their importance further
increases as many rivers in temperate and particularly in tropical
areas are perennial because of the melting glaciers during
summers providing freshwater sources to the people living in their
surrounding s.Different landform features developed by erosional
and depositional process of glaciers provide a scenic beauty to the
landscape that has promoted tourism activity in these areas and
thus a source of income to the local community.
4.7QUESTIONS :
1)Describe with illustrations the erosional landforms produced by
glaciers.
2)Briefly explain the depositional landforms produced by glaciers.
3)What is the essential condition for the development of karst
region?
4)Explain in brief erosional features of karst reg ion.Give suitable
diagrams
5)Explain with suitable diagrams the depositional landforms
produced in karst region.munotes.in
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Reference :
1.Arthur L Bloom, 2009 3rdedition: ‘Geomorphology -A Systematic
Analysis of Late Cenozoic landforms’, PHI Learning Private Ltd.
NewD e l h i .
2.Alan H.Strahler and Arthur N.Strahler, 2001 4thEdition : ‘Modern
Physical Geography’, John Wiley and Sons, INC. Delhi.
3.Pednekar, Shinde,Thakur…..(2015): Physical Geography,
F.Y.B.A. Semester I and II, Sheth Publishers Private Limited,
Mumbai
http://www.esi.utexas.edu/outreach/caves/karst.php
http://climatechange.democracyctr.org/blog/2012/04/19/why -
glaciers -are-important/
http://education.nationalgeographic.com/encyclopedia/glacier/
munotes.in
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Unit -5
WORK OF WIND AND WORK OF SEA -
WAVES
Unit Structure:
5.0.Objectives
5.1.Introduction to wind
5.2.Work of Wind
5.3.Erosional and Depositional Landforms of Wind.
5.4.Introduction to sea waves.
5.5.Work of Sea -waves
5.6.Erosional and Depositional Landforms of Sea -waves.
5.7.Concl usion.
5.8.Questions
5.0. OBJECTIVES:
To study the importance of wind and their types.
To study the work of wind as an agent erosion and
associated landforms.
To study the work of wind as an agent deposition and
associated landforms.
To study the importance of sea waves and their types.
To study the work of sea waves as an agent erosion and
associated landforms.
To study the work of sea waves as an agent deposition and
associated landforms.
5.1.INTRODUCTION:
Winds play an important role in the changing the w eather of
an area that influences various human activities in the world. Winds
are also responsible in shaping the landforms through different
types of aeolian processes .Winds also act as agents for dispersal
of plant seeds to produce various species in different areas. They
act as natural cleansing agent by removing and dispersing the air
pollution produced in an area. At times they are furious and maymunotes.in
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lead of spread of wild fires in the forest; destroy the standing crop,
bring down the trees and weak structures etc. The work of wind and
the features associated with it are explained below:
5.2.WORK OF WIND (AEOLIAN LANDFORMS):
Wind is an important agent of erosion in dese rts. Its work
involves erosion of dry, loose, and unprotected geomaterials and
their transportation and deposition. It is the most active agent of
erosion in arid and semi -arid regions of tropical and temperate
regions.
5.3.EROSIONAL AND DEPOSITIONAL LANDFOR MS
OF WIND:
There are three processes responsible for erosional and
depositional work carried by wind (f i g u r e5 . 1 . ) . These are:
i)Deflection :The process of removing, lifting and blowing
away dry and loose particles of sand and dust by winds.
ii)Abrasion :It breaks up rocks by sandblasting by wind when
they hit sand particles against standing rocks.
iii)Attrition : In this process the sand particles, while they are
moving collide against each other and are converted into
finer particles.
Figure: 5.1. Wind Actionmunotes.in
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Features produced by Wind Erosion :
Some of the features produced by wind erosion are as
follows:
i) Deflation Basin: emoval of sand particles in large amount
by strong winds blowing in a particular region gives rise to
the formation of a basin. This feature produced by wind
erosion is termed as deflation basin Figure 5 .2.
Figure 5.2: Deflation Basin
ii) Zeugen / Mushroom Rock :It is also known as mushroom
rocks in Death Valley California Figure 5.3. .T h i si sa n upstanding
rock in desert, caped with a harder stratum and undercut by wind at
base. It is indicative of differential erosion. The base is being softer,
more easily eroded rock. They are more common in arid area such
as eastern province of Saudi Arabia.
Figure 5.3. Mushroom rock
Zeugen may be as high as 30 meters. Ultimately they are
undercut and gradually worn away. Figure 5. 4.munotes.in
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Figure 5. 4.Z e u g e n
iii) Yardangs :Yardangs are formed by wind erosion when
bands of hard and soft rocks lie parallel to th ep r e v a i l i n g
winds in a desert region .Figure 5. 5. Such rocks are turned
into ridge and furrow landscape by wind and abrasion. The
belt of hard rock standup as rocky ribs up to 15 meters in
height yarda ngs are very in the central Asian deserts and in
the A tacama desert.
Figure :5.5.Yardangs
iv)Inselberg :In some desert areas erosion by wind has
removed all the original surface except for isolated pieces
which stand up as round topped masses of rocks called
Inselbergs .Figure 5. 6. Inselbergs are commo n in Australian
Desert, Kalahari Desert in Africa, Northwest Nigeria and
parts of Algeria.munotes.in
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Figure :5.6.Inselberg
v) Rock Windows: are formed by erosive action of a wind that
are more prominent in a particular direction and area/point
figure 5.7.
Figure: 5.7. Rock Windows
vi) Mesa: This landform feature is developed in semi or semi -
arid region where the erosion of upland is uniform on the top
giving rise to flat topped are called as Mesa figure 5.8
Figure: 5.8. Mesamunotes.in
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vii)Vetifacts or Dreikanters: Angu lar fragments of the rocks
developed by wind erosion in the stony desert area is termed
asVentifact or Dreikanters figure 5.9.
Figure :5.9.Vetifacts or Dreikanters
Features produced by wind deposition :When very powerful
wind blows across the des ert, carry large amounts of desert dust
and sand particles from one desert to another desert or in
surrounding areas. When wind velocity decrease such material is
immediately deposited, resulting in formation of some depositional
features by wind called as sand dunes (figure 5.10).
Figure 5.1 0.Sand D une
There are two types of sand dunes i ) Barkha n or crescent shaped
dunes and ii ) Self dunes.
i)Barkhan or crescent shaped sand dunes :
Barkhan is a crescent shaped dune, lies at righ ta n g l e st ot h e
prevailing wind Figure 5.11 .A barkhan usually develops frommunotes.in
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the accumulation of sand caused by a small obstruction like a
rock or some vegetation. As the mound of sand grows bigger
and bigger its two edges are slowly carried forward down -wind
and a typical cr escent shape slowly develops. The windward
face of barkhan is gently sloping but the lee -ward is steep and
slightly concave. A barkhan moves slowly forward as sand
particles are carried up the windward face and slip down the
lee-ward side. The height of ba rkhan ranges from a few meters
to 30 meters.
Figure: 5.11.Barkhan / Crescent shaped S andDunes
ii)Seif Dunes :Seif dune is generally long and straight dune,
which is parallel to the prevailing wind
Figure. 5.12.The corridors between the dunes are swept clear
of sand by this wind. The dunes are lengthe ned by the
prevailing wind. Sei f dunes are generally several hundred
meters high and many kilometers long. Many seif dunes occur
in that desert of Rajasthan a nd desert in Western Australia.
Figure: 5.12.Seif Dunesmunotes.in
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iii)Loess :Every year wind blows fine particles out of the deserts.
Some particles are blown into sea and some are deposited on
land. Fine particles deposited on the land outside desert are
called Loess. There are extensive deposits of loess in North
China. Loess in China are formed by dust blown out by wind
from Gobi Desert Loess deposits in China has been intensively
eroded by ri vers and produced ‘badland’ landscape.
Check your Progress:
Q. 1. Explain the importance of winds.
Q.2. Which processes are responsible for the work carried by wind?
Q.3. Explain the erosional landforms developed by wind action.
Q.4. Explain the depositi onal landforms developed by wind action.
5.4.INTRODUCTION TO SEA WAVES:
Sea waves are defined as undulation of seawater
characterized by well developed crests and troughs. The
generation of sea waves is probably because of the mechanism of
relea se of some of sort of energy caused by atmospheric circulation
of winds that is responsible for movement of fluids of two
contrasting densities (air and sea water) along the interfaces of two
masses of fluids of varying densities. Sea waves the most powerf ul
agent responsible for the formation of various landforms. Sea
waves play an important role in the coastal ecosystems function. Today
they are playing an important role in contemporary tourism of surfing
sports to earn large revenue in few naturally bes towed countries. Ocean
water currents help to move eroded debris and deposit it as slit,
sand and gravels along the coast. However, the coastline is
undergoing changes over a period of time due to the action of sea
waves, tides and ocean currents.
5.5.WORK OF SEA WAVES:
Various processes are involved in the work of sea waves
that produce different types of erosional and depositional landforms
in the coastal areas. Sea waves operate in the following ways to
transform the coastal landscape:munotes.in
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i) Corrosion: Sea w aves armed with rock debris of different
sizes and shapes charge against the base of the cliff and
wear them back by corrosion. Ocean currents and tides
complete the work by sweep in the eroded materials into the
sea.
ii) Attrition: The constantly moving sea waves that transport
beach materials such as boulders, pebbles, sand etc. These
waves also hurl these fragments against each other, until
they are broken by attrition into very small pieces.
iii) Hydrolic Action: Dashing sea waves against a cliff face
causes air in cracks and crevices to become suddenly
compressed. When the wave retreats, the air expands with
violent explosion. Again and again such action enlarges the
cracks and crevices and fragments are broken down.
5.6.EROSIONAL AND DEPOSITIONAL LANDFORMS
OFSEA WAVES:
Coastal Landforms of by Sea Wave Erosion :
i)Headlands ( Capes )and Bays : On exposed coasts, the
continued action of waves on rocks of various resistance
causes the coast lines to be eroded irregularly Figure 5.1 3.
This is particularly pronounc ed where hard rocks e.g. granite
basalt occurs in alternative bands with softer rocks e.g. sand
and clay. The soft rocks are worn back into inlets, bays and
harder rocks persists headlands capes etc.
Figure :5.13.H e a d l a n d sa n dB a y smunotes.in
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ii)Sea-cliff: A steep rocky coast rising almost vertically above
sea-level is called as sea -cliff. Figure :5.14.
iii)Wave -cut Platform :Generally any very steep rock facing
adjoining the coast forms cliff. The rate of recession
however, will depend on its geological structure, i.e. the
stratification and jointing of the rocks and their resistance to
wave attack. If the bed deep seaward, large block of rock will
be dislodged and fall into sea. The cliff will rise in series of
stapes. On the other han d, if the beds dip landwards, the cliff
will be more resistant to wave erosion. At the base of the cliff
the sea cuts a notch which gradually undermines the cliff as
the cliff recedes landwards and eroded base is left behind
called wave -cut platform Figure :5.15.
Figure :5.14.S e a -Cliff Figure :5.15.Wave -cut Platform
Figure 5.1 6: Wave cut platform, cliff and Sea Notch
v)Caves, Sea Arches and Sea Stacks and Sea Stump: These
minor erosional features are produced by wave action duri ng the
process of cliff formation. Prolonged wave attack on the base of
the cliff excavates holes. When two caves approach one anothermunotes.in
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from either side of the headland and unite, until, they form an arch.
Further erosion by waves will ultimately lead to t he total collapse of
the arch. The seaward portion of the headland will remain as a
pillar of rock known as a stack. In course of time these stubborn
stack will gradually be removed. The vertical rock pillars are eroded
leaving behind only the stump , which are only just visible above
the sea level, particularly at low tides Figure 5.1 7.
Figure: 5.17.Caves, SeaArches and SeaStacks and SeaStump
Figure: 5.18. Sea cave and Blow hole
Coastal Landforms of Sea Wave Deposition :
i)Beach :The most important depositional feature of the work
of deposition by sea waves is beach (Figure 5.19) .T h em a i n
action of constructive waves is to deposit mud, sand and
pebbles. When these materials deposited along a coa st,
form a gently sloping platform called a beach. Beaches
usually lie between high and low water levels, but storm
waves along some coast throw pebbles and stones well
beyond the normal level reached by waves at high tide. The
material deposited in this w ay produces a ridge called a
storm beach.munotes.in
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Figure :5.19.B e a c h
ii)Spit: Spit is a narrow, low ridge of sand or pebbles joined to
the land at one end and its oth er end is terminating in the se
Figure :5 . 2 0 . Sometimes, a spit develops at a headland and
projects across a bay. Its waves swing into the bay obliquely,
the end of the spit becomes curved or like a hook.
Figure :5 . 2 0 .S p i t
iii)Bar: Bar is very similar to spit. The bar which extends right
across ais very common type of bar. It starts as a spit
growing out from a headland, stretches across the bay to
next headland. Such bar is called a bay -barFigure: 5.21.munotes.in
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Figure :5 . 21.Types of Bars
iv)Lagoon: A shallow body of seawater separated fr om Open
Ocean by a spit or by Barrier Island or reef.
v)Tombolo: This feature is developed close to the coast
where the deposition of sand takes place connecting the
mainland with the coastal island is Tombolo.
Figure :5 . 2 2 . .Tombolo
Check Your Progress:
Q. 1. Explain the importance of sea -waves.
Q.2. How is sea wave generated?
Q.3. Which processes are responsible for the work carried by sea
waves?
Q.4. Explain the erosional landforms developed by sea waves.
Q.5. Explain the de positional landforms developed by sea waves.munotes.in
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5.7.CONCLUSION:
It is thus important to note that winds and sea waves as
geomorphic agents play a significant role in shaping and producing
different landforms in the arid and semi -arid regions in case of
winds a nd sea –waves along the coastal areas in the world.
Different landform features developed by erosional and depositional
process by wind and sea waves in respective areas provide a
scenic beauty to the landscape to promote tourism activity and thus
a source of income to the local community and the country. Besides
their role in the promoting the functioning of ecosystems in different
ecological area provides with necessary food nutrients at diffident
tropic levels in the food pyramid.
5.8.QUESTIONS:
1. With t he help of suitable diagrams explain the erosional
landforms developed by wind action.
2. Explain the depositional landforms developed by wind action.
Draw suitable diagrams.
3. Drawing suitable diagrams explain the erosional landforms
developed by sea wav es.
4. With the help of suitable diagrams explain the depositional
landforms developed by sea waves
References:
1.Arthur L Bloom, 2009 3rdedition: ‘Geomorphology -A Systematic
Analysis of Late Cenozoic landforms’, PHI Learning Private Ltd.
New Delhi.
2.Pedn ekar,Shinde,Thakur…..(2015): Physical Geography,
F.Y.B.A. Semester I and II, Sheth Publishers Private Limited,
Mumbai
munotes.in
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87Unit -6
PRACTICAL PART A:
LANDFORMS
Unit Structure:
6.0 Objectives
6.1 Introduction
6.2 Contour and Interpolation of contour lines
6.3 Identification of Contour landforms through cross sections,
6.4 Profiles –importance and types
6.5 Conclusions
6.6 Questions
6.0 OBJECTIVES
The study of landforms is facilitated with the help of contours.
Value of contour, it spacing and shape helps to identify the
nature of slope and the relief feature of the area.
The drawing of profiles facilitates the nature of surface landform.
Drawing of different types of relief and river profile assist in
comparative analysis of nature of relief between the regions.
6.1INTRODUCTION
In physical geography it is very important to understand the
nature of landform features for planning purposes and to study the
type of associated landuse. There are different techniques used for
understanding the relief features. Topographic maps represen t
natural and man -made features of the earth's surface. Relief
features in Topographical maps are represented with the help of
contour lines. Data of relief is represented on maps with the help of
isopleths technique called contours. Contours are the mos t
commonly used quantitative technique for representing relief.
Contour lines are imaginary lines joining points of equal elevation
above mean sea level. Since contour lines represent a particular
elevation therefore two different contour lines will never intersect
each other. However two or more contour lines can meet eachmunotes.in
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88other at a point to represent a cliff / caves. Thus expertise in
contour reading helps to identify the three dimensional relief at that
point on a map and its corresponding relief featur es on the ground.
Representation of landforms and terrain features by contour lines is
covered in this chapter to explain the basics of contour drawing and
understanding of relief.
6.2CONTOUR AND INTERPOLATION OF CONTOUR
LINES:
A) Contours are imaginary lines joining places having the same
elevation above mean sea level. A map representing landforms of
an area by contour is called a contour map. Method of depicting
relief features with the help of contours is very useful and multi -
resourceful. The contou r map helps to understand the nature of
topography of an area.
Earlier, ground surveys and leveling methods were used to
draw contours on topographical maps. However the invention of
topography and subsequent use of aerial photography have
reduced the imp ortance of conventional surveying, leveling and
mapping methods. In the contemporary period these aerial
photographs are used for topographical mapping.
Contours are drawn at different vertical intervals (V.I.) viz: ‘0’
meter, ‘100’ meters, and ‘200’ mete rs etc. above the mean seal
level Figure 6.1
Contours: Figure 6.1
This is known as contour interval which is ‘100’ meters
between two consecutive contours which remains constant on the
contour map.
This contour interval is usually constant on a given
topographical map. The horizontal distance (H.E.: Horizontal
Equivalent) varies from place to place depending upon the nature
of slope. The horizontal distance between two points is large whenmunotes.in
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89the slope is gentler (i.e. the consecutive contours are spaced apart)
and distance is less when the slope/gradient is steeper (i.e.
consecutive contours are closely spaced) on the topographical
map.
Following are some of the basic characteristics of contour lines:
A contour line is drawn to represent the places having equal
height.
Contour lines and their shapes represent the height and slope
or gradient of a landform.
Closely spaced contours reveal steep slope and widely spaced
contours represent gentle slope.
Itis important to note that when two or more contour lines meet
at a point they represent features of vertical slope such as
waterfalls or cliffs.
It is important to note that two contours of different height will
never intersect each other.
B) Interpolati on of contour lines by Arithmetic method:
It is a process of spacing the contours proportionately
between the plotted ground points by arithmetic method. It is
assumed that the slope of ground between two points
(height/depth) is uniform.
In this method t he positions of contour points between the guide
points are located by arithmetic calculations. For example, let
A.B.D, and C can be the guide points plotted on the map having
elevations of 607.4, 617.3, 612.5 and 604.3 feet respectively
(figure 6.2).LetAB=BD=CD=CA=1 ”o nt h ep l a na n dl e ti t
be required to locate the positions of 605, 610, 615 feet contours on
this lines. The vertical difference in elevation between A and B is
(617.3 –607.4) = 9.9 feet. Hence the distances of the contours
points from A will be:
Distance of 610 ft contour point = 1/9.9 * 2.6 = 0.26” (approx).
Distance of 615 ft contour point = 1/9.9 * 7.6 = 0.76” (approx).munotes.in
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Interpolation of contour lines: figure 6.2
These two contour points may be located on AB. Similarly,
the position of the contour points on the lines AC, CD, BD and also
AD and BC may be located.
Contour lines may then be drawn through appropriate
contour points as shown in figure (figure 6.2).
Check your progress:
1. Define Contour and explain its importance.
2. Which method is used for drawing contours?
6.3 IDENTIFICATION OF CONTOUR LANDFORMS
THROUGH CROSS SECTIONS:
Landforms of any area are associated with different types of
slopes and relief features. These landform features and slopes are
identified and studied with the help of contours by drawing cross
sections using topographical map of that area.munotes.in
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91Following are few cross sections of slopes and landforms
drawn with the help of contours:
a)Types of Slope: Slope can broadly be classified into gentle,
steep, concave, convex, uniform, undulating/irregular, and
terraced. The landform with varying slopes would reveal
contours of distinct spacing pattern on the topographical map.
i)Gentle slope: The angle or degree will be low when a slope is
gentle. In gentle slope the contours are widely spaced Figure
6.3.
Gentle slope: Fig. 6.3
ii)Steep slope: The angle or degree will be high when a slope is
steep. In steep slope the contours are closely spaced Figure
6.4.
Steep Slope: Fig. 6.4munotes.in
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92iii)Concave slope: The landfo rm has gentle slope in its lower
elevation and steeper slope in its higher elevation. Thus the
contours in lower elevation are spaced apart and in higher
elevation are closely spaces revealing a concave slope of the
land at that place Figure 6.6.
Concave Slope; Fig. 6.6
iv)Convex slope: The landform has steeper slope in its lower
elevation and gentler slope in its higher elevation. Figure
6.7.Thus the contours are spaced closely in lower elevation are
widely in higher elevation revealing a convex slope of the land
at that place.munotes.in
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Convex Slope; Fig. 6.7
v)Uniform Slope: When the slope of an area increases or
decrea ses per unit horizontal distance uniformly is called as
uniform slope. Figure 6.8
vi)
Uniform Slope: Fig. 6.8munotes.in
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94vii)Undulating/irregular Slope: It is a slope where the gradient
changes with short horizontal distances that can be gentler or
steeper thus producing concave and convex slopes. Figure 6.9
Undulating/irregular Slope: Figure 6.9
viii)Terraced/ Stepped Slope : The contours of terraced slope
alternately rise gently and then steeply with increasing altitude
of the landform. Figure 6.10
Terraced/ Stepped Slope: Figure 6.10munotes.in
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95b)Types of landforms: Following are some of the important types
of landforms that can be studied by drawing cross section
across the contours:
i) Conical Hill / A mount: Conical hill rises almost uniformly from
the surrounding land. A Conical hill with uniform slope and narro w
top is represented by concentric contours spaced almost evenly at
regular intervals. Figure 6.11
Conical Hill / A mount: Fig. 6.11
ii) Plateau: A widely stretched flat topped highland, with relatively
steeper a side rising above the adjoining plain or sea is called a
plateau. The contour lines representing plateau are rectangular in
shape which are normally close spaced at the margins with inner
most contour showing wide gap between its two sides Figure 6.12 munotes.in
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Plateau: Fig. 6.12
iii) Valley (‘V’ and ‘U’ Shaped valley): Valley is a land with deeper
steep sides lying between two highlands formed due to lateral
erosion by a river or a glarier.
‘V’ shaped valley: it resembles the letter ‘V’. A V shaped valley
occurs in mountainous areas.munotes.in
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‘V’ shaped valley: Fig. 6.13
The lower most part of the V shaped valley is shown by the
inner most contour line with very small space between two
consecutive contours and the lowest value ( lowest elevation) of the
contours is assigned to it.
The contour value increases outwards wit hu n i f o r mi n t e r v a l s
for all other contour lines. Figure 6.13
‘U’ shaped valley: A U shaped valley is formed by strong lateral
erosion of glaciers at high altitudes. The flat wide bottom and steep
sides makes it resemble the letter ‘U’ . The lowermost part of the U
shaped valley is shown by the inner most contour line with a wide
gap between its two sides. The contour value increases outwards
with uniform intervals for all other contour lines. 6.14munotes.in
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‘U’ shaped valley: Fig. 6.14
v) Pass, Saddle, Col and Gap: These landform features are
noticed in hilly regions.
(a)Pass: A Pass is found between two hills or mountains and serve
as a land route across the hill/ mountain range( Figure 6.1 5a ) .
(b)Sa ddle: It is a shallow depression between two peaks (Figure 6.
15 b).
(c)Col: AC o li sf o r m e db e t ween the ridges of a water -shed (Figure
6. 15 c ).munotes.in
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Pass: Figure 6.1 5( a )
Saddle: Figure 6.1 5( b )munotes.in
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Col: Figure 6.1 5( c )
(d)Gap: A gap is a low depression close to the ground found
between a ranges of hills (Figure 6.1 5d ) .
Gap: Figure 6.1 5( d )
vi) Cliff: A cliff is a steep and straight rock wall in the Rocky
Mountains or rocky coast, or rocky hills. Cliff is characterized by
sudden steep slope where three to four or more contour lines meet
at one point. Figure 6.16munotes.in
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Cliff: Fig. 6.16
i)Escarpment/ Scarp: an escarpment is a long abrupt and steep
slope of a hill/ a ridge/ or a plateau. It is formed as a result of
faulting or the erosion of an inclined hard rock. Figure 6.17
Escarpment/ Scarp: Figure 6.17
ii)Spur: A spur is an outward projection of high ground into a
lower one. It is represented as an outward bulged in the contour
lines Figure 6.18. In a spur higher contour bends towards the
lower contour.munotes.in
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Spur: Figure 6.18
iii)Gorge: A Gorge is a deep narrow valley with very steep slopes.
A Gorge usually develops in a region of hard rock’s where the
river carves out a steep sided valley for itself due to its
enormous capacity of vertical cutting. Figure 6.19
Gorge: Figure 6.19
x) Rapid and Waterfall: A waterfall is created in the channel of a
river that has a steep vertical slope with flowing water. A waterfall is
observed where two or more contour lines meet at a point in the
bed of a river.munotes.in
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103
Rapid: Fig. 6.20 (a)
Ar a p i di sam i n i a t u r ew a t e r f a l l .G e n e r a l l yt h e ya r ef o u n d
upstream from the main water fall. Sometimes they occur
independently. A rapid also has a considerable slope hence the
contours liens are closely spaced while crossing the valley. Rapids
are a step like structure formed due to erosion of soft rock and
resistant hard rock overlaying each other. Figure 6.20(a), (b).
Water -Fall: Figure 6.20 (b).
xi) Water -shed / Water divide: A watershed is the land area from
where water flows on the either sides of the slope and develops
small rills/streams. These are well identified in the
hilly/mountainous regions. Figure 6.21.munotes.in
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104
Water -shed / Water divide: Fig. 6.21
Check your progress :
1.Explain different types of slopes with the help of diagrammatic
representation.
2.Explain different types of relief features with the help of
diagrammatic representation.
6.4. RELIEF PROFILES –IMPORTANCE AND TYPES:
A relief profile is a line which shows the rise and fall of the
surface of the ground along a chosen line on a map. One of the
advanced techniques of representation of relief is to draw a relief
profiles. A profile of a relief feature acts as a visual aid in its
description and interpretation. Hence it is of particular interest to
geographers and especially geomorpholog ists who are interested in
the analysis of landforms and in the process of their upgradation
and degradation. Identifying landform features with the help of
contours is complex whereas profiles are relatively easy and useful
in understanding the relief fea tures.munotes.in
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105Broadly speaking, a profile which is also known as a section
means an outline of a relief (elevation or depression) along a
selected line. However, sometimes a distinction is made between a
section and profile. A Section is usually a cutting taken for a
geological section, whereas a profile is a outline of the surface relief
feature like profile of a river valley.
i)Serial / Simple profile: These are made by drawing a series of
profile or parallel profiles for showing features like a coastline;
edges of plateau; a series of spurs; a transverse profile of a
river; a junction of two contrasting topographical features etc.
Figure 11.22 explains the construction of a simple profile.
Serial / Simple profile: Figure 6.22
ii)Superimposed Profile: When a series of profile are
superimposed on a single plane it is called as superimposed
profile. These successive profiles are numbered for getting
clarity. Such profiles are generally used for representing
landforms wit h certain morphological uniformity as shown in
Figure 6.23. In other cases the serial profile are more useful.munotes.in
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106
Superimposed Profile: Figure 6.23
iii)Projected Profile: In the superimposed profiles, the successive
parallel profiles are placed on a common base line. However,
the lower parts of the profiles are hidden behind the higher
intervening altitudes.
Projected Profile: Figure 6.24
If only the visible parts of successive profiles are
represented on a common framework one gets a panoramic view of
foreground, middle ground and the sky line. Such profiles are
known as projected profile or compressed profile as shown in
Figure 6.24.
iv) Composite Profile: If the superimposed profile of a landform is
viewed carefully one can discern at the farthest end of such a
profile, a summit line, the skyline which provides a general outline
of the concerned la ndform features as viewed from a distance. Thismunotes.in
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107skyline can be represented by a profile or a line drawn by joining
the highest parts of a series of parallel profiles. Such a profile is
known as composite profile. Such profiles can be used for a
comparative analysis of the terrain types in a region or between
regions Figure 6.25.
Composite Profile: Figure 6.25
Check your progress:
1.What do you understand by the term relief profile?
2.Give different types of profile
3.Explain the use of profile in the study of landforms.
6.5 CONCLUSION:
This module therefore explains the importance of
quantitative techniques in identifying different types of slopes and
landform features. Comparative analysis and spatial differentiation
is therefore possible with the help of such geographical techniques
used in practical geography.munotes.in
Page 108
1086.6 QUESTIONS:
1)Explain giving examples the importance of contours in the
identification of landform features.
2)What is a relief profile? Giving different types of profiles explain
their importance.
3)Draw the cross sections and profile given in figure 11.4 to 11.25
References:
1.F.J.Monkhouse and H.R.Wilkinson (1956): ‘Maps and
Diagrams’, Methuen and Co.Ltd. New York.
2.R.L.Singh and Rana P.B.Singh (2004): ‘Elements of Practical
Geography’, Kalyani Publishers, New Delhi.
3.L.R.Singh (2005): ‘Fundamentals of Practic al Geography’,
Sharda Pustak Bhawan, Allahabad.
4.Gopal Singh (2001):‘Map Work and Practical Geography’, 4th
revised and enlarged edition, Vikas Publishing House Pvt. Ltd.
5.Dr. B. C. Punmia ( 1994 ): ‘Surveying’ Volume I, Laxmi
Publications Pvt.Ltd. New Del hi.
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Question Paper Pattern for Semester End Assessment implemented
From 2020-2021
For Geography courses at F.Y.B.A
Duration of examination - 3 hours
Total Marks - 100 (per semester )
N. B. : (1) All Question s (Question No. 1 to 5) is compulsory.
(2) Draw neat sketches and diagrams wherever necessary.
(3) Attach map supplement to the main answer book.
(4) Figures to the right indicate full marks.
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Q1. Attempt any One question (module 5) 20 marks
A)
B)
Q2. Attempt any Two questions ( module 1) 20 marks
A)
B)
C)
Q3. Attempt any Two questions ( module 2) 20 marks
A)
B)
C)
Q4. Attempt any Two questions ( module 3) 20 marks
A)
B)
C)
Q5. Attempt any Two questions ( module 4 ) 20 marks
A)
B)
C)
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