Fundamentals Of Physical Geography Class XI NCERT

145 Pages·2013·6.24 MB·English

C
ONTENTS
FOREWORD iii
UNIT I : GEOGRAPHY AS A DISCIPLINE 1-12
1. Geography as a Discipline 2
UNIT II : THE EARTH 13-38
2. The Origin and Evolution of the Earth 14
3. Interior of the Earth 21
4. Distribution of Oceans and Continents 30
UNIT III : LANDFORMS 39-74
5. Minerals and Rocks 40
6. Geomorphic Processes 45
7. Landforms and their Evolution 58
UNIT IV : CLIMATE 75-110
8. Composition and Structure of Atmosphere 76
9. Solar Radiation, Heat Balance and Temperature 79
10. Atmospheric Circulation and Weather Systems 88
11. Water in the Atmosphere 98
12. World Climate and Climate Change 103
UNIT V : WATER (OCEANS) 111-125
13. Water (Oceans) 112
14. Movements of Ocean Water 120
UNIT VI : LIFE ON THE EARTH 126-140
15. Life on the Earth 127
16. Biodiversity and Conservation 135
GLOSSARY 141-144
U
NIT
I
G D
EOGRAPHY AS A ISCIPLINE
This unit deals with
(cid:144) Geography as an integrating discipline; as a science of spatial
attributes
(cid:129) Branches of geography; importance of physical geography
CHAPTER
G D
EOGRAPHY AS A ISCIPLINE
Y
ou have studied geography as one of the of the earth’s surface. The understanding and
components of your social studies course the skills obtained in modern scientific
upto the secondary stage. You are techniques such as GIS and computer
already aware of some of the phenomena of cartography equip you to meaningfully
geographical nature in the world and its contribute to the national endeavour for
different parts. Now, you will study ‘Geography’ development.
as an independent subject and learn about the Now the next question which you may like
physical environment of the earth, human to ask is — What is geography? You know that
activities and their interactive relationships. earth is our home. It is also the home of many
Therefore, a pertinent question you can ask at other creatures, big and small, which live on
this stage is — Why should we study the earth and sustain. The earth’s surface is
geography? We live on the surface of the earth. not uniform. It has variations in its physical
Our lives are affected by our surroundings in features. There are mountains, hills, valleys,
many ways. We depend on the resources to plains, plateaus, oceans, lakes, deserts and
sustain ourselves in the surrounding areas. wilderness. There are variations in its social
Primitive societies subsisted on ‘natural means and cultural features too. There are villages,
of subsistence’, i.e. edible plants and animals. cities, roads, railways, ports, markets and
With the passage of time, we developed many other elements created by human beings
technologies and started producing our food across the entire period of their cultural
using natural resources such as land, soil and development.
water. We adjusted our food habits and This variation provides a clue to the
clothing according to the prevailing weather understanding of the relationship between the
conditions. There are variations in the natural physical environment and social/cultural
resource base, technological development, features. The physical environment has
adaptation with and modification of physical provided the stage, on which human societies
environment, social organisations and cultural enacted the drama of their creative skills with
development. As a student of geography, you the tools and techniques which they invented
should be curious to know about all the and evolved in the process of their cultural
phenomena which vary over space. You learn development. Now, you should be able to
about the diverse lands and people. You attempt the answer of the question posed
should also be interested in understanding the earlier as to “What is geography”? In very
changes which have taken place over time. simple words, it can be said that geography
Geography equips you to appreciate diversity is the description of the earth. The term
and investigate into the causes responsible for geography was first coined by Eratosthenese,
creating such variations over time and space. a Greek scholar (276-194 BC.). The word has
You will develop skills to understand the globe been derived from two roots from Greek
converted into maps and have a visual sense language geo (earth) and graphos (description).
GEOGRAPHY AS A DISCIPLINE 3
Put together, they mean description of the earth. changing earth and untiring and ever-active
The earth has always been seen as the abode human beings. Primitive human societies were
of human beings and thus, scholars defined directly dependent on their immediate
geography as, “the description of the earth as environment. Geography, thus, is concerned
the abode of human beings”. You are aware of with the study of Nature and Human
the fact that reality is always multifaceted and interactions as an integrated whole. ‘Human’
the ‘earth’ is also multi-dimensional, that is is an integral part of ‘nature’ and ‘nature’ has
why many disciplines from natural sciences the imprints of ‘human’. ‘Nature’ has influenced
such as geology, pedology, oceanography, different aspects of human life. Its imprints can
botany, zoology and meteorology and a be noticed on food, clothing, shelter and
number of sister disciplines in social sciences occupation. Human beings have come to terms
such as economics, history, sociology, political with nature through adaptation and
science, anthropology, etc. study different modification. As you already know, the present
aspects of the earth’s surface. Geography is society has passed the stage of primitive
different from other sciences in its subject societies, which were directly dependent on
matter and methodology but at the same time, their immediate physical environment for
it is closely related to other disciplines. sustenance. Present societies have modified
Geography derives its data base from all the their natural environment by inventing and
natural and social sciences and attempts their using technology and thus, have expanded the
synthesis. horizon of their operation by appropriating and
We have noted that there exist variations utilising the resources provided by nature. With
over the surface of the earth in its physical as the gradual development of technology, human
well as cultural environment. A number of beings were able to loosen the shackles of their
phenomena are similar and many are dissimilar. physical environment. Technology helped in
It was, therefore, logical to perceive geography reducing the harshness of labour, increased
as the study of areal differentiation. Thus, labour efficiency and provided leisure to
geography was perceived to study all those human beings to attend to the higher needs of
phenomena which vary over space. life. It also increased the scale of production
Geographers do not study only the variations and the mobility of labour.
in the phenomena over the earth’s surface The interaction between the physical
(space) but also study the associations with environment and human beings has been very
the other factors which cause these variations. succinctly described by a poet in the following
For example, cropping patterns differ from dialogue between ‘human’ and ‘nature’ (God).
region to region but this variation in cropping You created the soil, I created the cup, you
pattern, as a phenomenon, is related to created night, I created the lamp. You created
variations in soils, climates, demands in the wilderness, hilly terrains and deserts; I
market, capacity of the farmer to invest and created flower beds and gardens. Human
technological inputs available to her/him. beings have claimed their contribution using
Thus, the concern of geography is to find out natural resources. With the help of technology,
the causal relationship between any two human beings moved from the stage of
phenomena or between more than one necessity to a stage of freedom. They have put
phenomenon. their imprints everywhere and created new
A geographer explains the phenomena in possibilities in collaboration with nature. Thus,
a frame of cause and effect relationship, as it we now find humanised nature and
does not only help in interpretation but also naturalised human beings and geography
foresees the phenomena in future. studies this interactive relationship. The space
The geographical phenomena, both the got organised with the help of the means of
physical and human, are not static but highly transportation and communication network.
dynamic. They change over time as a result of The links (routes) and nodes (settlements of all
the interactive processes between ever types and hierarchies) integrated the space and
4 FUNDAMENTALS OF PHYSICAL GEOGRAPHY
gradually, it got organised. As a social science present world is being perceived as a global
discipline, geography studies the ‘spatial village. The distances have been reduced by
organisation’ and ‘spatial integration’. better means of transportation increasing
Geography as a discipline is concerned with accessibility. The audio-visual media and
three sets of questions: information technology have enriched the data
(i) Some questions are related to the base. Technology has provided better chances
identification of the patterns of natural of monitoring natural phenomena as well as
and cultural features as found over the the economic and social parameters.
surface of the earth. These are the Geography as an integrating discipline has
questions about what? interface with numerous natural and social
(ii) Some questions are related to the sciences. All the sciences, whether natural or
distribution of the natural and human/ social, have one basic objective, of
cultural features over the surface of the understanding the reality. Geography
earth. These are the questions about attempts to comprehend the associations of
where? phenomena as related in sections of reality.
Figure 1.1 shows the relationship of geography
Taken together, both these questions take
with other sciences. Every discipline, concerned
care of distributional and locational aspects of
with scientific knowledge is linked with
the natural and cultural features. These
geography as many of their elements vary over
questions provided inventorised information of
space. Geography helps in understanding the
what features and where located. It was a very
reality in totality in its spatial perspective.
popular approach during the colonial period.
Geography, thus, not only takes note of the
These two questions did not make geography
differences in the phenomena from place to
a scientific discipline till the third question was
place but integrates them holistically which
added. The third question is related to the
may be different at other places. A geographer
explanation or the causal relationships
is required to have a broad understanding of
between features and the processes and
all the related fields, to be able to logically
phenomena. This aspect of geography is related
integrate them. This integration can be
to the question, why?
understood with some examples. Geography
Geography as a discipline is related to
influences historical events. Spatial distance
space and takes note of spatial characteristics
itself has been a very potent factor to alter the
and attributes. It studies the patterns of
course of history of the world. Spatial depth
distribution, location and concentration of
provided defence to many countries,
phenomena over space and interprets them
particularly in the last century. In traditional
providing explanations for these patterns. It
warfare, countries with large size in area, gain
takes note of the associations and inter-
time at the cost of space. The defence provided
relationships between the phenomena over
by oceanic expanse around the countries of
space and interprets them providing
the new world has protected them from wars
explanations for these patterns. It also takes
being imposed on their soil. If we look at the
note of the associations and inter-relationships
historical events world over, each one of them
between the phenomena resulting from the
can be interpreted geographically.
dynamic interaction between human beings
In India, Himalayas have acted as great
and their physical environment.
barriers and provided protection but the
passes provided routes to the migrants and
GEOGRAPHY AS AN INTEGRATING DISCIPLINE invaders from Central Asia. The sea coast has
Geography is a discipline of synthesis. It encouraged contact with people from East and
attempts spatial synthesis, and history Southeast Asia, Europe and Africa. Navigation
attempts temporal synthesis. Its approach is technology helped European countries to
holistic in nature. It recognises the fact that colonise a number of countries of Asia and
the world is a system of interdependencies. The Africa, including India as they got accessibility
GEOGRAPHY AS A DISCIPLINE 5
through oceans. The geographical factors have econometrics. Maps are prepared through
modified the course of history in different parts artistic imagination. Making sketches, mental
of the world. maps and cartographic work require
Every geographical phenomenon undergoes proficiency in arts.
change through time and can be explained
temporally. The changes in landforms, climate, Geography and Social Sciences
vegetation, economic activities occupations and
Each social science sketched in Figure 1.1has
cultural developments have followed a definite
interface with one branch of geography. The
historical course. Many geographical features
result from the decision making process by relationships between geography and history
different institutions at a particular point of have already been outlined in detail. Every
time. It is possible to convert time in terms of discipline has a philosophy which is the raison
space and space in terms of time. For example, d’etre for that discipline. Philosophy provides
it can be said that place A is 1,500 km from roots to a discipline and in the process of its
place B or alternately, it can also be said that evolution, it also experiences distinct historical
place A is two hours away (if one travels by processes. Thus, the history of geographical
plane) or seventeen hours away (if one travels thought as mother branch of geography is
by a fast moving train). It is for this reason, included universally in its curricula. All the
time is an integral part of geographical studies social science disciplines, viz. sociology,
as the fourth dimension. Please mention other political science, economics and demography
three dimensions? study different aspects of social reality. The
Figure1.1 amply depicts the linkages of
branches of geography, viz. social, political,
geography with different natural and social
economic and population and settlements are
sciences. This linkage can be put under two
closely linked with these disciplines as each
segments.
one of them has spatial attributes. The core
concern of political science is territory, people
Physical Geography and Natural Sciences
and sovereignty while political geography is
All the branches of physical geography, as also interested in the study of the state as a
shown in Figure 1.1, have interface with natural spatial unit as well as people and their political
sciences. The traditional physical geography behaviour. Economics deals with basic
is linked with geology, meteorology, hydrology attributes of the economy such as production,
and pedology, and thus, geomorphology, distribution, exchange and consumption. Each
climatology, oceanography and soil geography of these attributes also has spatial aspects and
respectively have very close link with the
here comes the role of economic geography to
natural sciences as these derive their data from
study the spatial aspects of production,
these sciences. Bio-Geography is closely related
distribution, exchange and consumption.
to botany, zoology as well as ecology as human
Likewise, population geography is closely
beings are located in different locational niche.
linked with the discipline of demography.
A geographer should have some proficiency
The above discussion shows that
in mathematics and art, particularly in drawing
geography has strong interface with natural
maps. Geography is very much linked with the
and social sciences. It follows its own
study of astronomical locations and deals with
methodology of study which makes it distinct
latitudes and longitudes. The shape of the earth
from others. It has osmotic relationship with
is Geoid but the basic tool of a geographer is a
other disciplines. While all the disciplines have
map which is two dimensional representation
their own individual scope, this individuality
of the earth. The problem of converting geoids
into two dimensions can be tackled by does not obstruct the flow of information as in
projections constructed graphically or case of all cells in the body that have individual
mathematically. The cartographic and identity separated by membranes but the flow
quantitative techniques require sufficient of blood is not obstructed. Geographers use
proficiency in mathematics, statistics and data obtained from sister disciplines and
6 FUNDAMENTALS OF PHYSICAL GEOGRAPHY
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GEOGRAPHY AS A DISCIPLINE 7
attempt synthesis over space. Maps are very BRANCHES OF GEOGRAPHY (BASED ON
effective tools of geographers in which the SYSTEMATIC APPROACH)
tabular data is converted into visual form to
bring out the spatial pattern.
1. Physical Geography
BRANCHES OF GEOGRAPHY (i) Geomorphology is devoted to the study
of landforms, their evolution and related
Please study Figure 1.1 for recapitulation. It has
processes.
very clearly brought out that geography is an (ii) Climatology encompasses the study of
interdisciplinary subject of study. The study of structure of atmosphere and elements
every subject is done according to some of weather and climates and climatic
approach. The major approaches to study types and regions.
geography have been (i) Systematic and (iii) Hydrology studies the realm of water
(ii) Regional. The systematic geography approach over the surface of the earth including
is the same as that of general geography. This oceans, lakes, rivers and other water
approach was introduced by Alexander Von bodies and its effect on different life
Humboldt, a German geographer (1769-1859) forms including human life and their
while regional geography approach was activities.
developed by another German geographer and a (iv) Soil Geography is devoted to study the
contemporary of Humboldt, Karl Ritter processes of soil formation, soil types,
their fertility status, distribution and
(1779-1859).
use.
In systematic approach (Figure 1.2), a
phenomenon is studied world over as a whole,
2. Human Geography
and then the identification of typologies or
spatial patterns is done. For example, if one is (i) Social/Cultural Geography encom-
interested in studying natural vegetation, the passes the study of society and its
study will be done at the world level as a first spatial dynamics as well as the cultural
step. The typologies such as equatorial rain elements contributed by the society.
forests or softwood conical forests or monsoon (ii) Population and Settlement Geography
forests, etc. will be identified, discussed and (Rural and Urban). It studies population
delimited. In the regional approach, the world growth, distribution, density, sex ratio,
migration and occupational structure
is divided into regions at different hierarchical
etc. Settlement geography studies the
levels and then all the geographical phenomena
characteristics of rural and urban
in a particular region are studied. These
settlements.
regions may be natural, political or designated
(iii) Economic Geography studies economic
region. The phenomena in a region are studied
activities of the people including
in a holistic manner searching for unity in
agriculture, industry, tourism, trade,
diversity.
and transport, infrastructure and
Dualism is one of the main characteristics
services, etc.
of geography which got introduced from the
(iv) Historical Geography studies the
very beginning. This dualism depended on the
historical processes through which the
aspect emphasised in the study. Earlier scholars
space gets organised. Every region has
laid emphasis on physical geography. But
undergone some historical experiences
human beings are an integral part of the earth’s
before attaining the present day status.
surface. They are part and parcel of nature. They The geographical features also
also have contributed through their cultural experience temporal changes and these
development. Thus developed human form the concerns of historical
geography with emphasis on human activities. geography.
8 FUNDAMENTALS OF PHYSICAL GEOGRAPHY
Figure 1.2 : Branches of geography based on systematic approach
(v) Political Geography looks at the space 3. Biogeography
from the angle of political events and
The interface between physical geography
studies boundaries, space relations
and human geography has lead to the
between neighbouring political units, development of Biogeography which
delimitation of constituencies, election includes:
scenario and develops theoretical (i) Plant Geography which studies the
framework to understand the political spatial pattern of natural vegetation in
behaviour of the population. their habitats.
GEOGRAPHY AS A DISCIPLINE 9
(ii) Zoo Geography which studies the (c) Field Survey Methods
spatial patterns and geographic (d) Geo-informatics comprising
characteristics of animals and their techniques such as Remote
habitats. Sensing, GIS, GPS, etc.
(iii) Ecology /Ecosystem deals with the
The above classification gives a
scientific study of the habitats
comprehensive format of the branches of
characteristic of species.
geography. Generally geography curricula is
(iv) Environmental Geography concerns
taught and learnt in this format but this
world over leading to the realisation of
format is not static. Any discipline is bound
environmental problems such as land
to grow with new ideas, problems, methods
gradation, pollution and concerns for
and techniques. For example, what was once
conservation has resulted in the
introduction of this new branch in manual cartography has now been
geography. transformed into computer cartography.
Technology has enabled scholars to handle
BRANCHES OF GEOGRAPHY BASED ON REGIONAL large quantum of data. The internet provides
APPROACH (FIGURE1.3) extensive information. Thus, the capacity to
attempt analysis has increased tremendously.
1. Regional Studies/Area Studies
Comprising Macro, Meso and Micro GIS has further opened vistas of knowledge.
Regional Studies GPS has become a handy tool to find out exact
2. Regional Planning locations. Technologies have enhanced the
Comprising Country/Rural and Town/ capacity of attempting synthesis with sound
Urban Planning theoretical understanding.
3. Regional Development You will learn some preliminary aspects of
4. Regional Analysis these techniques in your book, Practical work
There are two aspects which are common
in Geography – Part I (NCERT, 2006). You will
to every discipline, these are:
continue to improve upon your skills and
(i) Philosophy
learn about their application.
(a) Geographical Thought
(b) Land and Human Interaction/
PHYSICAL GEOGRAPHY AND ITS IMPORTANCE
Human Ecology
(ii) Methods and Techniques This chapter appears in the book entitled
(a) Cartography including Computer Fundamentals of Physical Geography. The
Cartography contents of the book clearly reflect its scope.
(b) Quantitative Techniques/Statistical It is therefore, appropriate to know the
Techniques importance of this branch of geography.
Figure 1.3 : Branches of geography based on regional approach