NCERT CLASS 11: Notes on Fundamentals of Physical Geography
CONTENTS
FOREWORD UNIT I : GEOGRAPHY AS A DISCIPLINE
1. Geography as a Discipline UNIT II : THE EARTH
2. The Origin and Evolution ofthe Earth
3. Interior of the Earth
4. Distribution ofOceans and Continents UNIT III : LANDFORMS
5. Minerals and Rocks
6. Geomorphic Processes
7. Landforms and their Evolution UNIT IV : CLIMATE
8. Composition and Structure ofAtmosphere
9. Solar Radiation, Heat Balance and Temperature
10. Atmospheric Circulation and Weather Systems
11. Water in the Atmosphere
12. World Climate and Climate Change UNIT V : WATER (OCEANS)
13. Water (Oceans)
14. Movements of OceanWater UNIT VI : LIFE ON THE EARTH
15. Life on the Earth
16. Biodiversity and Conservation
Chapter-1-GEOGRAPHY AS A DISCIPLINE
What is Geography? Geography is concerned with the description and explanation of the areal
differentiation ofthe earth’s surface.is important for human beings.
Landformsprovide the base on which human activities arelocated. The plains are utilised
for agriculture.
Plateaus provide forests and minerals.
Mountains provide pastures, forests, touristspots and are sources ofrivers providing
waterto lowlands.
BRANCHES OF GEOGRAPHY
1. Physical Geography
(i) Geomorphology is devoted to the study oflandforms, their evolution and relatedprocesses.
(ii) Climatology encompasses the study ofstructure of atmosphere and elementsof weather
and climates and climatic types and regions.
(iii) Hydrology studies the realm ofwater over the surface of the earth includingoceans,
lakes, rivers and other waterbodies and its effect on different life forms including
human life and theiractivities.
(iv) SoilGeographyis devotedto studythe processes ofsoil formation, soil types, their
fertility status, distribution anduse.
2. Human Geography
(i) Social/Cultural Geography encom- passes the study of society and itsspatial dynamics
as well as the culturalelements contributed by the society.
(ii) Population andSettlementGeography (Rural and Urban). It studies populationgrowth,
distribution, density, sex ratio, migration and occupational structureetc. Settlement
geography studies thecharacteristics of rural and urbansettlements.
(iii) Economic Geography studies economic activities of the people including agriculture,
industry, tourism, trade, and transport, infrastructure andservices, etc.
(iv) Historical Geography studies the historical processes through which the space gets
organised. Every region has undergone some historical experiences before attaining the
present day status. The geographical features also experience temporal changes and
these form the concerns of historicalgeography.
(v) Political Geography looks at the space from the angle of political events and studies
boundaries, space relations between neighbouring political units,delimitation of
constituencies, election scenario and develops theoretical frameworkto understand
the political behaviour of the population.
3. Biogeography
The interface between physical geography and human geography has lead to thedevelopment
of Biogeography which includes:
(i) Plant Geography which studies the spatial pattern of natural vegetation intheir habitats.
(ii) Zoo Geography which studies the spatial patterns and geographiccharacteristics of
animals and theirhabitats.
(iii) Ecology /Ecosystem deals with the scientific study of the habitats characteristic ofspecies.
Chapter-2 THE EARTH
THE ORIGIN AND EVOLUTION OF THE EARTH:-EARLY THEORIES-
NebularHypothesis- by German philosopher Immanuel Kant. Mathematician Laplace revised it in
1796.
The hypothesis considered that the planets were formed out of a cloud ofmaterial associated
with a youthful sun, whichwas slowly rotating. Later in 1900, Chamberlainand Moulton
considered that a wandering star approached the sun.
As a result, a cigar-shapedextension of material was separated from thesolar surface.
As the passing star moved away,the material separated from the solar surfacecontinued to
revolve around the sun and it slowly condensed into planets
Binary theories- the argumentsconsidered of a companion to the sun to have
been coexisting.
Revised Nebular Hypothesis- By Otto Schmidt in Russia and Carl Weizascar in
Germany
They considered thatthe sun was surrounded by solar nebulacontaining mostly the
hydrogen and heliumalong with what may be termed as dust.
Thefriction and collision ofparticles ledto formation of a disk-shaped cloud and the planets
wereformed through the process ofaccretion.
MODERN THEORIES
Origin of the Universe:-
1. BigBangTheory- also called expanding universe hypothesis.
In the beginning, all matter forming the universe existed in one place in the formofa “tiny ball”
(singular atom) with an unimaginably small volume, infinite temperature and infinite density.
At the Big Bang the “tiny ball” exploded violently. This led to a huge expansion. It is now
generally accepted that theevent ofbig bang took place 13.7 billion years before the present. The
expansioncontinues even to the present day. As itgrew, some energy was converted into matter.
There was particularly rapidexpansion within fractions ofa second after the bang.
Thereafter, the expansion has slowed down. Within first three minutes from the Big Bang event,
the first atom began to form.
Within 300,000 years from the Big Bang, temperature dropped to 4,500 K(Kelvin)
and gave rise to atomic matter. The universe became transparent.
The expansion of universe means increase in space between the galaxies. An
alternative to this was Hoyle’s concept of steady state. It considered the universe to
be roughly the same at any point of time. However, with greater
evidence becoming available about the expanding universe, scientific community at
present favours argument of expanding universe.
The Star Formation
The distribution ofmatter and energy was noteven in the early universe.
These initial density differences gave rise to differences in gravitational forces and
it caused the matterto get drawn together. These formed the bases for development of
galaxies.
A galaxy contains a large number of stars. Galaxies spread overvast distances that are
measured in thousands of light-years.
A galaxy starts to form by accumulationof hydrogen gas in the form of a very large
cloud called nebula.
Eventually, growing nebula develops localized clumps ofgas.
Theseclumps continue to grow into even densergaseous bodies, giving rise to
formation ofstars. The formation ofstars is believed to havetaken place some 5-6
billion years ago.
A light year is a measure of distance andnot of time.
Light travels at a speed of 300,000 km/second. Considering this, the distances the
light will travel in one year is taken to be one light year. This equals to 9.461
1012 km. The meandistance between the sun and the earthis 149,598,000 km. In
terms of lightyears, it is 8.311 minutes.
Formation of Planets:-
The following are considered to be the stages in the development ofplanets :
The stars are localised lumps of gas within a nebula. The gravitational force within the
lumps leads to the formationof a core to the gas cloud and a huge rotating disc of gas
and dust developsaround the gas core.
the gas cloud starts getting condensed and the matter around the core develops into
small- rounded objects. These small-roundedobjectsbytheprocess ofcohesiondevelop in the
same period sometime about 4.6 billion years ago.
Planetesimals are a large number ofsmaller bodies.
Till recently (August 2006), Pluto was alsoconsideredaplanet. However, inameeting of
the International Astronomical Union, a decisionwas takenthatPlutolikeother
celestial into what is called planetesimals.objects
these large number ofsmall planetesimals accrete to form afewer large bodies in the
form ofplanets.
OUR SOLAR SYSTEM
Our Solar system consists ofeight planets.
Thenebula from which our Solar system is supposedto have been formed, started its collapse and
coreformation some time 5-5.6 billion years ago andthe planets were formed about 4.6 billion
yearsago.
Our solar system consists of the sun (the star), 8 planets, 63 moons, millions of smallerbodies
like asteroids and comets and huge quantity of dust-grains and gases.
Out of the eight planets, mercury, venus, earth and mars are called as the inner planets as they lie
between the sun and the belt ofasteroids the otherfourplanets are calledthe outerplanets.
Alternatively, the first four are called Terrestrial, meaning earth-like as theyare made up ofrock
and metals, and have relatively highdensities.
The rest four are called Jovian or Gas Giant planets. Jovian means jupiter-like. Mostof them are
much larger than the terrestrialplanets and have thick atmosphere, mostly ofheliumand
hydrogen.
All the planets were formedmaybe called‘dwarfplanet’. Somedataregarding
our solar system are given in the box below.
The difference between terrestrial and jovian planets can be attributed to the followingconditions:
(i) Theterrestrialplanetswereformedinthe close vicinityofthe parentstarwhere it was too
warm for gases to condense to solid particles. Jovian planets were formed at quite a distant
location.
(ii) The solar wind was most intense nearerthe sun; so, it blew offlots ofgas and dustfromthe
terrestrialplanets. The solarwindswere not all that intense to cause similarremoval ofgases from
the Jovianplanets.
(iii) The terrestrial planets are smaller and their lower gravity could not hold the escaping
gases
The Moon
only natural satellite of the earth. Early theory:-
In 1838, Sir George Darwin suggested that initially, the earth and the moon formed asingle
rapidly rotating body.
The whole mass became a dumb-bell-shaped body and eventually it broke.
It was also suggested that the material forming the moon was separated from what we
have at present the depression occupied by the Pacific Ocean.
Giant impact’ “the bigsplat Theory :-
A body ofthe size ofone to three times that ofmars collided into the earth sometime shortly
after the earth was formed. It blasted a large part of the earth into space.
This portion ofblasted material then continued to orbit the earth and eventually formed
into the present moon about 4.44 billion years ago.