1. PLANET EARTH IN A NUTSHELL
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2. EARTH: THE ONLY ABODE OF LIFE
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3. A UNIQUE PLANET
 Situated at the right distance from the Sun.
 Has oceans of liquid water on surface.
 Green vegetation provides life-supporting
oxygen.
 Wind and ocean currents maintain heat
balance and help moderate the temperature.
 Has a relatively large satellite that has tidal
effect.
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4. FROM A MOLTEN PAST
 Earth was formed some 4,500 million years
ago.
 Had no oceans, no oxygen in the atmosphere,
and no living beings.
 Heavy bombardment of rocks and internal
radioactive decay caused early Earth to melt.
 Heavier elements sank to the centre while
lighter ones rose to the surface, producing
Earth’s various layers.
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5. PEEPING INTO EARTH’S INTERIOR
Seismic waves
slow down when
they pass through
hot molten rocks
and speed up
while passing
through cold solid
rocks, which make
it possible to study
Earth’s inner
structure.
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6. LAYERS OF EARTH
From seismic
studies it is
known that the
Earth is
composed of
several layers,
somewhat like
the layers of
an onion.
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7. LAYERS OF EARTH
 The outermost layer is the crust, composed
mainly of compounds of aluminium and
silicates.
 The next layer is the mantle, composed mainly
of rocks containing iron and magnesium
silicates.
 The innermost layer is the core, made up of
mostly iron and nickel.
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8. LAYERS OF EARTH
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9. THE ‘SPHERES’ OF EARTH
 The crust and the upper portion of the mantle
are together known as the ‘lithosphere.’
 Much of Earth is covered by a layer of water or
ice called the ‘hydrosphere’.
 The thin layer of air that surrounds the Earth is
the ‘atmosphere’.
 The portion of the hydrosphere, atmosphere,
and solid land where life exists is together
known as the ‘biosphere’.
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10. EARTH’S MANTLE
 Unlike the crust, which is mostly hard rock, the
mantle is a highly viscous plastic-like material
that can flow.
 The molten mass in the mantle is in constant
motion, which makes the continental plates
move.
 The mantle is also the place where most
gemstones such as diamonds and garnets are
formed.
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11. EARTH’S CORE
 The core is divided into two layers, the outer
core and the inner core.
 Mainly made up of iron and nickel.
 Temperatures range from 4,000 to 7,500C.
 The outer core and the inner core together
produce Earth’s magnetism.
 Earth’s magnetism is what makes the magnetic
compass work.
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12. EARTH’S MOVING CONTINENTS
The German
meteorologist Alfred
Wegener had first
proposed in 1912
that the world’s
continents were
once joined together
in a giant
supercontinent
which he called
‘Pangaea.’
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13. MOVING CONTINENTS
Sometime around
200 million years
ago, Pangaea broke
up and the
fragments began to
move away from one
another, forming the
present-day
continents we see
today.
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14. FOOTPRINT OF CONTINENTS
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15. EARTH’S GRINDING PLATES
 Earth’s lithosphere, composed of a set of large
and small continental plates that are constantly
moving.
 When the plates move they either collide, or go
under the other, or slide past each other.
 Plate boundaries are subject to extreme
pressures and are the sites where violent
processes like earthquakes and volcanic
eruptions occur.
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16. FRACTURED EARTH
The moving plates give the Earth's crust the
appearance of a giant fractured globe.
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17. BUILDING MOUNTAINS
Where two
plates collide the
resulting
pressure is often
so great that it
deforms the
surface into folds
leading to
formation of high
mountain
ranges.
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18. RISE OF THE HIMALAYAS
Such collision
created a series of
long, parallel folds
in the Earth’s crust
 the Himalayan
range that
contains all the
worlds mountains
over 7,000 metres
in height.
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19. SPREADING SEA FLOOR
The mid-oceanic ridge is the region where Earth’s
crustal plates are moving apart, creating new ocean
floor.
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20. SEA FLOOR GOING UNDER
Destruction of ocean floor occurs at plate boundaries,
along areas called ‘subduction zones’ where oceanic
crust goes under either continental crust or oceanic
crust.
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21. RING OF FIRE
Subduction
zones are
regions of
high volcanic
activity and
have led to
the formation
of the
spectacular
mountain
chain around
the Pacific Ocean known as the ‘Ring of Fire.’
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22. DYNAMIC EARTH
 So, we now know that our Earth is a dynamic
planet.
 Directly or indirectly, plate tectonics influences
nearly all geologic processes.
 The knowledge of plate tectonics has given us
the power to understand violent geological
phenomena like earthquakes and volcanic
eruptions and to safeguard against loss of life
and property.
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23. EARTH’S PROTECTIVE ATMOSPHERE
 The Earth's atmosphere is a very thin layer of air
wrapped around a very large planet.
 Two gases make up the bulk of the Earth's
atmosphere: nitrogen (78%) and oxygen (21%).
Various trace gases make up the remainder.
 Based on temperature, the atmosphere is divided
into four layers: the troposphere, stratosphere,
mesosphere, and thermosphere.
 Energy is transferred between the Earth's surface
and the atmosphere via conduction, convection,
and radiation.
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24. A BLANKET OF AIR
One of the most vital components of Earth’s
immediate environment is its atmosphere 24

25. LAYERS OF EARTH’S ATMOSPHERE
The temperature of
the atmosphere
varies with height,
but not in a regular
manner.
The highest
temperature is
found in the
thermosphere,
which begins at an
altitude of 80 km.
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26. THE OZONE SHIELD
A layer of ozone
in the
stratosphere is
crucial to our
survival; this
layer filters out
harmful
ultraviolet rays
from the Sun.
But it is being
destroyed.
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27. WATER ON EARTH
The water of Earth's hydrosphere is not static;
it gets constantly recycled. Evaporation by
the Sun,
condensation
into cloud;
precipitation as
rain and flow
into rivers and
ocean maintain
the cycle.
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28. ROCKS OF MANY FORMS
 Rocks of Earth's lithosphere are mainly of three
types – sedimentary, metamorphic, and
igneous.
 The three types are constantly cycled through a
geological process known as the ‘rock cycle.’
 The process depends on temperature,
pressure, time and conditions within the Earth.
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29. EARTH’S ROCK CYCLE
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30. SEDIMENTARY ROCK
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31. METAMORPHIC ROCK
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32. IGNEOUS ROCK
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33. DAWN OF LIFE
 It is believed that all living organisms evolved
from single-cell organisms that appeared when
the first solid crust formed, almost 4,000 million
years ago.
 By 3,500 million years ago, the Earth’s oceans
were populated by one-celled organisms called
prokaryotes.
 In course of time, higher forms of life evolved
and today living forms occupy almost every nook
and corner of the globe.
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34. EARLIEST FOSSILS
Stromatolites are
a major
constituent of the
fossil record for
about the first
3.5 billion years
of life on Earth,
with their
abundance
peaking about
1,250 million
years ago.
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35. THE OXYGEN GIVERS
The atmosphere of early Earth did not have oxygen,
which appeared only after organisms called
cyanobacteria, commonly known as ‘blue-green
algae’ appeared about 3,000 million years ago.
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36. GREENING OF THE EARTH
 The earliest evidence of land plants and fungi
appears in the fossil record around 435 million
years ago.
 Plants play the most important part in the cycle
of nature.
 They are the only organisms that can make
their own food.
 All other animals including humans depend on
them for food.
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37. DIVERSE FORMS
 The first flowering plants – also called
angiosperms – appeared around 145 million
years ago
 Today, more than 250,000 species comprise
the Plant Kingdom.
 Some plants are so small they can barely be
seen. Others are taller than skyscrapers.
 Plants play an important role in the shaping of
the environment.
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38. ABUNDANCE OF LIFE
 As the oxygen level in atmosphere increased,
organisms, known as eukaryotes, appeared.
 Gradually, by 500 million years ago, there was
an explosion of multi-cellular organisms.
 By 435 million years ago the early vertebrates
had appeared in the ocean.
 By about 430 million years ago, primitive life
forms including plants and insects appeared on
land followed by spiders and amphibians.
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39. THE AGE OF DINOSAURS
Dinosaurs
emerged by
about 240
million years.
They were
reptiles and
most of them
hatched from
eggs.
But the dinosaurs were wiped out by a
cataclysmic event about 65 million years ago. 39

40. RISE OF MAMMALS
 The demise of the dinosaurs saw mammals
growing bigger and more diverse.
 Within 10,000,000 years after the death of the
dinosaurs, the world was filled with rodent-like
mammals, and large herbivorous and
carnivorous mammals.
 Around 1.8 million years ago, the earliest direct
ancestors of modern humans appeared in
Africa.
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41. THE HUMAN INVASION
 The first modern humans, Homo sapiens,
appeared on Earth about 195,000 years ago in
Africa.
 After spreading through Europe and Southeast
Asia, populations of modern humans moved
into North America in the north and Australia
in the south.
 Agriculture began about 12,000 years ago.
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42. EXPLODING POPULATIONS
 With the availability of assured food supply the
world population started rising sharply.
 From just one million in 10,000 BC it shot up to
27 million by 2000 BC. By AD 1000 it was 254
million.
 By AD 2000 the world population had crossed
the 6,000 million mark and is expected to
nearly double by 2050
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43. EXPLODING POPULATION
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44. THREAT TO EARTH’S BIOSPHERE
 Humans constitute only one of 4,500 species
of mammals that exist on Earth.
 The human species is only one species in the
estimated 30 to 100 million species that form
the Earth's complex biosphere.
 Yet, the damage that humans have wrought to
the biosphere is irreparable and may even spell
doom for many species.
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45. DISAPPEARING FORESTS
Despite their vital role as a carbon dioxide sink, the
tropical rainforests are being destroyed at a rate of
500,000 square km per year and will disappear soon.
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46. VANISHING WILDLIFE
Deforestation is also destroying the natural habitat
of several species, threatening their extinction.
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47. POLLUTED WATER BODIES
Indiscriminate discharge of industrial and domestic
waste in rivers and water bodies is seriously
degrading Earth’s water resources. 47

48. EARTH AS A HOT HOUSE
Increasing accumulation of
carbon dioxide in Earth’s
atmosphere due to burning
of fossil fuels has upset the
carbon dioxide balance in
the atmosphere, leading to
enhanced greenhouse
effect. This is causing the
Earth to get warmer, with
serious consequences.
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49. MELTING ICE CAPS
As the Earth heats up, Polar ice caps are melting,
threatening survival of several species. Warming of
the Poles also has serious impact on global weather.
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50. RECEDING GLACIERS
As the Earth becomes
hotter, glaciers are receding.
The Gangotri glacier, source
of the river Ganges, has
been receding at such an
alarming rate that
environmentalists fear that if
urgent measures are not
undertaken, a time may
come when the Ganges may
just disappear.
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51. SAVING PLANET EARTH
 Earth’s resources are limited; they need to be
conserved.
 Earth’s environment is fragile; it needs protection
from pollution and degradation.
 Carbon emission can be reduced by more
efficient use of energy and adoption of non-
conventional energy sources.
 For all living beings, including humans, the Earth
remains the only abode. It needs to be saved!
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52. Thank you!
Sandipan Dhar
Email id: sandipandhar@gmail.com
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