planet earth in a nutshell

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PLANET EARTH IN A NUTSHELL 1

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Page 1: Planet earth in a nutshell

PLANET EARTH IN A NUTSHELL

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Page 2: Planet earth in a nutshell

EARTH: THE ONLY ABODE OF LIFE

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Page 3: Planet earth in a nutshell

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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Page 4: Planet earth in a nutshell

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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Page 5: Planet earth in a nutshell

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.5

Page 6: Planet earth in a nutshell

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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Page 7: Planet earth in a nutshell

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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Page 8: Planet earth in a nutshell

LAYERS OF EARTH

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Page 9: Planet earth in a nutshell

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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Page 10: Planet earth in a nutshell

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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Page 11: Planet earth in a nutshell

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 7,500C.

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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Page 12: Planet earth in a nutshell

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.’ 12

Page 13: Planet earth in a nutshell

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.13

Page 14: Planet earth in a nutshell

FOOTPRINT OF CONTINENTS

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Page 15: Planet earth in a nutshell

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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Page 16: Planet earth in a nutshell

FRACTURED EARTH

The moving plates give the Earth's crust the

appearance of a giant fractured globe.16

Page 17: Planet earth in a nutshell

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.17

Page 18: Planet earth in a nutshell

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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Page 19: Planet earth in a nutshell

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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Page 20: Planet earth in a nutshell

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.20

Page 21: Planet earth in a nutshell

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.’21

Page 22: Planet earth in a nutshell

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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Page 23: Planet earth in a nutshell

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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Page 24: Planet earth in a nutshell

A BLANKET OF AIR

One of the most vital components of Earth’s

immediate environment is its atmosphere24

Page 25: Planet earth in a nutshell

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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Page 26: Planet earth in a nutshell

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.26

Page 27: Planet earth in a nutshell

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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Page 28: Planet earth in a nutshell

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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Page 29: Planet earth in a nutshell

EARTH’S ROCK CYCLE

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Page 30: Planet earth in a nutshell

SEDIMENTARY ROCK

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Page 31: Planet earth in a nutshell

METAMORPHIC ROCK

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Page 32: Planet earth in a nutshell

IGNEOUS ROCK

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Page 33: Planet earth in a nutshell

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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Page 34: Planet earth in a nutshell

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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Page 35: Planet earth in a nutshell

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.35

Page 36: Planet earth in a nutshell

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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Page 37: Planet earth in a nutshell

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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Page 38: Planet earth in a nutshell

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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Page 39: Planet earth in a nutshell

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

Page 40: Planet earth in a nutshell

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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Page 41: Planet earth in a nutshell

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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Page 42: Planet earth in a nutshell

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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Page 43: Planet earth in a nutshell

EXPLODING POPULATION

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Page 44: Planet earth in a nutshell

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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Page 45: Planet earth in a nutshell

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.45

Page 46: Planet earth in a nutshell

VANISHING WILDLIFE

Deforestation is also destroying the natural habitat

of several species, threatening their extinction.46

Page 47: Planet earth in a nutshell

POLLUTED WATER BODIES

Indiscriminate discharge of industrial and domestic

waste in rivers and water bodies is seriously

degrading Earth’s water resources. 47

Page 48: Planet earth in a nutshell

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.48

Page 49: Planet earth in a nutshell

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.49

Page 50: Planet earth in a nutshell

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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Page 51: Planet earth in a nutshell

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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Page 52: Planet earth in a nutshell

Thank you!

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Sandipan DharEmail id: [email protected]