1. The document describes the structure of the universe from the largest scale of billions of galaxies down to Earth's place in the Milky Way galaxy and solar system. It discusses the internal structure of Earth and how the continental drift theory explains the movement of crustal plates over time. 2. Key points covered include that Earth is able to support life because it receives the right amount of heat and light from the Sun, has water, and an atmosphere that regulates temperature. The continental drift theory proposes that Earth's crust is broken into plates that were once joined together in a supercontinent called Pangea before drifting apart. 3. Threats to Earth's fragile environment from human activity like pollution and overuse of resources

1. Chapter # 2
Our Home: The Earth

2. Our world is tiny speck in the universe. The
universe stretches away from us in all
directions. We do not know how big it is.
Most scientists believe that the universe came
into being about 15 billion years ago. It came
about in a gigantic explosion called the BIG
BANG.

3. •In the universe, there are billion of galaxies
scattered to the limits of the observable
universe.
•A galaxy is a community of stars.
•The MILKY WAY is an example of a galaxy
with a spiral shape.

4. There are three categories of galaxies, grouped
according to their shape:
•SPIRAL: They look like flat disks and bulges in
the center.

5. •ELLIPTICAL: They are more rounded often longer
in one direction.

6. •IRREGULAR: They appear neither disk-like nor
rounded.

7. •The sun is just one of the billion of stars within the
Milky Way Galaxy.
•The Milky Way is one of the 30 galaxies in as ‘cluster’
of galaxies called the LOCAL GROUP.
•Earth and the other planets came from the matter
that was left behind during the sun’s formation.

8. THE SOLAR SYSTEM AND THE
EARTH

9. •The Solar system is consisting of the Sun and
the other eight planets.
•The Sun is star lying at the center of the Solar
System.
•Other planets of the solar system are:

11. •Earth is the third planet of the solar system.
•The further away the planet is from the Sun
the lower the average temperature.

12. THE QUESTION IS WHY?
It is because those planets which are near to the Sun
receive more direct sunlight that’s why there
temperature is very hot such as Mercury , and the
planets which are further away from the Sun receive
less amount of sunlight such as Neptune.
The Earth has the lowest average temperature at 15
C.

13. WHY IS LIFE POSSIBLE ON
EARTH?
•Earth is the only planet in the Solar System
suitable for living things.
HOW?

14. The answer is,
The living things can only stay alive and grow when
water and air are present and the temperature is
right. There are elements that make up the
atmosphere. Among them are
•Air
•Temperature
•Vapor
•Rainfall
•Wind

16. •It gets the right amount of Sunlight from the
SUN.
•It has an atmosphere to help absorb heat from
the sun so that it will not be too hot.
•The atmosphere also helps to prevent the loss of
heat at night. That keeps it warm.
•It also has water that all living things need.

17. BUT!
•Mercury is not suitable for living things, as it
can be as cold as -175 C and as hot as 400 C.
•The sun is the source of giving us suitable
amount of heat which is required for living
things of the Earth.
•But what is the source of water on
Earth?

18. •Our Earth has freshwater in its rivers and lakes. All
living things need water for survival.
•About 70% of the Earth’s surface is covered with
water.
•97% of the water is saltwater
•3% is the freshwater
•Out of that 3% is found in rivers and lakes and the
other 2% is frozen in the form of ice sheets and
glaciers.

19. OCEANS AND CONTINENTS
Oceans are the lager bodies of water whose waters are the salty
water.

20. Continents are the lager land
masses of the Earth.

21. FORMATION OF THE
CONTINENTS

22. THE CONTINENETAL DRIFT THEORY
•The Earth’s outer layer is broken into great pieces called
‘crustal plates’.
•Scientists believed that once these pieces of the Earth’s crust
were joined together to form a huge land mass called PANGEA
(meaning ‘all land’ in Greek.
•Alferd Wegener was the first person who proposed that the
separate pieces of the Earth’s crust were once a huge land mass
and they gradually moved apart.
•This theory is called the ‘THE CONTINENTAL DRIFT
THEORY’.

25. THE INTERNAL STRUCTURE
OF THE EARTH

26. The Earth is not a solid mass. It is consists of three
basic layers
1. CRUST
•The crust is the outer most layer of the Earth.
•It is solid and varies in thickness from 6 to 70 km.
•It’s not a continuous layer it is broken into many
pieces.
•Theses pieces are called “CRUSTAL PLATES’’ ‘
•These pieces of the Earth’s crust float on the semiliquid mantle and are continuously moving.

27. 2. MANTLE
•It is a semi-liquid layer.
•Temperature here can reach up to 2000 C.
•The pieces of the Earth’s crust float on the
mantle.
•It is very hot and the heat causes ‘convection
currents’ to be formed here.
•Convection currents cause the plates to move.

28. CONVECTION CURRENTS

29. 3. CORE
•The core forms the centre
of the Earth.
•It is solid.
•The temperature here can
be as high as 5,000 C.

30. Evidences to support continental
drift theory

31. 1. FOSSILS.
Fossils of plants and reptiles have been found in Africa
and South America. This proves that these two
continents were once close to each other or were even
joined together, allowing animals like reptiles to travel
from one continent to the other easily.

32. 2. MINERALS
AND ROCKS
Scientists have matched rocks and minerals from
continents thought to have been separated. The rocks
and minerals have been found to be the same although
they are taken from different continents that are
separated by oceans.

33. •3. COAL DISTRIBUTION
•Coal can be found buried under the thick layers of snow and ice in the
Antarctica although it can only be formed in warm and wet conditions.
•It is fossil fuel formed million of years ago from trees, moss and other
vegetation.
•These plants were covered by layers of soil and rock.
•The pressure and heat gradually changed these buried plants into coal.
•The presence of coal in the cold and dry Antarctica means that once
Antarctica was joined together with the other continents as part of
Pangea and was in a hot and wet region.
•Coal was formed before Antarctic plate drifted away to its present
location.

34. OUR FRAGILE EARTH
WHAT DOES IT MEAN?

35. The answer is
Our Erath is full of resources e.g.
Water, oil, minerals, coal, gas , petrol etc
Many of these resources take billions of years to form .e.g coal
and oil.
There are some resources which are once used can not be
formed again such as water
So , with the increase in population
And the passing of time these resources are becoming less and a
time will come when they will become scarce.
We need to plan carefully how we use these resources so that
they can last long.

36. ANOTHER PROBLEM
Besides taking the Earth’ s resources , humans have
also dramatically changed the environment on the
Earth withy their activities.
Increase in the population cause clearing of
land for
•Farming
•Industries
•Fields
•Buildings etc.

37. Increase in population also cause
•Noise pollution
•Air pollution
•Water pollution
•Land pollution

38. NOISE POLLUTION

39. WATER POLLUTION

40. AIR POLLUTION

42. Now it is very difficult to correct the damage that is done to the
environment but we can help to reduce further destruction.

43. END NOTE
The Earth can provide us with what we
need.But we must not waste what we take
from it.Resources are precious and it is
our responsibility is to make good use of
them.

44. TAKE CARE OF OUR HOME
FOR WE HAVE ONLY ONE
EARTH

45. Universe
Billions of galaxies
Local Groups (30 galaxies)
The Milky Way
Billions of stars
(the Sun and the Solar system)
The Solar System
The
Sun
Mercury
Structure
– Core
- Mantle
- Crust
Continental Drift Theory
Venus
Earth
Jupiter
Saturn
Temperature
-Receives the right amount of
heat and light from the Sun
-- Suitable for light on Earth
Fragile Earth
Uranus
Neptune
Water
-Fresh water in rivers and
lakes
-- suitable for life on Earth

46. Q1. Define galaxy and Milky Way also
define the three categories of galaxies.
Q2. Why is life possible on Earth?
Q3. What is Pangea?
Q4. What does the Continental Drift
Theory tell us?

47. Q5. Write the procedure of
the formation of coal.
Q6. What is a plate
boundary?