The Earth formed around 4.5 billion years ago. It is the third planet from the sun and the only known planet capable of sustaining life. The Earth has a molten iron core, a solid silicate mantle, and a crust consisting of tectonic plates that migrate across the surface over millions of years. The Earth's atmosphere, hydrosphere, and biosphere support around 8.7 million known species of life. Humans depend on the biosphere and minerals of the Earth, though pollution poses threats to both the environment and human health.

1. THE EARTH

2. The Earth
Earth, also known as the world, Terra, or Gaia, is
the third planet from the Sun, the densest planet
in the Solar System, the largest of the Solar
System's four terrestrial planets, and the only
celestial body known to accommodate life. It is
home to about 8.74 million species. There are
billions of humans who depend upon its
biosphere and minerals.

3. Formation of the Earth
Earth was formed around four and a half billion
years ago. Within its first billion years, life
appeared in its oceans and began to affect its
atmosphere and surface, promoting the
proliferation of aerobic as well as anaerobic
organisms and causing the formation of the
atmosphere's ozone layer.

4. Composition and structure
Earth's lithosphere is divided into several rigid segments,
or tectonic plates, that migrate across the surface over
periods of many millions of years. Over 70% percent of
Earth's surface is covered with water, with the remainder
consisting of continents and islands which together have
many lakes and other sources of water that contribute to
the hydrosphere. Earth's poles are mostly covered with ice
that is the solid ice of the Antarctic ice sheet and the sea
ice that is the polar ice packs. The planet's interior remains
active, with a solid iron inner core, a liquid outer core that
generates the magnetic field, and a thick layer of relatively
solid mantle.

5. Composition and structure
Earth is a terrestrial planet, meaning that it is a
rocky body, rather than a gas giant like Jupiter.
It is the largest of the four terrestrial planets in
size and mass. Of these four planets, Earth
also has the highest density, the highest
surface gravity, the strongest magnetic field,
and fastest rotation, and is probably the only
one with active plate tectonics.

6. Other objects interacting with the Earth
Earth gravitationally interacts with other objects
in space, especially the Sun and the Moon.
During one orbit around the Sun, the Earth
rotates about its own axis 366.26 times,
creating 365.26 solar days, or one sidereal
year. The Moon is Earth's only natural satellite.
It began orbiting the Earth about 4.53 billion
years ago.

7. Shape
The mass of the Earth is approximately
5.98×1024 kg. It is composed mostly of iron,
oxygen, silicon, magnesium, sulfur, nickel,
calcium, and aluminium. Due to mass
segregation, the core region is believed to be
primarily composed of iron, with smaller
amounts of nickel, sulfur, and less than 1%
trace elements.

8. Layers
The Earth is divided into layers: the
Lithosphere, the Crust, the Upper Mantle, the
Mantle, the Asthenosphere, the Outer Core and
the Inner Core.

10. Pollution
Clouds of choking smog; beaches coated in oil;
rivers turned red by chemicals. All of these are
obvious examples of pollution. However, not all
types of pollution are easily seen. For example,
invisible plumes of gas may drift over our towns
and cities. They can cause asthma and chest
problems. They can also kill trees.

11. Pollution
Another problem is finding out the size of the
area affected. Winds can blow pollutants
across thousands of kilometres, from one side
of an ocean to the other. Chemicals flowing
down large rivers can pollute many countries
on their way to the sea.

12. Effects of pollution
1. Environment Degradation.
2. Human Health.
3. Global Warming: The increase in CO2 leads to melting
of polar ice caps which increases the sea level and pose
danger for the people living near coastal areas.
4. Ozone Layer Depletion: Ozone layer is the thin shield
high up in the sky that stops ultra violet rays from reaching
the earth. As a result of human activities, chemicals were
released into the atmosphere which contributed to the
depletion of ozone layer.

13. We must help the world!
Greenpeace is an independent global campaigning
organisation that acts to change attitudes and
behaviour, to protect and conserve the environment
and to promote peace. It is present in 40 countries
across Europe, the Americas, Asia, Africa and the
Pacific.
Greenpeace exists because this fragile earth deserves
a voice. It needs solutions. It needs change. It needs
action.

14. The Big Bang
The Big Bang Theory is the leading explanation
about how the universe began. At its simplest,
it talks about the universe as we know it
starting with a small singularity, then inflating
over the next 13.8 billion years to the cosmos
that we know today. The Big Bang theory
speculates that out of a great chaotic explosion
came all of the order and complexity that we
see around us today, with no intelligence
required to plan out, design or build anything.

16. In some years...
If we continue with pollution live won´t be
possible because the clima won´t be
appropiate. We wouldn´t be able to breath and
if the ozone layer continues breaking like it´s
doing now in some years we will disappear.

18. Videos
The Earth -
http://www.youtube.com/watch?v=JGXi_9A__Vc
The Big Bang -
http://www.youtube.com/watchv=wNDGgL73ih
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