Q What are the gases that make up the
Earth’s atmosphere?
A The Earth’s atmosphere is composed of
many gases. Nitrogen is the main gas found
in the atmosphere. It accounts for about 78
per cent and oxygen makes up 21 per cent.
The remaining one per cent is a combination
of carbon dioxide and water vapour. There
are also very small amounts of trace gases like
neon and helium that go to make up the
Earth’s atmosphere.
Planet Earth
Earth’s Atmosphere
The protective blanket of air that covers the Earth is called the
atmosphere. The Earth’s atmosphere not only prevents too
much heat from entering the planet, but also protects us from
asteroids and meteors. The Earth’s gravity helps hold the
atmosphere in place.
Quick Q’s:
1. What is a barometer?
A barometer is used to
measure the pressure
in the atmosphere.
When the pressure is
high, the weather will
be fine, sunny and still.
When it is low, the
weather will be stormy.
When the pressure
increases the liquid in
the barometer is
squeezed and when the
pressure decreases it is
released. This change
is recorded.
2. What is the
exosphere?
The exosphere is the
final layer of the
Earth’s atmosphere. It
extends way into outer
space. The air in the
exosphere is very thin,
but the temperature is
very high, because the
Sun’s rays shine
directly on it.
3. Why is the ozone
layer important?
The ozone layer is
important because it
stops harmful
ultraviolet rays from
the Sun from reaching
the Earth. If the rays
are allowed through
the atmosphere, they
can cause severe health
problems like skin
cancer. Chemicals
called CFCs have made
a hole in the ozone
layer above the North
and South Poles.
Q How many layers does the Earth’s
atmosphere have?
A The Earth’s atmosphere is composed of
several layers. These include the troposphere
and the stratosphere. Each layer is divided
according to the temperature and density of
air in that layer.
26
A warm blanket
The Earth is protected by layers of gases. SOHO sends
information about these layers back to Earth.
Long way out
The outer layers of the atmosphere extend far
into space.
Reflected radiation
by atmosphere
Infrared radiation
emitted by Earth
Absorbed
radiation
Reflected radiation
by Earth’s surface
Q What is the significance of the
troposphere in the weather pattern?
A The troposphere is the layer closest
to the Earth’s surface, and it is here that
weather is created. Air in the troposphere
rises and falls, helping to form clouds, rain
and snow. This layer stretches about 8–14.5
kilometres (5–9 miles) above sea level.
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