Download Make up of Atmosphere Reason Obviously, something happened to

Shortly after the earth
formed, its atmosphere
was very similar to that
of Venus indeed.
The table below
explains its composition.
Make up of
Atmosphere
Lots of Carbon dioxide
Lots of steam
Traces of methane and
ammonia
Reason
This was released by the ton in the
many volcanic eruptions early Earth
experienced.
The temperature of the earth was
very high (above boiling point). This
is due to the greenhouse effect
caused by all the carbon dioxide.
Also released in volcanic
eruptions.
Obviously, something happened to change our atmosphere (or
we would not be here!). The table overleaf shows how the
atmosphere of the Earth looks like today…. Then we will look
at how this change might have happened.
Gas
Nitrogen
Oxygen
Carbon Dioxide.
SEE PAGE 161 FOR A DIAGRAM OF
THE CARBON CYCLE.
Noble gases.
THESE ARE INERT, UNREACTIVE
GASES LIKE ARGON, AND
HELIUM.
Percentage of
atmosphere
78% (often referred to on
exams as around 80%)
21%
Less than 1%
Less than 1%
The following is a step by step guide as to how the atmosphere of the Earth changed
into what it is today
STEP ONE: THE EARTH COOLED,
EVENTUALLY DROPPING BELOW 100
DEGREES. THIS ALLOWED THE STEAM TO
CONDENSE TO FORM THE OCEANS
STEP TWO: MUCH OF THE CARBON
DIOXIDE REACTED WITH THE WATER IN
OCEANS AND WAS REMOVED FROM THE
ATMOSPHERE. THE REACTION FORMED
CARBONATE ROCKS E.G. LIMESTONE
STEP THREE: THE APPEARANCE OF WATER
KICKSTARTED THE EVOLUTION OF EARLY PLANT
LIFE. THIS PRODUCED THE OXYGEN WE SEE
TODAY (THROUGH PHOTOSYNTHESIS).
PHOTOSYNTHESIS ALSO HELPED REMOVE SOME
OF THE CARBON DIOXIDE THAT WAS LEFT.
STEP FOUR: THE OXYGEN PRODUCED REACTED
WITH THE METHANE AND AMMONIA. THESE
REACTIONS REMOVED THEM FROM THE
ATMOSPHERE AND THE REACTION WITH
AMMONIA PRODUCED ALL THE NITROGEN THAT
MAKES UP MOST OF TODAYS ATMOSPHERE.