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The Atmosphere
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In the beginning -
· The Earth was formed about Jupiter
4500 million years ago.
· The very first atmosphere mainly
consisted of hydrogen and
helium gases.
· Frozen giant planets like Saturn
and Jupiter still have
atmospheres like this but on the
warmer, smaller Earth these Saturn
light gases were largely lost into
space.
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The early atmosphere
· During the first billion years on Earth Mars
there was intense volcanic activity. This
produced the next early atmosphere.
· It would have contained large quantities
of carbon dioxide (CO2), along with
methane (CH4) , and ammonia (NH3).
· This is rather like the atmosphere on
Mars and Venus today. Venus
· The Earth's atmosphere would also
have contained water vapour which
condensed to form the oceans.
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Oxygen levels increase
· Carbon dioxide reacted with rocks and Earth
much became trapped in them.
· The evolution of algae some 3000
million years ago, and subsequently
plants which successfully colonised the
Earth's surface, led us towards the
present atmosphere.
· Their photosynthesis replaced carbon
dioxide with oxygen.
· Over a period of time billions of tonnes
of carbon dioxide became locked up in
Photosynthesis
fossil fuels.
increased
oxygen levels
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