Evolution of the Earth's Atmosphere

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When the Earth first formed 4.54 billion years ago, its surface was molten. As it cooled, volcanoes were formed. These volcanoes released various gases. Around 4600 million years ago the Earth’s atmosphere was made up of Carbon Dioxide, Water Vapour, Nitrogen, Ammonia, Hydrogen Chloride, Sulphur Dioxide, Hydrogen and the Noble gasses. There was no oxygen at this time. Oxygen only appeared in the atmosphere around 3500 million years ago when the first simple organisms began releasing it.

Most of the Earth’s atmosphere (78.08%) now is made up of Nitrogen. Another 20.95% is mage up of Oxygen. A number of other gases, including Argon and Carbon Dioxide, are present in trace amounts. The Carbon Dioxide levels in the atmosphere have lowered so much from what they were millions of years ago because over time the gas was dissolved in oceans and trapped underground and in sedimentary rocks.

As previously mentioned, water vapour was one of the gases that made up the atmosphere around 4600 million years ago. There was no water in liquid form then because temperatures were too hot. As the Earth began to cool, so did the water vapour. It cooled enough to condense and form oceans. The oceans were started as pools of water in low-lying areas. Minerals dissolved into these pools from both the air and the rocks that the water ran off. These new water pools became ideal for the basic organisms to form and live. The first living organisms on Earth used photosynthesis to make their energy. Photosynthesis is one of the main processes that removes Carbon Dioxide from the atmosphere. The equation for photosynthesis is: Carbon Dioxide + Water = Glucose + Oxygen

6CO2 + 6H20 = C6H12O6 + 6O2

It was this that led to less Carbon Dioxide and more Oxygen in our atmosphere today.

The graph above shows Carbon Dioxide levels and temperature changes since 1880. We can see that over the entire time period, both the Carbon Dioxide concentration and the temperature are rising. From...
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