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The Atmosphere (The atmosphere of the Earth today: 78% nitrogen , 21%…
The Atmosphere
The atmosphere of the Earth today: 78% nitrogen , 21% oxygen
The gases in the atmosphere have stayed pretty constant for around 200 million years. Before that there were huge changes.
There are also small proportions of other gases (eg carbon dioxide, water vapour and noble gases such as argon)
The Earth is around 4600 million years old and that means that scientists cannot be certain about the early atmosphere.
Scientists think that during the first billion years, there was intense volcanic activity.
These volcanoes released the gases that formed the atmosphere. One of these gases were water vapour.
As the Earth cooled, the water vapour condensed to form the oceans.
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In this early stage, the Earth's atmosphere consisted mainly of carbon dioxide with little or no oxygen.
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The early atmosphere consisted mainly of carbon dioxide with small but increasing amounts of nitrogen.
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The early atmosphere contained large amounts of carbon dioxide but the atmosphere today only contains a small amount.
Apart from the level of nitrogen, there are two obvious differences between the early atmosphere and the atmosphere today.
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At this stage,some of the carbon dioxide dissolved in the oceans to form a weak acid.
Over time, this formed sediments of carbonate rock on the sea bed.
Volcanoes also released other gases. These include nitrogen which gradually built up in the atmosphere.