Science : Gases in the atmosphere

gases in the atmosphere include :

nitrogen - 78%

oxygen - 21%

other gases (e.g. water vapour and noble gases such as argon) - 0.96%

carbon dioxide - 0.04%

• the gases in the atmosphere have stayed constant for about 200 million years

• scientist can not be certain of the early atmosphere as the earth is 4600 million years old

• scientist think that in the first billion years there was intense volcanic activity

• these volcanoes released the gases that formed the atmosphere one of these gases was water vapour

• as the earth cooled the water vapour condensed to form oceans

• volcanos also released huge amounts of carbon dioxide

• the earth contained more carbon dioxide and little to no oxygen

• the earths atmosphere then was very much like venues and mars atmosphere today

• the volcanoes also released nitrogen which built up in the atmosphere

• they released small amounts of methane and ammonia

• some of the carbon dioxide dissolved into the ocean which formed a weak acid

• this reacted with minerals in the sea to form precipitates

• over time this formed sediments of carbonate rocks on the sea bed

• some of the carbon dioxide in the sea was used to make corals and shells such as mussels

• when these died they formed the sedimentary rock limestone (this also removed carbon dioxide form the air)

• photosynthetic algae evolved in oceans

• photosynthesis produced oxygen which entered the atmosphere

• over the following billion years plants evolved and this increased the amount of oxygen in the atmosphere

• photosynthesis takes in carbon dioxide and the carbon can then be trapped into fossil fuels and again that causes the level of carbon dioxide to fall