chemistry of the atmosphere

• during the first billion years of earth's history, earth was covered in volcanoes that erupted and released many gases
• the early atmosphere was formed with the gases from the volcanoes
• the early atmosphere was mostly made up of carbon dioxide, with virtually no oxygen
• volcanic activity also released nitrogen, which built up of time, as well as water vapour and small amounts of methane and ammonia
• when the vapour in the atmosphere condensed, it formed the oceans
• lots of carbon dioxide was removed from the early atmosphere and formed carbon precipitates that formed sediments on the seabed
• green plants and algae evolved and absorbed some of the carbon dioxide so that they could carry out photosynthesis
• crude oil and natural gas are formed from deposits of plankton
• coal is a sedimentary rock made from thick plant deposits
• limestone is mostly made up of calcium carbonate
• as well as absorbing the carbon dioxide in the atmosphere, green plants and algae produced oxygen by photosynthesis
• algae evolved first
• over the next billion years after algae evolved, green plants also evolved
• as oxygen levels built up in the atmosphere over time, more complex life could evolve
• the composition of the atmosphere today is 80% nitrogen, 20% oxygen and small amounts of other gases (carbon dioxide, methane and water vapour)