history of the atmosphere

• Earth was formed 4.6 billion years ago
• now the earth is

  80% nitrogen

  20% oxygen

  <1% other gases
• in its first billion years, the earth had a lot of volcanic activity meaning lots of carbon dioxide, nitrogen and water vapour was released into the atmosphere.

  there were also small amounts of methane and ammonia
• the water vapour condensed to form oceans
• 2.7 billion years ago, plants and algae formed. They took in carbon dioxide and produced oxygen
• the CO2 was buried in sediment forming oil and trapping the gas
• coal is a sedimentary rock formed by dead plants
• limestone is a sedimentary rock that is made up of shells and skeletons of marine organisms