The Atmosphere

• What % of the Earths atmosphere is nitrogen?

  78%
• What % of the Earths atmosphere is oxygen?

  21%
• what are the other small proportions of gases in our atmosphere?

  Carbon dioxide, water vapour and noble gases such as argon
• How have the gases in our atmosphere stayed over 200 million years?

  Constant but before that there were huge changes.
• What were the changes to our atmosphere? part 1

  Early Earth- No crust, no life, molten surface (billions of years ago)

  Early Earth- Atmosphere full of CO2, methane and ammonia, volcanoes erupted constantly spewing water vapour and lava.
• What were the changes to our atmosphere? part 2

  Over millions of years- Surface solidified, when the temperature fell below 100℃ the water vapour condensed and fell as rain forming oceans and rivers.

  Millions of years after that- CO2 dissolved in the ocean, lowering the CO2 in the atmosphere, some CO2 reacted with minerals to make rocks e.g calcium carbonate (limestone)
• What were the changes to our atmosphere? part 3?

  over the next billion years- bacteria could photosynthesise and algae began to remove CO2 during photosynthesis and release oxygen, CO2 levels fell and oxygen began to appear in our atmosphere.

  Because of this: animals appeared
• What has happened to oxygen throughout the changing atmosphere?

  Oxygen has increased, as soon as plants and algae evolved the CO2 levels decreased as they could photosynthesise and breathe out oxygen.
• What has happened to water vapour throughout the changing atmosphere?

  Water vapour levels have decreased, the Earth cooled below 100℃ so the water vapour condensed and fell as rain to form oceans and rivers.
• What has happened to carbon dioxide throughout the changing atmosphere?

  Carbon dioxide has decreased, early Earth was full of CO2 with volcanoes constantly erupting. After oceans formed CO2 dissolved in the ocean and some reacted with minerals to form rocks, In the next billion years, bacteria could photosynthesise and began to remove CO2 and release oxygen. However CO2 has increased in the last 200 years due to the industrial revolution.
• What has happened to Nitrogen throughout the changing atmosphere?

  Nitrogen levels have increased through it being released by volcanoes and by bacteria converting ammonia into nitrogen.