level: the atmosphere
Questions and Answers List
level questions: the atmosphere
| Question | Answer |
|---|---|
| state the percentages of the earths present atmosphere | 78% nitrogen 21% oxygen 1% argon 0.4% other gases like CO2 |
| the current gases in the atmosphere have stayed quite consistent for how long | 200 million years |
| why can't scientists be certain of the worlds early atmosphere | the earth is around 4600 million years old so scientists cannot be certain about the early atmosphere |
| what did the earths early atmosphere mainly consist of | carbon dioxide with little to no traces of oxygen |
| how was water vapour, nitrogen and CO2 introduced in the early atmosphere | intense volcanic activity released these gasses |
| how were oceans first formed | the earth started to cool down and water vapour condensed to form oceans |
| what happened to CO2 levels as oceans were formed | it had decreased as CO2 dissolved in the oceans forming a weak acid which reacted with minerals in the sea to form precipitate which over time formed sediments of carbonate rock on the sea bed |
| what was the CO2 in the ocean used to make | corals, shells of organisms like mussels |
| how did O2 start to get introduced into the atmosphere | around 2.7b years ago, photosynthetic algae first evolved and produced oxygen |
| when could animals finally start to evolve | when oxygen levels reached a point where they could respire |
| how were the CO2 levels in the early atmosphere decreased | fossil fuel formation, dissolved in oceans, photosynthesis |