C1.1

Question 1

What gases made up the early atmosphere?

Answer 1

mainly carbon dioxide and water vapour with virtually no oxygen

Question 2

How were oceans formed?

Answer 2

volcanoes gave out lots of gas including carbon dioxide water vapour and small amounts of other gas
oceans formed when the earth cooled, the water vapour condensed and it rained for a long time

Question 3

What caused the levels of carbon dioxide to decrease and oxygen increase?

Answer 3

a lot of early carbon dioxide dissolved in oceans
marine organisms developed and took in some carbon dioxide. when they died, it became trapped in carbonate rocks

green plants removed carbon dioxide and added oxygen when they photosynthesised, causing oxygen levels to slowly increase

Question 4

What human activities are changing the Earth’s atmosphere?

Answer 4

burning fossil fuels- releases carbon dioxide

deforestation - increases carbon dioxide levels, trees can’t photosynthesise and remove it

livestock farming - releases large amounts of methane into the atmosphere, animals release it

Question 5

What gases make up today’s atmosphere?

Answer 5

Nitrogen -78%
Oxygen - 21%
Carbon dioxide, water vapour and noble gases make up the other 1%