C1 Topic 1 - The Earth's Sea And Atmosphere

Question 0

How did the modern atmosphere develop over millions of years?

Answer 0

1. Volcanoes released CO2, water vapour and other gases into the atmosphere. This is how the oceans formed.
2. Green plants evolved and removed most of the CO2 from the atmosphere, turning it into O2.
3. Rise in oxygen killed many early organisms but allowed for more complex ones to develop. Oxygen created the ozone layer (O3) which blocked rays from the Sun, allowing even more complex organisms to develop.

Question 1

What is the composition of today’s atmosphere?

Answer 1

78% nitrogen
21% oxygen
0.04% carbon
>1% other gases

Question 2

How is the atmosphere changing today?

Answer 2

Humans:
Burning fossil fuels
Deforestation
Livestock farming

Volcanic Activity:
Sulphur dioxide
Carbon dioxide

Question 3

How can we tell what the early atmosphere was like?

Answer 3

Scientists can analyse bubbles of air trapped in Antarctic ice cores, so the deeper the ice, the older the air.