The Early Atmosphere

Question 1

What was the earths early atmosphere like

Answer 1

Large amounts of carbon dioxide and water vapour, hardly any oxygen and small amounts of other gases

Question 2

Explain why scientists can not be certain about the composition of the early atmosphere

Answer 2

There were no humans around to measure the atmosphere, so they have to use clues. There are different sources of information, but not all the evidence leads to the same conclusion. This means that it is difficult to know exactly what the early atmosphere was like and how it has changed

Question 3

How have the levels of oxygen increased in the earths atmosphere

Answer 3

Earth cools and oceans formed
Forms of life evolve in the oceans and photosynthesis begins
Oxygen builds up in the oceans
Oxygen build up in the atmosphere

Question 4

How have the levels of carbon dioxide decreased in the earths atmosphere

Answer 4

Carbon dioxide dissolves in the oceans
Marine organisms used the dissolved carbon dioxide to make calcium carbonate for shells
The shells of dead marine organisms fall to the sea bed and become part of the sediment
Over millions of years the layers of sediment become squashed and form sedimentary rocks