4.9.1.2 - The Earth's early atmosphere

What happens to the theories made about our early atmosphere (and why)?

Theories about what was in the Earth’s early atmosphere and how the atmosphere was formed have changed and developed over time.

This is as evidence for the early atmosphere is limited

Why is the evidence for the early atmosphere limited?

Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years

What does one theory suggest formed the early atmosphere?

During the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere.

According to this theory what was the early atmosphere similar to?

At the start of this period the Earth’s atmosphere may have been like the atmosphere of Mars and Venus today - consisting mainly of carbon dioxide, with little to no oxygen gas

Explain this theory.

Due to volcanic activity, the atmosphere consisted of mainly carbon dioxide, with little to no oxygen gas

The volcanic activity also produced nitrogen, which gradually built up in the atmosphere, as well as small proportions of methane and ammonia.

Water vapour was also produced by volcanic activity that condensed to form the oceans

What was formed after the water vapour condensed?

When the water vapour condensed, it formed the oceans

What happened after oceans formed? (to carbon)

When the oceans formed carbon dioxide dissolved in the water,

Carbonates were then precipitated producing sediments on the seabed

This reduced the amount of carbon dioxide in the atmosphere

How are carbonate precipitates formed?

When the dissolved carbon dioxide goes through a series of reactions to form carbonate precipitates - these then produced sediments on the seabed