The Earth's early atmosphere

When was the earth formed?

4.6 billion years ago.

Describe what gases were present in the early atmosphere. (3)

• a large amount of CO2

• little or no oxygen

• small amounts of other gases, such as ammonia and methane

What gases were also released by volcanic activity?

water vapour

nitrogen (gradually built up because it is unreactive)

For approximately 200 million years, the proportions of different gases in the atmosphere have been relatively stable.

Describe the percentages of the modern atmosphere.

Nitrogen - 80%

Oxygen - 20%

Other gases - including CO2, water vapour and noble gases (less than 1%)