The Earth formed approximately 4.6 billion years ago.
Scientists cannot be certain about what gases made up the Earth’s early atmosphere.
The layers of gases that surround the Earth are known as the atmosphere.
The important gases in the atmosphere are nitrogen, oxygen, carbon dioxide and argon.
Ideas about how the atmosphere was produced and has changed have developed over time as new evidence has been discovered.
There is still not enough evidence for scientists to be certain about the composition of the Earth’s early atmosphere.
One theory suggests that the early atmosphere came from intense volcanic eruption.
The early atmosphere was similar to the atmospheres of Mars and Venus today due to volcanic activity, which released gases such as carbon dioxide, nitrogen, and water vapour.
The atmospheres of Mars and Venus today have a large amount of carbon dioxide, little or no oxygen, and small amounts of other gases, such as ammonia and methane.
Volcanic activity also released water vapour into the early atmosphere.
Vapour is a cloud of liquid particles, which condensed into water when the Earth cooled to form the oceans.
Nitrogen was probably also released by volcanoes which gradually built up in the atmosphere because it is unreactive.
When a mountain with a hole in the top expels lava, ash, gas and other materials, it is known as a volcanic eruption.