Developing the atmosphere

• 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.