AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The Earth's early atmosphere: One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans. At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
This theory explains how the early atmosphere formed.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
This theory explains how the early atmosphere formed. In the first billion years, Earth was hot and volcanically active. Eruptions released gases, including water vapour, carbon dioxide and nitrogen. As the planet cooled, water vapour condensed into liquid water, forming the oceans. The remaining gases formed an early atmosphere. Scientists suggest it was similar to the atmospheres of Mars and Venus today: mostly carbon dioxide, with little or no oxygen. For example, Venus has a dense carbon dioxide atmosphere, while Mars has a thin carbon dioxide atmosphere. This model is based on evidence from rocks, the composition of other planets and the behaviour of gases.
What earns the marks
- States that intense volcanic activity occurred during the first billion years of Earth’s existence.
- Explains that volcanoes released gases that formed the early atmosphere.
- Describes water vapour condensing to form the oceans as Earth cooled.
- Identifies carbon dioxide as the main gas in the early atmosphere, with little or no oxygen.
- Compares the early Earth atmosphere to the atmospheres of Mars and Venus today.
Common mistakes and how to put them right
Thinking the early atmosphere contained a lot of oxygen.
Put it right by stating that oxygen was little or absent until photosynthesis evolved.
Believing the oceans formed from volcanic lava rather than condensed water vapour.
Put it right by explaining that cooling water vapour condensed into liquid water.
Assuming Mars and Venus have oxygen-rich atmospheres.
Put it right by noting both are mainly carbon dioxide with little or no oxygen.
Exam tips
- Use the phrase ‘may have been’ to show the theory is a model, not a proven fact.
- Link each gas to its source: volcanoes released water vapour, carbon dioxide and nitrogen.
- When comparing to Mars and Venus, state the main gas and the lack of oxygen explicitly.
Try the lesson
The start of the The Earth's early atmosphere: One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans. At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas. lesson, made from checked teaching notes for this specification point.
Have a go first
According to the theory of the Earth's early atmosphere, which gas was the main gas in the atmosphere at the start of the first billion years?
Listen
This theory explains how the early atmosphere formed. In the first billion years, Earth was hot and volcanically active. Eruptions released gases, including water vapour, carbon dioxide and nitrogen. As the planet cooled, water vapour condensed into liquid water, forming the oceans. The remaining gases formed an early atmosphere. Scientists suggest it was similar to the atmospheres of Mars and Venus today: mostly carbon dioxide, with little or no oxygen. For example, Venus has a dense carbon dioxide atmosphere, while Mars has a thin carbon dioxide atmosphere. This model is based on evidence from rocks, the composition of other planets and the behaviour of gases. A strong answer earns marks for these points. States that intense volcanic activity occurred during the first billion years of Earth’s existence. Explains that volcanoes released gases that formed the early atmosphere. Describes water vapour condensing to form the oceans as Earth cooled. Identifies carbon dioxide as the main gas in the early atmosphere, with little or no oxygen. A common slip: Thinking the early atmosphere contained a lot of oxygen. Instead, stating that oxygen was little or absent until photosynthesis evolved. Exam tip: Use the phrase ‘may have been’ to show the theory is a model, not a proven fact.
Key words
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Formation of the early atmosphere
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Volcanic activity and outgassing
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Condensation and formation of oceans
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Comparison with Mars and Venus
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See every definition
- Formation of the early atmosphere
- One theory suggests intense volcanic activity released gases that formed the early atmosphere during the first billion years of the Earth's existence.
- Volcanic activity and outgassing
- Intense volcanic activity released gases, including water vapour, carbon dioxide and nitrogen, that formed the early atmosphere.
- Condensation and formation of oceans
- As the planet cooled, water vapour condensed into liquid water, forming the oceans.
- Comparison with Mars and Venus
- The early atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
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Test your understanding of The Earth's early atmosphere: One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans. At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
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