One theory proposes that volcanoes released gases that formed an early atmosphere mainly of carbon dioxide, with little or no oxygen. An alternative theory proposes that oxygen made up a substantial proportion of the early atmosphere.
Two research teams used evidence from ancient rocks to estimate the proportions of these gases in the early atmosphere.
| Team | Estimated carbon dioxide (%) | Estimated oxygen (%) |
|---|---|---|
| A | 63 | less than 1 |
| B | 48 | 3 |
A researcher concludes that the volcanic theory must be correct because it fits the estimates. Evaluate this conclusion.
79 exam-style questions on AQA GCSE Chemistry 9.1 The composition and evolution of the Earth's atmosphere, covering 9.1.1 The proportions of different gases in the atmosphere, 9.1.2 The Earth's early atmosphere, 9.1.3 How oxygen increased, and 9.1.4 How carbon dioxide decreased. Each one has a worked solution and a mark scheme showing where the marks go.