The composition of the Earth's atmosphere has changed dramatically over its 4.6-billion-year history.
Which row in the table correctly identifies the relative abundance of carbon dioxide (CO2\text{CO}_2CO2) in the Earth's early atmosphere, the overall trend in its atmospheric concentration over geological time to today, and a key process that drove this trend?
| Relative abundance in the early atmosphere | Overall trend to today | Key process driving this trend | |
|---|---|---|---|
| A | Trace component (<1%) | Decreased | Dissolution in oceans and condensation of water vapour |
| B | Major component (>90%) | Decreased | Photosynthesis and carbonate rock formation |
| C | Major component (>90%) | Increased | Volcanic outgassing and respiration |
| D | Trace component (<1%) | Increased | Combustion of fossil fuels and deforestation |
A Row A B Row B C Row C D Row D
Row A
Row B
Row C
Row D
Practise Edexcel GCSE Chemistry Earth and atmospheric science with exam-style questions for Foundation and Higher tier. 62 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
