Question 1: The Earth's early atmosphere was mainly composed of gases released from volcanic eruptions. It lacked oxygen and was rich in carbon dioxide, methane, and ammonia. Over time, processes such as photosynthesis transformed it into the oxygen-rich atmosphere we have today.

Answer: The early atmosphere was mainly made up of gases like carbon dioxide, methane, and ammonia, with little or no oxygen, formed by volcanic activity.

Question 1: Define 'greenhouse gases' and explain their role in Earth's early atmosphere.

Answer: Greenhouse gases trap heat in the atmosphere, helping to keep Earth warm; in the early atmosphere, they contributed to maintaining high temperatures necessary for volcanic and chemical processes.

Question 2: Describe the mechanism by which volcanic eruptions contributed to the composition of the early atmosphere.

Answer: Volcanic eruptions released gases like carbon dioxide, methane, ammonia, and sulphur compounds, which accumulated in the atmosphere over time.

Question 1: If the initial volume of volcanic gases released was 1 x 10^12 cubic metres and the proportion of carbon dioxide was 90%, calculate the volume of carbon dioxide released.

Answer: 9 x 10^11 cubic metres

Question 2: The current concentration of oxygen in the Earth's atmosphere is approximately 21% by volume. If the atmosphere's total volume is 4.2 x 10^9 cubic kilometres, calculate the volume of oxygen present in the atmosphere.

Answer: 8.82 x 10^7 cubic kilometres

Question 1: Design a simple experiment to simulate volcanic gas release and describe the safety precautions you would take.

Answer: Students could use a heated substance to simulate volcanic activity, releasing gases into a container with a safe venting system. Precautions include wearing safety goggles, gloves, and working in a well-ventilated area to avoid inhaling gases or contact with hot materials.

Question 1: A sample of ancient rock analysis indicates 0.05% sulphur in the atmosphere during early Earth. Discuss what this suggests about volcanic activity and atmospheric composition at that time.

Answer: The presence of sulphur suggests active volcanic eruptions releasing sulphur compounds, indicating a sulphur-rich atmosphere and high volcanic activity during early Earth.

Question 1: Explain how the development of photosynthesis led to the increase in oxygen levels in Earth's atmosphere. Include the impact on other atmospheric gases in your answer. (6 marks)

Answer: Photosynthesis by early cyanobacteria converted carbon dioxide into oxygen as a waste product. Over millions of years, this oxygen accumulated, transforming the atmosphere from reducing to oxidising. The increase in oxygen led to the decline of methane and ammonia, enabling the development of more complex life forms and changing climate conditions.

Question 1: Describe how knowledge of Earth's early atmosphere can influence current efforts to model climate change and predict future atmospheric changes.

Answer: Understanding Earth's early atmosphere helps scientists develop models of atmospheric evolution, enabling better predictions of how current greenhouse gas emissions may alter climate and atmospheric composition in the future.