Describe and explain how changes in the earth atmosphere, from the Precambrian Era (where the earth as occupied by volcanoes), have changed to form the surface of the Earth today and its atmosphere.

The Earth's atmospheric oxygen increased because plants and algae developed and used carbon dioxide for photosynthesis. This led to a decrease in atmospheric carbon dioxide levels. The origins of the oceans came about as a consequence of rapid cooling of water vapour. This led to a decrease in carbon dioxide as oceans absorbed this gas. Additionally, carbon dioxide was "locked up" in carbonate rocks. The advent of continental formation, namely a supercontinent, Pangaea, caused a reduction in the numbers of active volcanoes. Finally, nitrogen formed because ammonia in the Earth’s early atmosphere reacted with oxygen.