A storyboard that show the 6 different stages of Earth's atmosphere.
Back in the early days of Earth's Formation there was little atmosphere to speak of. At this time the majority of the atmosphere was composed of the gases produced from the volcanic eruptions that covered the Earth
4.6 Billion Years Ago
4 billion years ago the Earth cooled down allowing water to condense and form the Oceans. However, it was still too hot for living organisms on the surface so instead. they lived on the bottom of the Oceans using sulfur and other chemicals to survive while also producing oxygen
4 Billion Years Ago
After billions of years, the organisms at the bottom of the ocean produced enough oxygen to sustain allow for living things to survive on the surface. The evidence of the oxidation of the planet can be seen by the iron rich dirt that was turned red by the increase in oxygen
2.6 billion Years Ago
The prevalence in oxygen increased dramatically at this time. Such an increase allowed even larger oxygen breathing plants and animals to come to the surface. During this time, aerobic creatures thrived while the others were poisoned by oxygen
700 Million Years Ago
As seen behind me, huge trees cover the background. The reason trees could get to such a large size is due to the amount of oxygen at this time. During this period oxygen was nearly as abundant as in the present which resulted in these huge organisms.
400 Million Years Ago
Our atmosphere today is roughly 21% oxygen, which is good since we need it to survive. By now you can see the long journey it took to get to the point we are now with breathable air and blue skies.