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The Carboniferous period, during which oxygen amounted to 35% of the atmosphere by volume (this was around 300 million years ago). Nowadays the amount is 20.95%.

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What element in earths atmosphere was not present in the far past but is present now?

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What is the approximate percent of oxygen by volume present earths lower atmosphere?

Oxygen makes up about 21% of Earth's lower atmosphere by volume.


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Oxygen was not present in the Earth's atmosphere 3.6 billion years ago. The atmosphere at that time was primarily composed of carbon dioxide, nitrogen, methane, and water vapor. Oxygen began to accumulate in the atmosphere around 2.5 billion years ago as a result of photosynthetic organisms.


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It is believed that the early Earth's atmosphere did not contain significant amounts of oxygen. Oxygen began to accumulate in the atmosphere around 2.4 billion years ago due to the emergence of photosynthetic organisms.


Which is the approximate percentage by volume of oxygen present in earths atmosphere at location 2?

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