ATMOSPHERE HISTORY: How Did Oxygen Levels Change in the Geologic Past?

Atmosphere History

Last Updated: Dec 29, 2018

Earth’s Changing Atmosphere Composition

Atmosphere Composition

Oxygen isn’t the most abundant gas in Earth’s atmosphere composition.

Based on the relative volumes of the gases in Earth’s atmosphere, nitrogen is actually more than 3 times more than oxygen.

Because the troposphere is the lowest atmosphere layer, it contains 75 percent of atmosphere’s mass.

From largest to smallest, Earth’s atmosphere composition contains nitrogen, oxygen, argon, CO2 and trace gases.

But it never used to be like this in the past. Over time, Earth’s oxygen levels has changed significantly.

Atmosphere history and oxygen levels

Atmosphere History

Earth’s early atmosphere was filled with methane and ammonia. CO2 played a dominant role early in Earth’s history.

But after oxygen filled the air, it created a habitable planet. Since early Earth, oxygen levels have changed significantly.

For example, free oxygen levels peaked just before the age dinosaurs. Now, Earth’s blue skies are picturesque.

We have oxygen to thank for its impeccable beauty.

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