Checked content


Description This graph represents the concentration of oxygen in the atmosphere over the last 1000 million years. As a reference, the dashed red line shows the present concentration of 21%.

It should be noted that the O2 concentration variation which occurred in past periods can often be estimated only relatively coarsely. Therefore, the chart makes no claim to accuracy, but can only give a broad overview of change at the level of geological periods. This chart is based on the averaged data of several publications.

Explanation of the curve:

After having already begun in the Precambrian, the outgassing of oxygen from the oceans caused atmospheric oxygen to jump from 3% to 12% around the beginning of the Cambrian, because by then all oxygen sinks were finally saturated. Around the same time, the Cambrian explosion took place. During the Silurian and Devonian plants spread over the land, while the animal kingdom was still almost exclusively confined to the water. This caused a further rapid and continuous increase of the oxygen concentration. In the following period carbon burial brought the oxygen level to 35%, thus favoring overgrowth especially in insects. Amphibians and early reptiles were now present on land.

Massive volcanic activity at the Permian-Triassic transition caused not only a decline of the oxygen content to 15%, but also the largest mass extinction in geological history. The oxygen concentration then recovered over a long period and reached 26% again by the middle of the Jurassic, and probably even rose to 30% in the Cretaceous. During this time the largest dinosaurs evolved.

The end of the Cretaceous period is marked by an impact event, with climate change and a mass extinction. The oxygen level was only 23% 40 million years ago, and had reached the present value of 21% by 25 million years ago. Since then the level has remained constant, apart from fluctuations in the per thousand range.
  1. Gunnar Ries: Dicke Luft bei den Sauriern
  2. Geologiefznzzrz-Forum @ Geoversum: Massensterben an der Perm-Trias Grenze: Durch Sauerstoffmangel erstickt?
  3. Gigantismus, Fliegen und Antiaging: Sauerstoffreiche Luft löste vor 300 Millionen Jahren einen Innovationsschub aus
Date 2010-03-11 10:25 (UTC)
  • derivative work: WolfmanSF ( talk)

Applications-graphics.svg This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: Translated text to English. The original can be viewed here: Sauerstoffgehalt-1000mj.svg. Modifications made by WolfmanSF.

I, the copyright holder of this work, hereby publish it under the following license:
Public domain I, the copyright holder of this work, release this work into the public domain. This applies worldwide.
In some countries this may not be legally possible; if so:
I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

The following pages on Schools Wikipedia link to this image (list may be incomplete):

Did you know...?

All five editions of Schools Wikipedia were compiled by SOS Children. SOS Children's Villages believes that a decent childhood is essential to a happy, healthy. Our community work brings families new opportunities through education, healthcare and all manner of support. We have helped children in Africa for many years - you can help too...