Volcanoes are partly to thank for the air you’re breathing right now, a new study shows.

Billions of years ago, Earth had very little oxygen in its atmosphere, in part because most of the volcanoes on our planet were undersea. The mixture of gases and lavas that erupted from these volcanoes scrubbed out any oxygen floating around from the atmosphere and bound it into minerals.

But the breakup of and formation of two supercontinents that occurred in the transition from the Archaean period (3.8 to 2.5 billion years ago) to the Palaeoproterozoic increased the population of terrestrial volcanoes.

Terrestrial volcanoes could form because land masses were more stable under the new tectonic regime ushered in by the continental shift. These volcanoes erupt at higher temperatures than undersea volcanoes and so are less efficient at converting oxygen.

So the shift from undersea to terrestrial volcanoes allowed oxygen (produced by photosynthetic bacteria) to accumulate in the atmosphere, with profound implications for life on Earth.

"The rise of oxygen allowed for evolution of complex oxygen-breathing life forms," said study leader Lee Kump of Pennsylvania State University.

The study is detailed in the Aug. 30 issue of the journal Nature.

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