Editor's Summary
30 August 2007
Coming up for air
The rise of atmospheric oxygen levels so important to life on Earth occurred about 2.5 billion years ago. But evidence for the oxygen-producing cyanobacteria thought to be responsible for this event has been found in rocks 200 million years older. If these bacteria really did provide the oxygen, why the delay? Lee Kump and Mark Barley think that the Earth's tectonic evolution is the key. At first submarine volcanoes may have acted as a sink for oxygen, stopping it from escaping into the atmosphere. The pattern of volcanism then changed after a major tectonic episode of continental stabilization around 2.5 billion years ago, when submarine volcanism was abruptly diminished and less-reducing subaerial volcanoes became more common. So with less oxygen being taken up by submarine volcanoes, the stage was set for the rise of atmospheric oxygen.
News and Views: Palaeoclimate: Oxygen's rise reduced
Why did oxygen not appear in Earth's atmosphere until hundreds of millions of years after photosynthesizing organisms first produced it? Perhaps because reducing gases from undersea volcanoes claimed it first.
Timothy W. Lyons
doi:10.1038/4481005a
Letter: Increased subaerial volcanism and the rise of atmospheric oxygen 2.5 billion years ago
Lee R. Kump & Mark E. Barley
doi:10.1038/nature06058
First paragraph | Full Text | PDF (235K) | Supplementary information
