Volcanoes: Key to Earth's oxygen

STATE COLLEGE, Pa., Aug. 29 (UPI) -- A U.S.-Australian study suggested a switch from predominantly undersea volcanoes to a mix of undersea and terrestrial ones created Earth's oxygen.

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

But before 2.5 billion years ago, the Earth's atmosphere lacked oxygen, Kump noted. However, biomarkers in rocks 200 million years after than that period show oxygen-producing cyanobacteria were releasing oxygen at the same levels as today.

Kump said ancient Earth should have had an oxygen atmosphere but something was removing the oxygen.

Kump and colleagues suggest submarine volcanoes, producing a reducing mixture of gases and lavas, effectively scrubbed oxygen from the atmosphere, binding it into oxygen-containing minerals.

But about 2.5 billion years ago, when stabilized continental land masses arose and terrestrial volcanoes appeared, markers show oxygen began appearing in the atmosphere.

The study conducted by Kump and geology Professor Mark Barley of the University of Western Australia appears in the journal Nature.