New Oxygen research;great oxygenation event study (Introduction)

by David Turell , Tuesday, June 09, 2020, 22:20 (1418 days ago) @ David Turell

The role of volcanic gasses:

https://phys.org/news/2020-06-volcanic-earth-mantle-key-atmospheric.html

"Oxygen first accumulated in the Earth's atmosphere about 2.4 billion years ago, during the Great Oxidation Event. A long-standing puzzle has been that geologic clues suggest early bacteria were photosynthesizing and pumping out oxygen hundreds of millions of years before then. Where was it all going?

"Something was holding back oxygen's rise. A new interpretation of rocks billions of years old finds volcanic gases are the likely culprits.

***

"'The data demonstrates that an evolution of the mantle of the Earth could control an evolution of the atmosphere of the Earth, and possibly an evolution of life."

***

"The Archean Eon, when only microbial life was widespread on Earth, was more volcanically active than today. Volcanic eruptions are fed by magma—a mixture of molten and semi-molten rock—as well as gases that escape even when the volcano is not erupting.

"The Archean Eon, when only microbial life was widespread on Earth, was more volcanically active than today.

"Volcanic eruptions are fed by magma—a mixture of molten and semi-molten rock—as well as gases that escape even when the volcano is not erupting.

The new study combines that data with evidence from ancient sedimentary rocks to show a tipping point sometime after 2.5 billion years ago, when oxygen produced by microbes overcame its loss to volcanic gases and began to accumulate in the atmosphere.

"'Basically, the supply of oxidizable volcanic gases was capable of gobbling up photosynthetic oxygen for hundreds of millions of years after photosynthesis evolved," said co-author David Catling, a UW professor of Earth and space sciences. "But as the mantle itself became more oxidized, fewer oxidizable volcanic gases were released. Then oxygen flooded the air when there was no longer enough volcanic gas to mop it all up.'"

Comment: All the processes that evolved the Earth for life seem to have been involved in setting the high level of atmospheric oxygen we have now.