A study that examined 2.5-billion-year-old rocks from Australia has suggested that volcanic eruptions may have helped create the first “‘whiffs” of oxygen in the earth’s atmosphere by stimulating population surges of marine microorganisms.
The study was published in August in the Proceedings of the National Academy of Sciences, conducted by the University of Washington, the University of Michigan and other institutions.
“What has started to become obvious in the past few decades is there actually are quite a number of connections between the solid, nonliving Earth and the evolution of life,” said first author Jana Meixnerová, a UW doctoral student in Earth and space sciences.
“But what are the specific connections that facilitated the evolution of life on Earth as we know it?”
When the earth was young, it had no oxygen in the atmosphere. About 2.4 billion years ago, however, it began to be permanently filled with oxygen. This was likely due to an explosion of organisms that could photosynthesize.
In 2007, co-author Ariel Anbar at Arizona State University analyzed rocks from Mount McRae Shale in Western Australia. It was found that there was a short-term whiff of oxygen about 50 to 100 million years before it permanently populated the earth’s atmosphere.
The new study, led by co-corresponding author Joel Blum, examined the same rocks. It was found that large volcanic eruptions spewed out mercury into the upper atmosphere. The study suggests that a few million years before the temporary rise in oxygen, there was a spike in mercury.
The researchers argued that the lava and volcanic ash fields created by the eruptions released phosphorus into rivers that fertilized nearby coastal areas.
“There are other nutrients that modulate biological activity on short timescales, but phosphorus is the one that is most important on long timescales,” Meixnerová said.
“During weathering under the Archaean atmosphere, the fresh basaltic rock would have slowly dissolved, releasing the essential macro-nutrient phosphorus into the rivers. That would have fed microbes that were living in the shallow coastal zones and triggered increased biological productivity that would have created, as a byproduct, an oxygen spike.
