Our planet has seen plenty of extinctions since life emerged on its surface. Among them, there were five significant and well-known mass extinctions, also known as 'the big five.' The most famous of which was the mass extinction of the dinosaurs that happened approximately 65 million years ago.
Image Credit: NASA via Wikimedia Commons
Recently researchers supported by Stanford University and others discovered a previously unknown gigantic extinction, following clues provided by Canadian rocks that were formed billions of years ago. It is estimated that this extinction was even vaster than the above-mentioned mass extinction of the dinosaurs.
The scientists studied rocks found in Hudson Bay, Canada. They mainly looked at barite, a mineral that contains information about the amount of oxygen available in the atmosphere at that time. Ensuing this examination, it became apparent that Earth experienced massive changes in its biosphere approximately two billion years ago, showing an enormous drop in life.
Coinciding with this massive change was a period of rising levels of oxygen in Earth's atmosphere called the 'great oxidation event.' After the steep rise of oxygen followed a sudden decline. Life was probably not equipped for this sudden decline in oxygen, which lead to a mass extinction.
A different type of event is thought to be the causing force behind the mass extinction of the dinosaurs, namely a giant meteor impact - Image Credit: NASA/Don Davis
Erik Sperling, assistant professor of geological sciences at Stanford University, stated that the size of the biosphere throughout geologic history has always been one of the biggest mysteries in his field. This newfound proxy shows how intertwined the biosphere is with oxygen and co2 levels.
The new findings give scientists further data to help them estimate the extent of the previously mentioned great oxidation event. It is hypothesized that an abundance of photosynthesis stemming from microorganisms and weathering rocks created a tremendous amount of oxygen that was later abruptly halted when those microorganisms depleted their nutrient supply.
Steadily are getting to know more and more about Earth's biological history. We will keep an eye on this field to see what further discoveries will follow.
Sources and further reading: A productivity collapse to end Earth’s Great Oxidation / Stanford University press release / Great Oxidation Event / The big five mass extinctions
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